Department of Aeronautics and Astronautics

CM Oman commentary to NASA on Spacelab mission experiment development process

2023-06-15T03:23:38Z

CM Oman commentary to NASA on Spacelab mission experiment development process Oman, Charles Oman commentary on NASA life sciences Shuttle/Spacelab experiment development process prepared for NASA Life Sciences Strategic Planning Study Committee, April 1987. (Many suggestions were subsequently adopted.)

Space Shuttle/Spacelab-1 Research on Space Motion Sickness: AIAA NE Section Lecture

2023-06-15T03:43:16Z

Space Shuttle/Spacelab-1 Research on Space Motion Sickness: AIAA NE Section Lecture Oman, Charles Text of invited presentation to AIAA New England Section at Avco Everett Reseach Laboratory, March 1984

Telemetry Fault-Detection Algorithms: Applications for Spacecraft Monitoring and Space Environment Sensing

2025-02-11T19:58:16Z

Telemetry Fault-Detection Algorithms: Applications for Spacecraft Monitoring and Space Environment Sensing Carlton, Ashley; Morgan, Rachel; Lohmeyer, Whitney; Cahoy, Kerri Algorithms have been developed that identify unusual behavior in satellite health telemetry. Telemetry from solid-state power amplifiers and amplifier thermistors from 32 geostationary Earth orbit communications satellites from 1991 to 2015 are examined. Transient event detection and change-point event detection techniques that use a sliding window-based median are used, statistically evaluating the telemetry stream compared to the local norm. This approach allows application of the algorithms to any spacecraft platform because there is no reliance in the algorithms on satellite- or component-specific parameters, and it does not require a priori knowledge about the data distribution. Individual telemetry data streams are analyzed with the event detection algorithms, resulting in a compiled list of unusual events for each satellite. This approach identifies up to six events of up to six events that affect 51 of 53 telemetry streams at once, indicative of a spacecraft system-level event. In two satellites, the same top event date (4 December 2008) occurs over more than 10 years of telemetry from both satellites. Of the five spacecraft with known maneuvers, the algorithms identify the maneuvers in all cases. Event dates are compared to known operational activities, space weather events, and available anomaly lists to assess the use of event detection algorithms for spacecraft monitoring and sensing of the space environment.

Design of the Deformable Mirror Demonstration CubeSat (DeMi)

2025-02-11T20:02:40Z

Design of the Deformable Mirror Demonstration CubeSat (DeMi) Douglas, Ewan; Allan, Gregory; Barnes, Derek; Figura, Joseph S.; Haughwout, Christian A.; Gubner, Jennifer N.; Knoedler, Alex A.; LeClair, Sarah; Murphy, Thomas J; Nikolaos, Skouloudis; Merk, John; Opperman, Roedolph A.; Cahoy, Kerri L. The Deformable Mirror Demonstration Mission (DeMi) was recently selected by DARPA to demonstrate in-space operation of a wavefront sensor and Microelectromechanical system (MEMS) deformable mirror (DM) payload on a 6U CubeSat. Space telescopes designed to make high-contrast observations using internal coronagraphs for direct characterization of exoplanets require the use of high-actuator density deformable mirrors. These DMs can correct image plane aberrations and speckles caused by imperfections, thermal distortions, and diffraction in the telescope and optics that would otherwise corrupt the wavefront and allow leaking starlight to contaminate coronagraphic images. DeMi is provide on-orbit demonstration and performance characterization of a MEMS deformable mirror and closed loop wavefront sensing. The DeMi payload has two operational modes, one mode that images an internal light source and another mode which uses an external aperture to images stars. Both the internal and external modes include image plane and pupil plane wavefront sensing. The objectives of the internal measurement of the 140-actuator MEMS DM actuator displacement are characterization of the mirror performance and demonstration of closed-loop correction of aberrations in the optical path. Using the external aperture to observe stars of magnitude 2 or brighter, assuming 3-axis stability with less than 0.1 degree of attitude knowledge and jitter below 10 arcsec RMSE, per observation, DeMi will also demonstrate closed loop wavefront control on an astrophysical target. We present an updated payload design, results from simulations and laboratory optical prototyping, as well as present our design for accommodating high-voltage multichannel drive electronics for the DM on a CubeSat.

Using the Galileo Solid-State Imaging Instrument as a Sensor of Jovian Energetic Electrons

2019-04-11T00:14:00Z

Using the Galileo Solid-State Imaging Instrument as a Sensor of Jovian Energetic Electrons Carlton, Ashley; de Soria-Santacruz Pich, Maria; Kim, Wousik; Jun, Insoo; Cahoy, Kerri We quantitatively describe the Jovian energetic electron environment using the Solid State Imager (SSI) on the Galileo spacecraft. We post-process raw SSI images by removing the target object and dark current to obtain frames only with the radiation contribution. The camera settings (gain state, filter, etc.) are used to compute the energy deposited in each pixel, which corresponds to the intensity of the observed radiation hits (the actual measurements are expressed with the digital number (DN), from which the energy deposited can be computed). Histograms of the number of pixels versus energy deposited by incident particles from processed SSI images are compared with the results from 3D Monte Carlo transport simulations of the SSI using Geant4. We use Geant4 to simulate the response of the SSI instrument to mono-energetic electron environments from 1 to 100 MeV. We fit the modeled instrument response to the SSI data using a linear combination of the simulated mono-energetic histograms to match the SSI observations. We then estimate the spectra of the energetic electron environment at Jupiter, or we estimate the integral flux when there is lower confidence in the spectra fits. We validate the SSI results by comparing the environment predictions to the observations from the Energetic Particle Detector (EPD) on the Galileo spacecraft, examining the electron differential fluxes from 10’s of keV to 11 MeV. For higher energies (up to 31.0 MeV), we compare our findings with the NASA GIRE model, which is based on measurements from the Pioneer spacecraft. This approach could be applied to other sets of imaging data in energetic electron environments, such as from star trackers in geostationary Earth orbits.

Laser Beacon Tracking for High-Accuracy Attitude Determination

2025-02-11T20:02:40Z

Laser Beacon Tracking for High-Accuracy Attitude Determination Nguyen, Tam; Cahoy, Kerri CubeSat pointing capabilities have greatly improved in the past few years, paving the way for more sophisticated science and technology demonstration missions. Advances in attitude determination have led to the development of several CubeSat-sized attitude sensors capable of achieving fine attitude knowledge,most of which utilize natural light sources as references, such as in the case of star trackers and sun sensors. However, inertial-based attitude sensors often limit ground tracking capability of the satellite due to high ephemeris uncertainty of most CubeSats. Laser beacon tracking directly measures of the satellite’s attitude relative to a ground station or target, eliminating attitude errors induced in the coordinate frame conversion process. In addition, the use of a narrow-band artificial light source allows filtering techniques to be implemented, reducing the probability of false positives. In this paper, we present the development of a low-cost CubeSat-sized laser beacon camera along with detailed simulation development and results to demonstrate the attitude sensing performance of the module. The end-to-end simulation includes a laser link radiometry model, hardware model, atmospheric scintillation model, and sky radiance model at the beacon wavelength. Simulation results show that the laser beacon camera is capable of achieving an attitude accuracy of less than 0.1 mrad with a fade probability of less than 1% during daytime under most sky conditions for a satellite above 20-deg elevation in low-Earth orbit.

Active Polarimetric Measurements for Identification and Characterization of Space Debris

2025-02-11T19:58:16Z

Active Polarimetric Measurements for Identification and Characterization of Space Debris Pasqual, M. C.; Cahoy, K. L. A bench-top polarimeter ( λ = 1064 nm) is used to measure the polarimetric Bidirectional Reflectance Distribution Function (BRDF) of several common spacecraft materials in both bistatic and monostatic geometries. The Mueller matrix and polarimetric properties of each material were estimated as a function of the illumination and viewing angles. The findings expand upon previous research suggesting that active polarimetry may be useful for the remote characterization and identification of space debris.

Sensory Motor Conflict Theory for Motion Sickness: Oman letter to Reason

2019-04-12T20:43:20Z

Sensory Motor Conflict Theory for Motion Sickness: Oman letter to Reason Oman, Charles M. CM Oman (MIT) letter to JT Reason (U. Manchester) describing Sensory Motor Conflict Theory for motion sickness, as initially presented at NASA Vestibular Motion Sickness Workshop at Johnson Space Center November, 1978, and later elaborated in Oman, C. M. (1982). "A heuristic mathematical model for the dynamics of sensory conflict and motion sickness." Acta Otolaryngologica (Stockholm) 94(S392): 4-44.

Laser-Guide-Star Satellite for Ground-Based Adaptive Optics Imaging of Geosynchronous Satellites

2025-02-11T19:58:16Z

Laser-Guide-Star Satellite for Ground-Based Adaptive Optics Imaging of Geosynchronous Satellites Marlow, Weston; Carlton, Ashley; Hyosang, Yoon; Clark, James; Haughwout, Christian; Cahoy, Kerri; Males, Jared; Close, Laird; Morzinski, Katie In this study, the feasibility and utility of using a maneuverable nanosatellite laser guide star from a geostationary equatorial orbit have been assessed to enable ground-based, adaptive optics imaging of geosynchronous satellites with next-generation extremely large telescopes. The concept for a satellite guide star was first discussed in the literature by Greenaway and Clark in the early 1990s ("PHAROS: An Agile Satellite-Borne Laser Guidestar," Proceedings of SPIE, Vol. 2120, 1994, pp. 206-210), and expanded upon by Albert in 2012 ("Satellite-Mounted Light Sources as Photometric Calibration Standards for Ground-Based Telescopes," Astronomical Journal, Vol. 143, No. 1, 2012, p. 8). With a satellite-based laser as an adaptive optics guide star, the source laser does not need to scatter, and is well above atmospheric turbulence. When viewed from the ground through a turbulent atmosphere, the angular size of the satellite guide star is much smaller than a backscattered source. Advances in small-satellite technology and capability allowed the revisiting of the concept on a 6U CubeSat, measuring 10×20×30 cm. It is shown that a system that uses a satellite-based laser transmitter can be relatively low power (~1 W transmit power) and operated intermittently. Although the preliminary analysis indicates that a single satellite guide star cannot be used for observing multiple astronomical targets, it will only require a little propellant to relocate within the geosynchronous belt. Results of a design study on the feasibility of a small-satellite guide star have been presented, and the potential benefits to astronomical imaging and to the larger space situational awareness community have been highlighted.

Assessment of Radiometer Calibration With GPS Radio Occultation for the MiRaTA CubeSat Mission

2025-02-11T19:58:15Z

Assessment of Radiometer Calibration With GPS Radio Occultation for the MiRaTA CubeSat Mission Marinan, A. D.; Cahoy, K. L.; Bishop, R. L.; Lui, S. S.; Bardeen, J. R.; Mulligan, T.; Blackwell, W. J.; Leslie, R. V.; Osaretin, I. A.; Shields, M. The microwave radiometer technology acceleration (MiRaTA) is a 3U CubeSat mission sponsored by the NASA Earth Science Technology Office. The science payload on MiRaTA consists of a triband microwave radiometer and global positioning system (GPS) radio occultation (GPSRO) sensor. The microwave radiometer takes measurements of all-weather temperature (V-band, 50-57 GHz), water vapor (G-band, 175-191 GHz), and cloud ice (G-band, 205 GHz) to provide observations used to improve weather forecasting. The Aerospace Corporation's GPSRO experiment, called the compact total electron content and atmospheric GPS sensor (CTAGS), measures profiles of temperature and pressure in the upper troposphere/lower stratosphere (~20 km) and electron density in the ionosphere (over 100 km). The MiRaTA mission will validate new technologies in both passive microwave radiometry and GPSRO: 1) new ultracompact and low-power technology for multichannel and multiband passive microwave radiometers, 2) the application of a commercial off-the-shelf GPS receiver and custom patch antenna array technology to obtain neutral atmospheric GPSRO retrieval from a nanosatellite, and 3) a new approach to space-borne microwave radiometer calibration using adjacent GPSRO measurements. In this paper, we focus on objective 3, developing operational models to meet a mission goal of 100 concurrent radiometer and GPSRO measurements, and estimating the temperature measurement precision for the CTAGS instrument based on thermal noise Based on an analysis of thermal noise of the CTAGS instrument, the expected temperature retrieval precision is between 0.17 and 1.4 K, which supports the improvement of radiometric calibration to 0.25 K.

Interpolation Method for Update with Out-of-Sequence Measurements: The Augmented Fixed-Lag Smoother

2025-02-11T19:58:15Z

Interpolation Method for Update with Out-of-Sequence Measurements: The Augmented Fixed-Lag Smoother Yoon, Hyosang; Sternberg, D. C.; Cahoy, Kerri In this study, the authors propose a novel method to handle OOSMs in Kalman filtering. The proposed method, called the augmented fixed-lag smoother (AFLS), is based on the fixed-lag smoother (FLS) formulation, which has been shown to be optimal [10]. We generate the OOSM node from the two adjacent nodes, plug the generated estimations into the state vector and the covariance matrix, and update the filter with OOSMs using the FLS update equation. This approach gives a generalized solution that can handle any number of OOSMs. We also extend the AFLS algorithm to nonlinear system, called the extended AFLS (EAFLS), and give an application example on a satellite-tracking problem.

Interplanetary space weather effects on Lunar Reconnaissance Orbiter avalanche photodiode performance.

2025-02-11T19:58:16Z

Interplanetary space weather effects on Lunar Reconnaissance Orbiter avalanche photodiode performance. Clements, E. B.; Carlton, A. K.; Joyce, C. J.; Schwadron, N. A.; Spence, H. E.; Sun, X.; Cahoy, K. Space weather is a major concern for radiation-sensitive space systems, particularly for interplanetary missions, which operate outside of the protection of Earth's magnetic field. We examine and quantify the effects of space weather on silicon avalanche photodiodes (SiAPDs), which are used for interplanetary laser altimeters and communications systems and can be sensitive to even low levels of radiation (less than 50 cGy). While ground-based radiation testing has been performed on avalanche photodiode (APDs) for space missions, in-space measurements of SiAPD response to interplanetary space weather have not been previously reported. We compare noise data from the Lunar Reconnaissance Orbiter (LRO) Lunar Orbiter Laser Altimeter (LOLA) SiAPDs with radiation measurements from the onboard Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument. We did not find any evidence to support radiation as the cause of changes in detector threshold voltage during radiation storms, both for transient detector noise and long-term average detector noise, suggesting that the approximately 1.3 cm thick shielding (a combination of titanium and beryllium) of the LOLA detectors is sufficient for SiAPDs on interplanetary missions with radiation environments similar to what the LRO experienced (559 cGy of radiation over 4 years).

Implementation and validation of a CubeSat laser transmitter

2025-02-11T19:58:16Z

Implementation and validation of a CubeSat laser transmitter Kingsbury, R. W.; Caplan, D. O.; Cahoy, K. L. The paper presents implementation and validation results for a CubeSat-scale laser transmitter. The master oscillator power amplifier (MOPA) design produces a 1550 nm, 200mW average power optical signal through the use of a directly modulated laser diode and a commercial fiber amplifier. The prototype design produces high-fidelity M-ary pulse position modulated (PPM) waveforms (M=8 to 128), targeting data rates > 10 Mbit/s while meeting a constraining 8W power allocation. We also present the implementation of an avalanche photodiode (APD) receiver with measured transmitter-to-receiver performance within 3 dB of theory. Via loopback, the compact receiver design can provide built-in self-test and calibration capabilities, and supports incremental on-orbit testing of the design.

Atmospheric characterization of cold exoplanets with a 1.5-m space coronagraph

2025-02-11T20:02:40Z

Atmospheric characterization of cold exoplanets with a 1.5-m space coronagraph Maire, A. -L.; Galicher, R.; Boccaletti, A.; Baudoz, P.; Schneider, J.; Cahoy, K.; Stam, D.; Traub, W. Several small space coronagraphs have been proposed to characterize cold exoplanets in reflected light. Studies have mainly focused on technical feasibility because of the huge star/planet flux ratio to achieve in the close-in stellar environment (108-1010 at 0.2'). However, the main interest of such instruments, the analysis of planet properties, has remained highly unexplored so far. We performed numerical simulations to assess the ability of a small space coronagraph to retrieve spectra of mature Jupiters, Neptunes and super-Earths under realistic assumptions. We describe our assumptions: exoplanetary atmosphere models, instrument numerical simulation and observing conditions. Then, we define a criterion and use it to determine the required exposure times to measure several planet parameters from their spectra (separation, metallicity, cloud and surface coverages) for particular cases. Finally, we attempt to define a parameter space of the potential targets. In the case of a solar-type star, we show that a small coronagraph can characterize the spectral properties of a 2-AU Jupiter up to 10 pc and the cloud and surface coverage of super-Earths in the habitable zone for a few stars within 4-5 pc. Potentially, SPICES could perform analysis of a hypothetical Earth-size planet around α Cen A and B.

Trapped photoelectrons during spacecraft charging in sunlight

2025-02-11T19:58:15Z

Trapped photoelectrons during spacecraft charging in sunlight Cahoy, K.; Lai, S. T. For a dielectric spacecraft charging in sunlight, the potentials are different on the sunlit and dark sides. Differential charging of spacecraft surfaces can trap low-energy electrons by means of potential wells and barriers. The low-energy electrons are mostly photoelectrons and secondary electrons. Motivated by the recent interest in trapped photoelectrons measured by the Van Allen Probes in the radiation belts, we calculate the extent of the trapped photoelectron area and the potential barrier as a function of the dipole strength and sun angle using the monopole- dipole model. We find that the dipole strength is an important parameter in controlling the behavior of the potential wells and barriers. The usual inequality, 1/2 ≤ A ≤ 1 where A is the dipole strength, used in the monopole-dipole model can be relaxed and amended for finite sun angles. We then use a simple method to estimate the density of the trapped low-energy electrons in these areas. In sunlight charging, the low-energy electron population around the spacecraft is enhanced by the photoelectrons trapped inside the potential barrier.

Direct imaging of exoEarths embedded in clumpy debris disks

2025-02-11T20:02:40Z

Direct imaging of exoEarths embedded in clumpy debris disks Defrere, D.; Stark, C.; Cahoy, K.; Beerer, I. The inner solar system, where the terrestrial planets formed and evolve, is populated by small grains of dust produced by collisions of asteroids and outgassing comets. At visible and infrared wavelengths, this dust cloud is in fact the most luminous component in the solar system after the Sun itself and the Earth may appear similar to a clump of zodiacal dust to an external observer. Hence, the presence of large amounts of dust in the habitable zone around nearby main-sequence stars is considered as a major hurdle toward the direct imaging of exoEarths with future dedicated space-based telescopes. In that context, we address in this paper the detectability of exoEarths embedded in structured debris disks with future space-based visible coronagraphs and mid-infrared interferometers. Using a collisional grooming algorithm, we produce models of dust clouds that simultaneously and self-consistently handle dust grain dynamics, including resonant interactions with planets, and grain-grain collisions. Considering various viewing geometries, we also derive limiting dust densities that can be tolerated around nearby main-sequence stars in order to ensure the characterization of exoEarths with future direct imaging missions.

Combining laser frequency combs and iodine cell calibration techniques for Doppler detection of exoplanets

2025-02-11T20:02:40Z

Combining laser frequency combs and iodine cell calibration techniques for Doppler detection of exoplanets Cahoy, K.; Fischer, D.; Spronck, J.; Demille, D. Exoplanets can be detected from a time series of stellar spectra by looking for small, periodic shifts in the absorption features that are consistent with Doppler shifts caused by the presence of an exoplanet, or multiple exoplanets, in the system. While hundreds of large exoplanets have already been discovered with the Doppler technique (also called radial velocity), our goal is to improve the measurement precision so that many Earth-like planets can be detected. The smaller mass and longer period of true Earth analogues require the ability to detect a reflex velocity of ~10 cm/s over long time periods. Currently, typical astronomical spectrographs calibrate using either Iodine absorptive cells or Thorium Argon lamps and achieve ~10 m/s precision, with the most stable spectrographs pushing down to ~2 m/s. High velocity precision is currently achieved at HARPS by controlling the thermal and pressure environment of the spectrograph. These environmental controls increase the cost of the spectrograph, and it is not feasible to simply retrofit existing spectrometers. We propose a fiber-fed high precision spectrograph design that combines the existing ~5000-6000 A Iodine calibration system with a high-precision Laser Frequency Comb (LFC) system from ~6000-7000 A that just meets the redward side of the Iodine lines. The scientific motivation for such a system includes: a 1000 A span in the red is currently achievable with LFC systems, combining the two calibration methods increases the wavelength range by a factor of two, and moving redward decreases the 'noise' from starspots. The proposed LFC system design employs a fiber laser, tunable serial Fabry-Perot cavity filters to match the resolution of the LFC system to that of standard astronomical spectrographs, and terminal ultrasonic vibration of the multimode fiber for a stable point spread function.

CubeSat deformable mirror demonstration

2025-02-11T20:02:40Z

CubeSat deformable mirror demonstration Cahoy, K.; Marinan, A.; Kerr, C.; Cheng, K.; Jamil, S. The goal of the CubeSat Deformable Mirror Demonstration (DeMi) is to characterize the performance of a small deformable mirror over a year in low-Earth orbit. Small form factor deformable mirrors are a key technology needed to correct optical system aberrations in high contrast, high dynamic range space telescope applications such as space-based coronagraphic direct imaging of exoplanets. They can also improve distortions and reduce bit error rates for space-based laser communication systems. While follow-on missions can take advantage of this general 3U CubeSat platform to test the on-orbit performance of several different types of deformable mirrors, this first design accommodates a 32-actuator Boston Micromachines MEMS deformable mirror.

Planetary Imaging Concept Testbed Using a Recoverable Experiment-Coronagraph (PICTURE C)

2025-02-11T19:58:16Z

Planetary Imaging Concept Testbed Using a Recoverable Experiment-Coronagraph (PICTURE C) Cook, T.; Cahoy, K.; Chakrabarti, S.; Douglas, E.; Finn, S. C.; Kuchner, M.; Lewis, N.; Marinan, A.; Martel, J.; Mawet, D.; Mazin, B.; Meeker, S. R.; Mendillo, C.; Serabyn, G.; Stuchlik, D.; Swain, M. An exoplanet mission based on a high-altitude balloon is a next logical step in humanity's quest to explore Earthlike planets in Earthlike orbits orbiting Sunlike stars. The mission described here is capable of spectrally imaging debris disks and exozodiacal light around a number of stars spanning a range of infrared excesses, stellar types, and ages. The mission is designed to characterize the background near those stars, to study the disks themselves, and to look for planets in those systems. The background light scattered and emitted from the disk is a key uncertainty in the mission design of any exoplanet direct imaging mission, thus, its characterization is critically important for future imaging of exoplanets.

Effect of Longitude-Dependent Cloud Coverage on Exoplanet Visible Wavelength Reflected-Light Phase Curves

2025-02-11T19:58:16Z

Effect of Longitude-Dependent Cloud Coverage on Exoplanet Visible Wavelength Reflected-Light Phase Curves Webber, M. W.; Lewis, N. K.; Marley, M.; Morley, C.; Fortney, J. J.; Cahoy, K. We use a planetary albedo model to investigate variations in visible wavelength phase curves of exoplanets. Thermal and cloud properties for these exoplanets are derived using one-dimensional radiative-convective and cloud simulations. The presence of clouds on these exoplanets significantly alters their planetary albedo spectra. We confirm that non-uniform cloud coverage on the dayside of tidally locked exoplanets will manifest as changes to the magnitude and shift of the phase curve. In this work, we first investigate a test case of our model using a Jupiter-like planet, at temperatures consistent to 2.0 AU insolation from a solar type star, to consider the effect of H2O clouds. We then extend our application of the model to the exoplanet Kepler-7b and consider the effect of varying cloud species, sedimentation efficiency, particle size, and cloud altitude. We show that, depending on the observational filter, the largest possible shift of the phase curve maximum will be similar to 2 degrees-10 degrees for a Jupiter-like planet, and up to similar to 30 degrees (similar to 0.08 in fractional orbital phase) for hot-Jupiter exoplanets at visible wavelengths as a function of dayside cloud distribution with a uniformly averaged thermal profile. The models presented in this work can be adapted for a variety of planetary cases at visible wavelengths to include variations in planet-star separation, gravity, metallicity, and source-observer geometry. Finally, we tailor our model for comparison with, and confirmation of, the recent optical phase-curve observations of Kepler-7b with the Kepler space telescope. The average planetary albedo can vary between 0.1 and 0.6 for the 1300 cloud scenarios that were compared to the observations. Many of these cases cannot produce a high enough albedo to match the observations. We observe that smaller particle size and increasing cloud altitude have a strong effect on increasing albedo. In particular, we show that a set of models where Kepler-7b has roughly half of its dayside covered in small-particle clouds high in the atmosphere, made of bright minerals like MgSiO3 and Mg2SiO4, provide the best fits to the observed offset and magnitude of the phase-curve, whereas Fe clouds are found to be too dark to fit the observations.

Response of geostationary communications satellite solid-state power amplifiers to high-energy electron fluence.

2025-02-11T19:58:16Z

Response of geostationary communications satellite solid-state power amplifiers to high-energy electron fluence. Lohmeyer, Whitney; Carlton, Ashley; Wong, Frankie; Bodeau, Michael; Kennedy, Andrew; Cahoy, Kerri The key components in communications satellite payloads are the high-power amplifiers that amplify the received signal so that it can be accurately transmitted to the intended end user. In this study, we examine 26 amplifier anomalies and quantify the high-energy electron environment for periods of time prior to the anomalies. Building on the work of Lohmeyer and Cahoy (2013), we find that anomalies occur at a rate higher than just by chance when the >2 MeV electron fluence accumulated over 14 and 21 days is elevated. To try to understand “why,” we model the amplifier subsystem to assess whether the dielectric material in the radio frequency (RF) coaxial cables, which are the most exposed part of the system, is liable to experience electrical breakdown due to internal charging. We find that the accumulated electric field over the 14 and 21 days leading up to the anomalies is high enough to cause the dielectric material in the coax to breakdown. We also find that the accumulated voltages reached are high enough to compromise components in the amplifier system, for example, the direct current (DC) blocking capacitor. An electron beam test using a representative coaxial cable terminated in a blocking capacitor showed that discharges could occur with peak voltages and energies sufficient to damage active RF semiconductor devices.

Quantifying the average and the likelihood of increases in space weather indices and in situ measurements during Solar Cycles 20–23

2025-02-11T19:58:16Z

Quantifying the average and the likelihood of increases in space weather indices and in situ measurements during Solar Cycles 20–23 Lohmeyer, Whitney Q.; Pang, Anthony; Cahoy, Kerry; Shprits, Yuri It is known that space weather harshly affects spacecraft performance, yet spacecraft operations and understanding the cause of anomalies can be challenging due to the complexity of environmental metrics. In this work, we analyse five metrics and in-situ measurements (Kp, Dst, and AE index, and high-energy proton and electron flux) throughout Solar Cycles 20–23 (1964 to 2008), and provide a baseline for the environment during the phases of the solar cycles (maximum, minimum, declining or ascending). We define increased activity as activity greater than two median absolute deviations (MADs) above the average activity for each phase. MAD is used, rather than standard deviation, because it is more resilient to outliers. The average and MAD values are tabulated in Table 3 to Table 6. We determine the probability that increased activity occurs 3, 14 or 30 days before a random day to distinguish between increased/quiet activities and to aid in correlating intensifications of the environment and anomalous satellite performance.

First results on a new PIAA coronagraph testbed at NASA Ames

2025-02-11T20:02:40Z

First results on a new PIAA coronagraph testbed at NASA Ames Belikov, R.; Pluzhnik, E.; Connelley, M. S.; Witteborn, F. C.; Lynch, D. H.; Cahoy, K. L.; Guyon, O.; Greene, T. P.; McKelvey, M. E. Direct imaging of extrasolar planets, and Earth-like planets in particular, is an exciting but difficult problem requiring a telescope imaging system with 1010 contrast at separations of 100 mas and less. Furthermore, the current NASA science budget may only allow for a small 1-2 m space telescope for this task, which puts strong demands on the performance of the imaging instrument. Fortunately, an efficient coronagraph called the Phase Induced Amplitude Apodization (PIAA) coronagraph has been maturing and may enable Earth-like planet imaging for such small telescopes. In this paper, we report on the latest results from a new testbed at NASA Ames focused on testing the PIAA coronagraph. This laboratory facility was built in 2008 and is designed to be flexible, operated in a highly stabilized air environment, and to complement existing efforts at NASA JPL. For our wavefront control we are focusing on using small Micro-Electro- Mechanical-System deformable mirrors (MEMS DMs), which promises to reduce the size of the beam and overall instrument, a consideration that becomes very important for small telescopes. At time of this writing, we are operating a refractive PIAA system and have achieved contrasts of about 1.2×10-7 in a dark zone from 2.0 to 4.8 λ/D (with 6.6×10-8 in selected regions). In this paper, we present these results, describe our methods, present an analysis of current limiting factors, and solutions to overcome them.

Radio science measurements of atmospheric refractivity with Mars Global Surveyor

2025-02-11T19:58:16Z

Radio science measurements of atmospheric refractivity with Mars Global Surveyor Cahoy, Kerri; Hinson, David; Tyler, G. Leonard Radio occultation experiments with Mars Global Surveyor measure the refractive index of the Martian atmosphere from the surface to ~250 km in geopotential height. Refractivity is proportional to neutral density at low altitudes and electron density at high altitudes, with a transition at ~75 km. We use weighted least squares to decompose zonal refractivity variations into amplitudes and phases for observed wave numbers k=1-4 over the entire altitude range and use the results to analyze atmospheric structure and dynamics. The data set consists of 147 refractivity profiles acquired in December 2000 at summer solstice in the Martian northern hemisphere. The measurements are at an essentially fixed local time (sunrise) and at latitudes from 67deg to 70degN. Thermal tides appear to be responsible for much of the observed ionospheric structure from 80 to 220 km. Tides modulate the neutral density, which in turn, controls the height at which the ionosphere forms. The resulting longitude-dependent vertical displacement of the ionosphere generates distinctive structure in the fitted amplitudes, particularly at k=3, within plusmn50 km of the electron density peak height. Our k=3 observations are consistent with an eastward propagating semidiurnal tide with zonal wave number 1. Relative to previous results, our analysis extends the characterization of tides to altitudes well above and below the electron density peak. In the neutral atmosphere, refractivity variations from the surface to 50 km appear to arise from stationary Rossby waves. Upon examining the full vertical range, stationary waves appear to dominate altitudes below ~75 km, and thermal tides dominate altitudes above this transition region.

Communication satellite power amplifiers: current and future SSPA and TWTA technologies

2025-02-11T19:58:16Z

Communication satellite power amplifiers: current and future SSPA and TWTA technologies Aniceto, Raichelle; Cahoy, Kerri; Lohmeyer, Whitney This study captures the state of current satellite transponder technology, specifically, solid-state power amplifiers (SSPAs) and traveling wave tube amplifiers (TWTAs), and describes expected future advances, including GaN SSPAs. The findings of five previous SSPA and TWTA studies, including the 1991 European Space and Technology Center study, the 1993 National Aeronautics and Space Administration study, and three Boeing studies conducted in 2005, 2008, and 2013, are tabulated and summarized. The results of these studies are then compared with new analyses of two validated sources of amplifier data: a commercially licensed database, Seradata's Spacetrak, and a publicly available database, Gunter's Space Page. The new analyses consider a total of 18,902 amplifiers (6428 TWTAs, 2158 SSPAs, and 10,316 unspecified amplifiers) onboard 565 communications satellites launched from 1982 to 2016. This new study contains the largest number of satellites and amplifiers to date and compares output power, redundancy, and bandwidth capabilities. We find an increase in output power from the 1993 study of >200% for Ku-band TWTAs and C-band SSPAs, and >1000% increase for C-band TWTAs. The ratio of operational to redundant amplifiers is 10 times higher for TWTAs than SSPAs, and the majority of amplifiers over the past 30 years operate with bandwidth less than 100 MHz. A second analysis is conducted using failure records and telemetry of 16 geostationary satellites equipped with 659 amplifiers: 535 SSPAs and 124 TWTAs. We find that <2% of TWTAs and 5% of SSPAs experience anomalies. Overall, this research was performed to update and clarify how the power and bandwidth needs and redundancy trends of the SatCom community have evolved over the past 30 years.

Radiometer Calibration Using Colocated GPS Radio Occultation Measurements

2025-02-11T19:58:16Z

Radiometer Calibration Using Colocated GPS Radio Occultation Measurements Cahoy, K. L.; Blackwell, W. J.; Bishop, R.; Cohen, B.; Crail, C.; Cucurull, L.; Dave, P.; DiLiberto, M.; Erickson, N.; Fish, C.; Ho, S. P.; Leslie, R. V.; Milstein, A. B.; Osaretin, I. A. We present a new high-fidelity method of calibrating a cross-track scanning microwave radiometer using Global Positioning System (GPS) radio occultation (GPSRO) measurements. The radiometer and GPSRO receiver periodically observe the same volume of atmosphere near the Earth's limb, and these overlapping measurements are used to calibrate the radiometer. Performance analyses show that absolute calibration accuracy better than 0.25 K is achievable for temperature sounding channels in the 50-60-GHz band for a total-power radiometer using a weakly coupled noise diode for frequent calibration and proximal GPSRO measurements for infrequent (approximately daily) calibration. The method requires GPSRO penetration depth only down to the stratosphere, thus permitting the use of a relatively small GPS antenna. Furthermore, only coarse spacecraft angular knowledge (approximately one degree rms) is required for the technique, as more precise angular knowledge can be retrieved directly from the combined radiometer and GPSRO data, assuming that the radiometer angular sampling is uniform. These features make the technique particularly well suited for implementation on a low-cost CubeSat hosting both radiometer and GPSRO receiver systems on the same spacecraft. We describe a validation platform for this calibration method, the Microwave Radiometer Technology Acceleration (MiRaTA) CubeSat, currently in development for the National Aeronautics and Space Administration (NASA) Earth Science Technology Office. MiRaTA will fly a multiband radiometer and the Compact TEC/Atmosphere GPS Sensor in 2015.

Wavefront control in space with MEMS deformable mirrors for exoplanet direct imaging

2025-02-11T19:58:16Z

Wavefront control in space with MEMS deformable mirrors for exoplanet direct imaging Cahoy, K. L.; Marinan, A. D.; Novak, B.; Kerr, C.; Nguyen, T.; Webber, M.; Falkenburg, G.; Barg, A. To meet the high contrast requirement of 1 x 10(-10) to image an Earth-like planet around a sun-like star, space telescopes equipped with coronagraphs require wavefront control systems. Deformable mirrors (DMs) are a key element of a wavefront control system, as they correct for imperfections, thermal distortions, and diffraction that would otherwise corrupt the wavefront and ruin the contrast. The goal of the CubeSat DM technology demonstration mission is to test the ability of a microelectromechanical system (MEMS) DM to perform wavefront control on-orbit on a nanosatellite platform. We consider two approaches for an MEMS DM technology demonstration payload that will fit within the mass, power, and volume constraints of a CubeSat: (1) a Michelson interferometer and (2) a Shack-Hartmann wavefront sensor. We clarify the constraints on the payload based on the resources required for supporting CubeSat subsystems drawn from subsystems that we have developed for a different CubeSat flight project. We discuss results from payload laboratory prototypes and their utility in defining mission requirements.

Space weather radiation effects on geostationary satellite solid-state power amplifiers

2025-02-11T19:58:16Z

Space weather radiation effects on geostationary satellite solid-state power amplifiers Lohmeyer, W. Q.; Cahoy, K. L. In order to understand and mitigate the effects of space weather on the performance of geostationary (GEO) communications satellites, we analyze 16 years of archived telemetry data from Inmarsat, the UK-based telecommunications company. We compare 665,112 operational hours of housekeeping telemetry from two generations of satellites, designated as Fleet A and Fleet B. Each generation experienced 13 solid-state power amplifier (SSPA) anomalies for a total of 26 anomalies from 1996 to 2012. We compare telemetry from the Inmarsat anomalies with space weather observations, including data from the OMNI2 database, Geostationary Operational Environmental Satellites, the Advanced Composition Explorer Satellite, and Los Alamos National Laboratory (LANL) GEO observations; the evolution of the sunspot number; and the Kp index. Most SSPA anomalies for Fleet A occur as solar activity declines; Fleet B has not yet experienced a full solar cycle. For both fleets, the average value of Kp remained <2 over time periods of 2 days, 3 days, and 2 weeks around the time of anomaly, which suggests that the anomalies occurred at times of relatively quiet geomagnetic activity and that they were probably not solely caused by surface charging. From 1996 to 2009, the average of the 1.8-3.5MeV electron flux was 1.98 #/(cm(2)s st keV). Five of the 26 anomalies, unfortunately, do not have corresponding science observations (specifically, electron flux data in the LANL data set), so part of this study focuses on the 21 anomalies when science observations were available. Six out of 21 anomalies experienced a high-energy electron flux greater than 1.5 standard deviations above the mean of the log(10) of the flux between 7 and 14days prior to the anomaly. By contrast, a Monte Carlo simulation finds that on average, only 2.8 out of 21 (13%) of randomly assigned anomalies occur between 7 and 14days after an electron flux greater than 1.5 standard deviations above the mean. Our observations suggest that internal charging from either past elevated radiation belt fluxes or some conditions related to relativistic electron enhancements (either causally or accidentally) is most likely responsible for the SSPA anomalies. We next consider the timing of these anomalies with respect to the local time (LT) and season. Anomalies occur at all LT sectors with 46% (Fleet A) and 38.5% (Fleet B) in the midnight to dawn sector and 54% (Fleet A) and 46% (Fleet B) in the local noon to dusk sector. From the local time distribution, surface charging does not appear to be the sole causative agent of the anomalies. Understanding the connection between the space weather conditions and anomalies on subsystems and specific components on identical and similar geostationary communications satellites for periods of time longer than a solar cycle will help guide design improvements and provide insight on their operation during space weather events.

Mars atmospheric CO2 condensation above the north and south poles as revealed by radio occultation, climate sounder, and laser ranging observations

2025-02-11T19:58:15Z

Mars atmospheric CO2 condensation above the north and south poles as revealed by radio occultation, climate sounder, and laser ranging observations Cahoy, Kerri; Zuber, Maria; Hu, R. Y. We study the condensation of CO2 in Mars' atmosphere using temperature profiles retrieved from radio occultation measurements from Mars Global Surveyor (MGS) as well as the climate sounding instrument onboard the Mars Reconnaissance Orbiter (MRO), and detection of reflective clouds by the MGS Mars Orbiter Laser Altimeter (MOLA). We find 11 events in 1999 where MGS temperature profiles indicate CO2 condensation and MOLA simultaneously detects reflective clouds. We thus provide causal evidence that MOLA non-ground returns are associated with CO2 condensation, which strongly indicates their nature being CO2 clouds. The MGS and MRO temperature profiles together reveal the seasonal expansion and shrinking of the area and the vertical extent of atmospheric saturation. The occurrence rate of atmospheric saturation is maximized at high latitudes in the middle of winter. The atmospheric saturation in the northern polar region exhibits more intense seasonal variation than in the southern polar region. In particular, a shrinking of saturation area and thickness from LS similar to 270 degrees to similar to 300 degrees in 2007 is found; this is probably related to a planet-encircling dust storm. Furthermore, we integrate the condensation area and the condensation occurrence rate to estimate cumulative masses of CO2 condensates deposited onto the northern and southern seasonal polar caps. The precipitation flux is approximated by the particle settling flux which is estimated using the impulse responses of MOLA filter channels. With our approach, the total atmospheric condensation mass can be estimated from these observational data sets with average particle size as the only free parameter. By comparison with the seasonal polar cap masses inferred from the time-varying gravity of Mars, our estimates indicate that the average condensate particle radius is 8-22 mu m in the northern hemisphere and 4-13 mu m in the southern hemisphere. Our multi-instrument data analysis provides new constraints on modeling the global climate of Mars.

Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope

2025-02-11T19:58:16Z

Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope Maire, Anne-Lise; Galicher, Raphael; Boccaletti, Anthony; Baudoz, Pierre; Schneider, Jean; Stam, Daphne; Cahoy, Kerri; Traub, Wes High-contrast imaging is currently the only available technique for the study of the thermodynamical and compositional properties of exoplanets in long-period orbits, comparable to the range from Venus to Jupiter. The SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) project is a coronagraphic space telescope dedicated to the spectropolarimetric analysis of gaseous and icy giant planets as well as super-Earths at visible wavelengths. So far, studies for high-contrast imaging instruments have mainly focused on technical feasibility because of the challenging planet/star flux ratio of 10-8-10-10 required at short separations (200 mas or so) to image cold exoplanets. However, the main interest of such instruments, namely the analysis of planet atmospheric/surface properties, has remained largely unexplored. Aims. The aim of this paper is to determine which planetary properties SPICES or an equivalent direct imaging mission can measure, considering realistic reflected planet spectra and instrument limitation. Methods. We use numerical simulations of the SPICES instrument concept and theoretical planet spectra to carry out this performance study. We also define a criterion on the signal-to-noise ratio of the measured spectrum to determine under which conditions SPICES can retrieve planetary physical properties. Results. We find that the characterization of the main planetary properties (identification of molecules, effect of metallicity, presence of clouds and type of surfaces) would require a median signal-to-noise ratio of at least 30. In the case of a solar-type star <10 pc, SPICES will be able to study Jupiters and Neptunes up to -5 and -2 AU respectively, because of the drastic flux decrease with separation. It would also analyze cloud and surface coverage of super-Earths of radius 2.5 Earth radii at 1 AU. Finally, we determine the potential targets in terms of planet separation, radius and distance for several stellar types. For a Sun analog, we show that SPICES could characterize Jupiters (M ≥ 30 Earth masses) as small as 0.5 Jupiter radii at ≤2 AU up to 10 pc, and super-Earths at 1-2 AU for the handful of stars that exist within 4-5 pc. Potentially, SPICES could perform analysis of a hypothetical Earth-size planet around a Cen A and B. However, these results depend on the planetary spectra we use, which are derived for a few planet parameters assuming a solar-type host star. Grids of model spectra are needed for a further performance analysis. Our results obtained for SPICES are also applicable to other small (1-2 m) coronagraphic space telescopes.

SPICES: spectro-polarimetric imaging and characterization of exoplanetary systems.

2025-02-11T19:58:16Z

SPICES: spectro-polarimetric imaging and characterization of exoplanetary systems. Boccaletti, Anthony; Schneider, Jean; Traub, Wes; Lagage, Pierre-Olivier; Stam, Daphne; Gratton, Raffaele; Trauger, John; Cahoy, Kerri; Snik, Frans; Baudoz, Pierre; Galicher, Raphael; Reess, Jean-Michel; Mawet, Dimitri; Augereau, Jean-Charles; Patience, Jenny; Kuchner, Marc; Wyatt, Mark; Pantin, Eric; Maire, Anne-Lise; Vérinaud, Christophe SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) is a five-year M-class mission proposed to ESA Cosmic Vision. Its purpose is to image and characterize long-period extrasolar planets and circumstellar disks in the visible (450-900 nm) at a spectral resolution of about 40 using both spectroscopy and polarimetry. By 2020/2022, present and near-term instruments will have found several tens of planets that SPICES will be able to observe and study in detail. Equipped with a 1.5 m telescope, SPICES can preferentially access exoplanets located at several AUs (0.5-10 AU) from nearby stars (<25 pc) with masses ranging from a few Jupiter masses to Super Earths (∼2 Earth radii, ∼10 M) as well as circumstellar disks as faint as a few times the zodiacal light in the Solar System.

Exoplanet Albedo Spectra and Colors as a Function of Planet Phase, Separation, and Metallicity

2025-02-11T19:58:16Z

Exoplanet Albedo Spectra and Colors as a Function of Planet Phase, Separation, and Metallicity Cahoy, Kerri; Marley, Mark; Fortney, Jonathan First generation space-based optical coronagraphic telescopes will obtain images of cool gas- and ice-giant exoplanets around nearby stars. Exoplanets lying at planet-star separations larger than about 1 AU—where an exoplanet can be resolved from its parent star—have spectra that are dominated by reflected light to beyond 1 μm and punctuated by molecular absorption features. Here, we consider how exoplanet albedo spectra and colors vary as a function of planet-star separation, metallicity, mass, and observed phase for Jupiter and Neptune analogs from 0.35 to 1 μm. We model Jupiter analogs with 1× and 3× the solar abundance of heavy elements, and Neptune analogs with 10× and 30× the solar abundance of heavy elements. Our model planets orbit a solar analog parent star at separations of 0.8 AU, 2 AU, 5 AU, and 10 AU. We use a radiative-convective model to compute temperature-pressure profiles. The giant exoplanets are found to be cloud-free at 0.8 AU, possess H2O clouds at 2 AU, and have both NH3 and H2O clouds at 5 AU and 10 AU. For each model planet we compute moderate resolution (R = λ/Δλ ~ 800) albedo spectra as a function of phase. We also consider low-resolution spectra and colors that are more consistent with the capabilities of early direct imaging capabilities. As expected, the presence and vertical structure of clouds strongly influence the albedo spectra since cloud particles not only affect optical depth but also have highly directional scattering properties. Observations at different phases also probe different volumes of atmosphere as the source-observer geometry changes. Because the images of the planets themselves will be unresolved, their phase will not necessarily be immediately obvious, and multiple observations will be needed to discriminate between the effects of planet-star separation, metallicity, and phase on the observed albedo spectra. We consider the range of these combined effects on spectra and colors. For example, we find that the spectral influence of clouds depends more on planet-star separation and hence atmospheric temperature than metallicity, and it is easier to discriminate between cloudy 1× and 3× Jupiters than between 10× and 30× Neptunes. In addition to alkalis and methane, our Jupiter models show H2O absorption features near 0.94 μm. While solar system giant planets are well separated by their broadband colors, we find that arbitrary giant exoplanets can have a large range of possible colors and that color alone cannot be relied upon to characterize planet types. We also predict that giant exoplanets receiving greater insolation than Jupiter will exhibit higher equator-to-pole temperature gradients than are found on Jupiter and thus may exhibit differing atmospheric dynamics. These results are useful for future interpretation of direct imaging exoplanet observations as well as for deriving requirements and designing filters for optical direct imaging instrumentation.

Characterization of a semidiurnal eastward-propagating tide at high northern latitudes with Mars Global Surveyor electron density profiles

2025-02-11T19:58:16Z

Characterization of a semidiurnal eastward-propagating tide at high northern latitudes with Mars Global Surveyor electron density profiles Cahoy, Kerri; Hinson, David; Tyler, G. Leonard Apparent phase velocities of zonal structure, estimated from Mars Global Surveyor (MGS) electron density profiles, are used to identify and characterize SE1, the semidiurnal eastward-propagating tide with zonal wave number one, at high northern latitudes during the summer of Mars Year 26. SE1 shows impressive phase stability with altitude, season, and local time. SE1 maintains a presence at amplitudes between 5 and 15% of the zonal mean at 125 ± 10 km altitude for most of the summer season. Further analyses using MGS electron density profiles will contribute to the identification and characterization of nonmigrating tides in the upper atmosphere of Mars.

Physical characteristics and occurrence rates of meteoric plasma layers detected in the Martian ionosphere by the Mars Global Surveyor Radio Science Experiment

2025-02-11T19:58:16Z

Physical characteristics and occurrence rates of meteoric plasma layers detected in the Martian ionosphere by the Mars Global Surveyor Radio Science Experiment Withers, Paul; Mendillo, Michael; Hinson, David; Cahoy, Kerri Low-altitude plasma layers are present in 71 of 5600 electron density profiles from the Martian ionosphere obtained by the Mars Global Surveyor Radio Science experiment. These layers are produced by the ablation of meteoroids and subsequent ionization of meteoric atoms. The mean altitude of the meteoric layer is 91.7 +/- 4.8 km. The mean peak electron density in the meteoric layer is (1.33 +/- 0.25) x 10(10) m(-3). The mean width of the meteoric layer is 10.3 +/- 5.2 km. The occurrence rate of meteoric layers varies with season, solar zenith angle, and latitude. Seasonal variations in occurrence rate are particularly strong, often exceeding an order of magnitude. Meteoric layer altitude, peak electron density, and width are all positively correlated, with correlation coefficients of 0.3-0.4. Other correlation coefficients between the physical characteristics of meteoric layers and atmospheric or observational properties, such as scale height, solar zenith angle, and solar flux, have absolute values that are significantly smaller, indicating lack of correlation. The photochemical lifetime of plasma in meteoric layers is similar to 12 days and depends on altitude.

Nonlinear Optics for Frequency-Doubling in Nanosatellite Laser Communication

2025-02-11T20:02:40Z

Nonlinear Optics for Frequency-Doubling in Nanosatellite Laser Communication Clark, James; Cahoy, Kerri Free-space optical communication attracts interest due to its promise of higher data rates for similar size, weight, and power costs compared with radio systems. However, while satellite-to-ground optical communication has been tested from low Earth orbit and the Moon, intersatellite optical links are still an area of active research and development. Second-harmonic generation (SHG, or “frequency doubling”) with nonlinear optics may improve the link margins of laser systems that serve as crosslinks as well as downlinks. For example, the output of a 1550 nm laser could be doubled to 775 nm on command, allowing the satellite to use whichever wavelength is advantageous (e.g. improved detector and propagation properties), without spending the mass budget for an entire second laser system. Link-budget analysis suggests that a nanosatellite crosslink can gain 3-4 dB of link margin with a frequency-doubler. This improvement is largely driven by the reduction in beamwidth that comes with the higher frequency. It is not substantially greater than the improvement that comes with using the same narrower beamwidth at 1550 nm. However, SHG would allow a diffraction-limited system to use different beamwidths for beacon acquisition and communication without any moving parts.

Response of geostationary communications satellite solid-state power amplifiers to high-energy electron fluence

2025-02-11T19:58:16Z

Response of geostationary communications satellite solid-state power amplifiers to high-energy electron fluence Lohmeyer, Whitney; Carlton, Ashley; Wong, Frankie; Bodeau, Michael; Kennedy, Andrew; Cahoy, Kerri The key components in communications satellite payloads are the high-power amplifiers that amplify the received signal so that it can be accurately transmitted to the intended end user. In this study, we examine 26 amplifier anomalies and quantify the high-energy electron environment for periods of time prior to the anomalies. Building on the work of Lohmeyer and Cahoy (2013), we find that anomalies occur at a rate higher than just by chance when the >2 MeV electron fluence accumulated over 14 and 21 days is elevated. To try to understand “why,” we model the amplifier subsystem to assess whether the dielectric material in the radio frequency (RF) coaxial cables, which are the most exposed part of the system, is liable to experience electrical breakdown due to internal charging. We find that the accumulated electric field over the 14 and 21 days leading up to the anomalies is high enough to cause the dielectric material in the coax to breakdown. We also find that the accumulated voltages reached are high enough to compromise components in the amplifier system, for example, the direct current (DC) blocking capacitor. An electron beam test using a representative coaxial cable terminated in a blocking capacitor showed that discharges could occur with peak voltages and energies sufficient to damage active RF semiconductor devices.

End-to-end simulation of high-contrast imaging systems: methods and results for the PICTURE mission family

2025-02-11T20:02:40Z

End-to-end simulation of high-contrast imaging systems: methods and results for the PICTURE mission family Douglas, Ewan S.; Hewawasam, Kuravi; Mendillo, Christopher B.; Cahoy, Kerri L; Cook, Timothy A.; Finn, Susanna C. Finn; Howe, Glenn A.; Kuchner, Marc, J.; Lewis, Nikole K.; Marinan, Anne D.; Mawet, Dimitri; Chakrabarti, Supriya We describe a set of numerical approaches to modeling the performance of spaceflight high-contrast imaging payloads. Mission design for high-contrast imaging requires numerical wavefront error propagation to ensure accurate component specifications. For constructed instruments, wavelength and angle-dependent throughput and contrast models allow detailed simulations of science observations, allowing mission planners to select the most productive science targets. The PICTURE family of missions seek to quantify the optical brightness of scattered light from extrasolar debris disks via several high-contrast imaging techniques: sounding rocket (the Planet Imaging Concept Testbed Using a Rocket Experiment) and balloon flights of a visible nulling coronagraph, as well as a balloon flight of a vector vortex coronagraph (the Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph, PICTURE-C). The rocket mission employs an on-axis 0.5m Gregorian telescope, while the balloon flights will share an unobstructed off-axis 0.6m Gregorian. This work details the flexible approach to polychromatic, end-to-end physical optics simulations used for both the balloon vector vortex coronagraph and rocket visible nulling coronagraph missions. We show the preliminary PICTURE-C telescope and vector vortex coronagraph design will achieve 10−8 contrast without post-processing as limited by realistic optics, but not considering polarization or low-order errors. Simulated science observations of the predicted warm ring around Epsilon Eridani illustrate the performance of both missions.

Asymptotic analysis of numerical wave propagation in finite difference equations

2019-04-12T16:15:34Z

Asymptotic analysis of numerical wave propagation in finite difference equations Giles, M. (Michael); Thompkins, William T. An asymptotic technique is developed for analysing the propagation and dissipation of wave-like solutions to finite difference equations. It is shown that for each fixed complex frequency there are usually several wave solutions with different wavenumbers and the slowly varying amplitude of each satisfies an asymptotic amplitude equation which includes the effects of smoothly varying coefficients in the finite difference equation's. The local group velocity appears in this equation as the velocity of convection of the amplitude. Asymptotic boundary conditions coupling the amplitudes of the different wave solutions are also derived. A wave packet theory is developed which predicts the motion, and interaction at boundaries, of wavepackets, wave-like disturbances of finite length. Comparison with numerical experiments demonstrates the success and limitations of the theory. Finally an asymptotic global stability analysis is developed which gives results which agree with other stability analyses and which can be applied to a wider range of problems. March 1983; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1983; Includes bibliographical references (page 134)

A numerical analysis of 3-D inviscid stator/rotor interactions using non-reflecting boundary conditions

2019-04-10T12:33:25Z

A numerical analysis of 3-D inviscid stator/rotor interactions using non-reflecting boundary conditions Saxer, André P. (André Pierre) This dissertation presents a method for the computation of three-dimensional inviscid, transonic steady and unsteady flows, primarily in axial flow turbines. The work is divided into two major contributions. The first is an algorithm for the solution of the 3-D Euler equations which incorporates a second-order accurate numerical smoothing for non-uniform grids and steady-state non-reflecting boundary conditions. Fourier analysis applied to the linearized Euler equations is used to develop novel quasi-3-D non-reflecting boundary conditions at the inflow/outflow and at the stator/rotor interface. The accuracy, effectiveness and robustness of the boundary condition formulation is demonstrated through several subsonic and transonic test cases and through comparison with the standard 1-D formulation. The second contribution consists in the study of three specific flow phenomena occurring in an axial flow turbine.; First, the steady-state effects of an inlet spanwise stagnation temperature gradient in a transonic stage are analyzed. The mechanism for the migration of the temperature as well as the extent of the non-uniformity are assessed. Then, the secondary flow produced by a combined thermal and vortical inlet distortion on a downstream moving rotor is studied. The extent of the radial mixing for steady and unsteady flow is assessed as a function of the strength of the inlet disturbance. The third case is an analysis of the steady, unsteady and time-averaged flow fields in a highly loaded industrial transonic turbine stage. In particular, the unsteady shock interaction due to the impact of the stator trailing edge shock wave off the downstream rotor is studied. From the last two cases it is concluded that in many aspects the time-averaged results are extremely close to the steady-state values, even with strong unsteady shock interaction.; For each case the mechanisms for the creation of the secondary flow and deviations from a steady, uniform inlet conditions flow field are presented and analyzed. March 1992; Includes bibliographical references (pages 230-239)

Parametric dependencies of aeroengine flutter for flutter clearance applications

2019-04-10T12:33:44Z

Parametric dependencies of aeroengine flutter for flutter clearance applications Khalak, Asif, 1972- This thesis describes the effects of operational parameters upon aeroengine flutter stability. The study is composed of three parts: theoretical development of relevant parameters, exploration of a computational model, and analysis of fully scaled test data. Results from these studies are used to develop a rational flutter clearance methodology-a test procedure to ensure flutter-free operation. It is shown, under conditions relevant to aeroengines, that four nondimensional parameters are necessary and sufficient for flutter stability assessment of a given rotor geometry. We introduce a new parameter, termed the reduced damping, g/p*, which collapses the combined effects of mechanical damping and mass ratio (blade mass to fluid inertia). Furthermore, the introduction of the compressible reduced frequency, K*, makes it possible to uniquely separate the corrected performance map from the non-dimensional operating environment (including inlet temperature and pressure).; Simultaneous plots of the performance map of corrected mass flow and corrected speed, (mc,nc), with the (K*, g/p*) map provide a dimensionally complete and fully integrated view of flutter stability, as demonstrated in the context of a historic multimission engine. A parametric, .computational study was conducted using a 2D, linearized unsteady, compressible, potential flow model of a vibrating cascade. This study showed the independent effects of Mach number, inlet flow angle, and reduced frequency upon flutter stability in terms of critical reduced damping, which corroborates the 4D view of flutter stability. Test data from a full-scale transonic fan, spanning the full 4D parameter space, were also analyzed. A novel boundary fitting tool was developed for data processing, which can handle the generic case of sparse, multidimensional, binary data.; The results indicate that the inlet pressure does not alone determine the flight condition effects upon flutter, which necessitates the use of the complete 4D parameter set. Such a complete view of the flutter boundary is constructed, and sensitivities with respect to various parameters are estimated. A rational flutter clearance procedure is proposed. Trends in K* and g/p* allow one to rapidly determine the worst-cases for testing a given design. One may also use sensitivities to extend the results of sea level static (SLS) testing, if the worst case is relatively close to the SLS condition. August 2000; Includes bibliographical references (pages 223-228)

Measurements of rotor stalling in a matched and a mismatched multistage compressor

2019-04-10T12:33:42Z

Measurements of rotor stalling in a matched and a mismatched multistage compressor Silkowski, Peter D. (Peter Daniel) This paper presents the results from a set of experiments on stall inception in multistage axial flow compressors. The experiments were tailored to investigate phenomena having a wide range of time and length scales. This range of scales was motivated by two previously observed paths to stall. Parametric changes such as tip clearance, inlet distortion and mismatch were carried out to demonstrate the importance of component coupling in the stall inception process. Evidence is presented for the importance of the local compressor characteristic in determining where and when the initiation of the stall inception process will occur. Although the stall inception process may begin as a localized event, its growth into rotating stall is governed by the environment established by the coupling of the various compression system components. Finally, the tip flow field, specifically the rotor tip leakage jet, is shown to be a key feature in the stall inception process. April 1995; Includes bibliographical references (page 21)

A computational model for rotating stall and inlet distortions in multistage compressors

2019-04-10T12:33:43Z

A computational model for rotating stall and inlet distortions in multistage compressors Gong, Yifang, 1964- This thesis presents the conceptualization and development of a computational model for describing three-dimensional non-linear disturbances associated with instability and inlet distortion in multistage compressors. Specifically, the model is aimed at simulating the non-linear aspects of short wavelength stall inception, part span stall cells, and compressor response to three-dimensional inlet distortions. The computed results demonstrated the first-of-a-kind capability for simulating short wavelength stall inception in multistage compressors.; The adequacy of the model is demonstrated by its application to reproduce the following phenomena: (1) response of a compressor to a square-wave total pressure inlet distortion; (2) behavior of long wavelength small amplitude disturbances in compressors; (3) short wavelength stall inception in a multistage compressor and the occurrence of rotating stall inception on the negatively sloped portion of the compressor characteristic; (4) progressive stalling behavior in the first stage in a mismatched multistage compressor; (5) change of stall inception type (from modal to spike and vice versa) due to IGV stagger angle variation, and "unique rotor tip incidence" at these points where the compressor stalls through short wavelength disturbances. The model has been applied to determine the parametric dependence of instability inception behavior in terms of amplitude and spatial distribution of initial disturbance, and intra-blade-row gaps.; It is found that reducing the inter-blade row gaps suppresses the growth of short wavelength disturbances. It is also concluded from these parametric investigations that each local component group (rotor and its two adjacent stators) has its own instability point (i.e. conditions at which disturbances are sustained) for short wavelength disturbances, with the instability point for the compressor set by the most unstable component group. For completeness, the methodology has been extended to describe finite amplitude disturbances in high-speed compressors. Results are presented for the response of a transonic compressor subjected to inlet distortions. March 1999; Includes bibliographical references (pages 175-182)

Effects of inlet conditions on centrifugal diffuser performance

2019-04-12T16:15:33Z

Effects of inlet conditions on centrifugal diffuser performance Deniz, Sabri This report examines the influence of inlet flow conditions, including Mach number, flow angle, blockage, and axial flow non-uniformity, on the performance and operating range of a straight channel centrifugal compressor diffuser. The research was carried out in a unique facility specifically developed to provide the diffuser with a controlled inlet flow. The tests were carried out for inlet Mach number up to values greater than unity and for a range of inlet flow angles up to the onset of rotating stall. It was found that expressing the overall diffuser pressure recovery coefficient, defined using availability or mass averaged inlet total pressure, as a function of momentum averaged diffuser inlet flow angle yields a relationship which is essentially independent of diffuser inlet flow distortion, blockage, or Mach number. Further, the operating range of the diffuser was limited by the onset of rotating stall at a momentum averaged diffuser inlet flow angle ([alpha]crit = 70.5 ±0.5), which was also independent of the inlet flow field axial distortion and Mach number. The straight channel diffuser was designed to be comparable to a previously tested discrete passage diffuser and the performance of the two was compared; the overall pressure recovery of the former was found to be roughly 10% higher than that of the latter. Both diffuser types, straight channel and discrete passage diffuser showed similar behavior regarding the insensitivity of the performance and operating range to inlet flow axial non-uniformities and Mach number. The report also presents information on recent developments in the area of centrifugal compressor diffusers together with a detailed review of the open literature. March 1997; Includes bibliographical references (pages 169-190)

Effects of non-axisymmetric tip clearance on axial compressor performance and stability

2019-04-10T12:33:41Z

Effects of non-axisymmetric tip clearance on axial compressor performance and stability Graf, Martin Bowyer; Wong, Thomas S. (Thomas Sheung); Greitzer, E. M. (Edward M.), 1941-; Marble, Frank E.; Tan, Choon Sooi; Shin, Hyoun-Woo; Wisler, David C., 1941- The effects of circumferentially non-uniform tip clearance on axial compressor performance and stability have been investigated experimentally and analytically. A theoretical model for compressor behavior with non-axisymmetric tip clearance has been developed and used to design a series of first-of-a-kind experiments on a four-stage, low speed compressor. The experiments and computational results together show clearly the central physical features and controlling parameters of compressor response to non-axisymmetric tip clearance. It was found that the loss in stall margin was more severe than that estimated based on average clearance. The stall point was, in fact, closer to that obtained with uniform clearance at the maximum clearance level. The circumferential length scale of the tip clearance (and accompanying flow asymmetry) was an important factor in determining the stall margin reduction.; For the same average clearance, the loss in peak pressure rise was 50% higher for an asymmetry with fundamental wavelength equal to the compressor circumference than with wavelength equal to one-half the circumference. The clearance asymmetry had much less of an effect on peak efficiency; the measured maximum efficiency decrease obtained was less than 0.4 percent compared to the 8% decrease in peak pressure rise due to the asymmetric clearance. The efficiency penalty due to non-axisymmetric tip clearance was thus close to that obtained with a uniform clearance at the circumferentially-averaged level. The theoretical model accurately captured the decreases in both steady-state pressure rise and stable operating range which are associated with clearance asymmetry.; It also gave a good description of the observed trends of (i) increasing velocity asymmetry with decreasing compressor flow, and (ii) decreasing effect of clearance asymmetry with decreasing dominant wavelength of the clearance distribution. The time resolved data showed that the spatial structure of the pre-stall propagating disturbances in the compressor annulus was well represented and that the stability limiting process could be linked to the unsteady structure of these disturbance modes. The model was also utilized for parametric studies to define how compressor performance and stability is affected by the circumferential distribution of clearance, steady-state compressor pressure-rise characteristic, and system dynamic parameters. Sensitivity to clearance asymmetry was found to fall off strongly with the (asymmetry-related) reduced frequency and to increase with peak pressure rise and increasing curvature of the characteristic near the peak. September 1997; Statement of responsibility on title-page reads: M.B. Graf, T.S. Wong, E.M. Greitzer, F.E. Marble, C.S. Tan, H-W Shin, D.C. Wisler; Includes bibliographical references (pages 34-35)

Active stabilization of rotating stall and surge in a transonic single stage axial compressor

2019-04-09T15:42:32Z

Active stabilization of rotating stall and surge in a transonic single stage axial compressor Weigl, Harald Jürgen Rotating stall and surge have been stabilized in a transonic single-stage axial compressor using active feedback control. The control strategy is to sense upstream wall static pressure patterns and feed back the measured signal to an annular array of twelve separately modulated air injectors upstream of the rotor. At tip relative Mach numbers of 1.0 and 1.5, the control achieves a 11% and 3.5% reduction in stalling mass flow respectively. With control, the steady amount of injected air is equal to 3.6% of the design compressor mass flow. At a tip Mach number of 1.0 the stall inception dynamics and effective active control schemes are similar to results for low-speed axial compressors. The range extension can be achieved by individually damping the first and second spatial harmonics of the pre-stall rotating stall perturbations using constant gain feedback. The pre-stall dynamics are different at a tip Mach number of 1.5 than at the lower speed.; Both one-dimensional (surge) and two-dimensional (rotating stall) perturbations must be stabilized to increase the compressor operating range. At design speed, the instability is initiated by approximately 10 rotor revolutions of rotating stall followed by classic surge cycles. In accord with the results from a compressible stall inception analysis which has been applied to the compressor with actuation and refined based on forced response measurements, the zeroth, first, and second pre-stall harmonics each include more than one lightly damped mode which can grow into the large amplitude instability. Forced response testing has identified several modes traveling up to 150% of rotor speed for the first three spatial harmonics. Simple constant gain control cannot damp all of these modes and thus cannot stabilize the compressor at this speed.; Robust dynamic control is therefore used to stabilize the multiple modes which comprise the first three harmonic perturbations in this transonic region of operation. Eigenvalue perturbations are incorporated into an H [infinity] control design to directly address uncertainty in the dominant eigenvalue stability. July 1997; Includes bibliographical references (pages 297-302)

The effect of upstream rotor vortical disturbances on the time-average performance of axial compressor stators

2019-04-10T12:33:40Z

The effect of upstream rotor vortical disturbances on the time-average performance of axial compressor stators Valkov, Theodore V. (Theodore Valkov) Time-accurate Reynolds-averaged Navier-Stokes simulations have been carried out to investigate the impact of upstream rotor wakes and tip leakage vortices on the loss of a compressor stator. The objective is to (1) identify the unsteady flow mechanisms responsible for performance changes, (2) quantify these changes, and (3) extract useful design information. There are two generic mechanisms with significant impact on performance: reversible recovery of the energy in the disturbances (beneficial) and non-transitional boundary layer response (detrimental). For both wakes and tip leakage vortices, the impact of these mechanisms can be described in the same two-dimensional terms. In presence of unsteady flow, the efficiency of the design under consideration is 0.2 points higher than that obtained using a mixing-out steady flow approximation (0.5 points recovery benefit minus 0.3 points from boundary layer response). The effects of tip vortices and wakes are of comparable importance.; The impact of stator interaction with upstream wakes and vortices depends on the following parameters: axial spacing, loading, aid the frequency of wake fluctuations in the rotor frame. At reduced spacing, this impact becomes significant. For a spacing of 0.07 chords, stage efficiency is 0.6 points higher relative to the steady flow (1.2 points recovery benefit minus 0.6 points from boundary layer response). About 1/2 to 2/3 of the efficiency gain observed experimentally can be attributed to the interaction with upstream wakes and vortices. In the relative frame, wakes fluctuate in time. For fluctuation frequencies between 0.3-0.8 times the blade passing frequency, recovery does not occur, and there is a significant difference between the effects of fluctuating and steady wakes (with the same ensemble-averaged properties). The most important aspect of the tip vortex is the velocity defect, which is perceived by the stator in the same manner as a wake.; A model of recovery and boundary layer response in an embedded stage indicates that a mixing-out steady flow approximation underestimates stage efficiency by 0.3-0.5 points (for typical designs) and by 0.6-1.0 points (for closely-spaced blade rows). A region in design space exists where interaction has a beneficial and relatively constant impact on efficiency. Outside this region, interaction benefits rapidly disappear. For a typical blading diffusion factor of 0.45, the beneficial region is approximately delimited by the de Haller criterion. The detrimental aspects of boundary layer response may be mitigated by (a) selective removal of boundary layer fluid from the suction surface, or (b) tailoring of the blade loading to reduce loss in the front part of the blade. August 1997; Includes bibliographical references (pages 121-130)

A numerical investigation of a flutter in a transonic fan

2019-04-12T16:15:32Z

A numerical investigation of a flutter in a transonic fan Isomura, Kousuke The mechanism of the bending mode flutter of a modern transonic fan has been studied using a quasi-3D viscous unsteady code. The type of flutter in the scope of this research is that for a highly loaded blade with a tip relative Mach number just above unity, commonly referred to as transonic stall flutter. This type of flutter is often encountered in modern wide chord fans without a part span shroud. The code written as a part of this research uses an upwinding scheme with Roe's 3rd-order flux differencing, and Johnson and King's turbulence model with later modification by Johnson and Coakley. An extensive series of code validation calculations were performed and the reliability of the code has been verified against data and other calculational procedures. The calculations of the flow in this fan revealed that the source of the flutter is an oscillation of the passage shock, rather than a stall. As blade loading increases, the passage shock moves forward. Just before the passage shock unstarts, the stability of the passage shock decreases, and the shock oscillates at a large amplitude between unstarted position and started position with small blade vibration. The shock foot of the oscillating passage shock on the blade pressure surface exerts the dominant blade exciting force. October 1996; Includes bibliographical references (pages 155-158)

Blade passage flow structure effects on axial compressor rotating stall inception

2019-04-12T16:15:31Z

Blade passage flow structure effects on axial compressor rotating stall inception Hoying, Donald Andrew A new computational approach has been developed to study the inception of rotating stall in axial compressors. Using this approach the flow structures within the compressor blade passages have been examined in order to determine their influence on the process of rotating stall inception. Both two and three-dimensional numerical simulations were carried out. The two-dimensional computations showed a long wave-length (or modal) type of stall inception which was found to be well described by existing compressor stability models. The numerical results were used to directly confirm the various assumptions used in the formulation of the stability models. The three-dimensional computations of rotating stall displayed a short lengthscale type of stall inception with the same character as that seen in experiments. The central feature of the flow associated with the development of the short lengthscale stall cell was the tip clearance vortex moving forward of the blade row leading edge. Vortex kinematic arguments were used to provide a physical explanation of this motion. The resulting criteria for the inception of the short length-scale stall depends upon local flow phenomena related to the tip clearance flow. Thus, unlike the modal stall situation, the flow structure within the blade passages must be addressed when describing the stability of an axial compression system to short length-scale disturbances. December 1996; Includes bibliographical references (pages 125-130)

Rotor wake behavior in a transonic compressor stage and its effect on the loading and performance of the stator

2019-04-10T12:33:38Z

Rotor wake behavior in a transonic compressor stage and its effect on the loading and performance of the stator Durali, Mohammad The structure and behavior of wakes from a transonic compressor rotor and their effects on the loading and performance of the downstream stator have been studied experimentally. The rotor is 2 feet in diameter with a tip Mach number of 1.23 and a measured pressure ratio of 1.66. Time and space resolved measurements have been completed of the rotor and stator outlet flows, as well as of the pressure distribution on the surface of the stator blades. The data is analyzed and the rotor-stator viscous interaction is studied both qualitatively and quantitatively. It is found that the wakes from this rotor have large flow angle and flow Mach number variations from the mean flow, significant pressure fluctuations and a large degree of variation from blade to blade and from hub to tip. There is a significant total pressure defect and practically no static pressure variation associated with the stator wakes. Wakes from the rotor exist nearly undiminished in the exit flow of the stator and decay in the annular duct behind the stator. The pressure at all the points along the chord over each of the stator blades' surfaces, fluctuates nearly in phase in response to the rotor wakes, that is the unsteady chordwise pressure distribution is determined by the changes in angle of incidence to the blade and not by the local velocity fluctuations within the passage. There are large unsteady forces on the stator blade, induced by the rotor wakes, as high as 25% of the steady forces. The stator force due to the rotor wakes lags the incidence of the wake on the leading edge by approximately 1800 for most radii. April 1980; Also issued as: Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1980; Includes bibliographical references (leaves 44-45)

Role of flow alignment and inlet blockage on vaned diffuser performance

2019-04-10T12:33:39Z

Role of flow alignment and inlet blockage on vaned diffuser performance Phillips, Michael Stephen A computational investigation of the effects of inlet conditions on straight-channel diffuser performance is undertaken. The steady, three-dimensional, Navier-Stokes solver used for the investigation is found to adequately model the performance of a diffuser that has been previously examined experimentally. Results indicate that, contrary to the established view, vaned diffuser channel performance is weakly dependent on throat blockage. Rather, channel pressure rise is strongly affected by flow angle alignment with the diffuser centerline; misalignment of the flow can cause separation and reduced channel performance. This result challenges current design methods, and indicates that the designer is capable of sculpting the diffuser vanes to change the flow angle alignment, thus enabling control of both performance and range. In support of experimental results, overall diffuser performance is found to be largely independent of inlet axial distortion. Inlet nonuniformities are attenuated within the diffuser channel due to a spanwise work transfer which energizes regions of high flow angle misalignment, thus preventing the development of localized channel stall, and preserving good diffuser performance. This result indicates that axially twisted vanes, which are tailored for nonuniform inlet flow, may be unnecessary; simple untwisted vanes display no loss of performance when subjected to severe inlet distortion. September 1997; Includes bibliographical references (pages 81-84)

Dynamic control of rotating stall in axial flow compressors using aeromechanical feedback

2019-04-09T19:17:11Z

Dynamic control of rotating stall in axial flow compressors using aeromechanical feedback Gysling, Daniel L. Dynamic control of rotating stall in an axial flow compressor has been implemented using aeromechanical feedback. The control strategy developed used an array of wall jets upstream of a single stage compressor which were regulated by locally reacting reed valves. These reed valves responded to pressure perturbations in the flow that were associated with small amplitude perturbations that precede rotating stall. The control strategy was designed such that the combined system of compressor plus the reed valve controller was stable in previously unstable operating conditions. A 10% decrease in the stalling flow coefficient was achieved using this dynamic feedback control strategy, and the stable flow range was extended with no noticeable change in the steady state performance of the compression system.; The experimental demonstration is the first use of aeromechanical feedback to extend the stable operating range of an axial flow compressor, as well as the first use of locally reacting feedback and dynamic compensation techniques to stabilize rotating stall in an axial flow compressor. The design of the experiment was based on a two-dimensional model of the rotating stall dynamics which incorporated the effect of aeromechanical feedback. The physical mechanism responsible for rotating stall in axial flow compressors was examined with focus on the role of dynamic feedback in stabilizing compression system instability. The effectiveness of the aeromechanical control strategy was predicted, and experimentally demonstrated, to be a function of a set of non-dimensional control parameters that determine the interaction of the control strategy and the rotating stall dynamics.; Predictions based on linear stability analyses and non-linear numerical simulations agreed qualitatively with the steady state and time resolved experimental data. During the experimental investigations, large amplitude, one-dimensional acoustic oscillations were observed in the compression system with aeromechanical feedback stabilization. Based on these observations, the role of the compression system parameters in the acoustic oscillations was examined analytically and a method was developed to reduce these oscillations. The mechanism responsible for the generation of self-excited acoustic oscillations, and the implications for dynamic control of compression system instabilities was also examined. August 1993; Includes bibliographical references (pages 250-252)

Active control of rotating stall in axial compressors

2019-04-10T12:33:35Z

Active control of rotating stall in axial compressors Paduano, James D. (James Donald) An active control system has been implemented on a low-speed single-stage axial compressor. This control system stabilizes the perturbations which normally lead to rotating stall, thus extending the range of operation of the compressor to a flow coefficient 23% below the natural stall flow coefficient. Sensing of the perturbations which precede stall is accomplished using a circumferential set of hot wires mounted at an axial station ahead of the rotors. Actuation is accomplished by a set of 12 high-response inlet guide vanes, whose individual deflections can be controlled independently by a digital computer. The feedback scheme used in this work is motivated by a recently developed model for rotating stall. In this model, the perturbation axial velocity as a function of circumferential position at any axial station completely determines the state of the system.; Furthermore, circumferential sinusoidal waves of the perturbation are the fundamental eigenmodes, and these eigenmodes develop as rotating waves around the annulus. When the eigenvalues associated with these eigenmodes become unstable, the system diverges into rotating stall. Therefore, feedback stabilization of these rotating waves is used as the technique to eliminate rotating stall. The model for rotating stall is extended to include the effects of high-response inlet-guide-vane actuation. This model is then converted from a system of partial differential equations (PDEs) to a set of ordinary differential equations (ODEs). This conversion will be shown to yield a model to which standard control and identification techniques can be applied. The experimental investigation consisted of two main parts. The first part is systematic identification of the relevant compressor dynamics.; The procedures described yield an accurate model of the compressor input-output behavior over the frequency range of interest (DC to twice rotor rotation frequency), for flow coefficients which span the entire range of stable and unstable (stabilized) operation of the system. This identification verifies the basic behavior predicted by the model and provides quantitative information for control system design. The second part of the experimental investigation is active stabilization. The goal of active control is to extend the range of the compressor to the lowest flow coefficient possible. It is shown that, in the compressor studied, the circumferential sinusoidal modes go unstable in succession - first mode, followed by second, followed by third, as flow coefficient is reduced. Thus, additional range of the compressor is gained for each additional mode stabilized. March 1992; Includes bibliographical references (p. 231-233)

Active control of rotating stall in a three-stage axial compressor

2019-04-12T16:15:30Z

Active control of rotating stall in a three-stage axial compressor Haynes, Joel M. Stall inception in a three-stage axial compressor has been suppressed over a range of previously unstable operating points through the feedback of velocity perturbations to the inlet flow field. Perturbations were generated using 12 individually actuated guide vanes at the compressor inlet. The operating range was extended by 7.8% to a slope of 0.9 on the pressure rise characteristic. Over this range data describing the compressor's pressure rise and torque were collected. Flow field measurements upstream of the compressor revealed the excitation of spatial harmonics in the annular flow field before stall inception. With or without feedback, a spatial mode was observed to grow into a stall cell without a discontinuity of amplitude or position. The decrease in the stall inception mass flow as a result of damping the critical spatial mode indicated the importance of spatial modes in the stall inception process in this compressor.; Destabilization was originally caused by the first mode. After stabilizing an under-damped mode, the flow range was extended until the next sequential mode became unstable. The independent behavior of the modes before stall inception is described by four versions of a small disturbance model of compressor dynamics adapted from that of Moore and Greitzer. The two more sophisticated versions are presented here for the first time. The models require a description of the compressor's geometry, knowledge of its pressure rise characteristic, and some versions require a lag parameter characterizing the pressure rise response lag. The response lag parameter which enabled the models to most accurately predict the open-loop compressor dynamics was consistent with published values. The open-loop modal dynamics were determined experimentally and could be accurately described by the dynamics represented in the simplest model.; The open-loop dynamics were measured for the first three modes over a range of stable and formerly unstable operating points. The more elaborate models gave accurate predictions of the closed-loop compressor performance, and the most accurate one predicted the flow range extension with less than 1.5% error. June 1993; Includes bibliographical references (pages 183-185)

Control of the unsteady flow in a stator blade row interacting with upstream moving wakes

2019-04-10T12:33:33Z

Control of the unsteady flow in a stator blade row interacting with upstream moving wakes Valkov, Theodore V. (Theodore Valkov) A computational study of the unsteady flow in a 2-D stator blade row interacting with upstream rotor wakes has been carried out. A direct spectral-element Navier-Stokes solver has been used for the laminar flow regime (Re<10,000). Turbulent calculations (Re>106 are based on the Baldwin-Lomax turbulence model. The rotor wakes are represented by velocity distortions moving along the inlet boundary of the computational domain. After interception, the rotor wake migrates towards the pressure surface of the stator blades where it forms a pair of counter-rotating vortices. A moving series of such vortex pairs is the dominant form of unsteady flow over the pressure surface. The unsteady flow over the suction surface is characterized by a street of co-rotating vortices, produced in the leading edge region. These vortices consist of boundary layer fluid distorted and detached by the passing wakes.; Downstream of the leading edge, each of these vortices induces an associated, opposite-sign vortex. The blade loading fluctuations arising from wake interaction, are of two kinds. First, a strong pressure pulse occurs on the leading edge upon wake interception. This pulse is a potential flow effect associated with the excess tangential velocity in the wake. Second, a moving pattern of pressure fluctuations, associated with the vortices, is present over the blade surface. The pressure fluctuations are negative on the suction surface, and positive on the pressure surface. The unsteady flow features over the suction surface can be adequately represented by linearized perturbation calculations, where the disturbance flow associated with the wakes is linearized about a steady viscous flow. Three parameters influence the unsteady flow over the suction surface-stator blade loading, excess wake momentum in the stator frame, and wake reduced frequency.; The strength of the disturbance flow vortices is directly proportional to the wake momentum and decreases at higher reduced frequencies. An adverse pressure gradient results in stronger vortices and pressure fluctuations. On the pressure surface, the amount of unsteady flow depends on the excess wake momentum only. Strategies for controlling the unsteady flow are simulated using appropriate blade surface boundary conditions. Fluid removal from the suction surface prevents formation of vortices and reduces the associated loading disturbances. Fluid injection from the pressure surface reduces the pressure fluctuations there. January 1993; Includes bibliographical references (pages 63-66)

Feedback stabilization of compression systems

2019-04-12T16:15:28Z

Feedback stabilization of compression systems Simon, Jonathan S. (Jonathan Seth) An experimental and analytical study was conducted on the use of feedback stabilization to extend the stable operating range of compression and pumping systems. Prevention of surge, in aircraft gas turbine engines, an instability characterized by violent system wide oscillations in pressure, and flow, primarily motivated this research. However, such instabilities arise as a result of the non-monotonic pressure/flow relations of the axial and/or centrifugal compressors used in gas turbine engines and the results of this research can therefore be applied to many other compression and pumping systems which also employ these types of devices. The frequency response of a centrifugal compressor was measured to validate a lumped parameter model of this component. The results showed that the model is useful for control design and analysis purposes.; Modeling the flow development process as a first order lag was shown to account for observed phenomena that were not predicted by a quasi-steady model. Theoretical limitations to the control of this class of systems that are imposed by bounded actuation and stability robustness requirements were characterized and quantified. The limitations are shown to depend strongly on the choice of actuator and sensor. The influence of actuator/sensor selection was further defined by systematically evaluating a diverse range of available options. The practical difficulty, as well as the number of viable options, were found to depend primarily on the slope of the compressor pressure rise characteristic and the system B-parameter, which represents the relative amount of fluid compliance to inertia.; An important result is that only options which can be considered dynamically close-coupled to the compressor are viable for systems with B-parameter and non-dimensional slope substantially greater than unity. One particular close-coupled scheme, a control valve at the compressor exit with compressor mass flow feedback, was examined in detail and experimentally demonstrated. Although the system of interest can also be stabilized with a passive flow restriction, it is shown that the use of feedback control reduces the steady state pressure loss across the valve required for stabilization. The benefits are greatest for systems with relatively steep slopes at high flow. Includes bibliographical references (pages 244-250)

Computational simulation of unsteady flow in transonic compressor rotor

2019-04-09T15:21:26Z

Computational simulation of unsteady flow in transonic compressor rotor Owen, Philip Ray The unsteady flow about a section of a modern first stage transonic compressor rotor was simulated using a finite difference approximation to the two-dimensional, Reynolds averaged, unsteady, compressible, viscous Navier-Stokes equations. The computation was performed in both steady state and time-accurate modes, and the results compared. The time-accurate results were analyzed in some detail. Two frequency regimes were observed. High frequency unsteadiness due to vortex shedding was found at frequencies varying between 11 KHz and 19 KHz. A low frequency cycle was also observed at 365 Hz. The low frequency cycle produced significant variations in blade force and moment. It also modulated the strength and frequency of the vortex shedding. Arguments were advanced to explain the mechanics of the vortex street formation in terms of a single free shear layer instability. The variations in shedding strength and frequency were related to movement of the separation point. A wholly satisfactory normalization of the frequencies was not found. The low frequency cycle was analyzed as a quasi-steady sequence of events stemming from movement of a shock wave spanning the blade passage. The possibility was entertained that the cycle was due to purely numerical sources, but no likely mechanism was found. October 1986; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1986; Includes bibliographical references (pages 57-58)

Aerodynamics of aircraft engines : stride and stumbles

2019-04-10T12:33:32Z

Aerodynamics of aircraft engines : stride and stumbles Cumpsty, N. A. Summary: Attempts to understand and predict the aerodynamic behaviour of compressors and turbines in aircraft gas turbines have been encouraged by the intense competitive pressure which exists. Many of the apparently most difficult problems have been overcome using suitable numerical analysis, for example the calculation of three-dimensional transonic flows has been particularly successful. It is seemingly paradoxical that the numerical methods are relatively very good for flows which are traditionally regarded as difficult, but do less well at predicting efficiency when the flow is well behaved in the conventional aerodynamical sense, such as fully attached flows. The numerical methods do not necessarily give insight into the flow that is seen as most helpful to the designer and it can be useful to complement them with simpler approaches to the problem which seek to capture the essential features of the flow. The aerodynamics of aircraft engine fans are used to illustrate these points. Although numerical methods have been very successful with aeroengine fan blading they have been less successful with the multistage compressor. The reasons for this, primarily the difficulty of prescribing the boundary conditions, are discussed in this paper. The analysis of flow in multistage compressors still stumbles along with empirical methods, much of it based on data published over twenty years ago. A second area where stumbling has occurred is the prediction of flutter of blading, particularly fan blading; as recently as 1990 there were major in-flight failures due to flutter of a fan in civil airline service. To this day there is no reliable method of predicting the operating boundaries of flutter, and testing the engine over the entire operating range of altitude and speed is the only reliable method of ensuring safe operation. September 1992; Includes bibliographical references (leaves 21-22)

A numerical analysis of 3-D inviscid stator/rotor interactions using non-reflecting boundary conditions

2019-04-09T18:39:00Z

An analytical and numerical study of the second-order effects of unsteadiness on the performance of turbomachines

2019-04-10T12:33:31Z

An analytical and numerical study of the second-order effects of unsteadiness on the performance of turbomachines Fritsch, Gerd A linear approach in two dimensions is used to investigate the second-order effects of unsteadiness on the efficiency of turbomachines. The three main themes are the identification of physical nature and location of unsteady loss mechanisms, the magnitude of the associated losses and their effect on the time-mean efficiency, and the assessment of the modeling accuracy of numerical simulations with respect to unsteady loss. A mathematically rigorous link is established between linear waves in a compressible, two-dimensional flow and the efficiency drop associated with their dissipation. The analysis is applied to the mixing loss at the interface in a steady simulation of rotor/stator interaction in a turbine and to the study of unsteady loss mechanisms. Two unsteady loss mechanisms are considered. Unsteady Circulation Loss, i.e.; the transfer of mean-flow energy to kinetic energy associated with vorticity shed at the trailing edge in response to an unsteady circulation, was first considered by Keller (1935) and later by Kemp and Sears (1955). Keller's original work is extended to compressible, homentropic flows. The use of simulations to obtain circulation amplitudes avoids the limitations of thin-airfoil theory and yields a loss measure realistic for modern turbomachines. For the Unsteady Viscous Loss mechanism, i.e. the dissipation induced by pressure waves in unsteady boundary layers, the high-reduced-frequency limit and a near-wall approximation are used to obtain the local velocity distribution in the laminar Stokes sublayer and the corresponding time-mean dissipation. The input to the model are the unsteady pressure gradients along a blade surface obtained from an unsteady simulation. A numerical study of the errors due to modeling approximation is included.; Both sources of loss are small but not negligible. It is found that numerical smoothing shifts the principal locus of unsteady dissipation from boundary layers to the freestream, reducing the magnitude of the loss models input and the predicted loss. June 1992; Based on the author's Sc. D. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992; Includes bibliographical references (pages 147-152)

Experimental investigation of flow distortion effects on the performance of radial discrete-passage diffusers

2019-04-09T18:30:08Z

Experimental investigation of flow distortion effects on the performance of radial discrete-passage diffusers Filipenco, Victor Gregory A swirling-radial-flow generator has been developed for the study of fluid-dynamic phenomena in radial passage- and vaneless-diffusers. A unique feature of the swirling-flow generator is the capability of providing a wide range of diffuser inlet flow conditions. This is accomplished by means of a very-high-solidity rotating radial-outflow nozzle cascade in conjunction with annular cross-flow injection/suction slots in the flow-path walls immediately upstream and downstream of the rotor blading. The rotor generates a shockless and weak-wake axisymmetric transonic swirling flow which can be tailored to provide a desired level of diffuser inlet flow-field axial distortion by means of cross-flow injection and/or suction through the annular slots.; A complete test-facility was designed and constructed based on this concept and was utilized to study effects of inlet flow-field axial distortion on the pressure-recovery performance and stability of a modem high-performance gas-turbine-engine radial discrete-passage diffuser. It was shown that the diffuser pressure-recovery coefficient, if based on the inlet availability-averaged total pressure, correlates well with the diffuser inlet momentum-averaged flow angle independent of flow-field axial distortion and Mach number over the wide flow parameter range investigated. It was argued that the generally accepted high sensitivity of diffuser pressure recovery performance to inlet flow distortion and boundary-layer blockage is largely due to inappropriate quantification of the diffuser inlet flow-field parameters.; Time resolved pressure measurements in the vaneless space between the rotor and diffuser showed that the diffuser operating range is limited by the onset of rotating stall triggered by the loss of flow stability in the diffuser, independent of the rotor operating point (if overall compression system instability did not occur first). It was found that the loss of flow stability in the diffuser occurred at a critical value of the diffuser inlet momentum-averaged flow angle and corresponding overall-diffuser pressure recovery coefficient (based on the availability-averaged total pressure), independent of inlet flow-field distortion and Mach number, over the wide flow parameter range investigated.; A simple analytical consideration of an idealized diffuser consisting of a constant-area mixing duct followed by an isentropic-flow diffuser was used to show that the observed insensitivity of the diffuser pressure-recovery performance to inlet flow-field distortion can be attributed to rapid mixing of the flow. It was shown that measurements of the static pressure distribution along the centerline of an individual diffuser-passage support this hypothesis. September 1991; Based on the author's Ph. D. thesis, Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991; Includes bibliographical references (pages 185-189)

UNSFLO : a numerical method for the calculation of unsteady flow in turbomachinery

2019-04-10T12:33:29Z

UNSFLO : a numerical method for the calculation of unsteady flow in turbomachinery Giles, M. (Michael) Introduction: There are four principal sources of unsteadiness in a single stage of a turbomachine in which there is one row of stationary blades (stators) and one row of moving blades (rotors). As shown in Fig. 1.1, wake/rotor interaction causes unsteadiness because the stator wakes, which one can consider to be approximately steady in the stator frame of reference, are unsteady in the rotor frame of reference since the rotor is moving through the wakes and chopping them into pieces. This causes unsteady forces on the rotor blades and generates unsteady pressure waves. Although the stator wakes are generated by viscosity, the subsequent interaction with the rotor blades is primarily an inviscid process and so can be modelled by the inviscid equations of motion. This allows two different approaches in numerical modelling. The first is to perform a full unsteady Navier-Stokes calculation of the stator and rotor blades.; The second is to perform an unsteady inviscid calculation for just the rotor blade row, with the wakes being somehow specified as unsteady inflow boundary conditions. This latter approach is computationally much more efficient, but assumes that one is not concerned about the unsteady heat transfer and other viscous effects on the rotor blades. Potential stator/rotor interaction causes unsteadiness due to the fact that the pressure in the region between the stator and rotor blade rows can be decomposed approximately into a part that is steady and uniform, a part that is non-uniform but steady in the rotor frame (due to the lift on the rotor blades) and a part that is non-uniform but steady in the stator frame (due to the lift on the stator blades).; As the rotor blades move, the stator trailing edges experience an unsteady pressure due to the non-uniform part that is locked to the rotors, and the rotor leading edges experience an unsteady pressure due to the non-uniform part that is locked to the stators. This is a purely inviscid interaction which is why it is labelled a "potential" interaction. There are again two approaches to modelling this interaction. The first is an unsteady, inviscid calculation of the stator and rotor blade rows. The second is an unsteady, inviscid calculation of just one of the blade rows, either the stator or the rotor, with the unsteady pressure being specified as a boundary condition. The latter approach is more efficient, but unfortunately the situation in which the potential stator/rotor interaction becomes important is when the spacing between the stator and rotor rows is extremely small, and/or there are shock waves moving in the region between them.; Consequently, one does-not usually know what values to specify as unsteady boundary conditions. The first two sources of unsteadiness were both due to the relative motion of the stator and rotor rows. The remaining two sources are not. The viscous flow past a blunt turbine trailing edge results in vortex shedding, very similar to the Karman vortex street shed behind a cylinder. In fact real wakes lie somewhere between the two idealized limits of a Karman vortex street and a turbulent wake with steady mean velocity profile. It is believed that provided the integrated loss is identical the choice of model does not affect the subsequent interaction with the downstream rotor blade row. However, this is an assumption which needs to be investigated sometime in the future. The importance of vortex shedding lies in the calculation of the average pressure around the blunt trailing edge, which determines the base pressure loss, a significant component of the overall loss.; There is also experimental evidence to suggest that the vortex shedding can be greatly amplified under some conditions by the potential stator/rotor interaction. Finally, there can be unsteadiness due to the motion of the stator or rotor blades. The primary concern here is the avoidance of flutter. This is a condition in which a small oscillation of the blade produces an unsteady force and moment on the blade which due to its phase relationship to the motion does work on the blade and so increases the amplitude of the blade's unsteady motion. This can rapidly lead to very large amplitude blade vibrations, and ultimately blade failure. May 1991; Includes bibliographical references (pages 89-91)

Newton solution of steady two-dimensional transonic flow

2019-04-10T12:33:30Z

Newton solution of steady two-dimensional transonic flow Giles, M. (Michael) A new method is developed for the solution of the steady, two-dimensional Euler equations for transonic flows. The discrete steady-state equations are derived in conservative finite-volume form on an intrinsic streamline grid, and are solved using Newton's method. Direct solution of the linear system of Newton equations is shown to be more efficient than iterative solution. Test cases include duct, cascade, and isolated airfoil flows, and demonstrate the speed and robustness of the method. The accuracy of the solutions is verified by comparison against values obtained analytically, experimentally and by other numerical methods. October 1985; Also issued as: Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1985; Includes bibliographical references (pages 167-169)

Analysis and design of transonic cascades with splitter vanes

2019-04-12T16:15:26Z

Analysis and design of transonic cascades with splitter vanes Youngren, H. H. (Harold Hayes) A new computational method, MISES, is developed for turbomachinery design and analysis applications. The method is based on the fully coupled viscous /inviscid method, ISES, and is applicable to blade-to-blade analysis of axial fan and compressor stator or rotors with optional splitter vanes. Quasi-three dimensional effects for stream surface radius, streamtube thickness and wheel rotation may be included. The flow is modeled with the steady Euler equations and the integral boundary layer equations. A robust Newton-Raphson method is used to solve the coupled non-linear system of equations, requiring only several minutes for solution on a typical workstation. Design options are implemented for either single surface or camber redesign. The method is exercised by comparison with transonic cascade tests to validate the quasi-three-dimensional formulation. The results show excellent correlation to measured pressure distributions and loss levels. The multiple blade capability is demonstrated by comparison to test data for a supersonic cascade with splitter vane. New splitter vane configurations for improving the performance of the supersonic cascade are explored, resulting in large increases in turning and reduced loss. Includes bibliographical references (pages 162-164)

Condensation of supersaturated organic vapors in a supersonic nozzle

2019-04-09T18:35:25Z

Condensation of supersaturated organic vapors in a supersonic nozzle Dawson, Daniel Bogert Experiments were performed involving condensation of supersaturated benzene and chloroform vapors in a supersonic nozzle, with compressed air as the carrier gas. Experiments showed that the magnitude of the water vapor content of the carrier air made no observable difference in the condensation behavior of either fluid. It was demonstrated that addition of small amounts of these fluids to the carrier air tended to reduce the thickness of the boundary layer in the nozzle. Comparison of experimental results with theory show, without making any adjustments to physical properties of condensate droplets to account for size, that incidence of condensation for chloroform can be predicted by the revised theory of nucleation, whereas benzene incidence can be predicted by neither revised nor classical theory. These results, combined with prior data on other fluids, show that at present neither theory seems to be generally applicable. In support of previous conclusions, the problem may well be the assumption that bulk properties may be assigned to small (30 - 50 molecules) droplets of condensate. (Author). April 1967; Includes bibliographical references

Blade scale effects of tip leakage

2019-04-12T16:15:26Z

Blade scale effects of tip leakage Martinez-Sanchez, Manuel; Gauthier, R. P. The effects of blade-tip leakage in a turbine are investigated by modeling the stage as an incomplete actuator disk. It is found that the spanwise flow redistribution due to the gap is such as to produce a uniform unloading of the blades, despite the very concentrated leakage. Partial lift retention at the blade tip is accounted for based on a leakage jet-free stream collision model which successfully predicts the roll-up of the leakage flow. The predicted efficiency loss due to the gap correlates well with experimental data. October 1990; Includes bibliographical references (leaves 43-44)

A systematic study of supersonic jet noise

2019-04-09T16:42:46Z

A systematic study of supersonic jet noise Louis, Jean F. (Jean François); Letty, Richard M.; Patel, Jayantilal R. The purpose of this work is to study the acoustic fields associated with two different nozzle configurations; a rectangular and a circular. Both nozzles are designed with the same exit Mach number and have an identical momentum and energy flux. By presenting a comparison of the two nozzles, it proposed to establish and identify the dominant noise generating mechanisms. A basic difference in shape changes the relative importance of different noise mechanisms. The other main aim of this study is to establish scaling laws of supersonic jet noise. A shock tube is a very versatile apparatus for such an analysis. By first changing the driver, driven pressure and molecular weights, a wide range of stagnation pressures and temperatures could be achieved. The case with which these conditions are simulated is, however, traded off with the short test time, of the order of milliseconds. A short test time allows the use of a heat sink nozzle and eliminates the use of an anechoic chamber.; So far tests have been made in the range of 1000-5000°R, for different levels of expansion and an exit Mach number of 2.7. In comparing the two nozzles, it is found that the rectangular nozzle is indeed quieter than the circular nozzle. The rectangular nozzle is more effective under overexpanded conditions, and a factor of 1.6 in acoustic efficiency at low temperature (1200°R) and about 3 at high temperature is related to a rapid deceleration of the jet through a system of strong shocks. The low acoustic efficiency of the overexpanded rectangular jet is related to a rapid deceleration of the jet through a system of strong shocks. At high temperature, this effect is not observed because an important density ratio exists across the shear layer which becomes very unstable due to the Taylor instability.; For both the circular and rectangular nozzle, the effect of temperature showed an increase in the directivity angle at high temperature which is correlated to an increase in eddy convective velocity, rather than refraction due to density gradients, which seems to play a secondary role. The low temperature overexpanded jet showed a difference of about 2.6 db in the OPWL between the two nozzles. However, at this condition, for the rectangular nozzle, a difference of 8 db between the maximum and minimum noise direction is observed. Hence, a suitable orientation of the nozzle could cause a considerable reduction in the noise level. The rectangular nozzle seems to be very effective under overexpanded conditions. The scaling laws, which are in the preliminary stages, were developed for the change in the OPWL as a function of stagnation pressure. For the circular nozzle, additional scaling was done for temperature and acoustic efficiency.; These scaling laws need to be verified for additional temperatures. Also, further work should be initiated in the potential use of the rectangular nozzle as a noise suppressor and as a model for better comprehension of noise generating mechanisms. December 1971; Includes bibliographical references (leaves 39-40)

Separation of turbulent, incompressible flow from a curved, backward-facing step

2019-04-12T16:15:25Z

Separation of turbulent, incompressible flow from a curved, backward-facing step Nice, George Roland; Tseng, W.-Y. (Wu-Yang); Moses, Hal Lynwood An experimental investigation of turbulent, incompressible flow separation over curved and sharp, backward-facing steps is presented with results for various step heights. Mean velocities in the separating boundary layer as well as the downstream shear layer were recorded. The static pressure in the separated region was determined with a spherical probe. With the curved step, the boundary layer separated at approximately 28 degrees: the reattachment lengths were somewhat less and the base pressures slightly higher than those with the sharp step. October 1966; Includes bibliographical references

Unsteady radial transport in a transonic compressor stage

2019-04-10T12:33:38Z

Unsteady radial transport in a transonic compressor stage Kotidis, Petros Anestis A technique, based on the operation of a dual-hot wire-aspirating probe with frequency response of at least 18 kHz and uncertainty less than 0.005 to full scale in mass fraction units, has been developed to measure time resolved concentration in unsteady, compressible flows. The goal of the experimental part of this research effort was to obtain time resolved measurements of spanwise transport in a transonic compressor. This was achieved by injecting a circumferentially oriented, thin sheet of tracer gas in front of the compressor and detecting the foreign fluid molecules at the rotor exit The experiments were conducted at the MIT Blowdown Facility using the Air Force High Through Flow Compressor Stage as the test article. During a preliminary data reduction procedure, it was discovered that the signals from the probe's hot wires lag in time with respect to the signal from the companion total pressure probe.; A correction incorporated in the data reduction schemes to account for this, eliminated most of the negative entropy regions observed in previous experiments with this probe. Several conclusions have been drawn from the experimental observations. First, up to 5% of the compressor mass flow moved along the blade span. Second, the migrating fluid was found primarily in the blade wakes at the measurement location. Third, this fluid moved towards both hub and tip in the blade wakes. Fourth, the radially convected fluid had high entropy, much higher than that of the average flowfield. Fifth, the "inviscid core" fluid moves preferentially towards the suction side of the blade passage and away from the pressure side. A simple model was developed to explain the spanwise fluid transport Gertz's 2-D wake vortex street model was extended into a quasi 3-D form.; The 2-D model was fitted to the data at four spanwise locations and the spanwise variation of the parameters of the vortex street (such as vortex strength and core size) were determined. The model fit showed the shedding frequencies to be the same [17 (+/-) 0.4 kHz] at all four spanwise locations, suggesting that the vortex shedding is coherent along the span. The spanwise pressure gradient created by the variation of vortex strength led to substantial spanwise transport in the vortex cores. The model predicted the transport to the hub, but underestimated the transport to the tip by a factor of five. The measured spanwise transport can explain the previously observed discrepancy between predicted (viscous+normal shock losses) and measured spanwise distributions of adiabatic efficiency in the tip regions of transonic compressors (assuming the radial outflow to be primarily in regions of separated flow on the blades). September 1989; Includes bibliographical references (pages 212-219)

Induced strain actuation of composite plates

2019-04-10T12:33:37Z

Induced strain actuation of composite plates Lazarus, Kenneth B.; Crawley, Edward F. Two models of induced strain plate actuator/substrate systems are developed and verified experimentally. Equations relating the actuation strains produced by the strain actuators to the induced strains found in the system are derived for both models. In addition, the plate strain energy relations are also developed. Exact and approximate solutions are formulated for isotropic and anisotropic plate systems. Exact solutions are found for actuator/substrate systems with free-free, free-free boundary conditions, and a general procedure for solving the strain energy equations with a Rayleigh-Ritz approximate solution is formulated for systems with arbitrary boundary conditions and external loads. Specific solutions are detailed for cantilever plate systems, including a discussion of the assumed modes selected. A model for predicting the actuation strains produced by a specific class of induced strain actuators, piezoceramic actuators, is also developed.; The non-linear properties of piezoceramics are discussed and the important effects of such non-linearities are accounted for by developing a strain dependent model for the actuation strains created in piezoceramics. The models developed were verified through experimentation via two sets of plate test articles. The first set of simple test articles were used to verify the accuracy of the basic induced strain actuation models, the strain dependence of piezoceramic actuation strains, and a semi-empirical solution procedure. The second, more representative, set of large cantilever plate test articles verified the ability of the models to predict the strains induced in systems with extensive stiffness couplings and complicated boundary conditions, and the Ritz model.; Agreement between the solutions predicted by the induced strain actuator models and the experimentally measured deformations was excellent, verifying the effectiveness of using induced strain actuation for shape control of structures such as aeroelastic lifting surfaces and components of intelligent structures. March 1989; Originally written by Mr. Lazarus as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1989; Includes bibliographical references (pages 126-128)

Surge dynamics and unsteady flow phenomena in centrifugal compressors

2019-04-10T12:33:36Z

Surge dynamics and unsteady flow phenomena in centrifugal compressors Fink, David Allan Detailed time resolved measurements of centrifugal compressor surge has been obtained on an automotive turbocharger for two very different compression systems one with a large downstream volume and one with a much smaller downstream volume. These measurements show impeller stall at the inducer tips to be a key phenomena in initiating surge. The inducer tip stall, which is dominant over other types of stall in the compressor, is observed to be non-rotating and asymmetric due to the presence of an asymmetric downstream volute. The most severe stalling of the impeller occurs at a circumferential position nearest the volute tongue position and is due to a circumferential flow distortion set up by the . volute. The vaneless diffuser is seen to be destabilizing but does not initiate surge by abrupt stalling. Rotating stall was found to be unimportant in surge initiation. New evidence is presented concerning the dynamic behavior of the compressor characteristics in surge operation.; Instantaneous compressor characteristics in surge when operating in a large volume(large B-parameter) system are found to be flatter than the time averaged ones for a small volume(small B-parameter) stabilized system. A physical mechanism accounting for the difference between the two measured characteristics is the slow development time and differing circumferential extent of the inducer stall present. The flatness of the large B characteristic contrasts with the characteristic of an axial. compressor operating in surge and leads to slow growth of the surge massflow instability. A dynamic model has been developed which includes effects of speed variations, compressibility, and time lags. The inclusion of speed variations changes the time domain behavior of the compression system substantially from the results obtained with constant speed.; A precursor period of mild surge whose length depends on the amount of throttling is shown to be present before deep surge and is due to the speed variations. Both speed variations and time lags in compressor behavior are shown to introduce a stabilizing effect on compressor behavior in mild surge. The results of this model agree qualitatively as well as quantitatively with the measured experimental system dynamic behavior. The dynamic behavior observed has some properties of importance for the new field of active control of surge instabilities in centrifugal compressors. The flatness of the instantaneous compressor characteristic, the existence of a mild surge precursor period, and slow growth of the surge instability are favorable conditions for a relatively simple active control strategy to stabilize the compression system and eliminate surge. Also the dynamic model developed may be useful for exploring alternative active control strategies. June 1988; Includes bibliographical references

A coupled Euler/Navier-Stokes algorithm for 2-D unsteady transonic shock/boundary-layer interaction

2019-04-12T16:15:29Z

A coupled Euler/Navier-Stokes algorithm for 2-D unsteady transonic shock/boundary-layer interaction Allmaras, Steven R. (Steven Richard) This thesis presents a coupled Euler/Navier-Stokes algorithm for solving 2-D unsteady transonic flows. The flowfield is described by a Defect formulation, where separate Euler and Navier-Stokes algorithms are used on overlapping grids and are coupled through wall transpiration fluxes. The work is separated into three major contributions. The first contribution is a new algorithm for the solution of the 2-D unsteady Euler equations. The algorithm incorporates flux-splitting to capture shocks crisply and with minimal oscillations. To reduce numerical errors, grid independent second order accuracy is achieved for both steady and unsteady flows. This is done by a formulation in which both solution averages and gradients are stored for each cell. The scheme allows no decoupled modes; hence, no explicitly added artificial is necessary. The second contribution is a Thin-Shear-Layer Navier-Stokes algorithm for viscous regions.; The algorithm uses two-point differencing across the boundary layer, which is second order accurate for both inviscid and viscous terms on nonsmooth grids. Fluxsplitting is used for the streamwise discretization to capture shocks. The spatial discretization of this scheme also admits no decoupled modes and does not require added artificial dissipation. A semi-implicit time integration is employed, which allows a time step determined by the streamwise grid spacing only. The algorithm uses a dynamic coordinate rescaling to evolve the viscous grid to the changing boundary layer thickness. The final contribution of the work is a explicit relaxation procedure for coupling the Euler and Navier-Stokes algorithms together. The coupling is through boundary conditions-specified outer edge values for the viscous solution and wall transpiration fluxes for the Euler solution. Computational results are presented for a series of duct geometries.; The test cases are used to demonstrate the accuracy of the Euler algorithm, the Navier-Stokes algorithm, and the fully coupled algorithm. Results are compared with analytic theory, experimental results, and other computational methods. March 1989; Originally issued as: Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1989; Includes bibliographical references (pages 238-243)

Effects of compressor endwall suction and blowing on stability enhancement

2019-04-11T09:01:14Z

Effects of compressor endwall suction and blowing on stability enhancement Lee, Norman Kai Wing An experimental investigation was carried out to examine the effects on stall margin of flow injection into, and removal out of, the endwall region of an axial compressor blade row. A main goal was to identify the mechanism by which wall treatment suppresses stall in turbomachines. To simulate the relative motion between blade and treatment, the injection and removal took place through a slotted hub rotating beneath a cantilevered stator row. Overall performance data and detailed (time-averaged) flow-field measurements were obtained. Both injection and removal increased the stalling pressure rise, but neither was as effective as the complete treatment. This implies that removal of high blockage flow is not the only reason behind the observed stall margin improvement in a casing or hub treatment, and that injection also contributes to stall suppression. The results also indicated that, for a given variation of injection, the increase in stall pressure rise is linked to the streamwise momentum of the injected flow. January 1988; Includes bibliographical references

UNSFLO : a numerical method for unsteady inviscid flow in turbomachinery

2019-04-10T22:52:01Z

UNSFLO : a numerical method for unsteady inviscid flow in turbomachinery Giles, M. (Michael) Introduction: There are four principal sources of unsteadiness in a single stage of a turbomachine in which there is one row of stationary blades (stators) and one row of moving blades (rotors). As shown in Fig. 1.1, wake/rotor interaction causes unsteadiness because the stator wakes, which one can assume to be approximately steady in the stator frame of reference, are unsteady in the rotor frame of reference since the rotor is moving through the wakes and chopping them into pieces. This causes unsteady forces on the rotor blades and generates unsteady pressure waves. Although the stator wakes are generated by viscosity, the subsequent interaction with the rotor blades is primarily an inviscid process and so can be modelled by the inviscid equations of motion. This allows two different approaches in numerical modelling. The first is to perform a full unsteady Navier-Stokes calculation of the stator and rotor blades.; The second is to perform an unsteady inviscid calculation for just the rotor blade row, with the wakes being somehow specified as unsteady inflow boundary conditions. This latter approach is computationally much more efficient, but assumes that one is not concerned about the unsteady heat transfer and other viscous effects on the rotor blades. Potential stator/rotor interaction causes unsteadiness due to the fact that the pressure in the region between the stator and rotor blade rows can be decomposed approximately into a part that is steady and uniform, a part that is non-uniform but steady in the rotor frame (due to the lift on the rotor blades) and a part that is non-uniform but steady in the stator frame (due to the lift on the stator blades).; As the rotor blades move, the stator trailing edges experience an unsteady pressure due to the non-uniform part that is locked to the rotors, and the rotor leading edges experience an unsteady pressure due to the non-uniform part that is locked to the stators. This is a purely inviscid interaction which is why it is labelled a "potential" interaction. There are again two approaches to modelling this interaction. The first is an unsteady, inviscid calculation of the stator and rotor blade rows. The second is an unsteady, inviscid calculation of just one of the blade rows, either the stator or the rotor, with the unsteady pressure being specified as a boundary condition. The latter approach is more efficient, but unfortunately the situation in which the potential stator/rotor interaction becomes important is when the spacing between the stator and rotor rows is extremely small, and/or there are shock waves moving in the region between them.; Consequently, one does not usually know what values to specify as unsteady boundary conditions. The first two sources of unsteadiness were both due to the relative motion of the stator and rotor rows. The remaining two sources are not. The viscous flow past a blunt turbine trailing edge results in vortex shedding, very similar to the Karman vortex street shed behind a cylinder. In fact real wakes lie somewhere between the two idealized limits of a Karman vortex street and a turbulent wake with steady mean velocity profile. It is believed that provided the integrated loss is identical the choice of model does not affect the subsequent interaction with the downstream rotor blade row. However, this is an assumption which needs to be investigated sometime in the future. The importance of vortex shedding lies in the calculation of the average pressure around the blunt trailing edge, which determines the base pressure loss, a significant component of the overall loss.; There is also experimental evidence to suggest that the vortex shedding can be greatly amplified under some conditions by the potential stator/rotor interaction. Finally, there can be unsteadiness due to the motion of the stator or rotor blades. The primary concern here is the avoidance of flutter. This is a condition in which a small oscillation of the blade produces an unsteady force and moment on the blade which due to its phase relationship to the motion does work on the blade and so increases the amplitude of the blade's unsteady motion. This can rapidly lead to very large amplitude blade vibrations, and ultimately blade failure. October 1988; Includes bibliographical references

Two-dimensional transonic aerodynamic design and analysis using the Euler equations

2019-04-11T09:01:13Z

Two-dimensional transonic aerodynamic design and analysis using the Euler equations Drela, Mark A method is developed for the solution of the steady two-dimensional Euler equations with viscous corrections for transonic design and analysis problems. The steady finite volume integral equations are formulated on an intrinsic streamline grid, and are solved using a global Newton method. Conservative differencing together with artificial bulk viscosity in supersonic regions permit correct shock capturing. The design capability of the method stems from the streamline-based grid and Newton solution method, which allow both direct and inverse boundary conditions and constraints to be readily applied to the governing equations. For all boundary condition types, the effects of boundary layers and wakes on the inviscid flow are modeled by the displacement thickness concept. The boundary layer and wake parameters are described by compressible integral boundary layer equations which are coupled to the inviscid flow and are included in the global Newton solution scheme. This coupling procedure gives stable convergence for flows with limited separation regions. A transition criterion based on the Orr-Sommerfeld equation is developed and applied to transitional separation bubbles. Accurate drag predictions are obtained for subsonic and shocked transonic airfoils. Design examples involving airfoils and cascades are presented. February 1986; Originally presented as the author's thesis (doctoral-Massachusetts Institute of Technology)--under the title: Two-dimensional transonic aerodynamic design and analysis using the Euler equations; Includes bibliographical references (pages 139-143)

Experimental investigation of Stator hub treatment in an axial flow compressor

2019-04-12T16:17:49Z

Experimental investigation of Stator hub treatment in an axial flow compressor Prell, Mark E. An experiment was carried out to examine the effects, on stator stall margin and performance, of a slotted hub treatment rotating beneath the stator of an axial flow compressor. The compressor was run with this hub treatment and the results compared to those taken with a smooth rotating hub. It was determined that, for the configuration tested, the hub treatment was ineffective in the improvement of stall margin but resulted in a measurably higher static pressure rise across the stator and a significant decrease in flow deviation and blockage in the stator midspan region. Although it is the hub section of the stator that sets the stall limit in this configuration, measurements of the stator exit flow field indicated that the type of stall that is occurring is a blade stall rather than a pure wall stall. Absence of a wall stall is thus seen as a key possibility for the lack of stall margin improvement. July 1981; Includes bibliographical references (page 29)

Measurements of aerodynamic damping on the MIT transonic rotor

2019-04-10T12:34:00Z

Measurements of aerodynamic damping on the MIT transonic rotor Crawley, Edward F. A method has been developed and demonstrated for the direct measurement of aerodynamic forcing and aerodynamic damping of a transonic compressor. The method is based on the inverse solution of the structural dynamic equations of motion of the blade disk system in order to determine the forces acting on the system. The disturbing and damping forces acting on a given blade are determined if the equations of motion are expressed in individual blade coordinates. If the structural dynamic equations are transformed to multi blade coordinates, the damping can be measured for blade-disk modes, and related to a reduced frequency and inter blade phase angle. To measure the aerodynamic damping in this way, the free response to a known excitation is studied. This method of force determination was demonstrated using a specially instrumented version of the MIT Transonic Compressor run in the MIT Blowdown Compressor Test Facility.; Unique on-rotor instrumentation included piezoelectric displacement transducers to monitor the displacement of each blade, three accelerometers to measure in plane motion of the disk and a leading edge mounted total pressure transducer. Resonance tests performed prior to installation of the rotor in the tunnel indicate that the blade disk structural interaction is dominated by the rigid body inertial coupling of the disk. An analytical model was developed for this inertial coupling. The model was verified by extensive testing of the tuned and severely mistuned rotor. No regions of aeroelastic instability were found while testing the rotor in the Blowdown Facility, but three forms of forced vibration were encountered. When operated in rotating stall, the blades were strongly excited at the fundamental frequency of stall cell excitation and those higher harmonics in proximity to blade resonances.; At the fundamental frequency, the blade bending loading decreased as the blade entered the stall cell and increased as smooth flow was reestablished over the blade. In runs near the operating point, the rotor was aerodynamically excited by a controlled two-per-revolution fixed upstream disturbance. The disturbance was sharply terminated midway through the test and the ring down of the rotor monitored. Analysis of the data in terms of multiblade modes led to a direct measurement of aerodynamic damping for several interblade phase angles. During all runs, the third circumferential harmonic of the blade displacement was strongly excited by wakes shed from three evenly spaced upstream struts. The addition of a two per revolution fixed upstream disturbance caused a marked decrease in the third harmonic response, suggesting a nonlinear mechanism either in the upstream wake production or in the aerodynamic response of the rotor.; It may therefore be possible to alleviate some forced vibrations by the deliberate introduction of upstream disturbances. February 1981; Includes bibliographical references (page 80)

Sound generation from a transonic compressor stage

2019-04-10T12:34:00Z

Sound generation from a transonic compressor stage Schaffner, Joan Elsa; Ingard, K. Uno Some aspects of the sound pressure wave characteristics produced by a transonic compressor stage are studied by the use of a simplified mathematical model involving flow parallel to a moving corrugated board. The critical parameters of the system are correlated with the various unknowns in the mathematical model resulting in a suitable representation of the physical system. The analysis is first performed for the rotor alone, calculating the sound pressure wave upstream and downstream from the rotor, spinning at a tip speed Mach number of 1.2. The model is then modified to account for the stator blade row, 3/4" axially displaced from the rotor. A study of the reflective characteristics of the stator blade row is performed with the result that the reflective characteristic due to straightening of the flow is much more significant than that due to the physical hardware. The complete description for the sound pressure wave in the three regions: upstream of the rotor, downstream of the stator, and between the rotor and the stator, is determined. The results of this analysis are presented in the form of graphs showing: 1) the reflection coefficients, RF and RS , as functions of tip speed, 2) the pressure wave magnitude as a function of rotor tip speed for specific values of flow speed, 3) the axial dependence of the pressure wave magnitude in the region between the rotor and stator, 4) the ratios PO/P1 , PO/P2 , and P1/P2 as functions of Mt . Experimental data obtained prior to this analysis at the M.I.T. Blowdown Facility is presented and shown to correlate quite favorably with the theoretical determination of the pressure ratios presented. July 1981; Includes bibliographical references (pages 64-65)

Flow visualization study of the inlet vortex phenomenon

2019-04-12T16:17:48Z

Flow visualization study of the inlet vortex phenomenon De Siervi, Francesca The inlet vortex phenomenon was experimentally investigated in a water tunnel, using hydrogen bubble flow visualization techniques. Several inlet ambient flow combinations were studied, including an inlet and ground plane configuration in a known shear as well as an irrotational flow, and a double (twin) inlet configuration in an irrotational flow. This latter situation created a boundary layer free analogue of the ground plane and enabled investigation of inlet vortex formation in flow essentially free of ambient vorticity. The three dimensional inlet flow field and the vortex formation mechanisms were determined by marking material lines and observing their path and deformation as they are convected from a far upstream location into the inlet. Two basic mechanisms of inlet vortex generation were found. For flows possessing a vertical component of ambient vorticity, the amplification of this vorticity as the vortex lines are stretched and drawn into the inlet results in the formation of an inlet vortex. However, an inlet vortex does not require the presence of ambient vorticity to form. It can also be created in an irrotational flow, with an inlet in crosswind. In this situation, it is accompanied by a variation in circulation along the axial length of the inlet. The ratio of inlet velocity to upstream velocity is an important parameter in determining the generation of an inlet vortex for both mechanisms. July 1981; Includes bibliographical references (page 99)

Noise and performance of propellers for light aircraft : final report

2019-04-10T12:33:59Z

Noise and performance of propellers for light aircraft : final report Succi, G. P. (George Peter); Larrabee, E. Eugene; Dunbeck, Peter Brian; Munro, David Herbert; Zimmer, Jeffrey Alan; Ingard, K. Uno; Kerrebrock, Jack L. Introduction and Summary: The project "Noise and Performance of Propellers for Light Aircraft," Contract #NASl-15154 between NASA Langley and MIT, has now been completed, and the main results obtained are summarized in this report and its appendices. The primary practical objective of the study was to explore the possibility of reducing the noise from a general aviation type propeller without altering significantly its aerodynamic performance or the engine characteristics. After an extensive study of this question, involving aerodynamic and acoustic theory, design, construction and wind tunnel testing of model propellers, design and manufacturing of full scale propellers and, finally, flight tests, we are pleased to report that for one of the propellers tested an overall reduction of 4.8 dBA as measured in a flight test was achieved.; The theory deals with aerodynamics and acoustics of lightly loaded propellers with subsonic tip speeds and includes studies of the effects of sweeping the blades, altering the radial load distribution, and changing the number of blades. These studies lead to new insight into the general problem of sound generation from moving bodies. Of particular value are the algorithms, which are well suited for computer coding. The wind tunnel tests involved three propellers, 1/4 scale, including a replica of a fixed pitch propeller used on a 150 HP single engine airplane. The other two propellers were designed to have the peak radial load distribution shifted inboard. The acoustic wind tunnel which was used in these tests enabled measurement not only of the radiated sound field but also the thrust and torque of the propeller. In addition, the load distribution was determined indirectly from wake surveys.; Sound pressure signatures were obtained at different locations and speeds (up to a tip Mach number of 0.75) and compared with theoretical predictions in which only the shape and motion of the propeller were needed as input parameters; no empirical adjustments were made. Agreement to within a few percent was obtained throughout except in the presence of a transonic "buzz" instability which was encountered within a narrow speed range. On the basis of the theoretical analysis and its verification in the model tests, a two-bladed fixed pitch propeller was designed for a 150 HP single engine airplane. Flight tests with this propeller indicated about the same performance as the production propeller for that airplane, but the maximum sound level during a full power flyover at 1000 feet was found to be 4.8 dBA lower. A second propeller, with three blades and fixed pitch, was designed for the Ohio State University 180 HP single engine airplane.; Flight tests of this propeller have not yet been made at this time. July 1980; Project Manager: G. P. Succi ; Contributors: E.E. Larrabee, P.D. [i.e. P. B.] Dunbeck, D.H. Munro, J.A. Zimmer; Principal Investigators: K.U. Ingard, J.L. Kerrebrock; Includes bibliographical references (pages 22-23); Final report. February 24, 1978 to July 31, 1980

Time accurate internal flow solutions of the thin shear layer equations

2019-04-12T16:17:47Z

Time accurate internal flow solutions of the thin shear layer equations Bush, Robert Hull An implicit factored algorithm for the solution of the thin shear layer approximation of the Navier-Stokes equations is described and explicit boundary conditions are developed for internal flow problems. This scheme is compared to theoretical predictions and experimental data, as well as to other more thoroughly tested numerical schemes. The examples presented demonstrate the ability of the factored algorithm to accurately predict internal flow fields and provide insight into the difficulties associated with the numerical simulation of internal flow fields. February 1981; Includes bibliographical references (page 58)

Design of the MIT Breakdown Turbine Facility

2019-04-10T12:33:58Z

Design of the MIT Breakdown Turbine Facility Epstein, Alan H. (Alan Henry); Guenette, Gerald R. (Gerald Roger); Norton, Robert J. G. Summary: This report details the design, construction, and preliminary testing of a short duration (0.4 sec) test facility capable of testing 0.5 meter diameter, film cooled, high work aircraft turbine stages under conditions which rigorously simulate actual engine conditions. The simulation capability of the facility extends up to 40 atm inlet pressure at 2500 0K (40000F) turbine inlet temperatures. The facility is intended primarily for the exploration of unsteady, three-dimensional fluid mechanics and heat transfer in modern turbine stages. April 1985; Includes bibliographical references (page 151)

Unconventional blade design for compressors

2019-04-12T16:17:47Z

Unconventional blade design for compressors Gopalakrishnan, S. One of the factors causing the low efficiency of axial flow compressors operating at decreased flow rates is the flow separation at blade extremities. To postpone this tendency to separate to lower flow rates, compressor blades were designed with increased chord at the blade extremities, which are immersed in the hub and casing boundary layers. The experimental results have shown that the stage static pressure rise is not significantly altered when the modification is used, but the rotor and stage efficiencies are significantly higher at low flow rates. A lifting vortex, similar to that encountered on delta wings at moderate angles of attack, has been observed near the hub region of the modified rotor. The observed differences in the turning through the rotor have been explained satisfactorily using a model incorporating the effects of the lifting vortex. The model also demonstrates that the total drag of the modified rotor can be expected to be smaller than that of the conventional rotor at low flow rates. In the Appendix, some theories based on the lifting line approach are described, which predict the behavior of a stationary cascade facing an inlet flow with spanwise variations in the angle of attack. The comparison of the theoretical results with the very limited amount of experimental data available is considered satisfactory. May 1969; Also issued as: Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1969; Includes bibliographical references (leaves 64-66)

Some observations of the vibrations of slender rotating shafts

2019-04-10T12:33:55Z

Some observations of the vibrations of slender rotating shafts Dugundji, John; Buellesbach, Monica M.; Wright, Mary A. (Mary Anne Jackson), 1941- The linear theory of a slender, initially bowed, rotating shaft is reviewed for both free and forced vibrations, and found to compare well with a simple experiment on such a shaft. The shaft behavior passing through the critical speed is described in detail, and the maximum bowed-out static deflection of the shaft was found dependent on the external damping and the initial bowing. The amplitude of the oscillatory deflections of the shaft due to gravity loads increased somewhat near the critical speed, but these increases were small compared to the large static deflection of the shaft. During rapid passage through the critical speed, low frequency whirling modes were excited transiently. At higher rotation speeds, the second critical speed was observed, and also the first mode was excited subharmonically and appeared as a backward whirl mode relative to the rotating shaft. March 1982; Includes bibliographical references (page 29)

Quantitative investigation of inlet vortex flow field

2019-04-10T19:18:08Z

Quantitative investigation of inlet vortex flow field Shin, Hyoun-Woo; Shippee, Cheryl (Cheryl Lynn) A quantitative investigation of the flow field of an inlet in cross-wind has been carried out for various operating conditions, including flow regimes representative of aircraft engine inlets at take-off. The measurements were made to show the influence of two non-dimensional parameters, height of the inlet above the ground to the inlet diameter ratio (H/D), and velocity ratio (Ui/Ue), on the vortex strength (i.e., circulation) and the position of the vortex inside the inlet. In general, as H/D is decreased and/or Ui/Ue is increased, the vortex strengthens. In addition, at an operating condition where a strong inlet vortex was present, the circulation of both the inlet and trailing vortices was determined. These were found to be essentially equal in magnitude but opposite in sign, verifying a previous hypothesis concerning the vortical structure of the flow. Qualitative flow visualization has been done to examine two aspects of the inlet/trailing vortex flow field. One is the nature of the transition between regimes in which an inlet vortex is present and those in which no inlet vortex exists. The other deals with the extent of the separated region on the inlet body. The results of this study were used to support a conceptual model of the formation of an inlet/trailing vortex system for an inlet in a cross-wind. March 1984; Includes bibliographical references (leaf 126)

Channel flow modeling of impingement cooling of a rotating turbine blade

2019-04-12T16:15:45Z

Channel flow modeling of impingement cooling of a rotating turbine blade Koo, JaHye Jenny Local heat transfer distributions in impingement cooling have been measured by Kreatsoulas [1] and Preiser [2] for a range of conditions which model those in actual turbine blades, including the effects of rotation. These data were reported as local Nusselt numbers, but referred to coolant supply conditions. By means of a channel flow modeling of the flow in the supply and impingement passages, the same data are here presented in terms of local Nusselt number distributions such as are used in design. The results in this form are compared to the nonrotating impingement results of Chupp [3] and to the rotating but non-impingement results of Morris [4]. Rotation reduces the mean Nusselt numbers from these found by Chupp by about 30 percent, and introduces important radial variations which are sensitive to rotation and to leading edge stagger angle. December 1984; Includes bibliographical references (leaf 29)

An investigation of rotating stall in a single stage axial compressor

2019-04-12T16:15:42Z

An investigation of rotating stall in a single stage axial compressor Montgomery, Stephen Ross; Braun, Joseph J. The rotating stall characteristics of a single stage axial flow compressor were investigated. The number of stall cells and their propagation velocities were found with and without stator blades. The measured velocities were compared with those predicted by Stenning's theory, assuming the downstream pressure fluctuations to be negligible, and correlation within 25% was obtained over a wide range of stall patterns. It was found that the pressure fluctuations caused by rotating stall were less downstream of the rotor than upstream; the minimum reduction across the rotor was 40% with stator blades, and 75% without stator blades. It was also found that, for the compressor tested, the stator blades decreased, the number of stall cells and tended to induce rotating stall at larger mass flow rates. May 1955; Thesis written jointly by both authors: Thesis (M.S.)--Massachusetts Institute of Technology. Dept. of Mechanical Engineering, 1955; Includes bibliographical references

FORTRAN program for calculating three-dimensional, inviscid, rotational flows with shock waves in axial compressor blade rows : I--user's manual

2019-04-12T16:15:43Z

FORTRAN program for calculating three-dimensional, inviscid, rotational flows with shock waves in axial compressor blade rows : I--user's manual Thompkins, William T. Summary: A FORTRAN-IV computer program has been developed for the calculation of the inviscid transonic/supersonic flow field in a fully three-dimensional blade passage of an axial compressor rotor or stator. Rotors may have dampers (part-span shrouds). MacCormack's explicit time-marching method is used to solve the unsteady Euler equations on a finite difference mesh. This technique captures shocks and smears them over several grid points. Input quantities are blade row geometry, operating conditions and thermodynamic quantities. Output quantities are three velocity components, density and internal energy at each mesh point. Other flow quantities are calculated from these variables. A short graphics package is included with the code, and may be used to display the finite difference grid, blade geometry and static pressure contour plots on blade-to-blade calculation surfaces or blade suction and pressure surfaces. Flows in four transonic compressor rotors have been analyzed and compared with exit flow field measurements and intra-blade static density measurements obtained with a gas fluorescence technique. These comparisons have generally shown that the computed flow fields accurately model the experimentally determined passage shock positions and overall aerodynamic performance. The computer code was developed and generally run on a large minicomputer system, a Digital Equipment Corporation PDP-ll/70, with run times of two to three days. The code has also been run on several main-frame computers (IBM 3033, IBM 360/678, UNIVAC 1110, CDC 7600 and a CRAY-1). Typical run times on an IBM 3033 have been found to be 5-10 hours. September 1981; Includes bibliographical references (pages 81-82)

A study of outlet guide vanes

2019-04-10T12:33:55Z

A study of outlet guide vanes Qvale, Einar Björn A criterion for design of unstalled compressor blades has been proposed, and a set of outlet guide vanes has been designed according to this criterion and has been tested. A typical compressor stator and outlet guide vane configuration has been tested and compared with the new design. The tests show that the new design gives considerably higher pressure coefficients and lower pressure losses. June 1963; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1963; Includes bibliographic references

Secondary flow and losses in a compressor cascade

2019-04-12T16:15:41Z

Secondary flow and losses in a compressor cascade Soderberg, Olof E. Three ways in which secondary flow can be generated in a straight compressor cascade have been investigated. 1. Wakeflow. The inlet flow is characterized by a constant inlet angle and a varying stagnation pressure over the span. 2. Skewed flow. The inlet flow is characterized by a constant stagnation pressure and a varying inlet angle over the span. 3. Skewed wakeflow. The inlet flow is characterized by a variation of both stagnation pressure and inlet angle over the span. For a certain combination of inlet angle and stagnation pressure distribution (presented in a formula) in the skewed wakeflow case no secondary flow is generated behind the cascade. The kinetic energy of the secondary flow was found to be very small in all three cases. The secondary flow itself did not create any losses but the blades stalled in the skewed flow layer and in the skewed wakeflow layer causing great losses. The stream pressure and the tangential blade force were lower in the disturbed flow region. A small perturbation theory (for a non-viscous, incompressible fluid) had been developed to describe analytically the secondary flow. Formulae readily adaptable for numerical calculations of flow deviation angles, kinetic energy of the secondary flow, and tangential blade force are presented. Good and satisfactory correlation of theory and experiment was found. Applied to compressor design the results imply: The secondary flow is very small and may occur as an overturning or an underturning of the flow at the casings depending on the actual design. The kinetic energy of the secondary flow may be neglected when considering the losses. The ends of the blades stall in the skewed boundary layer at the casings causing losses. This could be reduced by twisting the blade ends to account for the increased incidence angle. The stream pressure varies in spanwise direction through the boundary layer on the casings. August 1958; Also issued as: Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1958; Includes bibliographical references

Three-dimensional laminar boundary layer in curved channels with acceleration

2019-04-10T12:33:53Z

Three-dimensional laminar boundary layer in curved channels with acceleration Senoo, Y. A theory is developed for two families of three-dimensional laminar boundary layers; namely, for the boundary layer on the parallel plane end walls of a curved channel with logarithmic spiral side walls, and for the boundary layer on the plane end wall of a concentric circular-arc channel having a particular family of accelerated or decelerated main flows. The second case shows the influence of acceleration and deceleration of a curved main flow. Numerical calculations show that acceleration makes the boundary layer thin and deceleration makes it thick, but the variation of thickness due to pressure gradient is very small compared with that in the two-dimensional case. The first case can be compared to the flow in a cascade. In this case, the variation of the width of the channel is directly related to the variation of the main flow velocity. According to the calculation, the boundary layer is thicker in an accelerated flow through a converging logarithmic spiral channel than in the decelerated flow through the same channel in the opposite direction. It is suspected that converging side walls make the end-wall boundary layer thick and that the effect of convergence is dominant over the effect of accelerated main flow. Experimental data on the end wall of a turbine nozzle cascade were compared with theoretical predictions, with fair agreement across the nozzle and along the center line of the nozzle. November 1956; Includes bibliographical references

Cascade performance with accelerated or decelerated axial velocity

2019-04-10T12:33:54Z

Cascade performance with accelerated or decelerated axial velocity Kubota, Shigeo A theoretical method to estimate the effect of axial velocity change through a cascade was investigated. The change of axial velocity was reproduced by distributing sinks and sources within the blade passages, and the conclusions are set forth in some simple formulae. Some graphs for the numerical evaluation of the performance of NACA 65 series cascades were prepared, and several examples were compared with experimental data. September 1959; Includes bibliographical references (page 27)

Boundary layer separation ; preliminary report

2019-04-12T16:15:40Z

Boundary layer separation ; preliminary report Moses, Hal Lynwood The phenomenon of incompressible boundary layer separation and the existing methods of predicting it are discussed. The failure of these theories in many cases clearly indicates a need for further investigation. A program is proposed that, it is hoped, will improve the present situation. The study is directed primarily at turbulent flow, but the laminar case is treated as well. A theoretical method is presented which involves the ability of the boundary layer to transfer momentum to the fluid near the wall by shear stress. The apparatus, which has already been built for the experimental investigation, is described. Due to its flexibility, the apparatus should prove valuable in comparing and improving methods of predicting separation. May 1962; Includes bibliographical references; Preliminary report

A study of the end wall boundary layer in an axial compressor blade row

2019-04-10T12:33:52Z

A study of the end wall boundary layer in an axial compressor blade row Moore, Raymond W. (Raymond William); Richardson, David L. Turbulent end wall boundary layers in the hub region of axial compressor blade rows have been studied in the Gas Turbine Laboratory. Both analytical and experimental work are presented. An attempt was made to predict the growth of the boundary layer momentum thickness as it passes through a cascade of blades using the momentum integral equation and several assumptions This calculation was compared with measurements taken along an assumed free streamline in a stationary cascade of blades supplied with an artificially skewed inlet boundary layer. From this comparison, the relative influence of individual terms in the momentum integral equation is deduced. The effects of inlet skewing and cross flow in the boundary layer in the region between blades is described. Two methods of representing main and cross flow velocity profiles are compared with experimental data. October 1955; Errata sheet inserted in front; At head of title: Shear flow in bends; Includes bibliographical references (page 12)

Boundary layer on an airfoil in a cascade

2019-04-10T12:33:52Z

Boundary layer on an airfoil in a cascade Peterson, Carl R. A study of the turbulent boundary layer on an airfoil in a cascade is presented. The major portion of the observations are on the suction surface of the airfoil. The effect of added diffusion across the cascade due to a three-dimensional flow is included. Empirical equations describing the boundary layer in terms of momentum and displacement thickness growth as a function of free-stream diffusion are developed. Shape factor is also related to free-stream diffusion. A reasonable check with an existing separation criterion is observed. An appendix contains a discussion of chord-wise integrating of various boundary layer parameters. December 1958; This report was originally the authors master's thesis: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1958); Includes bibliographical references

A cascade tunnel for investigation of rotating stall

2019-04-12T16:15:40Z

A cascade tunnel for investigation of rotating stall Kriebel, Anthony R.; Stenning, Alan H. (Alan Hugh) A test apparatus which will reproduce the rotating stall phenomenon found in axial compressors has been constructed and installed in the main wind tunnel circuit of the Gas Turbine Laboratory. The test section consists of a two dimensional, circular, radial outflow cascade between two flat plates. The cascade was designed to reproduce the pressure distribution, and hence the stall characteristics, of a typical rectilinear cascade. The air entry angle to the cascade is controlled by a variable angle nozzle ring so that the cascade may be stalled and unstalled in operation, Provision has been made for removal of wall boundary layers by suction, and for changing the setting of the cascade stagger angle. By a simple modification, the blades may be supported elastically to permit torsional vibrations. Independent variation of the Reynolds number and Mach number of the air stream is possible. Visual observations of the flow using Schlieren and Interferometer equipment can be made through windows in the walls of the test section. In preliminary tests, rotating stall has been observed and the research program will commence in August of 1954. JUN 1954 --hand-stamped on title-page; 'Stall flutter phenomena in axial flow machines' terminal report -- title-page; Includes bibliographical references; Terminal report; June 1954

Temperature wake in an adverse pressure gradient

2019-04-09T18:19:32Z

Temperature wake in an adverse pressure gradient Sturek, Walter B. (Walter Beynon) A study is made of the flow pattern resulting from the presence of a temperature wake in a uniform velocity field subjected to various adverse pressure gradients. Dimensionless temperature profiles and velocity profiles are presented. A velocity defect appears in the region of high temperature, and the magnitude of the adverse pressure gradient over the range investigated has no effect on the spreading of the temperature wake. A simple theoretical approach is presented which correlates well with the experimental results. The implications of the experimental results and the theoretical approach are discussed with reference to an axial compressor with a temperature wake in the fluid stream at the inlet. June 1961; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1961; Includes bibliographical references

Comparative study of tip clearance effects in compressors and turbines

2019-04-12T16:15:39Z

Comparative study of tip clearance effects in compressors and turbines Yokoyama, Eiji The influence of tip clearance on the lift distribution along a blade span was studied on linear compressor and turbine cascades. The wall boundary layer was removed by means of the image technique. The lift distribution in the span direction was found to be almost similar for both compressor and turbine cascades having the similar velocity diagrams. The lift acting on the blades increases toward the blade tip. The phenomena were explained theoretically by considering the velocity induced by tip vortices on the blade surface. May 1961; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1961; Includes bibliographical references

Stall propagation in axial compressors

2019-04-09T16:01:19Z

Stall propagation in axial compressors Stenning, Alan H. (Alan Hugh) A theory of stall propagation in a cascade of airfoils of high solidity has been developed which includes the effects of finite blade chord and of the boundary layer response to changes in angle of attack. The theory is valid for small perturbations in velocity about a mean flow- condition with finite pressure rise across the cascade, provided that the pressure fluctuations behind the cascade are much smaller than those ahead of the cascade. The solution for the velocity of stall propagation indicates that the velocity increases with the wave length of the stall cell, tending towards a limiting value for very large stall cells. The wave length of the stall cells at the beginning of rotating stall is dependent on the magnitude of the boundary layer time delay. The theory predicts propagation velocities within 25% over a wide range of wave lengths for a stationary circular cascade and a rotating blade row which have been tested. The experiments have confirmed that an increase in wave length is accompanied by an increase in propagation velocity if other parameters are unchanged. April 1955; Includes bibliographical references

Stall propagation in a cascade of airfoils

2019-04-10T12:33:48Z

Stall propagation in a cascade of airfoils Kriebel, Anthony R. An experimental investigation of stall propagation in a stationary circular cascade by means of high speed schlieren and interferometer photography is described. This investigation suggests an analytical approach to the problem which is valid only for an isolated blade row in an infinite flow field but which is not restricted to small unsteady perturbations or an assumed simplified cascade geometry. Conditions necessary for the existence of the assumed type of stall cells are described and equations are derived for the velocity of stall cell propagation. The propagation velocities predicted for the theoretical potential flow-model correlate with all the experimental values measured in an isolated rotor within 15%. Analysis of the flow model predicts a tendency for the assumed type of stall cell to split with increasing incidence of the mean flow through the blade row which appears to correlate with the experimental observation of a trend for increasing numbers of cells in the rotor. August 1956; Also issued as: Thesis (Sc.D.) Massachusetts Institute of Technology. Dept. of Mechanical Engineering, 1956; Includes bibliographical references

The effect of tip clearance on an axial flow fan

2019-04-12T16:15:38Z

The effect of tip clearance on an axial flow fan Ryan, Francis J. (Francis James); Ōhashi, Hiroshi The effect of tip clearance on the performance of a single stage axial flow (6000 cfm) fan was investigated for tip clearances ranging from 0.003 in. to 0.252 in. It was found that, at the rated flow, the stagnation pressure rise (mass flow weighted) across the fan rotor was a maximum for the smallest tip clearance and a minimum for the largest tip clearance. However, it was found also that at the rated flow, the stagnation pressure rise was larger at a tip clearance of 0.022 in. than at a tip clearance of 0.015 in. At a flow of 4000 cfm (two thirds of rated flow) the effect of tip clearance was found to be negligible over the entire range of clearances tested. At flows in excess of 6500 cfm, the stagnation pressure rise was highest for a tip clearance of 0.022 in. Plotting a performance map of stagnation pressure rise across the rotor versus volume flow also revealed that as the peak pressures became higher, these peaks shifted to lower values of flow. This would indicate a shifting of the surge line vertically and horizontally on the performance map as the tip clearance is varied. The flow pattern in the original fan, as manufactured, was investigated also. This revealed that, at the rated flow, the suction sides of the stator blades were stalled over approximately the after one-half of their surface while the pressure sides were completely unstalled. This study also showed that, at all flows tested, the flow pattern at the rotor tip was somewhat turbulent, while the pattern at the rotor root was stable at high flows but became very unstable at low flows. At flows below 000 cfm reversal of flow started near the rotor tip. May 1955; AT head of title: Three-dimensional flow in turbo-machine research; Includes bibliographical references (page 18)

A light scattering investigation of droplet growth in nozzle condensation

2019-04-12T16:15:37Z

A light scattering investigation of droplet growth in nozzle condensation Roberts, Richard, Sc. D. Massachusetts Institute of Technology /, by Richard Roberts An experimental and theoretical study has been made of the condensation of water vapor (with air carrier) in a supersonic nozzle in order to investigate the possible existence of condensate droplets which are substantially larger than predicted by the standard application of classical condensation theory. Droplet size was measured using light scattering techniques, which when combined with the total mass concentration of condensate, provided limits on the maximum and average droplet size. It was found that approximately one part in 10 of the droplet concentration reached a size a factor of 10 greater than predicted by the classical theory . . .The maximum droplet size, furthermore, was not seen to decrease proportionately as the nucleation zone was approached, indicating that the larger droplets are formed during the early stages of condensation. Inconclusive evidence suggests that this occurs following the completion of nucleation but before the vapor supply is exhausted. A calculation procedure which allowed the separation of the nuclei into a distribution of sizes, arising from a varying stability criterion and radius dependent growth rate, resulted in the establishment of a qualitatively correct distribution shape but no theoretical substantiation of an aging or coarsening mechanism. A separate application of Brownian coagulation theory to surface-averaged condensation theory resulted in the prediction that the average droplet size increased by a factor of between 2.5 and 4. No conclusion could be drawn concerning the actual existence of this size increase due to the level of uncertainty in the determination of average droplet size. February 1969; Also issued as: Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1969; Includes bibliographical references (leaves 82-87)

Boundary layer effects on airfoil lift

2019-04-10T12:33:47Z

Boundary layer effects on airfoil lift Schneider, Kurt H. (Kurt Herbert) A study of the discrepancy in lift between potential flow calculations and experiments was made. In potential flow the fluid is assumed to follow the contour of the airfoil, forming a stagnation point at the geometric center of the trailing edge. In the flow of a viscous fluid around an airfoil a boundary layer forms along the surface of the airfoil changing its effective shape. The pressure at the trailing edge is approximately equal to the static pressure at upstream infinity. Detail stagnation and static pressure and flow direction surveys were made near the trailing edge on a 50 inch chord NACA 0015 airfoil with trailing edge thickness increased to three per cent chord. By the use of thin airfoil theory, modified to include terms. of second order, good agreement with published experiments in lift and pressure distribution is obtained. Using Teledeltos paper, an electrical analog of the flow around the NACA 0015 airfoil in the tunnel was made. A method was developed for determining velocity directly from the analog. September 1958; Includes bibliographical references (leaves 48-49)

The design of axial inducers for turbo-pumps

2019-04-09T16:47:17Z

The design of axial inducers for turbo-pumps Stenning, Alan H. (Alan Hugh) In many turbopump applications it is desirable to run the pump at the highest possible speed to minimise the size and weight of the unit and facilitate matching with a drive turbine. Frequently, a limit on rotational speed is imposed by pump cavitation with its associated deterioration in performance and structural damage. For conventional single sided centrifugal pumps cavitation occurs when the suction specific speed ... exceeds 8-10,000 (1) so that for such pumps the maximum rotational speed without cavitation is determined by the flow and the suction head available. To permit operation at higher speeds an inducer or boost pump may be mounted in front of the main pump (f ig. 1). A typical axial inducer is simply a very lightly loaded axial pump which raises the pressure of the fluid sufficiently to avoid cavitation in the main pump. It has been found possible to operate inducers successfully at suction specific speeds up to 30,000, so that considerable reductions in total pump weight can be achieved when they are employed. Of course, since the inducer is simply a lightly loaded pump which is capable of handling a cavitating fluid, the functions of inducer and main pump may be combined by designing the main pump so that the inlet is lightly loaded. However, it is not always convenient to do this and in many applications conventional centrifugal pumps are still used, preceded by a separate inducer. The objective of this report is to put the design of such inducers on a rational basis by developing a method of calculating blade shapes for the optimum pressure distribution. February 1958; Includes bibliographical references (page 15)

Experiments on turbulent boundary layers along a circular cylinder with and without separation

2019-04-08T07:21:34Z

Experiments on turbulent boundary layers along a circular cylinder with and without separation Fernholz, Hans; Gibson, Paul. Massachusetts Institute of Technology. Gas Turbine Laboratory Summary: Experiments were conducted in a turbulent boundary-layer near separation along a circular cylinder with the flow in the axial direction. The pressure gradient along the axis of the cylinder could be varied such that it was possible to maintain three boundary-layer configurations close to separation or with regions of reversed flow: 1. A turbulent boundary-layer with skin friction zero. 2. A turbulent boundary layer with a separated region and reattachment further downstream with skin friction zero. 3. A turbulent boundary layer with a region of small but constant skin friction and normal separation. Pressure and skin friction along the cylinder wall,. as well as mean velocity profiles in the boundary-layer, were measured. August 1967; Includes bibliographical references

The three-dimensional turbulent boundary layer in a free vortex diffuser

2019-04-12T16:15:37Z

The three-dimensional turbulent boundary layer in a free vortex diffuser Gardow, Ernest Bernhard Experimental velocity profiles and static pressure measurements were obtained from the flow in a free vortex diffuser. The purpose of the study was to obtain additional three dimensional boundary layer data and to compare it with existing theories. Free vortex diffuser behavior under varying inlet angles was also studied. The boundary layer profiles correlated well with an existing model for three dimensional boundary layers generated by transverse pressure gradients. From this model boundary layer cross flow can be approximately predicted using a shearless flow analysis for the outer part of the boundary layer and an empirical correlation for the inner portion. At high inlet swirl angles, a separation ring followed by reattachment was found in the diffuser. January 1958; Addendum sheet inserted; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1958; Includes bibliographical references (page 27)

A two-dimensional design method for highly-loaded blades in turbomachines

2019-04-10T15:46:17Z

A two-dimensional design method for highly-loaded blades in turbomachines Dang, Thong Quoc A practical design method for highly-loaded blades in an isolated cascade is presented in this thesis. The flow is assumed to be incompressible and inviscid. The upstream inlet flow condition is taken to be uniform. The present goals of this research are to provide a practical numerical code for the design problem, and a non-linear theory which can be easily expanded to three-dimensions. The theory is based in part on the Clebsh formulation. The blade profile is determined iteratively through the blade boundary conditions using a "smoothing" technique. A practical numerical code is presented for the design problem using "partial smoothing". The program gives very fast convergence solutions with satisfactory accuracy for practical solidity range.; A practical design method for highly-loaded blades in an isolated cascade is presented in this thesis. The flow is assumed to be incompressible and inviscid. The upstream inlet flow condition is taken to be uniform. The present goals of this research are to provide a practical numerical code for the design problem, and a non-linear theory which can be easily expanded to three-dimensions. The theory is based in part on the Clebsh formulation. The blade profile is determined iteratively through the blade boundary conditions using a "smoothing" technique. A practical numerical code is presented for the design problem using "partial smoothing". The program gives very fast convergence solutions with satisfactory accuracy for practical solidity range. Includes bibliographical references; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1983.

Rotor wake transport in turbomachine stators

2019-04-10T12:33:46Z

Rotor wake transport in turbomachine stators Kumar, Ajay; Kerrebrock, Jack L. The mechanism of rotor wake interaction with stators has been examined experimentally by using helium, injected into the rotor wakes, as a tracer for the wake fluid. Time averaged helium Drofiles downstream of the stator, measured with a thermal conductivity cell, indicate the time averaged distribution of rotor wake fluid at the stator exit. The results are in qualitative agreement with the wake transport theory of Kerrebrock and Mikolajczak, but indicate the need for accounting for differential radial drifts of the wake fluid which encounters the motion and pressure sides of the stator blades. They also indicate that the wake transport theory is valid only when the stators flow is not separated. February 1971; Includes bibliographical references (leaf 12)

A new transformation and integration scheme for the compressible boundary layer equations, and solution behavior at separation

2019-04-12T22:52:15Z

A new transformation and integration scheme for the compressible boundary layer equations, and solution behavior at separation Drela, Mark A new coordinate and variable transformation for the two-dimensional boundary layer equations is presented. The normal coordinate is stretched with a scaling length determined by the local solution. The boundary layer thickness is then essentially constant in computational space for the most types of flows, including separation bubbles and rapidly growing turbulent boundary layers. Similarity solutions can be obtained for all wedge flows. Two finite difference schemes are presented: the Shifted Box Scheme and the Double-Shifted Box Scheme. Both schemes are more resistant to streamwise profile oscillations than the standard Keller's Box Scheme. All governing equations, including the turbulence model, are solved simultaneously as a fully coupled system. This is faster and more robust than conventional weak-coupling iteration schemes. The solution scheme implementation presented makes no restriction on one boundary condition. Any point or integral quantity such as edge velocity, wall shear, displacement thickness, or some functional relationship between two or more of such quantities can be prescribed. The behavior of the boundary layer solution near separation is investigated. It is demonstrated that non-unique solutions always exist whenever an adverse pressure gradient is specified. This bifurcation of the solution is responsible for inability of calculations with prescribed pressure or edge velocity to be carried past separation. Includes bibliographical references

Optimal mistuning for enhanced aeroelastic stability of transonic fans

2019-04-12T22:40:48Z

Optimal mistuning for enhanced aeroelastic stability of transonic fans Hall, Kenneth C.; Crawley, Edward F. An inverse design procedure was developed for the design of a mistuned rotor. The design requirements are that the stability margin of the eigenvalues of the aeroelastic system be greater than or equal to some minimum stability margin, and that the mass added to each blade be positive. The objective was to achieve these requirements with a minimal amount of mistuning. Hence, the problem was posed as a constrained optimization problem. The constrained minimization problem was solved by the technique of mathematical programming via augmented Lagrangians. The unconstrained minimization phase of this technique was solved by the variable metric method of Broyden, Fletcher, and Shanno. The bladed disk was modelled as being composed of a rigid disk mounted on a rigid shaft. Each of the blades were modelled with a single tosional degree of freedom. Adamcyzk and Goldstein's linearized aerodynamic model for the unsteady moment coefficients in a supersonic cascade was applied at the typical section. The resulting non-self-adjoint eigenvalue problem is of the form Aq = XBq. The eigenvalues and eigenvectors of this eigenvalue problem were found by a fourth-order Runge-Kutta line integration of the derivatives of the eigenvalues and eigenvectors. It was shown that mass mistuning does not introduce damping into the system, and that a necessary but not sufficient condition for stability is that the blade be self damped. The results of the optimization showed that an optimally mistuned rotor can achieve a given stability margin for a much lower level of mistuning than alternate mistuning. However, it was shown that optimal mistuning is sensitive to errors in mistuning. Small errors in the implementation of optimal mistuning can severely reduce the gains in stability achieved by optimal mistuning. Alternate mistuning, on the other hand, is relatively insensitive to errors in mistune. Carried out in the Gas Turbine and Plasma Dynamics Laboratory, MIT, supported by the NASA Lewis Research Center under grant NSG-3079; November 1983; N84-16180 --Microfiche header; Bibliography: p. 94-96

Flutter and forced response of mistuned rotors using standing wave analysis

2019-04-10T15:29:08Z

Flutter and forced response of mistuned rotors using standing wave analysis Bundas, David J.; Dugundji, John The torsion flutter and forced response of tuned and mistuned cascades is examined using a standing wave approach, as opposed to the traditional traveling wave approach used in cascades aerodynamic models. The motion of the blades and the corresponding cascade aerodynamic loads are expressed in terms of standing wave modes and arbitrary transient motion, by fitting the sinusoidal force coefficients in terms of ratios of polynomials in the Laplace transform variable, sometimes referred to as Pade approximants. Whitehead's two dimensional, incompressible aerodynamic model is expressed in this transient form and is used to solve the flutter and forced response problems. Results obtained with the transient, standing wave analysis for the flutter and forced response are similar to those obtained by traveling wave analyses, but they yield the transient decay rate associated with vibrations of the blades, as opposed to the structural damping required for flutter obtained by the traveling method. The standing wave analysis presented here may prove to be more versatile for dealing with certain applications such as mistuned rotors, "localized" blade flutter, low engine order excitation, transient impulses on the rotor, and coupling in with forced response and dynamic shaft problems. First published as the author's thesis (M.S.) in the M.I.T. Dept. of Aeronautics and Astronautics, 1983; Massachusetts Inst. of Tech. --Microfiche header; March 1983; N84-24586 --Microfiche header; NASA Grant no. NAG3-214; Includes bibliographical references

Lifting-line theory for subsonic axial compressor rotors

2019-04-11T09:01:18Z

Lifting-line theory for subsonic axial compressor rotors McCune, James E. (James Elliot); Dharwadkar, Shashikant Prabhakar The three-dimensional compressible vortex theory of an axial compressor rotor or ducted fan is extended by relating blade loading to blade geometry in the lifting-line approximation. The resulting integral equation, which is valid up to high subsonic Mach numbers, is solved for both design and off-design problems. It is shown that three-dimensional effects must be taken into account, for rotors with non-uniform spanwise loading, in order to obtain accurate predictions of flow angles and other performance parameters. July 1972; Includes bibliographical references (leaf 25)

The time dependent magnetohydrodynamic generator

2019-04-11T09:01:18Z

The time dependent magnetohydrodynamic generator Oliver, David A. (David Anthony), 1939- Introduction: Low magnetic Reynolds number magnetohydrodynamic generators as would be utilized in power plants are conceived of as steady state D.C. devices. Unsteady phenomena may exist in such generators however. Fluctuations induced fluid mechanically or through combustion may develop into amplifying magnetoacoustic instabilities. In addition to possible instabilities appearing in the bulk of the flow, there exist other important unsteady situations in which the generator must operate. These include the transient response of the generator to changes in load conditions, start up and shut down, coupled unsteady interactions of the generator with the power grid, and the response of the generator to faults such as electrode wall break down or the sudden imposition of a short along the insulator wall. Many of these unsteady situations involve large changes in the amplitudes of the fluid mechanical and electrical variables and therefore require a large amplitude unsteady theory.; In the present work we present a description of unsteady quasi one dimensional magnetohydrodynamic generator flows and propose a highly accurate explicit time dependent method of predicting the time response of such flows. This method of calculation is capable of treating MHD flows under subsonic, supersonic, and transonic flow conditions, arbitrary nonuniformities in electric fields and currents, strong interaction parameters, and with normal shocks present in the duct. In Part II a formulation of the appropriate magnetohydrodynamic fluid equations for quasi-one-dimensional flow is given. In Part III a description of the Lorentz forces and Lorentz power in the flow is given. In Part IV a finite difference operator for the unsteady nonlinear MHD equations is proposed and its stability and accuracy characteristics are described.; In Parts VI and VII, illustrations of this analysis are presented for two unsteady generator situations of contemporary interest: (1) the growth and evolution of large amplitude magnetoacoustic fluctuations under conditions of strong interaction, and (2) the behavior of the generator to changes in loading. March 1974; Includes bibliographical references (page 24)

The display of multi-dimensional flows in turbomachinery

2019-04-12T16:17:53Z

The display of multi-dimensional flows in turbomachinery Probst, Harris Carey; Oliver, David A. (David Anthony), 1939- Introduction: As part of a general development of computational techniques for multidimensional flows through turbomachine passages and over turbomachine blading at the M.I.T. Gas Turbine Laboratory, display techniques and programs have been developed for the visualization and interpretation of the computed flows. These display programs have been developed for the Adage AGT-30 system implemented at the Electronic Systems Laboratory at M.I.T. In the present report two major programs are described and illustrated. These are programs for the display of the turbomachine blading and flow passage geometry and for the display of contours of any scalar fluid variable in the flow passage. The manner in which the system is used is as follows. The turbomachine blading and flow passage geometrical data exist on an Adage tape. The output of the fluid dynamic calculation which is presently done on the OS/370 system is connected on OS/370 to an Adage compatible tape. This tape which represents the computed flow is then viewed on the Adage system. August 1972

Noise generation by shock-turbulence interaction

2019-04-11T09:01:17Z

Noise generation by shock-turbulence interaction Kiang, David Tien Sik; Tam, Christopher Kwong Wah; Kerrebrock, Jack L. The noise produced by convection of turbulence through an oblique shock wave has been measured and compared to theoretical predictions by Ribner and Kerrebrock. There is excellent agreement with the theoretical prediction that, for a fixed turbulent input, the downstream noise pressure (divided by the mean pressure), should first increase very rapidly, and then decrease as the normal Mach number of the shock is increased from unity to values of the order of 1.5. This behavior implies that a part of the noise from supersonic jets should behave similarly, with a sharp increase, then a decrease as the nozzle pressure ratio is raised from unity. October 1970; Includes bibliographical references (leaf 10)

Attenuation of sound in lined ducts

2019-04-10T22:52:05Z

Attenuation of sound in lined ducts Cho, Young-chung; Ingard, K. Uno Extensive computations have been carried out of the attenuation characteristics of resonator and porous type duct liners in rectangular and circular ducts. First the frequency dependence of the attenuation constant and the phase velocity of the fundamental duct mode are obtained for a large number of duct and liner parameters. Then, assuming that the fundamental mode is dominant in the lined duct element, the octave band transmission losses have been computed. The effect of the shape of the input spectrum is discussed and shown explicitly for three different spectra, namely, a "flat" spectrum and spectra with slopes of + 6 dB per octave and - 6 dB per octave, respectively. Finally the effect of the length of the duct liner on the octave band transmission loss has been computed. It is found that the octave band transmission loss does not increase linearly with the length of the duct liner, particularly in regions where the attenuation varies strongly with frequency. September 1974; Includes bibliographical references (page 264)

The prediction of inter-electrode breakdown in magnetohydrodynamic generators

2019-04-11T09:01:15Z

The prediction of inter-electrode breakdown in magnetohydrodynamic generators Oliver, David A. (David Anthony), 1939- Introduction: In this paper, a method of calculation of inter-electrode electrical breakdown phenomena in magnetohydrodynamic generators is presented. Interelectrode breakdown is observed to occur in experimental MHD generators with channel pressures near atmospheric whenever the Hall voltage between adjacent electrode segments exceeds a critical value which varies between 30 and 100 volts. When breakdown occurs, the local Hall voltage across the segments decreases suddenly and a large axial current is believed to flow over the insulator segment. If the generator volume to surface area is large enough, the breakdown current can drive into the electrode wall under the action of the Lorentz force and cause physical destruction of the channel wall.; Since the breakdown development is an inherently unsteady electrical shorting occurring in general within a turbulent, compressible fluid mechanical boundary layer, the description of the flow will be framed in terms of the turbulent fluid equations with Lorentz forces present. The time scale for development of the breakdown arc for MHD generators operating under power generation conditions can be estimated to be of the order of 10-3 sec. The turbulent fluctuations at the Reynolds numbers of interest have time scales of the order of 10-6 sec. Thus, the fluid will be described in terms of mean velocity, pressure, temperature, etc., over the turbulent time scale, but these mean variables will be considered to be functions of time over the electrical breakdown time scale. The breakdown arc can in general be expected to be a three dimensional phenomenon. Experimental evidence bearing on this point in MHD generator channels is at this time still contradictory.; Examination of the electrode walls of combustion driven generators reveals definite spots along the magnetic field direction of the electrode at which arc damage occurs. In closed cycle generators, however, careful image converter diagnostic of the discharge structure in the magnetic field direction indicates that electrothermal arc streamers which are significantly nonuniform in the axial direction across the electrode are quite uniform in the magnetic field direction along the electrode and essentially layered or two dimensional structures. In the present study we shall treat the two dimensional breakdown arc within the context of a two dimensional boundary layer theory. Three dimensional models can follow the initial results of a two dimensional model if the two dimensional model proves inadequate in describing experimental observations. In Part II a formulation of the unsteady fluid equations for the electrode wall boundary layer is presented.; In Part III expressions for the turbulent transport terms are presented and discussed. In Part IV the electrical problem is formulated and the procedure for calculation of the instantaneous electric field and current distribution corresponding to the instantaneous distribution of velocity and electrical conductivity in the boundary layer region is presented. In Part V a computational procedure for the solution of the unsteady boundary layer equations with Lorentz forces is described. March 1974; Includes bibliographical references (page 24)

The M.I.T. Blowdown Compressor Facility

2019-04-10T22:52:04Z

The M.I.T. Blowdown Compressor Facility Kerrebrock, Jack L. A Blowdown Compressor Test Facility has been developed which allows aerodynamic testing of full-scale compressor stages at low cost. The rotor is brought to speed in vacuum, a diaphragm is opened, and the test gas allowed to flow for a time of the order of one tenth second, during which the rotor is driven by its own inertia. Both "steady state" performance evaluation and detailed time resolution of the flow on the blade-passing time scale have been demonstrated in a preliminary way for a two-foot diameter transonic rotor with tangential Mach number of 1.2 and nominal pressure ratio of 1.6. May, 1972; Includes bibliographical references (leaf 70)

Small disturbances in compressor annuli with swirl, throughflow and entropy variation

2019-04-12T16:17:51Z

Small disturbances in compressor annuli with swirl, throughflow and entropy variation Kerrebrock, Jack L. Introduction: Control of the radiation of sound from the compressors and turbines of jet engines depends to a great extent on understanding of the propagation of acoustical modes in the ducting, the general design approach being to choose the numbers of blades in interacting rows so that no propagating mode will be strongly excited. The conditions for non-propagation or "cutoff" are therefore critical to this procedure. Another application of modal analysis is found in the linear three dimensional flow theory of turbomachinery. Here the complete isentropic flow field of the compressor rotor is represented as a superposition of normal modes. To date, most such modal treatments have either neglected the effect of average flow velocity in the turbomachine duct, or considered the acoustical disturbances to propagate in a gas at rest in a coordinate system moving with the average flow velocity.; This approach is correct if the resulting (moving) coordinate system is inertial, but in general is not correct for rotating coordinate systems. In the context of compressor analyses, it is valid for uniform axial flow, as applied by McCune, for example, but incorrect for swirl, as applied by Morfey.Indeed, as we shall show, the classical technique of dividing small disturbances into the three classes of vorticity, entropy, and sound fluctuations, which do not interact to first order, is not valid in rotating flows. Thus, a generalization of the concepts of sound and turbulence is needea. Such a generalization will not be achieved in the present work, but it is hoped that a few steps will be made in this direction. The general equations for pressure disturbances in an inhomogeneous swirling gas have been given by Blokhintsev, who also obtained the general equation for an isentropic gas.; Apparently the only other analyses of pressure wave behavior in rotating fluids are those of Salant and Sozou. The former considered the effects of a solid body rotation on the symmetric normal modes, i.e., modes with no tangential nonuniformity. The latter treated the same type of disturbance in a Rankine vortex. The main purpose of the present analysis is to provide a consistent modal acoustic treatment for compressor annuli with large swirl and throughflow, and with radial variations of entropy. The mean flow will be assumed uniform in the axial and tangential directions, so that the results are applicable only sufficiently far upstream and downstream of blading that the first order variations in these directions have died out. As might be expected, the analysis is nevertheless somewhat complex.; While a general treatment will be given, for arbitrary radial variations of entropy and tangential and axial velocity, analytical solutions for the radial eigenfunctions are available only for some special cases. These do include three important cases, namely, 1) isentropic flow with solid body rotation and constant axial velocity, 2) isentropic flow with free vortex rotation and constant axial velocity, and 3) flow with negligible mean velocity but with radial entropy variation. The first of these represents the conditions behind inlet guide vanes, though not with complete consistency, as will be noted below. The second represents quite accurately the conditions behind high-work fan rotors, except for the effects of entropy variation. The last case gives some insight into the effects of such variations. October 1970; Includes bibliographical references (leaf 25)

The development of a perturbed, incompressible, turbulent boundary layer

2019-04-10T22:52:03Z

The development of a perturbed, incompressible, turbulent boundary layer Handa, Hisayuki The response of a fully-developed equilibrium turbulent boundary layer to a small disturbance was observed experimentally under low-Mach number conditions: a turbulent boundary layer in an axisymmetric channel under zero pressure gradient was perturbed by a single fence like two dimensional protuberance, and the subsequent development of the velocity profile, the turbulent-shear-stress profile, and the wall shear stress was recorded by a constant-temperature hot-wire anemometer and a Preston tube. The height of the five roughness elements used ranged from 0.011 to 0.100 inches (2-15% of the original boundary layer thickness). The perturbation effects are observable only in the vicinity of their origin and each parameter undergoes an individual recovery process. The wall shear stress exhibits a unique style in its development. A perturbed turbulent-shear-stress profile shows a maximum as in the case of a turbulent boundary layer in an adverse pressure gradient. The analysis of the data has revealed a self-preserving feature of the developing velocity profile in form for small enough disturbances: the wall region of the boundary layer is in a local equilibrium after 30 roughness-heights and the unaffected outer layer retains its original characteristics. January 1969; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1969; Includes bibliographical references (leaves 27-29, 2nd group)

Condensation of supersaturated organic vapors in a supersonic nozzle

2019-04-08T07:26:31Z

Wall-shear-stress and laminarisation in accelerated turbulent compressible boundary-layers

2019-04-12T16:17:51Z

Wall-shear-stress and laminarisation in accelerated turbulent compressible boundary-layers Nash-Weber, James Ludlow Turbulent-laminar transition in compressible, steeply-accelerated, adiabatic, turbulent boundary layers on a smooth wall was investigated experimentally in the ranges of Mach and Reynold's numbers typical of nozzles used in propulsive devices. Correlation of the present and previously published data suggests that the transition of such a shear layer may be predicted by consideration of its trajectory on a plane having an acceleration parameter K and a Reynold's number R [sigma] 2 as coordinates. An ab initio design method has been developed, based on these findings, which will ensure laminar flow before and at the throat of a sufficiently small nozzle operating at sufficiently small total pressure. A new type of surface-pilot was developed and calibrated and used to measure wall shear stresses in both transitional and non transitional flows. Decrease of wall shear-stress in lamina rising flows was found. General-purpose computer programs for data-reduction, surface-pilot calibration and interpretation and boundary layer development predictions were developed. April 1968; Includes bibliographical references

Effect of swirl on turbulent jets in ducted streams

2019-04-09T19:01:02Z

Effect of swirl on turbulent jets in ducted streams Morton, Harmon Lindsay An experimental and theoretical program of research has been carried out to determine the effect of swirl on the mixing of a turbulent jet in a ducted stream. The term swirl is used to describe a flow pattern within the jet where mean streamlines are spirals. It has been found experimentally that the mixing rate of a turbulent jet with a surrounding stream can be increased by a factor of three due to the presence of swirl. Three dimensionless parameters, one of which is the jet nozzle to test section diameter ratio, have been used to describe the experimental results. The well-known integral technique has been used to predict the mean flow field of the turbulent jet in a ducted stream. Velocity profiles and turbulent eddy viscosity have been evaluated from turbulent free jet data. The increased mixing due to swirl has been explained in part by the adverse pressure gradient along the jet centerline associated with a decaying swirl and also by an increase in the magnitude of the Reynolds shear stresses within the jet. The calculation procedure divides the flow into two regions - one before the jet attaches to the wall and one after. Two possible correlations giving first order effects of swirl strength on local eddy viscosity are found to give good results for both the ducted jet and the free jet (a jet exhausting into a still fluid). Comparison of data with theory for the axial position of jet attachment is good for all cases studied. December 1968; Includes bibliographical references (leaves 46-47)

On the theory of shear flow

2019-04-11T09:01:14Z

On the theory of shear flow Hawthorne, W. R. (William R.) In this report are collected together some introductory notes on the theory of the three-dimensional, steady flow of an inviscid fluid. The equations of motion are discussed and transformed and expressions for the streamwise or secondary vorticity derived both for incompressible and compressible flow. A special form of the Clebsch Transformation is used to show that three linearizing approximations are possible, depending on the order of magnitude of the stagnation pressure gradient and the disturbance to the upstream flow. The equations for each approximation are developed in turn and are applied to some elementary examples of the flow through actuator discs, over slender bodies and thin airfoils--isolated and in cascade, the flow in curved channels, and about thick struts, airfoils and through cascades of large deflection. October 1966; Includes bibliographical references

Wave drag in transonic axial compressors

2019-04-12T16:17:50Z

Wave drag in transonic axial compressors Okurounmu, Olufemi Profiles of fluid properties, including flow angle, static and total pressures have been obtained behind a free wheeling 8" diameter transonic rotor. The latter consists of 40 blades with double circular arc profiles, a hub to tip diameter ratio of 0.80 and a mean solidity of 0.94. The variation of stagger angle along the blade span is such that the local relative velocity is aligned with the blade chord at a design point corresponding to an inlet axial Mach number of 0.6 and a rotor speed of 35,000 RPM. The profiles show strong evidence of the existence of standing acoustic waves in the flow passage at transonic relative Mach numbers. A strong drag rise is observed at subsonic relative Mach numbers (MT) close to unity, the slope of the drag curve being negative at MT = 1, but turning positive again shortly after MT = 1. For MT < 1, a remarkably good correlation is observed between the spanwise mean of the measured drag and previous 2-D pressure drag measurements on similar profiles. At low supersonic relative Mach numbers, the drag due to shocks in the blade passages appears to overshadow the wave drag, and as yet, there is no definitive way to isolate the contribution of the wave drag experimentally. Computed values of the wave drag at these speeds, based on McCune's analysis for a non-lifting blade row, are "compared" with the measured drag. A linearized theory is presented for obtaining the induced drag of an axial compressor blade row subjected to- any- arbitrary blade loading distribution. The blades are replaced at their leading edges by bound vortex lines of varying strength along the span, and the induced drag obtained from the induced velocity field of the resulting trailing helical vortex sheets. Use of this lifting line approach restricts the useful range of the theory to relative Mach numbers less than unity, since such a quasi 2-D theory would not be applicable to transonic flows which are believed to be inherently three dimensional. November 1967; Also issued as: Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1968; Includes bibliographical references

Boundary layer separation in internal flow

2019-04-12T16:15:35Z

Boundary layer separation in internal flow Moses, Hal Lynwood; Chappell, John R.; Goldberger, Tomas An investigation of incompressible turbulent boundary layer separation in internal flow is presented with experimental results for a variable geometry, two-dimensional diffuser and two conical diffusers. A simple analytical model is adopted, which consists of wall boundary layers and a one-dimensional, inviscid core. Several approximate boundary layer methods and the possibility of extending them into the separated region are examined. With a limited amount of separated flow, the calculated pressure agrees reasonably well with the experimental results and gives a fair indication of maximum diffuser performance. The limitations of the model to the more general problem, as well as the problem of singularities and downstream stability, are discussed. September 1965; Includes bibliographical references

Upstream history and apparent stress in turbulent boundary layers

2019-04-12T16:15:36Z

Upstream history and apparent stress in turbulent boundary layers Goldberg, Perry A comprehensive experimental and analytical study specifically designed to investigate upstream history and apparent stresses in incompressible, two-dimensional, turbulent boundary layers has been conducted. Hot-wire measurements of turbulent shear stress and longitudinal turbulence intensity, as well as velocity profiles and wall shear stress measurements, were made for six different pressure distributions. It was found that the turbulent shear stress is dependent upon the upstream history of the flow and not a unique function of the local velocity profile. A simple equation for the dissipation integral . . . with a constant K was found to represent the data well. This expression was used with the mean-flow energy integral equation to obtain a practical method for predicting turbulent boundary layer behavior which accounts for upstream history. The predictions made with this method for the six pressure distributions of this study and for others extracted from the literature agreed well with the experimental data. May 1966; Also issued as: Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Thesis. 1966. Ph.D; Includes bibliographical references (leaves 43-45, second group)

Separation of turbulent, incompressible flow from a curved, backward-facing step

2019-04-08T08:39:45Z

Thin airfoils in rotational flow

2019-04-10T12:33:45Z

Thin airfoils in rotational flow Kotansky, Donald Richard The problem of rotational or shear flow about thin airfoils has been investigated theoretically and experimentally. The theoretical approach is based on the concept of a lifting line in a bounded shear flow whose primary flow velocity profile may be expressed in terms of elementary linear, hyperbolic, and / or circular functions. The solution of the linearized equations of motion is reduced to the solution of a characteristic value problem whose form is dependent on the geometry of the primary flow. The characteristic value problem is solved for four different velocity profiles including that of a monotonic-matched linear profile ( a layer of constant vorticity fluid bounded by layers of uniform flow ) which serves as a model for the experimental shear flows. The experimental work includes the measurement of local lift coefficients and spanwise lift distributions on thin symmetrical airfoils in monotonic shear flows for three values of the ratio of airfoil chord to shear layer thickness. The results of the lifting line theory show good agreement with the experimental data within the range of applicability, i.e. within the linear region of the CL, a relationship and for flow geometries where the distortion ( spanwise convection ) of the surfaces of constant stagnation pressure is negligible. The assumption that the local lift coefficient is a function only of the local angle of attack and the two-dimensional characteristic of the airfoil section ( a fundamental assumption of lifting line theory ) is investigated experimentally through a consideration of local pressure coefficient distributions. An approximate correction to the lifting line theory is suggested for flows in which the distortion of surfaces of constant stagnation pressure cannot be neglected. September 1965; Also issued as: Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Thesis. 1966. Sc.D; Includes bibliographical references (leaves 88-90)

Vortex decay in a conical diffuser

2019-04-12T16:15:34Z

Vortex decay in a conical diffuser So, Kwan-Lok The behavior of vortex flow in a conical diffuser has been studied in this report. The flow considered here is a steady, incompressible, axially symmetric one. The present experimental investigation has resulted in the establishment of five flow regimes. These regimes represent three basic types of rotating flow and two transitional phenomena. In Regime 1 the flow is a laminar, one-celled vortex. In Regime 3 the flow is also a one-celled vortex, but turbulent, In Regime 5 the flow is a turbulent, two-celled vortex. Regime 2 represents the transition of a one-celled vortex flow from laminar to turbulent. This transition is characterized by the formation of a bubble along the axis. Regime 4 shows another transitional phenomenon. This transition is the breakdown of a two-celled vortex into a one-celled vortex, but the character of this breakdown is still not fully explored. These regimes can be considered as the steps that the flow in the diffuser must go through as the flow rate or swirl is increased. The number associated with these regimes indicates the order of change from one regime to another. In Regimes 1,3, and 5, similarity in the velocity profiles does exist, but not in Regimes 2 and 4. For simplicity Regime 3 was selected as the basis for a theoretical model. The initial requirement that the total head in the outer region of the flow be conserved proved unsuccessful. When this condition was dropped in favor of the moment of axial momentum, a theoretical development at least qualitatively in agreement with the observed vortex decay is achieved. It is felt that the neglect of turbulent shear stresses in the analysis is largely responsible for the discrepancy that exists between theory and experiment. September 1964; Errata sheet inserted; Includes bibliographical references; Preliminary report

Wake induced blade forces in turbo-machines

2019-04-10T12:33:44Z

Wake induced blade forces in turbo-machines Lefcort, Malcolm D. (Malcolm David) The wake interaction problem in a turbo-machine has been simulated in a water table. The pressure distribution over a compressor blade during the passage of a wake shed by an upstream wake generator has been determined experimentally using specially developed piezo-electric pressure transducers. The results indicate that the theory developed by R. X. Meyer for wakes that are very thin with respect to the blade chord is generally valid. The theory has been extended to cover the case of wakes of finite thickness. The peak unsteady force amounted to at least 23% of the steady lift force assuming a steady lift coefficient of 1. November 1962; Includes bibliographical references (leaves 45-46)

Centrifugal effect on the boundary layer on a blade of an axial turbo-machine

2019-04-12T16:17:55Z

Centrifugal effect on the boundary layer on a blade of an axial turbo-machine Olsson, Erik K. A. A study of the effect of centrifugal force acting on the turbulent boundary layer of a blade in a turbo-machine is presented. The study includes experimental work conducted in an apparatus featuring an annular cascade of compressor blades, designed to simulate the flow in a compressor. This is a case of three-dimensional turbulent boundary layer flow end the objects of the study were to find the magnitude of the cross-flow and gain a better understanding of the skewed boundary layers. It is found that the cross-flow which develops in the boundary layer is small with velocities of the order of 1/10 of the through-flow velocities. The study further resulted in the development of a model of skewed, turbulent velocity-profiles, involving two "universal" analytical functions and four parameters. This model has been used with success to describe the measured velocity-profiles. The use of the model and the general result that the cross-flow is small has made it possible to find solutions to the boundary layer integral equations written in a "streamline" coordinate system. Application of the calculation method for the experimental data has been made successfully. A loss parameter is defined and an extension to include the crossflow losses is suggested. April 1962; Issued also as: Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1962; Includes bibliographical references

An investigation of cavitating inducers for turbopumps

2019-04-09T17:31:23Z

An investigation of cavitating inducers for turbopumps Mullan, Philip Joseph The experimental performance of two axial inducers is presented. One of the :designs is analytical and includes radial equilibrium considerations. The other is a simple helix, with a constant pitch angle. The performance data consists of two parts; conventional non-cavitating pump performance, and performance with cavitation. High speed pictures of the cavitation formations were taken. May 1959; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1959; Includes bibliographical references (leaf [18])

Skewed turbulent boundary layers

2019-04-10T22:52:07Z

Skewed turbulent boundary layers Nelson, Warren G. (Warren George) The problem of predicting the growth of incompressible, skewed, turbulent boundary layers on smooth surfaces is considered. It is supposed that sufficient initial information and a complete knowledge of the external pressure distribution is given. A computation scheme is devised which makes use of the two momentum integral relations and an auxiliary equation. The formulation of the latter is based on the empirical observation that if a velocity profile is plotted in a holograph plane the outer portion is nearly always linear. A theoretical means of describing velocity distributions is formulated. These theoretical profiles contain two "universal"- functions and five parameters that are functions of the surface coordinates only. The "universal" functions are derived analytically and. compared with experiment. Finally, a comparison of theoretical and experimental velocity profiles suggests that the proposed computation scheme is only applicable to situations where gradients of flow quantities in the cross-flow direction are not too large. Therefore, the scheme is probably better suited to the external flow over wings, etc., than to flows in turbomachinery. August 1959; Includes bibliographical references (pages [48]-[49])

The influence of tip clearance on stall limits of a rectilinear cascade of compressor blades

2019-04-12T16:17:54Z

The influence of tip clearance on stall limits of a rectilinear cascade of compressor blades Khabbaz, Ghassan R. (Ghassan Raji) An experimental study of the influence of tip clearance on the stall limits of compressor blades was conducted on a two dimensional rectilinear cascade. By using the mirror and image technique the end wall boundary layer in the gap was dispensed with. The clearance was found to relieve the pressure gradient and to retard stalling. The loading on the blade near the slot was found to be higher than that at a distance further along. August 1959; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1959; Includes bibliographical references (leaves 20-21)

Asymmetric inlet flow in axial turbomachines

2019-04-12T16:17:53Z

Asymmetric inlet flow in axial turbomachines Seidel, Barry S. (Barry Stanley) A modified actuator disc analysis is made which, through an improved prediction of the blade forces, attempts to give closer correspondence with experiment than the previous theory. The fluid is assumed inviscid and incompressible. Perturbations to the two-dimensional flow through an isolated blade row are considered. The steady flow equations of motion and continuity are linearized. According to experiments conducted on an isolated compressor rotor, the present theory offers an improvement, compared to previous theory, in the prediction of distortion attenuation, effects of flow rate, and effects of varying chord/spacing ratio. May 1959; Includes bibliographical references (leaves 53-55)

A secondary flow approach to the inlet vortex flow field

2019-04-10T11:41:58Z

A secondary flow approach to the inlet vortex flow field Viguier, Henri Charles A theoretical study is presented of the fluid mechanics of the inlet vortex (or ground vortex). The vorticity field associated with this phenomenon is investigated using a secondary flow approach. In this approach the flow is assumed to be composed of an irrotational primary flow and a weak shear flow, with the vortex filaments associated with the latter being regarded as convected (and deformed) by the former. The potential flow field induced by the inlet-ground plane combination is computed using the three-dimensional panel method code developed by Hess, Mack and Stockman. Using this analysis, material lines (which coincide with vortex lines) can be tracked between a far upstream location, where the vorticity can be taken as known, and the engine face location. The deformation of the material lines thus shows directly the generation and amplification of the streamwise component of vorticity which is responsible for the velocity distortion at the compressor face. Two representative flow configurations are considered, one with headwind only and one with the flow at forty-five degrees to the inlet axis of symmetry. The results so far yield only qualitative information; however they do appear to provide some insight into one mechanism of inlet vortex formation. Includes bibliographical references

Prediction of three-dimensional compressible turbulent boundary layers on transonic compressor blades

2019-04-10T15:55:52Z

Prediction of three-dimensional compressible turbulent boundary layers on transonic compressor blades Usab, William J., Jr. (William James) A small crossflow approximation to the full three dimensional compressible turbulent boundary layer equations for turbomachine blade rows is developed by taking advantage of the nature of blade geometry and inviscid flow field when an intrinsic coordinate system is used. The resulting system of equations is solved by Keller's box scheme, providing the capability of numerically calculating compressible turbulent boundary layers on transonic compressor blades to a good approximation. The scheme is checked with two known solutions of incompressible flow over unloaded zero thickness blades. It is then applied to the first stage of a NASA Low-aspect-ratio rotor blade for which the inviscid flow field is available. The results give insight to the three-dimensional boundary layer character of transonic compressor blades, caused by an imbalance of centrifugal and Coriolis forces within the boundary layer. Includes bibliographical references

Experiments on turbulent boundary layers along a circular cylinder with and without separation

2019-04-12T16:17:52Z

Detailed time resolved measurements and analysis of unsteady flow in a transonic compressor

2019-04-10T19:14:57Z

Detailed time resolved measurements and analysis of unsteady flow in a transonic compressor Ng, Wing Detailed time and space resolved measurements for a transonic compressor stage have been completed in the MIT Blowdown Compressor Facility. The stage studied was a new first stage for a NASA two-stage machine which incorporated low-aspect-ratio blading. This rotor has an inlet hub/tip ratio of 0.375, aspect ratio of 1.56 and an inlet relative Mach number of 1.38. The purposes of the test were to compare the results obtained by the Blowdown technique with those found by steady state testing at NASA Lewis Research Center, and to provide new time resolved data on the blade-to-blade flow in the rotor and stator. Data were obtained by surveys with a five diaphragm high frequency response probe and by tip casing transducers. The stage was tested at 100% design speed. Time resolved estimates of efficiency were obtained by direct measurement of stagnation pressure together with calculation of stagnation temperature by the Euler equation using measured tangential flow Mach number. Test results showed that the rotor achieved an adiabatic efficiency of 0.895 at a total pressure ratio of 1.677. The stage achieved an adiabatic efficiency of 0.862 at a total pressure ratio of 1.658. Corrected mass flow at design was measured to be 33.3 Kg/s with respect to air. Time averaged flow quantities in general agree very well with results from steady state tests at NASA Lewis Research Center. A significant difference was observed in the variation of efficiency with radius, with a low efficiency region near mid-span not observed in the steady state testing. Moreover, the measured rotor efficiency in the "core flow" between the blade wakes for the supersonic region is lower than can be explained by normal shock losses. Large streamwise vorticity is observed at the blade trailing edge in the inner half of the annulus, which may be associated with shock termination at the sonic radius. Includes bibliographical references

Three-dimensional vorticity-induced flow effects in highly-loaded axial compressors

2019-04-09T17:04:15Z

Three-dimensional vorticity-induced flow effects in highly-loaded axial compressors Tan, Choon Sooi A new analytical method is proposed for the study of flow through highly-loaded turbomachine stages. The technique is used in the present study in order to: (i) analyze the three-dimensional induced effects of the viscous blade wakes in an isolated rotor; and (ii) to study the effects of the passage of distorted flow through an axial compressor rotor or stator. In Part I (GT&PDL Report Number 141), it is found, in contrast with the more familiar situation behind aircraft wings, that the induced effects of the vorticity in the (viscous) wakes are important in practical axial turbomachinery; for example, the flow angles through highly-loaded rotors are modified to a significant extent by such wake effects. The induced disturbances grow in strength within a certain distance downstream of the blade row before beginning to decay inversely with such axial distance.; In agreement with earlier predictions, pressure disturbances and vorticity disturbances cannot be decoupled in swirling flow. Similarly, in part II (GT&PDL Report Number 151), it is found that major differences arise on comparing two-dimensional with three-dimensional analyses, both for rectilinear and for annular configurations. Further, only the last of these three-dimensional analyses can adequately describe the true flow phenomena in highly-loaded turbomachines. This is because such a description properly includes both centrifugal effects together with two important distinct types of vorticity: the trailing vorticity and the vorticity associated with any stagnation pressure gradients present. Such an analysis predicts, a strongly persisting downstream pressure field which in many cases increases before again beginning to decay inversely with the axial distance downstream, both for free-vortex stators and rotors.; By contrast, three-dimensional wheel flow analysis predicts indefinitely persisting downstream disturbances. Further, a purely two-dimensional theory indicates for a stator, the downstream static pressure to be uniform, while even a three-dimensional rectilinear cascade theory would predict only an exponentially decaying pressure field. The amplitude of the above persistent downstream disturbances decreases for free-vortex downstream flow as the number of significant circumferential harmonics of the inlet distortion increases. These analytical results agree well with available experimental data recently obtained in annular cascades. January, 1980; This is part 1. Part 2 issued as his Asymmetric inlet flows through axial compressors, GT & PDL report no. 151; Originally presented as the author's thesis, (Ph. D.)--in the M.I.T. Dept. of Aeronautics and Astronautics, 1978; Includes bibliographical references (pages 184-188)

Asymmetric inlet flows through axial compressors

2019-04-12T16:13:10Z

Asymmetric inlet flows through axial compressors Tan, Choon Sooi A new analytical method is proposed for the study of flow through highly-loaded turbomachine stages. The technique is used in the present study in order to: (i) analyze the three-dimensional induced effects of the viscous blade wakes in an isolated rotor; and (ii) to study the effects of the passage of distorted flow through an axial compressor rotor or stator. In Part I (GT&PDL Report Number 141), it is found, in contrast with the more familiar situation behind aircraft wings, that the induced effects of the vorticity in the (viscous) wakes are important in practical axial turbomachinery; for example, the flow angles through highly-loaded rotors are modified to a significant extent by such wake effects. The induced disturbances grow in strength within a certain distance downstream of the blade row before beginning to decay inversely with such axial distance.; In agreement with earlier predictions, pressure disturbances and vorticity disturbances cannot be decoupled in swirling flow. Similarly, in part II (GT&PDL Report Number 151), it is found that major differences arise on comparing two-dimensional with three-dimensional analyses, both for rectilinear and for annular configurations. Further, only the last of these threedimensional analyses can adequately describe the true flow phenomena in highly-loaded turbomachines. This is because such a description properly includes both centrifugal effects together with two important distinct types of vorticity: the trailing vorticity and the vorticity associated with any stagnation pressure gradients present. Such an analysis predicts, a strongly persisting downstream pressure field which in many cases increases before again beginning to decay inversely with the axial distance downstream, both for free-vortex stators and rotors.; By contrast, three-dimensional wheel flow analysis predicts indefinitely persisting downstream disturbances. Further, a purely two-dimensional theory indicates for a stator, the downstream static pressure to be uniform, while even a three-dimensional rectilinear cascade theory would predict only an exponentially decaying pressure field. The amplitude of the above persistent downstream disturbances decreases for free-vortex downstream flow as the number of significant circumferential harmonics of the inlet distortion increases. These analytical results agree well with available experimental data recently obtained in annular cascades. January, 1980; This is Part 2. Part 1 issued as his Three-dimensional vorti-city-induced flow effects in highly-loaded axial compressors , GT & PDL report no. 131; Originally presented as part of the author's thesis (Ph. D.)--in the M.I.T. Dept. of Aeronautics and Astronautics, 1978; Includes bibliographical references (pages 130-134)

A computational study of the flow in a transonic axial compressor using an inviscid, three-dimensional finite difference

2019-04-10T14:24:36Z

A computational study of the flow in a transonic axial compressor using an inviscid, three-dimensional finite difference Haymann-Haber, Guido A computational study of the flow in a Transonic Axial Compressor has been performed. This compressor has a tip Mach number of 1.2 and an inlet hub to tip ratio of 0.5. The numerical procedure used is a fully three-dimensional, inviscid, finite difference algorithm. MacCormack's two-step, explicit second order accurate scheme was used. A total of 30,600 mesh points were used. The results were compared to space and time resolved exit flow measurements, and to quantitative density visualization pictures. Among the most significant features resolved by the computation, was an unusual shock structure, which had earlier been observed in the experiments. The general agreement of the computation with The experiment is good, except in regions dominated by viscous flow. Many of the effects of viscosity can be anticipated from the inviscid flow field. May 1979; Originally presented as the author's thesis, M.S., in the M.I.T. Dept. of Aeronautics and Astronautics, 1979; Includes bibliographical references (leaf 82)

Three-dimensional incompressible and compressible Beltrami flow through a highly-loaded isolated rotor

2019-04-12T16:13:10Z

Three-dimensional incompressible and compressible Beltrami flow through a highly-loaded isolated rotor Tan, Choon Sooi An analysis is proposed for the three-dimensional incompressible and compressible Beltrami flow through a heavily loaded isolated rotor. It is found that, in agreement with previous analyses on disturbances in swirling flows, the Beltrami vorticity-induced disturbances are not purely convected by the mean flow. The disturbances, which induce a persisting static pressure field, can be shown to grow linearly in strength close to the blade-row before beginning to decay inversely with axial distance downstream. This is again in agreement with previous analyses on swirling flow in which the disturbances had their origin in the viscous blade wakes. It is further shown that this analysis only agrees with the earlier analysis, in which vorticity-induced disturbances are assumed to be purely convected by the mean flow, in the limit of large numbers of blades and in a downstream region very close to the blade row. The two analyses differ considerably further downstream; that is, this analysis can predict the downstream evolution of the three-dimensional disturbances while the earlier cannot. October 1979; Includes bibliographical references (pages 78-79)

Turbulent mixing in swirling flow

2019-04-10T14:24:44Z

Turbulent mixing in swirling flow Cheng, Wai Kong The effect of swirl on the mixing of two gas streams of the same density in coaxial annular geometry has been examined. The flow is studied via a fluorescent tracer, 2-3 biacetyl. Through direct excitation, collisional excitation, and collisional de-excitation of the tracer, the turbulent transport, molecularly mixed and unmixed regions in the flow are visualized. A three dimensional structure flattened in the azimuthal direction is observed. It is suggested that this structure is the result of the growth of the unstable azimuthal modes as limited by a turbulent eddy viscosity. September 1978; Originally presented as the author's thesis, Sc. D. in the M.I.T. Dept. of Aeronautics and Astronautics, 1979; Includes bibliographical references (leaf 49)

Flutter analysis of a tuned rotor with rigid and flexible disks

2019-04-12T16:13:19Z

Flutter analysis of a tuned rotor with rigid and flexible disks Dugundji, John The flutter behavior of a simple tuned rotor with a rigid and a flexible disk is reviewed. In Part A, the rotor assembly is assumed to consist of a rigid disk with N uniform flexible blades attached around the circumference, so that the blades are coupled only by aerodynamic forces. Both traveling wave and standing wave flutter analyses are conducted, and are shown to be equivalent. The relations between traveling and standing wave air forces are described in detail. The standing wave analysis is shown to be more versatile for some applications than the simpler traveling wave analysis. Applications are made to pure bending flutter and pure torsion flutter of the rotor assembly. Comments are made on combined bending-torsion flutter. In Part B, the rotor disk is assumed flexible and shrouds may be present. The blades are here coupled structurally as well as aerodynamically. The corresponding vibration and flutter behavior is examined. July 1979; Includes bibliographical references (page 58)

Stalled flow performance of a single stage transonic compressor

2019-04-12T16:13:20Z

Stalled flow performance of a single stage transonic compressor Bartlett, Frederick Girard; Greitzer, E. M. (Edward M.), 1941- The stalled flow performance of a single stage transonic compressor is examined, using data from the MIT Gas Turbine Laboratory's Blowdown Compressor Facility. Measurements of the blowdown corrected weightflow are included, as well as stage exit static to inlet total pressure rise, and rotating stall cell measurements. A comparison of the flow blockage, as represented by stall cell circumferential extent, with the blowdown corrected weightflow is made. The 100% design speed stalled flow performance characteristic is presented. Radial traverse.data is also presented including flow angles, static and total pressures, and Mach number components. Originally presented as the first author's thesis, M.S. in the M.I.T. Dept. of Mechanical Engineering, 1978; Includes bibliographical references (page 48)

The interaction of sound with turbulent flow

2019-04-12T16:13:19Z

The interaction of sound with turbulent flow Succi, G. P. (George Peter) Introduction: In the now classical theory of sound from turbulent flow by Lighthill boundaries were not considered. Further, it was assumed that the turbulent flow field was not altered by sound emission. For closed systems, such as cavities and waveguides, discrete modes may be excited. It is possible that the coupling between the flow field and acoustic modes is strong enough to alter the primary flow field. Under such conditions acoustically induced flow instabilities such as whistles occur. The objective of this thesis is to study the turbulent excitation of duct modes and the conditions for possible instabilities. Chapter One reviews the theory of turbulent excitation of sound in free space. The induced acoustic field is calculated in three ways. The sound field is determined by time-domain Green's function technique for both Lighthill's quadrupole source model and Ribner's equivalent distribution of monopoles.; The omission of turbulent shear interactions in an isotropic monopole model of the turbulence is demonstrated. The sound field is also determined by a frequency-domain Green's function technique for a monopole distribution. Time and frequency domain calculations yield identical results for the monopole source distribution. However, the frequency domain technique allows the analysis to be extended to Chapter Two examines the excitation of axial pipe modes by turbulent flow theoretically and experimentally. The experiment is performed by drawing air through a cylindrical pipe. The observations demonstrate that mode excitation diminishes as the flow speed increases. This is attributed to end losses which increase with flow speed. A Green's function, based on the measured pressure reflection coefficients, is used to predict the variation in spectra with flow. Chapter Three demonstrates the excitation of transverse modes in pipes experimentally.; Air is drawn through a small orifice into a rectangular duct. Pronounced asymmetric peaks are observed at the first few cutoff frequencies. The asymmetric nature of the peaks and relative spectral intensity are again explained by Green's function techniques. For high frequencies, where a large number of modes can propagate, the spectra resembles the free-space jet spectra. In this frequency range, the duct radiation impedance asymptotically approaches the free space impedance, hence the similar response to similar source distributions. Chapter Four examines feedback instabilities, cases where the emitted sound field alters the jet flow itself. The chapter concentrates on screech tones of circular orifices having length to diameter ratios between one half and two. The frequency dependence of the screech on Mach number and length is explained by a kinematic analysis of the feedback loop.; It is further demonstrated that the frequency of the feedback instability must be approximately equal to that of an acoustic made for screech to occur. Similar observations are presented with regard to air jets impinging on plates. In conclusion two mechanisms exist whereby the acoustic energy from a turbulent jet can be concentrated at select frequencies. The first is the selective response of a medium with boundaries to a random source. The spectral line shape for such cases is accounted for by Green's function techniques. The second mechanism is the feedback instability which requires coupling of the jet flow to the acoustic field. Here the modification of the jet flow must be considered to determine the excitation frequencies. It is recommended that future work be done on the screech instability. The influence of the acoustic cavity mode on the feedback instability should be examined in greater detail.; In particular, the convection speed of jet column disturbances with and without adjacent resonators should be determined experimentally. Furthermore, the mechanism which limits the amplitude of the screech should be determined. June 1977; Originally presented as the author's thesis, Ph. D. in the M.I.T. Dept. of Physics, 1977; Includes bibliographical references (pages 217-224)

Heat transfer measurements in turbines

2019-04-10T14:24:43Z

Heat transfer measurements in turbines Louis, Jean F. (Jean François); Demirjian, Ara Manuel; Topping, Richard Francis A blowdown turbine facility and an experimental program for the study of heat transfer in cooled turbines are described. The blowdown facility introduces the concept of using short duration experiments to test turbines by scaling the metal surface temperatures down to room temperature, and consequently scaling pressures and mass flow rates so that Reynolds, Mach and Prandtl numbers are kept unchanged. Hence, the Nusselt number is also unchanged. The short operating time assures that the surfaces remain nearly isothermal and that fast instrumentation, pressure transducers and thin film gauges can be used to record average and unsteady pressures and heat transfer. For example, the instrumentation is able to resolve heat transfer and pressure fluctuation induced by rotating blades passing over the stationary shrouds. Both the operation and demonstration runs of the blowdown facility are described. Finally, a two dimensional steady flow film cooling experiment yields heat transfer coefficients under conditions which model the average tangential flow over the stationary shrouds of the turbine under test in the blowdown facility. The results indicate that the curvature of the shroud leads to an increase of heat transfer by 15% and the separation of the coolant flow at the injection edge reduces the cooling effectiveness just downstream of the injection slot. Includes bibliographical references (leaf 17)

Spherical pressure probe for retrieving freestream pressure and directional data

2019-04-10T14:24:42Z

Spherical pressure probe for retrieving freestream pressure and directional data Figueiredo, William Arthur A spherical pressure probe designed to time resolve the total and static pressure and freestream radial and rotational flow angles in turbomachine flow fields was found to produce accurate results for flow angles over a range of 200 in both the radial and rotational directions. Reynolds number based on the probe sphere diameter had negligible effect over the range 14,000 to 92,000. There is a weak Mach number dependence, but the probe is usable up to a Mach number of 0.90. Calibration curves are plotted for M = 0.27, 0.7, and 0.9. These results were found by calibration in steady flow. From the probe dimensions and transducer response it is judged that the probe should have frequency response better than 30 kHz. August 1977; Includes bibliographical references (page 52)

Fluorescent visualization for turbomachine research

2019-04-10T14:24:42Z

Fluorescent visualization for turbomachine research Epstein, Alan Harry The quantitative gas fluorescence flow visualization technique using 2,3 butanedione as a tracer, has been refined and improved. Upgrading of the imaging system is responsible for the principal improvement. The technique has been applied to air flows in order to demonstrate its suitability to conventional compressor -testing. The possibility of using butanedione to measure static gas temperature has been explored by modeling. It has been found to be feasible only when a time lag after excitation of 1 ms is acceptable. March 1978; Includes bibliographical references (page 21)

Calculation of a self-consistent, low frequency electrostatic field in the drift-kinetic approximation

2019-04-12T16:13:18Z

Calculation of a self-consistent, low frequency electrostatic field in the drift-kinetic approximation Beasley, Cloyd Orris, 1933-; Meier, H. K. Massachusetts Institute of Technology; Rij, W. I. van. Oak Ridge National Laboratory; McCune, James E. (James Elliot) We derive an asymptotic series in [omega]p -2 , the inverse-square plasma frequency, for the self-consistent, low frequency electrostatic field in tori. The derivation is consistent with the drift-kinetic ordering and may be used in either instability or equilibrium calculations. We find that in a time-dependent formalism, the electric field is completely determined to first order in a drift-kinetic expansion. July 1977; Includes bibliographical references (pages 22-23)

Luminescent visualization of molecular and turbulent transport in a plane shear layer

2019-04-12T16:13:16Z

Luminescent visualization of molecular and turbulent transport in a plane shear layer Bates, Stephen Cuyler The purpose of this work is to contribute to the fundamental understanding of fluid turbulence by visualizing its detailed flow structures. Examination of these coherent structures gives information about the turbulent flow that cannot be deduced from its statistics. This information should reduce the role of empiricism in the analysis of turbulence. The experimental method chosen is to visualize a turbulent plane free shear layer using stop-action photography of a phosphorescing trace gas. Choice of 1) direct photo-excitation, 2) collisional excitation, or 3) collisional de-excitation of the phosphorescencing gas with a planar light beam, permits identification of the emission with a cross-sectional map of the material from one stream that is 1) throughout the flow, 2) molecularly mixed with material from the other free stream (alone), or 3) molecularly unmixed. The plane shear layer visualized has been specified experimentally. Extant requirements for self-preservation are insufficient in general, and make the claim of self-preservation for the experimental flow only probable and not definite. A large data set using all three variations of the visualization technique show structures that imply a large amount of new information about turbulent mixing and turbulent processes. The data shows the structures to be simply connected, with slow variation out of the mean flow plane. Specifically, there is a simply connected region of mixed fluid that always separates material entering the layer from the free streams. Collisional excitation and quenching data strongly imply a turbulent mixing process of random bursting from the free stream, followed by internal viscous decay. The complementary process of turbulent entrainment is recorded in the quenching photos as nibbling of the free stream by the layer, together with a randomly occurring large local amplification of this nibbling, previously thought to be engulfment by the boundary. June 1977; Originally presented as the author's thesis, (Sc. D.)--in the M.I.T. Dept. of Aeronautics and Astronautics, 1977; Includes bibliographical references (pages 123-124)

Uniform-inlet three-dimensional transonic Beltrami flow through a ducted fan

2019-04-10T14:24:41Z

Uniform-inlet three-dimensional transonic Beltrami flow through a ducted fan Cheng, Wai Kong Introduction: This report is a continuation of a line of analytical treatment of three dimensional flows in compressor or ducted fans. In the earlier theories [1,2,9,10], the blade row is modelled as a set of spinning lifting lines and the induced velocities are treated as acoustic perturbations. While these studies have been useful in advancing our knowledge of the three dimensional nature of the flow, it has been difficult until now to correlate the theory with experiments. The reason, of course, is that the strong overall swirl induced by such blade rows is by no means a small perturbation in practical applications. It is realized that the high pressure stage of a compressor usually has a large number of blades (~40 to 100). Therefore although the collective effect of all the bales can be a large disturbance, each blade contributes only a small disturbance. Thus a linearized theory is still possible.; To extend the previous acoustic theory to a rotor with large turning we may still represent the blades as superpositions of source and lifting lines, but we have to calculate the exit flow by linearizing about a non-zero (and large) swirl velocity profile. This is the approach taken by the theory proposed by McCune and Hawthorne [3]. They calculated the velocities induced by the trailing vorticity of a nonuniformly loaded rectilinear cascade for incompressible flow. This work was later generalized to the compressible case by Morton [4]. Cheng [5] treated incompressible flow in an annular geometry. In that analysis the blades are represented as lifting lines of nearly constant circulation, and the exit flow is therefore, to lowest order, of "free vortex" type. Linearizing about the free vortex flow, the velocity induced by the trailing vortex sheets due to nonuniform blade bonding are calculated in [5] to order 61.; It is the purpose of this report to treat the general compressible case, including the results of Ref. [5] as the incompressible limit. The result of this analysis also serves as the Green's function for constructing a lifting surface theory for transonic rotors with practical loading. Before going into the details of the theory, let us examine some simple pictures of its findings. The nonuniformly loaded blades shed off the excess circulation as wakes. The induced velocity of the wakes is found to cause a "downwash" at the blade which has the effect of partially nullifying the nonuniformity in loading. This can easily be understood by a consideration of the wake system of a blade. Fig. 1 shows a blade with the tip region more heavily loaded than the inboard stations. 'We can see that the wake induces a tangential velocity component which lowers the angle of attack at the high work (tip) region and increases that of the low work (hub) region.; Another major development is the mode matching of the upstream and downstream flow. The presence of the strong swirl makes the acoustic mode shapes downstream drastically different from those upstream. For example, we can have upstream hyperbolic modes in a transonic rotor while all the downstream modes are elliptic because the relative velocity is subsonic there. Simple mode-wise matching is no longer possible. In the present work, a method of mixed-mode matching is developed. A result is that a pure tone downstream (upstream) can excite a whole spectrum of tones upstream (downstream). In particular, any source downstream can excite the acoustic radiations upstream of a transonic rotor. Errata sheet inserted; Includes bibliographical references (page 50)

Comparison of three dimensional quasi-linear large swirl theory with measured outflow from a high-work compressor rotor

2019-04-12T16:13:13Z

Comparison of three dimensional quasi-linear large swirl theory with measured outflow from a high-work compressor rotor Chen, Lee-Tzong; McCune, James E. (James Elliot) A three-dimensional perturbation theory for incompressible strongly swirling flow in an annulus is applied to predict the outflow from a high-work compressor rotor (1)(2). A comparison of the analytical result with the experimental result is presented. The theory treats inviscid, incompressible flow through a highly loaded blade row in a long annular duct with uniform inlet. Trailing vorticity is shed from each blade which is represented by a lifting line of bound vorticity. The flow field between successive sheets of vorticity is assumed to be irrotational. The theoretical results are compared to data obtained in the M.I.T. Blowdown Compressor Test Facility (3). The mean circulation distribution is estimated from the mean pitchwise Mach number obtained from the experiment. The agreement of the predicted mean axial and radial velocity with the experimental results represents one confirmation of the theory. The pitchwise-varying velocity are evaluated by the theory at an axial distance of .02 tip radius which corresponds to the probe position if the lifting line is placed slightly ahead, but almost along the trailing edge of the blade. The theory predicts well the pitchwise variation of the velocity due to the effect of shed vorticity which results from the spanwise variation of circulation. The effect is pronounced near the blade tips. Corrections of the theory due to compressibility are omitted here, but will be available shortly. September 1975; Includes bibliographical references (page 37)

Collapse of the inter-electrode breakdown arc in the magnetic field direction

2019-04-12T16:13:14Z

Collapse of the inter-electrode breakdown arc in the magnetic field direction Oliver, David A. (David Anthony), 1939- A two-dimensional inter-electrode breakdown arc which is uniform in the magnetic field direction is shown to be unstable. The growth time for the instability is of the order of the arc development time. It is unlikely that a fully steady two-dimensional arc is ever established. The relationship of the instability to recent experiments revealing an inherently three-dimensional breakdown is discussed. July 1975; Includes bibliographical references (leaf 9)

An experimental and computational study of the flow in a transonic compressor rotor

2019-04-12T16:13:15Z

An experimental and computational study of the flow in a transonic compressor rotor Thompkins, William T. A comprehensive investigation of the flow field produced by an isolated transonic compressor rotor has been completed. This rotor has an overall diameter of two feet, an inlet hub/tip ratio of 0.5, a tip Mach number of 1.2 and a total pressure ratio of 1.65. The time resolved three dimensional exit flow produced by this rotor was experimentally measured with sufficient spatial and temporal resolution to determine velocity components and pressures inside individual blade wakes and in the surrounding flow. A numerical calculation of the steady inviscid three dimensional through-flow was computed using MacCormack's second order accurate time-marching scheme. Comparisons between the numerical solution, the exit flow measurements, and measurements of the intra-blade static density field obtained by gas fluorescence showed that the inviscid computation accurately models transonic compressor aerodynamics and rotor blade pressure distributions in the upstream portion of the passages, the viscous effects influencing mainly the downstream portions. It is felt that such a computation procedure has great potential as a compressor design and development tool especially when coupled with a suitable boundary layer analysis. May 1976; Includes bibliographical references (pages 69-71)

Accurate, efficient difference operators for the turbulent field equations

2019-04-10T14:24:41Z

Accurate, efficient difference operators for the turbulent field equations Oliver, David A. (David Anthony), 1939- Introduction: A potentially powerful method for predicting and describing turbulent flow fields is that of utilizing a finite number of moments of the instantaneous Navier-Stokes equations. This sequence of moment equations is closed by theoretical modelling of the unknown correlations at the closure moment level. The use of an eddy viscosity which is "closed" in terms of the mean velocity gradient represents a familiar first order closure. A wide variety of turbulent flow fields are currently under investigation including boundary layers, shear layers, vortices, and wakes. Surveys of the general methods utilizing various closure models may be found in Reynolds 11], Mellor and Herring [2], and Donaldson [3]. The field equations for the turbulent flow which result from these moment equations are generally lengthy, simultaneous, non-linear partial differential equations of the initial value class.; Very little attention has been given to the mathematical structure of these non-linear systems and to the development of accurate numerical methods for their solution. In many flows of interest, diffusion processes are always present in sufficient strength to give the equations a strong parabolic character. Most workers have therefore adopted fully implicit difference operators for the spatial derivatives and have then utilized iterative methods for solving the non-linear implicit equations. These fully implicit operators are apparently selected because of the unconditional stability which such operators provide for linear systems. In many highly non-equilibrium turbulent flows, the convective, production, and turbulent decay processes are stronger than the diffusive processes. In such situations the iterative techniques become slow in convergence or may not converge at all.; In addition, fully implicit difference operators are only first order accurate and require a fine mesh spacing to properly resolve the structure of the flow. In the present work we offer a new class of second order accurate non-linear difference operators which are consistent, unconditionally stable (in the extended sense for the non-linear system discussed below), and which do not require iterative techniques for the solution of non-linear implicit equations. Hence these operators are highly efficient. We begin in Part II by discussing simple non-linear diffusion and convections equations and their possible difference operators. In Part III we examine a more complex non-linear diffusion equation which is representative of that which arises in mixing length closure models. It is here that the essential feature of the difference operator proposed in this work is presented. In Part IV we turn attention directly to the turbulent field equation models currently under investigation.; Here we summarize these equations in a single archetypal form and we present the archetypal form of the difference operator for their solution. July 1975; Includes bibliographical references (page 18)

Exit flow from a transonic compressor rotor

2019-04-12T16:13:12Z

Exit flow from a transonic compressor rotor Thompkins, William T.; Kerrebrock, Jack L. Summary: The three dimensional unsteady flow field behind a transonic compressor rotor with a design pressure ratio of 1.6 at a tip Mach number of 1.2 has been resolved on the blade-passing time scale, using the M.I.T. Blowdown Compressor Facility. Quantities determined were total and static pressures, tangential flow angle and radial flow angle. The spatial and temporal resolution achieved was sufficient to determine velocity components inside individual blade wakes and in the surrounding flow. From these measurements the flow structure is described at stations immediately behind the rotor and one chord downstream. Some dominant features of the flow just behind the rotor are large radial velocity components, large static pressure fluctuations near the blade wakes, and definite unsteadiness (in rotor coordinates) of the wakes. The wake behavior one chord downstream is described in terms of the effect of the strong mean swirl on the behavior of shear disturbances. In the outer portion of the annulus, where the mean flow approximates a solid body rotation, a strong, persistent oscillatory flow is found with 16 periods in the circumference as roughly predicted by theory. In the inner portion of the annulus the disturbances attenuate axially. September 1975; Includes bibliographical references (page 6-8)

Wake behavior downstream of a transonic compressor rotor

2019-04-09T16:12:35Z

Wake behavior downstream of a transonic compressor rotor Stephens, Harry Elias Measurements of the static pressure resolved in radial and axial directions downstream of a transonic compressor rotor have been harmonically analyzed. The investigation is part of a program addressing the behavior of disturbances in strongly swirling flows. There is evidence that the wakes are radially outward and carry static pressure disturbances with them. The harmonic analysis of the static pressure measured at the tip radius indicates a shift toward higher frequency of the peak in the power spectrum as the flow proceeds downstream. It is suggested that this increasing frequency associated with the power peak results from the wakes being convected downstream in a fluid which has increasing swirl velocity as it travels away from the rotor. August 1974; Also issued as: Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1974; Includes bibliographical references (page 64)

Attenuation of sound in lined circular ducts

2019-04-12T16:13:11Z

Attenuation of sound in lined circular ducts Cho, Young-chung; Ingard, K. Uno In the previous report, we have used approximate expressions for the wall impedance for the discussion of sound attenuation in lined circular ducts. For instance, Eq. (2.5) has been used for the wall impedance of a circular duct lined with a resonator with a resistive screen, and Eq. (2.8) for a circular duct lined with a porous material. If the ratio of the duct radius to the liner thickness (D/L) is large and the sound frequency is large, the impedance given in Eq. (2.5) or Eq. (2.8) is a good approximation for a lined circular duct. However, when either one of these conditions is not fulfilled, the radial spread of the wave in the liner imposes some effects on the sound attenuation, whereas no wave spreading takes place in the liner of a rectangular duct. In this addendum we derive expressions for the wall impedance of lined circular ducts, accounting for the cylindrical spreading of the waves within the liner. The assumption of a locally reacting surface is still made. On the basis of the impedance thus obtained, the attenuation characteristics of a circular lined duct are computed for a wide range of parameters. April 1975; This is an addendum to Gas Turbine Laboratory Report No. 119. --Preface

Market share model for a multi-airport system

2019-04-10T10:39:10Z

Market share model for a multi-airport system Cohas, François Because capacity at existing airports was limited and/or because the cost of congestion was becoming unacceptable, several large cities around the world have had to build a second or third major commercial airport to keep up with the demand for air transportation. Such groups of competing airports are called multi-airport systems (M.A.S.) There is extensive historical evidence suggesting that multi-airport systems have often been poorly understood, resulting in disastrous investments such as the construction of airports that remained underused for very long periods of time. The purpose of this paper is to provide a better understanding of the ways M.A.S.s function. First, we consider qualitative characteristics of multi-airport systems, showing the importance of market forces. Then, we build an airport market share model that captures the dynamics of the market, where airlines and air passengers select an airport on the basis of a broad range of factors. Case studies are carried out for several origin-destination markets out of three large metropolitan areas: New York, Washington-Baltimore, and the San Francisco Bay Area. The results show that an airport market share can be well approximated by using few explanatory variables: frequency of service and average fare at the designated airport, and average fare at competing airports. In spite of the relative simplicity of our statistical model, we obtain a good fit between observed and predicted market shares. The explanatory variables are statistically significant and the estimated elasticities (direct price, frequency, and cross-price) are consistent with intuition. We conclude by highlighting the limitations of the model and by suggesting some implications concerning the construction of new airports in metropolitan areas and the potential for regional airports to alleviate the congestion problems at large metropolitan airports. Cover title; June 1993; Includes bibliographical references (pages 149-152)

Analysis of aircraft fleets of U.S. major airlines since deregulation

2019-04-12T14:02:11Z

Analysis of aircraft fleets of U.S. major airlines since deregulation Ferrer José The purpose of this thesis is to relate the U.S. Major airlines changing use of aircraft to aviation policy and technology since deregulation of the U.S. airline industry enacted in 1978. First, a study of the airline fleet mix was carried out in order to understand how airlines have composed their fleets in the past and how they are preparing for the future. Airlines have responded very favorably to any changes in aircraft characteristics that have the potential to lower operational costs, such as the introduction of two-crew member cockpits and the acquisition of twin-engined aircraft whenever possible. Airline fleets are primarily made up of low capacity/short range aircraft, which is an indication of airlines concentrating in domestic markets where frequency of service is critical. The shift towards the usage of more fuel efficient and quieter aircraft engines is evident. How the airlines actually operated their aircraft fleets in both domestic and international markets was also examined. The analysis focused on relating aircraft characteristics with the aircraft operation data published by the United States Department of Transportation. It was found that these airlines have concentrated their operations mostly in the domestic arena, representing 84.6% of total aircraft miles flown at the beginning of deregulation in 1978 and only decreasing to 84.1 % by 1990. There has been an increase of 70% in the total number of miles flown. The cause for this growth can be attributed to numerous airline mergers, and the expansion to the international arena in search of new markets. In addition, airlines are flying their aircraft further. Traffic results indicate that aircraft may have been scheduled more cycles per day and that air traffic congestion has been increasing since deregulation. Cover title; Vita; Includes bibliographical references

Tradespace Investigation of a Telescope Architecture for Next-generation Space Astronomy and Exploration

2019-04-10T20:12:01Z

Tradespace Investigation of a Telescope Architecture for Next-generation Space Astronomy and Exploration Cataldo, Giuseppe; Chodas, Mark; Dave, Pratik; Dixit, Atray; Hall, Sherrie; Harris, Robert; Hayhurst, Dustin; Hicks, Fernando; Jewison, Christopher; Josan-Drinceanu, Ioana; Karlow, Brandon; McCarthy, Bryan; Owens, Andrew; Peters, Eric; Shaw, Margaret; Sternberg, David; Voelbel, Kathleen; Wu, Marcus Humanity’s endeavor to further its scientific understanding of the celestial heavens has led to the creation and evolution of increasingly powerful and complex space telescopes. Space telescopes provide a view of the solar system, galaxy, and universe unobstructed by Earth’s atmosphere and have profoundly changed the way people view space. In an effort to further advance space telescope capability and achieve the accompanying scientific understanding, the Massachusetts Institute of Technology (MIT), specifically, course 16.89 Space Systems Engineering, explored the tradespace of architectural enumerations encompassed within the design of an ultraviolet-optical-infrared (UVOIR) space telescope located at Sun-Earth Lagrangian Point Two (SE-L2). SE-L2 presents several advantages as an operating location for a UVOIR telescope such as a thermally stable environment and an orbit that allows the telescope to maintain a constant orientation with respect to all of the primary sources of heat and light. The main disadvantages associated with SE-L2 are caused by its relatively large distance from Earth, which marginalizes the effectiveness of real-time telerobotics because of latency and increases the cost of communications, launch, and servicing. Course 16.89 believes that, for this UVOIR application, the strengths of this operating location outweigh its weaknesses and therefore decided to explore the family of opportunities associated with SE-L2. This course used appropriate performance and system metrics to quantify the effectiveness of the aforementioned architectures and create a Pareto front of viable architectures. Evaluating the designs along the Pareto front allowed the course to characterize and group architectures and present these group-types to stakeholders for the selection of an optimal space telescope according to stakeholder requirements and resources. This course also developed sensitivity analysis, which allowed for a greater understanding of how architectural decisions affect the performance of the satellite. Segmentation, modularity, assembly, autonomy, and servicing were key aspects of this multidimensional analysis given the 16.8-meter class size and location of the telescope. Within the respective operating environment and for a spacecraft of similar characteristics, this model will allow stakeholders to predict the long-term operational effectiveness of different space telescope architectures and capture the synergistic effects of combining various architectural decisions into a spacecraft design. The following sections step through the aforesaid analysis and design efforts conducted in 16.89 beginning with Section III, which explicitly performs the stakeholder analysis and articulates the requirements of the mission. Section IV gives an overview of past designs and expands upon the architecture enumerations pertinent to this project, while Section V presents the methods and metrics by which those architectures will be evaluated and the system metrics which will be balanced and optimized in the creation of this space telescope. Section VI will present the model validation of this project and Section VII will discuss the results and analyses of the project. Finally, Section VIII will explore the future work opportunities of this project, while Section IX will present the conclusions and recommendations drawn from this project.

Mixed-Initiative Strategies for Real-time Scheduling of Multiple Unmanned Vehicles

2019-04-12T21:59:10Z

Mixed-Initiative Strategies for Real-time Scheduling of Multiple Unmanned Vehicles Clare, A. S.; Macbeth, J. C,; Cummings, M. L. Advances in autonomy have made it possible to invert the typical operator-to-unmanned vehicle ratio so that a single operator can now control multiple heterogeneous Unmanned Vehicles (UVs). Real-time scheduling and task assignment for multiple UVs in uncertain environments will require the computational ability of optimization algorithms combined with the judgment and adaptability of human supervisors through mixed-initiative systems. The goal of this paper is to analyze the interactions between operators and scheduling algorithms in two human- in-the-loop multiple UV control experiments. The impact of real-time operator modifications to the objective function of an optimization algorithm for multi-UV scheduling is described. Results from outdoor multiple UV flight tests using a human-computer collaborative scheduling system are presented, which provide valuable insight into the impact of environmental uncertainty and vehicle failures on system effectiveness.

One Work Analysis, Two Domains: A Display Information Requirements Case Study

2019-04-12T07:36:08Z

One Work Analysis, Two Domains: A Display Information Requirements Case Study Cummings, M. L.; Tappan, J.; Mikkelsen, C. d observations, among other techniques. Given the time and resources required, we examine how to generalize a work domain analysis technique, namely the hybrid Cognitive Task Analysis (hCTA) method across two domains in order to generate a common set of display information requirements. The two domains of interest are field workers troubleshooting low voltage distribution networks and telecommunication problems. Results show that there is a high degree of similarity between the two domains due to their service call nature, particularly in tasking and decision-making. While the primary differences were due to communication protocols and equipment requirements, the basic overall mission goals, functions, phases of operation, decision processes, and situation requirements were very similar. A final design for both domains is proposed based on the joint requirements.

Teamwork in controlling multiple robots

2019-04-10T11:51:36Z

Teamwork in controlling multiple robots Gao, F.; Cummings, M. L.; Bertuccelli, L. F. Simultaneously controlling increasing numbers of robots requires multiple operators working together as a team. Helping operators allocate attention among different robots and determining how to construct the human-robot team to promote performance and reduce workload are critical questions that must be answered in these settings. To this end, we investigated the effect of team structure and search guidance on operators’ performance, subjective workload, work processes and communication. To investigate team structure in an urban search and rescue setting, we compared a pooled condition, in which team members shared control of 24 robots, with a sector condition, in which each team member control half of all the robots. For search guidance, a notification was given when the operator spent too much time on one robot and either suggested or forced the operator to change to another robot. A total of 48 participants completed the experiment with two persons forming one team. The results demonstrate that automated search guidance neither increased nor decreased performance. However, suggested search guidance decreased average task completion time in Sector teams. Search guidance also influenced operators’ teleoperation behaviors. For team structure, pooled teams experienced lower subjective workload than sector teams. Pooled teams communicated more than sector teams, but sector teams teleoperated more than pool teams.

Interface Design for Unmanned Vehicle Supervision through Hybrid Cognitive Task Analysis

2019-04-10T11:51:35Z

Interface Design for Unmanned Vehicle Supervision through Hybrid Cognitive Task Analysis Macbeth, J. C.; Cummings, M. L.; Bertuccelli, L. F.; Surana, A. While there is currently significant interest in developing Unmanned Aerial Systems (UASs) that can be supervised by a single operator, the majority of these systems focus on Intelligence, Surveillance, and Reconnaissance (ISR) domains. One domain that has received significantly less attention is the use of multiple UASs to insert or extract supplies or people. To this end, MAVIES (Multi-Autonomous Vehicle Insertion-Extraction System) was developed to allow a single operator the ability to supervise a primary cargo Unmanned Aerial Vehicle (UAV) along with multiple scouting UAVs. This paper will detail the development of the design requirements generated through a Hybrid Cognitive Task Analysis (hCTA) and the display that resulted from these efforts. A major innovation in the hCTA process in this effort was the alteration of the traditional decision ladder process to specifically identify decision-making tasks that must be augmented with automation.

A Model-Based Measure to Assess Operator Adherence to Procedure

2019-04-12T21:59:06Z

A Model-Based Measure to Assess Operator Adherence to Procedure Stimpson, A. J.; Buinhas, L. S.; Bezek, S.; Boussemart, Y.; Cummings, M. L. Procedures play an important role in domains where humans interact with critical, complex systems. In such environments, the operator’s ability to correctly follow a given set of procedures can directly impact system safety. A quantitative measure of procedural adherence during training for complex system opera-tion would be useful to assess trainee performance and evaluate a training program. This paper presents a novel model-based objective metric for quantifying procedural adherence in training. This metric is sensi-tive to both the number and nature of procedural deviations, and can be used with cluster analysis to classi-fy trainee performance based on adherence. The metric was tested on an experimental data set gathered from volunteers using aircraft maintenance computer-based training (CBT). The properties of the metric are discussed, along with future possibilities.

Operator Performance in Long Duration Control Operations: Switching from Low to High Task Load

2019-04-10T21:35:32Z

Operator Performance in Long Duration Control Operations: Switching from Low to High Task Load Thornburg, K. M.; Peterse, H.P.M.; Liu, A.M. Long duration, low task load environments are typical for nuclear power plant control rooms, where operators, after hours of operating under a low task load situation, may have to shift to a high task load situation. The effects of time-on-task and boredom due to low task load will be an important consideration for the design of new nuclear power plant control rooms, which will rely more heavily on automation. This paper describes a research study of performance in a simulated nuclear control room environment, where 36 participants responded to an alarm during a 4 hour long experiment where the alarm onset time and the availability of distractions were varied. The results indicate that operators perform better in a sterile environment and that the duration of non-active time before the alarm influences operator performance.

Using Variable-Rate Alerting to Counter Boredom in Human Supervisory Control

2019-04-10T08:46:49Z

Using Variable-Rate Alerting to Counter Boredom in Human Supervisory Control Mkrtchyan, A. A.; Macbeth, J. C.; Solovey, E. T.; Ryan, J. C.; Cummings, M. L. A low task load, long duration experiment was conducted to evaluate the impact of cyclical attention switching strategies on operator performance in supervisory domains. The impetus for such a study stems from the lack of prior work to improve human-system performance in low task load supervisory domains through the use of design interventions. In this study, a design intervention in the form of auditory alerts is introduced and the effects of the alerts are examined. The test bed consists of a video game-like simulation environment, which allows a single opera-tor the ability to supervise multiple unmanned vehicles. Each participant in the study completed two different four hour sessions, with and without the alerts. The results suggest that the alerts can be useful for operators who are dis-tracted for a considerable amount of time, but that the alerts may not be appropriate for operators who are able to sustain directed attention for prolonged periods.

Using Discrete Event Simulation to Model Multi-Robot Multi-Operator Teamwork

2019-04-12T21:58:19Z

Using Discrete Event Simulation to Model Multi-Robot Multi-Operator Teamwork Gao, F.; Cummings, M. L. With the increasing need for teams of operators in controlling multiple robots, it is important to understand how to construct the team and support team processes. While running experiments can be time consuming and expensive, the use of simulation models is an alternative method. In this study, we built a discrete event simulation model that represents multi-robot multi-operator teamwork. Preliminary results show that the model can generate performance measures consistent with experimental results.

Modeling teamwork of multi-human multi-agent teams

2019-04-09T18:27:02Z

Modeling teamwork of multi-human multi-agent teams Gao, F. Teamwork is important when humans work together with automated agents to perform tasks requiring monitoring, coordination, and complex decision making. While human-agent teams can bring many benefits such as higher productivity, adaptability and creativity, they may also fail for various reasons. It is important to understand the tradeoffs in teamwork. The purpose of this research is to investigate the process and outcomes of human-agent teamwork by running experiments and building quantitative simulation models. Preliminary results are discussed as well as future directions. We expect this research to deepen the under-standing of human-agent teamwork and provide recommendations for the design of teams and agents to support teamwork.

Modeling the Impact of Operator Trust on Performance in Multiple Robot Control,

2019-04-12T21:59:07Z

Modeling the Impact of Operator Trust on Performance in Multiple Robot Control, Gao, F.; Clare, A. S.; Macbeth, J. C.; Cummings, M. L. We developed a system dynamics model to simulate the impact of operator trust on performance in multiple robot control. Analysis of a simulated urban search and rescue experiment showed that operators decided to manually control the robots when they lost trust in the autonomous planner that was directing the robots. Operators who rarely used manual control performed the worst. However, the operators who most frequently used manual control reported higher workload and did not perform any better than operators with moderate manual control usage. Based on these findings, we implemented a model where trust and performance form a feedback loop, in which operators perceive the performance of the system, calibrate their trust, and adjust their control of the robots. A second feedback loop incorporates the impact of trust on cognitive workload and system performance. The model was able to replicate the quantitative performance of three groups of operators within 2.3%. This model could help us gain a greater understanding of how operators build and lose trust in automation and the impact of those changes in trust on performance and workload, which is crucial to the development of future systems involving humanautomation collaboration.

Investigating the Efficacy of Network Visualizations for Intelligence Tasks

2019-04-10T19:20:14Z

Investigating the Efficacy of Network Visualizations for Intelligence Tasks Berardi, C.; Solovey, E. T.; Cummings, M. L. There is an increasing requirement for advanced analytical methodologies to help military intelligence analysts cope with the growing amount of data they are saturated with on a daily basis. Specifically, within the context of terror network analysis, one of the largest problems is the transformation of raw tabular data into a visualization that is easily and effectively exploited by intelligence analysts. Currently, the primary method within the intelligence domain is the node-link visualization, which encodes data sets by depicting the ties between nodes as lines between objects in a plane. This method, although useful, has limitations when the size and complexity of data grows. The matrix offers an alternate perspective because the two dimensions of the matrix are arrayed as an actors x actors matrix. This paper describes an experiment investigating node-link and matrix visualization techniques within social network analysis, and their effectiveness for the intelligence tasks of: 1) identifying leaders and 2) identifying clusters. The sixty participants in the experiment were all Air Force intelligence analysts and we provide recommendations for building visualization tools for this specialized group of users.

Comparing the Performance of Expert User Heuristics and an Integer Linear Program in Aircraft Carrier Deck Operations

2019-04-11T00:56:27Z

Comparing the Performance of Expert User Heuristics and an Integer Linear Program in Aircraft Carrier Deck Operations Ryan, J. C.; Banerjee, A. G.; Cummings, M. L.; Roy, N. Planning operations across a number of domains can be considered as resource allocation problems with timing constraints. An unexplored instance of such a problem domain is the aircraft carrier flight deck, where, in current operations, replanning is done without the aid of any computerized decision support. Rather, veteran operators employ a set of experience based heuristics to quickly generate new operating schedules. These expert user heuristics are neither codified nor evaluated by the United States Navy; they have grown solely from the convergent experiences of supervisory staff. As unmanned aerial vehicles (UAVs) are introduced in the aircraft carrier domain, these heuristics may require alterations due to differing capabilities. The inclusion of UAVs also allows for new opportunities for on-line planning and control, providing an alternative to the current heuristic-based replanning methodology. To investigate these issues formally, we have developed a decision support system for flight deck operations that utilizes a conventional integer linear program-based planning algorithm. In this system, a human operator sets both the goals and constraints for the algorithm, which then returns a proposed schedule for operator approval. As a part of validating this system, the performance of this collaborative human–automation planner was compared with that of the expert user heuristics over a set of test scenarios. The resulting analysis shows that human heuristics often outperform the plans produced by an optimization algorithm, but are also often more conservative.

The Need for Command and Control Instant Message Adaptive Interfaces: Lessons Learned from Tactical Tomahawk Human-in-the-Loop Simulations

2019-04-12T21:43:37Z

The Need for Command and Control Instant Message Adaptive Interfaces: Lessons Learned from Tactical Tomahawk Human-in-the-Loop Simulations Cummings, M. L. In the recent development of a human-in-the-loop simulation test bed designed to examine human performance issues for supervisory control of the Navy’s new Tactical Tomahawk missile, measurements of operator situation awareness (SA) and workload through secondary tasking were taken through an embedded instant messaging program. Instant message interfaces (otherwise known as “chat”), already a means of communication between Navy ships, allow researchers to query users in real-time in a natural, ecologic setting, and thus provide more realistic and unobtrusive measurements. However, in the course of this testing, results revealed that some subjects fixated on the real-time instant messaging secondary task instead of the primary task of missile control, leading to the overall degradation of mission performance as well as a loss of SA. While this research effort was the first to quantify command and control performance degradation as a result of instant messaging, the military has recognized that in its network centric warfare quest, instant messaging is a critical informal communication tool, but has associated problems. Recently a military spokesman said that managing chat in current military operations was sometimes a “nightmare” because military personnel have difficulty in handling large amounts of information through chat, and then synthesizing knowledge from this information. This research highlights the need for further investigation of the role of instant messaging interfaces both on task performance and situation awareness, and specifies how the associated problems could be ameliorated through adaptive display design.

Partitioning Complexity in Air Traffic Management Task

2019-04-10T21:43:00Z

Partitioning Complexity in Air Traffic Management Task Cummings, M. L.; Tsonis, C. Cognitive complexity is a term that appears frequently in air traffic control (ATC) research literature, yet there is little principled investigation of the potential sources of cognitive complexity. Three distinctly different sources of cognitive complexity are proposed which are environmental, organizational, and display. Two experiments were conducted to explore whether or not these proposed components of complexity could be effectively partitioned, measured, and compared. The findings demonstrate that sources of complexity can be decomposed and measured and furthermore, the use of color in displays, a display design intervention meant to reduce environmental complexity, can actually contribute to it.

Automation and Accountability in Decision Support System Interface Design

2019-04-12T21:55:09Z

Automation and Accountability in Decision Support System Interface Design Cummings, M. L. When the human element is introduced into decision support system design, entirely new layers of social and ethical issues emerge but are not always recognized as such. This paper discusses those ethical and social impact issues specific to decision support systems and highlights areas that interface designers should consider during design with an emphasis on military applications. Because of the inherent complexity of socio-technical systems, decision support systems are particularly vulnerable to certain potential ethical pitfalls that encompass automation and accountability issues. If computer systems diminish a user’s sense of moral agency and responsibility, an erosion of accountability could result. In addition, these problems are exacerbated when an interface is perceived as a legitimate authority. I argue that when developing human computer interfaces for decision support systems that have the ability to harm people, the possibility exists that a moral buffer, a form of psychological distancing, is created which allows people to ethically distance themselves from their actions.

Operator Scheduling Strategies in Supervisory Control of Multiple UAVs

2019-04-11T09:22:33Z

Operator Scheduling Strategies in Supervisory Control of Multiple UAVs Cummings, M. L.; Mitchell, P. J. The application of network centric operations to time-constrained command and control environments will mean that human operators will be increasingly responsible for multiple simultaneous supervisory control tasks. One such futuristic application will be the control of multiple unmanned aerial vehicles (UAVs) by a single operator. To achieve such performance in complex, time critical, and high risk settings, automated systems will be required both to guarantee rapid system response as well as manageable workload for operators. Through the development of a simulation test bed for human supervisory control of multiple independent UAVs by a single operator, this paper presents recent efforts to investigate workload mitigation strategies as a function of increasing automation. A humanin- the-loop experiment revealed that under low workload conditions, operators’ cognitive strategies were relatively robust across increasing levels of automated decision support. However, when provided with explicit automated recommendations and with the ability to negotiate with external agencies for delays in arrival times for targets, operators inappropriately fixated on the need to globally optimize their schedules. In addition, without explicit visual representation of uncertainty, operators tended to treated all probabilities uniformly. This study also revealed that operators that reached cognitive saturation adapted two very distinct management strategies, which led to varying degrees of success. Lastly, operators with management-by-exception decision support exhibited evidence of automation bias.

Effects of Single versus Multiple Warnings on Driver Performance

2019-04-12T21:52:17Z

Effects of Single versus Multiple Warnings on Driver Performance Cummings, M. L.; Kilgore, R. M.; Wang, E.; Tijerina, L.; Kochhar, D. S. Objective: To explore how a single master alarm system affects drivers’ responses when compared to multiple, distinct warnings. Background: Advanced driver warning systems are intended to improve safety, yet inappropriate integration may increase the complexity of driving, especially in high workload situations. This study investigated the effects of auditory alarm scheme, reliability, and collision event-type on driver performance. Method: A 2x2x4 mixed factorial design investigated the impact of two alarm schemes (master vs. individual) and two levels of alarm reliability (high and low) on distracted drivers’ performance across four collision event-types (frontal collision warnings, left and right lane departure warnings, and follow vehicle fast approach). Results: Participants’ reaction times and accuracy rates were significantly affected by the type of collision event and alarm reliability. The use of individual alarms, rather than a single master alarm, did not significantly affect driving performance in terms of reaction time or response accuracy. Conclusion: Even though a master alarm is a relatively uninformative warning, it produced statistically no different reaction times or accuracy results when compared to information-rich auditory icons, some of which were spatially located. In addition, unreliable alarms negatively impacted driver performance, regardless of event type or alarm scheme. Application: These results have important implications for the development and implementation of multiple driver warning systems.

The Impact of Intelligent Aiding for Multiple Unmanned Aerial Vehicle Schedule Management

2019-04-12T21:46:47Z

The Impact of Intelligent Aiding for Multiple Unmanned Aerial Vehicle Schedule Management Cummings, M. L.; Brzezinski, A. S.; Lee, J. D. There is increasing interest in designing systems such that the current many-to-one ratio of operators to unmanned vehicles (UVs) can be inverted. Instead of lower-level tasks performed by today’s UV teams, the sole operator would focus on high-level supervisory control tasks. A key challenge in the design of such single-operator systems will be the need to minimize periods of excessive workload that arise when critical tasks for several UVs occur simultaneously. Thus some kind of decision support is needed that facilitates an operator’s ability to evaluate different action alternatives for managing a multiple UV mission schedule in real-time. This paper describes two decision support experiments that attempted to provide UAV operators with multivariate scheduling assistance, with mixed results. Those automated decision support tools that provided more local, as opposed to global, visual recommendations produced superior performance, suggesting that meta-information displays could saturate operators and reduce performance.

Identifying Predictive Metrics for Supervisory Control of Multiple Robots

2019-04-09T15:31:01Z

Identifying Predictive Metrics for Supervisory Control of Multiple Robots Crandall, J. W.; Cummings, M. L. In recent years, much research has focused on making possible single operator control of multiple robots. In these high workload situations, many questions arise including how many robots should be in the team, which autonomy levels should they employ, and when should these autonomy levels change? To answer these questions, sets of metric classes should be identified that capture these aspects of the human-robot team. Such a set of metric classes should have three properties. First, it should contain the key performance parameters of the system. Second, it should identify the limitations of the agents in the system. Third, it should have predictive power. In this paper, we decompose a human-robot team consisting of a single human and multiple robots in an effort to identify such a set of metric classes. We assess the ability of this set of metric classes to (a) predict the number of robots that should be in the team and (b) predict system effectiveness. We do so by comparing predictions with actual data from a user study, which is also described.

Automation Architecture for Single Operator, Multiple UAV Command and Control,

2019-04-11T00:56:20Z

Automation Architecture for Single Operator, Multiple UAV Command and Control, Cummings, M. L.; Bruni, S.; Mercier, S.; Mitchell, P. J. In light of the Office of the Secretary Defense’s Roadmap for unmanned aircraft systems (UASs), there is a critical need for research examining human interaction with heterogeneous unmanned vehicles. The OSD Roadmap clearly delineates the need to investigate the “appropriate conditions and requirements under which a single pilot would be allowed to control multiple airborne UA (unmanned aircraft) simultaneously.” Toward this end, in this paper, we provide a meta-analysis of research studies across unmanned aerial and ground vehicle domains that investigated single operator control of multiple vehicles. As a result, a hierarchical control model for single operator control of multiple unmanned vehicles (UV) is proposed that demonstrates those requirements that will need to be met for operator cognitive support of multiple UV control, with an emphasis on the introduction of higher levels of autonomy. The challenge in achieving effective management of multiple UV systems in the future is not only to determine whether automation can be used to improve human and system performance, but how and to what degree across hierarchical control loops, as well as determining the types of decision support that will be needed by operators given the high-workload environment. We address when and how increasing levels of automation should be incorporated in multiple UV systems and discuss the impact on not only human performance, but more importantly, on system performance.

Developing Lunar Landing Vehicle Display Requirements through Content Analysis of Apollo Lunar Landing Voice Communications

2019-04-12T21:50:48Z

Developing Lunar Landing Vehicle Display Requirements through Content Analysis of Apollo Lunar Landing Voice Communications Smith, C. A.; Cummings, M. L.; Sim, L. The lengthy period since the Apollo landings limits present-day engineers attempting to draw from the experiences of veteran Apollo engineers and astronauts in the design of a new lunar lander. In order to circumvent these limitations, content analyses were performed on the voice transcripts of the Apollo lunar landing missions. The analyses highlighted numerous inefficiencies in the design of the Apollo Lunar Module displays, particularly in the substantial use of the cognitive resources of the Lunar Module Pilot in the performance of low-level tasks. The results were used to generate functional and information requirements for the next-generation lunar lander cockpit.

Past, Present And Future Implications Of Human Supervisory Control In Space Missions

2019-04-10T19:54:43Z

Past, Present And Future Implications Of Human Supervisory Control In Space Missions Sim, L.; Cummings, M.L.; Smith, C. A. Achieving the United States’ Vision for future Space Exploration will necessitate far greater collaboration between humans and automated technology than previous space initiatives. However, the development of methodologies to optimize this collaboration currently lags behind development of the technologies themselves, thus potentially decreasing mission safety, efficiency and probability of success. This paper discusses the human supervisory control (HSC) implications for use in space, and outlines several areas of current automated space technology in which the function allocation between humans and machines/automation is sub-optimal or under dispute, including automated spacecraft landings, Mission Control, and wearable extra-vehicular activity computers. Based on these case studies, we show that a more robust HSC research program will be crucial to achieving the Vision for Space Exploration, especially given the limited resources under which it must be accomplished.

The Impact of Multi-layered Data-blocks on Controller Performance

2019-04-11T00:55:50Z

The Impact of Multi-layered Data-blocks on Controller Performance Cummings, M.L.; Tsonis, C.; Rader, A. As a consequence of the push to increase National Airspace System capacity, air traffic control displays will not only have to show the increasing number of aircraft, but also all the associated data such as airspeed and altitude. The representation of aircraft data and associated relational information, often superimposed on a map, leads to cluttered displays, which could negatively affect controller performance, especially as aircraft numbers increase. To investigate these issues further, an experiment was conducted that examined the effect of increasing data-block lines on controller performance in an aircraft vectoring task. Data-block design, the primary factor, varied in the number of lines displayed (2-5). In addition a data-block information priority factor was examined that addressed the frequency of information access across data-block lines. Results demonstrated that while task load, measured as an increasing number of planes under control, negatively influenced reaction times and task accuracy, the number of lines in a data block was not statistically significant. However there was a trend towards reduced performance when data-blocks exceeded more than three lines on a base layer. In addition, the data blocks that contained prioritized information across levels promoted faster reaction times, but at a cost of lower situation awareness. This research demonstrated that the design of data-blocks should consider the balance between reduction in data-block interaction time against the need to allow enough interaction time to build situation awareness.

Design and Evaluation of Path Planning Decision Support for Planetary Surface Exploration

2019-04-11T00:30:07Z

Design and Evaluation of Path Planning Decision Support for Planetary Surface Exploration Marquez, J. J.; Cummings, M.L. Human intent is an integral part of real-time path planning and re-planning, thus any decision aiding system must support human-automation interaction. The appropriate balance between humans and automation for this task has previously not been adequately studied. In order to better understand task allocation and collaboration between humans and automation for geospatial path problem solving, a prototype path planning aid was developed and tested. The focus was human planetary surface exploration, a high risk, time-critical domain, but the scenario is representative of any domain where humans path plan across uncertain terrain. Three visualizations, including elevation contour maps, a novel visualization called levels of equal costs, and a combination of the two were tested along with two levels of automation. When participants received the lower level of automation assistance, their path costs errors were less than 35% of the optimal, and they integrated manual sensitivity analysis strategies. When participants used the higher level of automation assistance, path costs errors were reduced to a few percentages, and they saved on average 1.5 minutes in the task. However, this increased performance came at the price of decreased situation awareness and automation bias.

Predicting Controller Capacity in Remote Supervision of Multiple Unmanned Vehicles

2019-04-09T16:24:57Z

Predicting Controller Capacity in Remote Supervision of Multiple Unmanned Vehicles Cummings, M.L.; Mitchell, P. J. In the future vision of allowing a single operator to remotely control multiple unmanned vehicles, it is not well understood what cognitive constraints limit how many vehicles and related tasks a single operator can manage. This paper illustrates that when predicting the number of unmanned aerial vehicles (UAVs) a single operator can control, it is important to model the sources of wait times caused by human-vehicle interaction, especially since these times could potentially lead to system failure. Specifically, these sources of vehicle wait times include cognitive reorientation and interaction wait time, queues for multiple vehicle interactions, and loss of situation awareness wait times. When wait times were included, predictions using a multiple homogeneous and independent UAV simulation dropped by up to 67%, with loss of situation awareness as the primary source of wait time delays. Moreover this study demonstrated that even in a highly automated management-by-exception system, which should alleviate queuing and interaction wait times, operator capacity is still affected by situation awareness wait time, causing a 36% decrease over the capacity model with no wait time included.

The Impact of Heterogeneity on Operator Performance in Future Unmanned Vehicle Systems

2019-04-12T21:49:05Z

The Impact of Heterogeneity on Operator Performance in Future Unmanned Vehicle Systems Nehme, C. E.; Meckeci, B.; Crandall, J. W.; Cummings, M.L. Recent studies have shown that with appropriate operator decision support and with sufficient automation, inverting the multiple operators to single-unmanned vehicle control paradigm is possible. These studies, however, have generally focused on homogeneous teams of vehicles, and have not completely addressed either the manifestation of heterogeneity in vehicle teams, or the effects of heterogeneity on operator capacity. An important implication of heterogeneity in unmanned vehicle teams is an increase in the diversity of possible team configurations available for each operator, as well as an increase in the diversity of possible attention allocation schemes that can be utilized by operators. To this end, this paper introduces a discrete event simulation (DES) model as a means to model a single operator supervising multiple heterogeneous unmanned vehicles. The DES model can be used to understand the impact of varying both vehicle team design variables (such as team composition) and operator design variables (including attention allocation strategies). The model also highlights the sub-components of operator attention allocation schemes that can impact overall performance when supervising heterogeneous unmanned vehicle teams. Results from an experimental case study are then used to validate the model, and make predictions about operator performance for various heterogeneous team configurations.

Auditory Decision Aiding in Supervisory Control of Multiple Unmanned Aerial Vehicles

2019-04-12T21:46:46Z

Auditory Decision Aiding in Supervisory Control of Multiple Unmanned Aerial Vehicles Donmez, B.; Cummings, M.L.; Graham, H. D. This paper investigates the effectiveness of sonification, continuous auditory alert mapped to the state of a monitored task, in supporting unmanned aerial vehicle (UAV) supervisory control. Background: UAV supervisory control requires monitoring each UAV across multiple tasks (e.g., course maintenance) via a predominantly visual display, which currently is supported with discrete auditory alerts. Sonification has been shown to enhance monitoring performance in domains such as anesthesiology by allowing an operator to immediately determine an entity's (e.g., patient) current and projected states, and is a promising alternative to discrete alerts in UAV control. However, minimal research compares sonification to discrete alerts, and no research assesses the effectiveness of sonification for monitoring multiple entities (e.g., multiple UAVs). Method: An experiment was conducted with 39 military personnel, using a simulated setup. Participants controlled single and multiple UAVs, and received sonifications or discrete alerts based on UAV course deviations and late target arrivals. Results: Regardless of the number of UAVs supervised, the course deviation sonification resulted in 1.9 s faster reactions to course deviations, a 19% enhancement from discrete alerts. However, course deviation sonification interfered with the effectiveness of discrete late arrival alerts in general, and with operator response to late arrivals when supervising multiple vehicles. Conclusions: Sonifications can outperform discrete alerts when designed to aid operators to predict future states of monitored tasks. However, sonifications may mask other auditory alerts, and interfere with other monitoring tasks that require divided attention.

Paying Attention to the Man behind the Curtain

2019-04-12T21:49:04Z

Paying Attention to the Man behind the Curtain Cummings, M.L.; Thornburg, K. M. In the push to develop smart energy systems, designers have increasingly focused on systems that measure and predict user behavior to effect optimal energy consumption. While such focus is an important component in these systems' success, designers have paid substantially less attention to the people on the other side of the energy system loop-the supervisors of power generation processes. Smart energy systems that leverage pervasive computing could add to these supervisory control operators' workload. They'll have to predict possible power plant load and production changes caused by environmental and plant events, as well as dynamic system adaptation in response to consumer behaviors. Contrary to many assumptions, inserting more automation, including distributed sensors and algorithms to postprocess data, won't necessarily reduce operators' workload or improve system performance.

Learning Sparse Gaussian Graphical Model with l0-regularization

2019-04-10T21:13:31Z

Learning Sparse Gaussian Graphical Model with l0-regularization Mu, Beipeng; How, Jonathan For the problem of learning sparse Gaussian graphical models, it is desirable to obtain both sparse structures as well as good parameter estimates. Classical techniques, such as optimizing the l1-regularized maximum likelihood or Chow-Liu algorithm, either focus on parameter estimation or constrain to speci c structure. This paper proposes an alternative that is based on l0-regularized maximum likelihood and employs a greedy algorithm to solve the optimization problem. We show that, when the graph is acyclic, the greedy solution finds the optimal acyclic graph. We also show it can update the parameters in constant time when connecting two sub-components, thus work efficiently on sparse graphs. Empirical results are provided to demonstrate this new algorithm can learn sparse structures with cycles efficiently and that it dominates l1-regularized approach on graph likelihood.

Augmentation of Power Output of Axisymmetric Ducted Wind Turbines by Porous Trailing Edge Disks

2019-04-11T06:13:39Z

Augmentation of Power Output of Axisymmetric Ducted Wind Turbines by Porous Trailing Edge Disks widnall, sheila; byron, james; florin, peter This paper presents analytical and experimental results that demonstrated that the power output from a ducted wind turbine can be dramatically increased by the addition of a trailing edge device such as a porous disk. In addition, the trailing edge device can be designed to be geometrically adaptable, allowing the turbine to spin up at low wind speeds and providing relief from aerodynamic loads at high wind speeds.

Brainstem processing of vestibular sensory exafference: implications for motion sickness etiology

2019-04-10T12:02:35Z

Brainstem processing of vestibular sensory exafference: implications for motion sickness etiology Oman, Charles; Cullen, Kathleen The origin of the internal “sensory conflict” stimulus causing motion sickness has been debated for more than four decades. Recent studies show a subclass of neurons in the vestibular nuclei and deep cerebellar nuclei that respond preferentially to passive head movements. During active movement, the semicircular canal and otolith input (“reafference”) to these neurons is cancelled by a mechanism comparing the expected consequences of self-generated movement (estimated with an internal model- presumably located in the cerebellum) with the actual sensory feedback. The un-cancelled component (“exafference”) resulting from passive movement normally helps compensate for unexpected postural disturbances. Notably, the existence of such vestibular “sensory conflict” neurons had been postulated as early as 1982, but their existence and putative role in posture control, motion sickness has been long debated. Here we review the development of “sensory conflict” theories in relation to recent evidence for brainstem and cerebellar reafference cancellation, and identify some open research questions. We propose that conditions producing persistent activity of these neurons, or their targets, stimulates nearby brainstem emetic centers – via an as yet unidentified mechanism. We discuss how such a mechanism is consistent with the notable difference in motion sickness susceptibility of drivers as opposed to passengers, human immunity to normal self-generated movement, and why head restraint or lying horizontal confers relative immunity. Finally, we propose that fuller characterization of these mechanisms, and their potential role in motion sickness could lead to more effective, scientifically based prevention and treatment for motion sickness. Penultimate version of manuscript accepted 4/20/14, and after minor edits, published online May 18, 2014 at Springer Online First as DOI 10.1007/s00221-014-3973-2

The Role of Human-Automation Consensus in Multiple Unmanned Vehicle Scheduling

2019-04-10T08:55:59Z

The Role of Human-Automation Consensus in Multiple Unmanned Vehicle Scheduling Cummings, M.L.; Clare, A.; Hart, C. Objective: This study examined the impact of increasing automation replanning rates on operator performance and workload when supervising a decentralized network of heterogeneous unmanned vehicles. Background: Futuristic unmanned vehicles systems will invert the operator-to-vehicle ratio so that one operator can control multiple dissimilar vehicles, connected through a decentralized network. Significant human-automation collaboration will be needed due to automation brittleness, but such collaboration could cause high workload. Method: Three increasing levels of replanning were tested on an existing, multiple unmanned vehicle simulation environment that leverages decentralized algorithms for vehicle routing and task allocation, in conjunction with human supervision. Results: Rapid replanning can cause high operator workload, ultimately resulting in poorer overall system performance. Poor performance was associated with a lack of operator consensus for when to accept the automation‟s suggested prompts for new plan consideration, as well as negative attitudes towards unmanned aerial vehicles in general. Participants with video game experience tended to collaborate more with the automation, which resulted in better performance. Conclusion: In decentralized unmanned vehicle networks, operators who ignore the automation‟s requests for new plan consideration and impose rapid replans both increase their own workload and reduce the ability of the vehicle network to operate at its maximum capacity. Application: These findings have implications for personnel selection and training for futuristic systems involving human collaboration with decentralized algorithms embedded in networks of autonomous systems.

Global vs. local decision support for multiple independent UAV schedule management

2019-04-10T08:01:10Z

Global vs. local decision support for multiple independent UAV schedule management Cummings, M.l; Brezezinski, A. As unmanned aerial vehicles (UAVs) become increasingly autonomous, time-critical and complex single-operator systems will require advance prediction and mitigation of schedule conflicts. However, actions that mitigate a current schedule conflict may create future schedule problems. Decision support is needed allowing an operator to evaluate different mission schedule management options in real-time. This paper describes two decision support visualisations for single-operator supervisory control of four independent UAVs performing a time-critical targeting mission. A configural display common to both visualisations, called StarVis, graphically depicts current schedule problems, as well as projections of potential local and global schedule problems. Results from an experiment showed that subjects using the locally optimal StarVis implementation had better performance, higher situational awareness, and no significant increase in workload over a more globally optimal implementation of StarVis. This research effort highlights how the same decision support design applied at different abstraction levels can produce different performance results.

Supporting Intelligent and Trustworthy Maritime Path Planning Decisions

2019-04-10T15:04:23Z

Supporting Intelligent and Trustworthy Maritime Path Planning Decisions Cummings, M.L.; Buchin, M.; Carrigan, G.; Donmez, B. The risk of maritime collisions and groundings has dramatically increased in the past five years despite technological advancements such as GPS-based navigation tools and electronic charts which may add to, instead of reduce, workload. We propose that an automated path planning tool for littoral navigation can reduce workload and improve overall system efficiency, particularly under time pressure. To this end, a Maritime Automated Path Planner (MAPP) was developed, incorporating information requirements developed from a cognitive task analysis, with special emphasis on designing for trust. Human-in-the-loop experimental results showed that MAPP was successful in reducing the time required to generate an optimized path, as well as reducing path lengths. The results also showed that while users gave the tool high acceptance ratings, they rated the MAPP as average for trust, which we propose is the appropriate level of trust for such a system.

Modeling Workload Impact in Multiple Unmanned Vehicle Supervisory Control

2019-04-12T07:32:34Z

Modeling Workload Impact in Multiple Unmanned Vehicle Supervisory Control Donmez, B.D.; Nehme, C.; Cummings, M.L. Discrete event simulations for futuristic unmanned vehicle (UV) systems enable a cost and time effective methodology for evaluating various autonomy and human automation design parameters. Operator mental workload is an important factor to consider in such models. We present that the effects of operator workload on system performance can be modeled in such a simulation environment through a quantitative relation between operator attention and utilization, i.e., operator busy time used as a surrogate real-time workload measure. In order to validate our model, a heterogeneous UV simulation experiment was conducted with 74 participants. Performance based measures of attention switching delays were incorporated in the discrete event simulation model via UV wait times due to operator attention inefficiencies (WTAI). Experimental results showed that WTAI is significantly associated with operator utilization (UT), such that high UT levels correspond to higher wait times. The inclusion of this empirical UT-WTAI relation in the discrete event simulation model of multiple UV supervisory control resulted in more accurate replications of data, as well as more accurate predictions for alternative UV team structures. These results have implications for the design of future human-UV systems, as well as more general multiple task supervisory control models.

Human-Automation Collaboration in Complex Multivariate Resource Allocation Decision Support Systems

2019-04-11T12:34:09Z

Human-Automation Collaboration in Complex Multivariate Resource Allocation Decision Support Systems Cummings, M.L.; Bruni, S. In resource allocation problems for systems with moving planning horizons and significant uncertainty, typical of supervisory control environments, it is critical that some balance of human-automation collaboration be achieved. These systems typically require leveraging the computational power of automation, as well as the experience and judgment of human decision makers. Human-automation collaboration can occur through degrees of collaboration from automation-centric to human-centric, and such collaboration is inherently distinct from previously-discussed levels of automation. In the context of a command and control mission planning task, we show that across a number of metrics, there is no clear dominant human-automation collaboration scheme for resource allocation problems using three distinct instantiations of human-automation collaboration. Rather, the ultimate selection for the best resource allocation decision support system will depend on a cost-benefit approach that could include mitigation of workload, conformance to intended design characteristics, as well as the need to maximize overall mission performance.

Supervised vs. Unsupervised Learning for Operator State Modeling in Unmanned Vehicle Settings

2019-04-11T12:34:09Z

Supervised vs. Unsupervised Learning for Operator State Modeling in Unmanned Vehicle Settings Boussemart, Y.; Cummings, M.L.; Las Fargeas, J.; Roy, N. In this paper, we model operator states using hidden Markov models applied to human supervisory control behaviors. More specifically, we model the behavior of an operator of multiple heterogeneous unmanned vehicle systems. The hidden Markov model framework allows the inference of higher operator states from observable operator interaction with a computer interface. For example, a sequence of operator actions can be used to compute a probability distribution of possible operator states. Such models are capable of detecting deviations from expected operator behavior as learned by the model.The difficulty with parametric inference models such as hidden Markov models is that a large number of parameters must either be specified by hand or learned from example data.We compare the behavioral models obtained with two different supervised learning techniques and an unsupervised hidden Markov model training technique. The results suggest that the best models of human supervisory control behavior are obtained through unsupervised learning. We conclude by presenting further extensions to this work.

Operator Choice Modeling for UAV Visual Search Tasks

2019-04-10T12:31:42Z

Operator Choice Modeling for UAV Visual Search Tasks Bertuccelli, L.F.; Cummings, M.L. Unmanned aerial vehicles (UAVs) provide unprecedented access to imagery of possible ground targets of interest in real time. The availability of this imagery is expected to increase with envisaged future missions of one operator controlling multiple UAVs. This research investigates decision models that can be used to develop assistive decision support for UAV operators involved in these complex search missions. Previous human-in-the-loop experiments have shown that operator detection probabilities may decay with increased search time. Providing the operators with the ability to requeue difficult images with the option of relooking at targets later was hypothesized to help operators improve their search accuracy. However, it was not well understood how mission performance could be impacted by operators performing requeues with multiple UAVs. This work extends a queuing model of the human operator by developing a retrial queue model (ReQM) that mathematically describes the use of relooks. We use ReQM to generate performance predictions through discrete event simulation. We validate these predictions through a human-in-the-loop experiment that evaluates the impact of requeuing on a simulated multiple-UAV mission. Our results suggest that, while requeuing can improve detection accuracy and decrease mean search times, operators may need additional decision support to use relooks effectively.

Predictive models of human supervisory control behavioral patterns using hidden semi-Markov models

2019-04-11T12:29:05Z

Predictive models of human supervisory control behavioral patterns using hidden semi-Markov models Boussemart, Y.; Cummings, M.L. Behavioral models of human operators engaged in complex,time-critical high-risk domains, such as those typical in Human Supervisory Control (HSC) settings, are of great value because of the high cost of operator failure. We propose that Hidden Semi-Markov Models (HSMMs) can be employed to model behaviors of operators in HSC settings where there is some intermittent human interaction with a system via a set of external controls. While regular Hidden Markov Models (HMMs) can be used to model operator behavior, HSMMs are particularly suited to time-critical supervisory control domains due to their explicit representation of state duration. Using HSMMs,we demonstrate in an unmanned vehicle supervisory control environment that such models can accurately predict future operator behavior both in terms of states and durations.

Human-Automation Path Planning Optimization and Decision Support

2019-04-10T08:01:07Z

Human-Automation Path Planning Optimization and Decision Support Cummings, M.L.; Marquez, J.J.; Roy, N. Path planning is a problem encountered in multiple domains, including unmanned vehicle control, air traffic control, and future exploration missions to the Moon and Mars. Due to the voluminous and complex nature of the data, path planning in such demanding environments requires the use of automated planners. In order to better understand how to support human operators in the task of path planning with computer aids, an experiment was conducted with a prototype path planner under various conditions to assess the effect on operator performance. Participants were asked to create and optimize paths based on increasingly complex path cost functions, using different map visualizations including a novel visualization based on a numerical potential field algorithm. They also planned paths under degraded automation conditions. Participants exhibited two types of analysis strategies, which were global path regeneration and local sensitivity analysis. No main effect due to visualization was detected, but results indicated that the type of optimizing cost function affected performance, as measured by metabolic costs, sun position, path distance and task time. Unexpectedly, participants were able to better optimize more complex cost functions as compared to a simple time-based cost function.

,The Impact of Human-Automation Collaboration in Decentralized Multiple Unmanned Vehicle Control

2019-04-11T12:27:33Z

,The Impact of Human-Automation Collaboration in Decentralized Multiple Unmanned Vehicle Control Cummings, M.L.; How, J.; Whitten, A.; Toupet, O. For future systems that require one or a small team of operators to supervise a network of automated agents, automated planners are critical since they are faster than humans for path planning and resource allocation in multivariate, dynamic, time-pressured environments. However, such planners can be brittle and unable to respond to emergent events. Human operators can aid such systems by bringing their knowledge-based reasoning and experience to bear. Given a decentralized task planner and a goal-based operator interface for a network of unmanned vehicles in a search, track, and neutralize mission, we demonstrate with a human-on-the-loop experiment that humans guiding these decentralized planners improved system performance by up to 50%. However, those tasks that required precise and rapid calculations were not significantly improved with human aid. Thus, there is a shared space in such complex missions for human–automation collaboration.

Collaborative Exploration with a Micro Aerial Vehicle: A Novel Interaction Method for Controlling a MAV with a Hand-Held Device

2019-04-11T12:27:00Z

Collaborative Exploration with a Micro Aerial Vehicle: A Novel Interaction Method for Controlling a MAV with a Hand-Held Device Pitman, D.; Cummings, M.L. In order to collaboratively explore an environment with a Micro Aerial Vehicle (MAV), an operator needs a mobile interface, which can support the operator’s divided attention. To this end, we developed the Micro Aerial Vehicle Exploration of an Unknown Environment (MAV-VUE) interface, which allows operators with minimal training the ability to remotely explore their environment with a MAV. MAV-VUE employs a concept we term Perceived First-Order (PFO) control, which allows an operator to effectively “fly” a MAV with no risk to the vehicle. PFO control utilizes a position feedback control loop to fly the MAV while presenting rate feedback to the operator. A usability study was conducted to evaluate MAV-VUE. This interface was connected remotely to an actual MAV to explore a GPS-simulated urban environment.

Assessing Operator Strategies for Real-time Replanning of Multiple Unmanned Vehicles

2019-04-11T12:26:59Z

Assessing Operator Strategies for Real-time Replanning of Multiple Unmanned Vehicles Clare, A.S.; Maere, P.C.P.; Cummings, M.L. Future unmanned vehicles systems will invert the operator-to-vehicle ratio so that one operator controls a decentralized network of heterogeneous unmanned vehicles. This study examines the impact of allowing an operator to adjust the rate of prompts to view automation-generated plans on system performance and operator workload. Results showed that the majority of operators chose to adjust the replan prompting rate. The initial replan prompting rate had a significant framing effect on the replan prompting rates chosen throughout a scenario. Higher initial replan prompting rates led to significantly lower system performance. Operators successfully self-regulated their task-switching behavior to moderate their workload.

Field Testing of a Quad Rotor Smartphone Control System

2019-04-11T12:24:53Z

Field Testing of a Quad Rotor Smartphone Control System Cummings, M.L.; Jackson, K.; Quimby, P.; Pitman, D. With recent regulatory efforts to reduce restrictions placed on the operation of Micro Air Vehicles (MAVs) in the United States, it is likely that in the next few years, these vehicles will become commonplace in the commercial marketplace as they are in military environments. In order to reduce the barrier to entry for operations of MAVs, customers of these systems will require ease of operation as well as minimal training time in order to reduce costs. To this end, a smartphone application was developed to control a quadrotor remotely in the exploration of an unknown environment, and tested for users with only three minutes of training. Initial motion capture room tests produced encouraging results for localization and target identification tasks, however, such environments are inherently artificial and the extensibility of such results is limited. A follow-on outdoor field study was conducted in order to compare the indoor and outdoor results and to assess operator performance in a realistic environment. Performance on the outdoor localization tasks was comparable to the indoor study, however, participants generally performed slightly worse on the target identification task in the outdoor experiment, attributed to camera image quality and GPS localization issues. Other issues such as wind and flight safety considerations are discussed.

Boredom and Distraction in Multiple Unmanned Vehicle Supervisory Control

2019-04-11T12:24:53Z

Boredom and Distraction in Multiple Unmanned Vehicle Supervisory Control Cummings, M.L.; Mastracchio, C.; Thornburg, K.M.; Mkrtchyan, A. Operators currently controlling Unmanned Aerial Vehicles report significant boredom, and such systems will likely become more automated in the future. Similar problems are found in process control, commercial aviation, and medical settings. To examine the effect of boredom in such settings, a long duration low task load experiment was conducted. Three low task load levels requiring operator input every 10, 20, or 30 minutes were tested in a our-hour study using a multiple unmanned vehicle simulation environment that leverages decentralized algorithms for sometimes imperfect vehicle scheduling. Reaction times to system-generated events generally decreased across the four hours, as did participants’ ability to maintain directed attention. Overall, participants spent almost half of the time in a distracted state. The top performer spent the majority of time in directed and divided attention states. Unexpectedly, the second-best participant, only 1% worse than the top performer, was distracted almost one third of the experiment, but exhibited a periodic switching strategy, allowing him to pay just enough attention to assist the automation when needed. Indeed, four of the five top performers were distracted more than one-third of the time. These findings suggest that distraction due to boring, low task load environments can be effectively managed through efficient attention switching. Future work is needed to determine optimal frequency and duration of attention state switches given various exogenous attributes, as well as individual variability. These findings have implications for the design of and personnel selection for supervisory control systems where operators monitor highly automated systems for long durations with only occasional or rare input.

Unloved Aerial Vehicles: Gutting its UAV plan, the Air Force sets a course for irrelevance

2019-04-10T20:54:26Z

Unloved Aerial Vehicles: Gutting its UAV plan, the Air Force sets a course for irrelevance Spinetta, L.; Cummings, M.L. This month's cover article challenges Air Force leader on the subject of unmanned aerial vehicles. Lt. Col. Lawrence Spinetta and Missy Cummings see disaster, or at least a long-term slide into irrelevance, in recent decisions that appear to under value UAVs in caparison with manned fighters and bombers.

Shared Authority Concerns in Automated Driving Applications

2019-04-11T09:01:58Z

Shared Authority Concerns in Automated Driving Applications Cummings, M.L.; Ryan, J.C. Given the move toward driverless cars, which includes the more short-term goal of driving assistance, what the appropriate shared authority and interaction paradigms should be between human drivers and the automation remains an open question until more principled research and testing has occurred. It is unclear at this time how robust driverless cars are to system failures (including human failures) and operations in degraded sensor environments. Automation onboard such vehicles is inherently brittle and can only account for what it is programmed to consider. Communication between what is technically a very complex system to a human population of extreme variability in driving skills and attention management will be difficult, since the driver will need to be appropriately informed of the state of the system, including limitations, and will need to build appropriate trust in the automation’s capabilities (neither too much or too little). Further complicating this problem is the significant body of research demonstrating that automated systems can lead to boredom, which encourages distraction. This leaves operators unaware of the state of the vehicle (aka, mode confusion) and ill-suited to respond quickly and appropriately in case of a potential accident. Over time, operator skill degradation due to automation use can further reduce the human ability to respond to emergent driving demands, and will likely lead to risk homeostasis even in normal operations. Each of these issues are well-known to the human systems engineering community, but it is unclear that these issues are being considered by driverless car designers or that manufactures are conducting human-in-the-loop tests with representative members of the driving population. Until these tests show that the vehicles account for the aforementioned issues, driverless cars will not be safe for unrestricted access and use on U.S. roadways. Moreover, there are significant socio-technical considerations that do not appear to be a concern in the push to introduce this technology on a wide scale. The utilitarian approach quoted by many in the press, i.e., that driverless cars will eventually kill people but that this should be acceptable due to the likely reduction in overall deaths (which is not yet proven) demonstrates an insensitivity to a deontological perspective that causes many people to be uncomfortable with such a significant shift in responsibility and accountability to computers.

Operator Objective Function Guidance for a Real-time Unmanned Vehicle Scheduling Algorithm

2019-04-11T12:24:13Z

Operator Objective Function Guidance for a Real-time Unmanned Vehicle Scheduling Algorithm Clare, A.S.; Cummings, M.L.; How, J.; Whitten, A.; Toupet, O. Advances in autonomy have made it possible to invert the typical operator-to-unmanned-vehicle ratio so that asingle operator can now control multiple heterogeneous unmanned vehicles. Algorithms used in unmanned-vehicle path planning and task allocation typically have an objective function that only takes into account variables initially identified by designers with set weightings. This can make the algorithm seemingly opaque to an operator and brittle under changing mission priorities. To address these issues, it is proposed that allowing operators to dynamically modify objective function weightings of an automated planner during a mission can have performance benefits. A multiple-unmanned-vehicle simulation test bed was modified so that operators could either choose one variable or choose any combination of equally weighted variables for the automated planner to use in evaluating mission plans. Results from a human-participant experiment showed that operators rated their performance and confidence highest when using the dynamic objective function with multiple objectives. Allowing operators to adjust multiple objectives resulted in enhanced situational awareness, increased spare mental capacity, fewer interventions to modify the objective function, and no significant differences in mission performance. Adding this form of flexibility and transparency to automation in future unmanned vehicle systems could improve performance, engender operator trust, and reduce errors.

MVL@50: Historical photos of MIT Man Vehicle Lab 1962-2012

2019-04-10T20:03:12Z

MVL@50: Historical photos of MIT Man Vehicle Lab 1962-2012 Oman, Charles; Young, Laurence; Newman, Dava; Hoffman, Jeffrey; Zotos, Elizabeth Historical photos shown at 50th anniversary celebration of the MIT Man Vehicle Laboratory Photographs shown at 50th Anniversary celebration of the MIT Man Vehicle Laboratory, September 14, 2012

Oman 65th program, photos and letters

2019-04-11T10:42:39Z

Oman 65th program, photos and letters Young, Laurence; Zotos, Elizabeth 2009 Program, letters and photos from CM Oman's 65th birthday symposium Program, letters and photo archive from MVL Director CM Oman's 65th birthday symposium, March 5 in 37-252

40 Years of MIT MVL Memories

2019-04-12T20:49:08Z

40 Years of MIT MVL Memories Oman, Charles 385 photos shown at May 2009 symposium honoring MVL Director C.M. Oman Shows MIT aero astro colleagues and students, and NASA, NSBRI, USN and USAF collaborators between 1996-2009

Supplementary material for nonparameteric adaptive control of time varying systems using gaussian processes

2019-04-10T22:35:13Z

Supplementary material for nonparameteric adaptive control of time varying systems using gaussian processes Chowdhary, Girish; Kingravi, Hassan A.; How, Jonathan P.; Vela, Patricio A. Real-world dynamical variations make adaptive control of time-varying systems highly relevant. However, most adaptive control literature focuses on analyzing systems where the uncertainty is represented as a weighted linear combination of fixed number of basis functions, with constant weights. One approach to modeling time variations is to assume time varying ideal weights, and use difference integration to accommodate weight variation. However, this approach reactively suppresses the uncertainty, and has little ability to predict system behavior locally. We present an alternate formulation by leveraging Bayesian nonparametric Gaussian Process adaptive elements. We show that almost surely bounded adaptive controllers for a class of nonlinear time varying system can be formulated by incorporating time as an additional input to the Gaussian kernel. Analysis and simulations show that the learning-enabled local predictive ability of our adaptive controllers significantly improves performance. This technical report has supplementary material for "Bayesian Nonparametric Adaptive Control of Time-varying Systems using Gaussian Processes" American Control Conference paper

Bayesian Nonparametric Adaptive Control using Gaussian Processes

2019-04-12T20:47:13Z

Bayesian Nonparametric Adaptive Control using Gaussian Processes Chowdhary, Girish; Kingravi, Hassan A.; How, Jonathan P.; Vela, Patricio A. Most current Model Reference Adaptive Control (MRAC) methods rely on parametric adaptive elements, in which the number of parameters of the adaptive element are fixed a priori, often through expert judgment. An example of such an adaptive element are Radial Basis Function Networks (RBFNs), with RBF centers pre-allocated based on the expected operating domain. If the system operates outside of the expected operating domain, this adaptive element can become non-effective in capturing and canceling the uncertainty, thus rendering the adaptive controller only semi-global in nature. This paper investigates a Gaussian Process (GP) based Bayesian MRAC architecture (GP-MRAC), which leverages the power and flexibility of GP Bayesian nonparametric models of uncertainty. GP-MRAC does not require the centers to be preallocated, can inherently handle measurement noise, and enables MRAC to handle a broader set of uncertainties, including those that are defined as distributions over functions. We use stochastic stability arguments to show that GP-MRAC guarantees good closed loop performance with no prior domain knowledge of the uncertainty. Online implementable GP inference methods are compared in numerical simulations against RBFN-MRAC with preallocated centers and are shown to provide better tracking and improved long-term learning. This technical report is a preprint of an article submitted to a journal.

Efficient Distributed Sensing Using Adaptive Censoring-Based Inference

2019-04-12T20:47:12Z

Efficient Distributed Sensing Using Adaptive Censoring-Based Inference Mu, Beipeng; Chowdhary, Girish; How, Jonathan P. In many distributed sensing applications it is likely that only a few agents will have valuable information at any given time. Since wireless communication between agents is resource-intensive, it is important to ensure that the communication effort is focused on communicating valuable information from informative agents. This paper presents communication efficient distributed sensing algorithms that avoid network cluttering by having only agents with high Value of Information (VoI) broadcast their measurements to the network, while others censor themselves. A novel contribution of the presented distributed estimation algorithm is the use of an adaptively adjusted VoI threshold to determine which agents are informative. This adaptation enables the team to better balance between the communication cost incurred and the long-term accuracy of the estimation. Theoretical results are presented establishing the almost sure convergence of the communication cost and estimation error to zero for distributions in the exponential family. Furthermore, validation through numerical simulations and real datasets show that the new VoI-based algorithms can yield improved parameter estimates than those achieved by previously published hyperparameter consensus algorithms while incurring only a fraction of the communication cost. This technical report is a preprint of work submitted to a journal.

Efficient distributed information fusion using value of information based censoring

2025-05-20T12:24:45Z

Efficient distributed information fusion using value of information based censoring Mu, Beipeng; How, Jonathan P.; Chowdhary, Girish In many distributed sensing applications, not all agents have valuable information at all times. Therefore, requiring all agents to communicate at all times can be resource intensive. In this work, the notion of Value of Information (VoI) is used to improve the efficiency of distributed sensing algorithms. Particularly, only agents with high VoI broadcast their measurements to the network, while others censor their measurements. New VoI realized data fusion algorithms are introduced, and an in depth analysis of the costs incurred by these algorithms and conventional distributed data fusion algorithms is presented. Numerical simulations are used to compare the performance of the VoI realized algorithms with traditional data fusion algorithms. A VoI based algorithm that adaptively adjusts the criterion for being informative is presented and shown to strike a good balance between reduced communication cost and increased accuracy.

Information-Theoretic Motion Planning for Constrained Sensor Networks

2025-02-06T18:38:02Z

Information-Theoretic Motion Planning for Constrained Sensor Networks Levine, Daniel; Luders, Brandon; How, Jonathan P. This paper considers the problem of online informative motion planning for a network of heterogeneous sensing agents, each subject to dynamic constraints, environmental constraints, and sensor limitations. Prior work has not yielded algorithms that are amenable to such general constraint characterizations. In this paper, we propose the Information-rich Rapidly-exploring Random Tree (IRRT) algorithm as a solution to the constrained informative motion planning problem that embeds metrics on uncertainty reduction at both the tree growth and path selection levels. IRRT possesses a number of beneficial properties, chief among them being the ability to find dynamically feasible, informative paths on short timescales, even subject to the aforementioned constraints. The utility of IRRT in efficiently localizing stationary targets is demonstrated in a progression of simulation results with both single-agent and multiagent networks. These results show that IRRT can be used in real-time to generate and execute information-rich paths in tightly constrained environments.

Investigation of the F117A Vortical Flow Characteristics Preliminary Results

2019-04-10T19:15:36Z

Investigation of the F117A Vortical Flow Characteristics Preliminary Results Vermeersch, Sabine The investigation of the vortical flow around the F117A Stealth Fighter is presented in order to demonstrate the capability to resolve leading edge vortices with an adaptive finite element solver for the Euler equations. The major goal is to capture vortex breakdown at high angles of attack. This work presents the five main steps involved in a typical study of the flow characteristics of a complete aircraft : the definition of the model geometry, the realization of a suitable grid around the discretized model, the implementation of a flow solver, the subsequent analysis of the flow field and the comparison to experimental data sets. The computational data are compared to the lift curves of the aircraft obtained in a subsonic 5' x 7' wind tunnel. The occurance and location of vortex breakdown is determined by performing flow visualization in the tunnel. Five cases are computed for this work. Each case is studied at Mach 0.3 and angles of attack range between 7 and 30 degrees.

Adaptive Mesh Euler Equation Computations of Vortex Breakdown in Delta Wing Flow

2019-04-12T20:59:34Z

Adaptive Mesh Euler Equation Computations of Vortex Breakdown in Delta Wing Flow Modiano, David A solution method for the three-dimensional Euler equations is formulated and implemented. The solver uses an unstructured mesh of tetrahedral cells and performs adaptive refinement by mesh-point embedding to increase mesh resolution in regions of interesting flow features. The fourth-difference artificial dissipation is increased to a higher order of accuracy using the method of Holmes and Connell. A new method of temporal integration is developed to accelerate the explicit computation of unsteady flows. The solver is applied to the solution of the flow around a sharp edged delta wing, with emphasis on the behavior of the leading edge vortex above the leeside of the wing at high angle of attack, under which conditions the vortex suffers from vortex breakdown. Large deviations in entropy, which indicate vortical regions of the flow, specify the region in which adaptation is performed. Adaptive flow calculations are performed at ten different angles of attack, at seven of which vortex breakdown occurs. The aerodynamic normal force coefficients show excellent agreement with wind tunnel data measured by Jarrah, which demonstrates the importance of adaptation in obtaining an accurate solution. The pitching moment coefficient and the location of vortex breakdown are compared with experimental data measured by Hummel and Srinivasan, with which fairly good agreement is seen in cases in which the location of breakdown is over the wing. A series of unsteady calculations involving a pitching delta wing were performed. The use of the acceleration technique is validated. A hysteresis in the normal force is observed, as in experiments, and a lag in the breakdown position is demonstrated.

System Identification and Active Control of a Turbulent Boundary Layer

2019-04-09T15:55:16Z

System Identification and Active Control of a Turbulent Boundary Layer Rathnasingham, Ruben An experimental investigation is made into the active control of the near-wall region of a turbulent boundary layer using a linear control scheme. System identification in the boundary layer provides optimal transfer functions that predict the downstream of characteristics of the streamwise velocity and wall pressure fluctuation using an array of upstream flush-mounted sensors that are sensitive to spanwise shear. Enhanced direction techniques isolated the large scale turbulent motion and improved the downstream correlations resulting in greater controllability. The techniques were based on the conditioned spectral analysis between adjacent sensors to extract the most correlated flow structures that span the distance between them. The control is applied using a spanwise array of resonant actuators that introduce a pair of streamwise vortices into the flow. Control experiments were carried out for a single and multiple input/output configurations. The single output results show that a maximum reduction of 34% is achieved in the streamwise velocity fluctuation. This reduction is greatest at the point of optimization but spans over a few hundred viscous lengths downstream of the actuator and about 50 viscous lengths in the spanwise and wall-normal directions. The wall pressure fluctuation and the mean wall shear stress (measured approximately using mean velocity profiles near the wall) was reduced by 17% and 7% respectively. The multiple-input/single-output configuration resulted in a wider spatial influence of the control while maintaining the maximum reductions in the fluctuations. The multiple-input/multiple-output configuration showed a marked increase in the spatial extent of the control (primarily in the spanwise direction), at the expense of a lower reduction in the fluctuations (maximum of 30% and 15% for the streamwise velocity and wall pressure respectively). The bursting frequency was computed from a VITA algorithm applied to the streamwise velocity fluctuation. The bursting frequency was reduced at all threshold levels examined but the maximum reduction of 23% occurred at a threshold level of 3. The spanwise spatial correlation was measured at different streamwise locations downstream of the actuator array. This result suggests that the reduction in turbulent fluctuations obtained using the current control scheme was achieved by reducing the strength of the most coherent flow structures and to inhibit their ability to interact with each other by increasing their average spanwise separation by more than 25% (from ~ 90l* to 120l*).

A Comparison of Numerical Schemes on Triangular and Quadrilateral Models

2019-04-12T20:59:33Z

A Comparison of Numerical Schemes on Triangular and Quadrilateral Models Lindquist, Dana Rae

Numerical Simulation of Hypersonic Flow Over a Blunt Leading Edge Delta Wing

2019-04-09T16:14:16Z

Numerical Simulation of Hypersonic Flow Over a Blunt Leading Edge Delta Wing Lee, Kuok Ming Euler and Navier-Stokes results are presented for a blunt delta wing at Mach 7.15 and 300 angle of attack. The viscous calculations were done at a Reynolds number based on chord of 5.85 x 106 with freestream and wall temperatures set to 74K and 288K respectively. The inviscid simulations were carried out using a finite volume, central difference code written by Roberts [21] and Goodsell [7]. The Navier-Stokes results were obtained on the semi-implicit extension of the inviscid code, developed by Loyd [17]. The inviscid results showed a strong shock on the windward side of the wing at a stand-off angle of about -5' from the body. As the flow traverses around the leading edge it accelerates strongly through an expansion fan. On the upper surface of the wing, separation occurs at about 60% span resulting in a region of reverse cross stream flow. The viscous calculations display a similar shock structure. Furthermore the boundary layer on the windward side is thin and variations in the circumferential direction are small. The flow on the leeward side of the wing separates in 2 places. The primary separation occurs just inside of the leading edge, and the secondary separation region is located further inboard. The inviscid CL and CD are 0.547 and 0.383 respectively, whereas the viscous values are 0.547 and 0.386. The viscous component contributes only an insignificant 2.32 x 10- S to the CD of the Navier-Stokes calculations.

A Semi-Implicit Navier-Stokes Solver and Its Application to a Study of Separated Flow about Blunt Delta Wings

2019-04-12T20:59:32Z

A Semi-Implicit Navier-Stokes Solver and Its Application to a Study of Separated Flow about Blunt Delta Wings Loyd, Bernard A novel semi-implicit scheme for the Navier-Stokes equations is presented and evaluated. The semi-implicit scheme combines an implicit temporal integration in the bodynormal directions with explicit temporal integrations in the streamwise and cross stream directions. Thus, advantages of both explicit and implicit schemes are retained in the semi-implicit scheme. Numerical stiffness due to disparate physical scales in the normal direction is eliminated, since stability of the algorithm depends only on relatively coarse streamwise and cross stream grid spacing, not on the typically fine normal spacing. Approximate factorization is unnecessary and only one matrix inversion per multi-stage time step is required. Computations show that while a explicit scheme employing multigrid and residual smoothing and a fully implicit scheme are competitive for inviscid calculations, the semi-implicit scheme is superior for viscous flow calculations. Efficiency of the semi-implicit scheme is exploited in a study of flow separation around delta wings with blunt leading edges. Three-dimensional laminar vortical flows over two 65* swept semi-infinite elliptical wings of thickness to chord ratio 1 : 11.55 and 1 : 20 at Moo = 1.6, ReL = 106, and angles of attack of 40, and 8*, and a 60* swept elliptical wing with t/c = 1 : 11.55 at Moo = 1.4, ReL = 2 x 106 and a = 14* are considered. In these flow cases, separation line locations are fixed not by a particular geometric factor (eg. sharp leading edge), but by interaction of physical and geometric factors. Solutions with the semi-implicit scheme are shown to be significantly more efficient than solutions with a corresponding explicit scheme. Two distinct leading edge separation processes are identified: separation due to shock-less flow recompression leeward of the leading edge expansion in the t/c = 11.55, a = 40 case and separation involving a leading edge shock in the remaining cases.

Visualization of Three Dimensional CFD Results

2019-04-10T13:24:33Z

Visualization of Three Dimensional CFD Results We have developed an interactive graphics system for the display of three dimensional CFD solutions on unstructured hexahedral grids. This system is implemented on a high-performance graphics supercomputer. Visualization methods employed are shaded color surface plots, integration of particle trajectories, interpolation of volumetric data onto a plane, interpolation of planar data onto a line segment, and extraction of numerical quantities from a plane. We have used this graphics system to examine the inviscid flow about the NTF delta wing, as solved by Becker, and found that it allows us to locate flow features quickly. We were unable to find a satisfactory method to visualize the three dimensional mesh structure. With the exception of particle path integration, the algorithms we have implemented can be used to visualize any volumetric data.

Planning under Uncertainty using Nonparametric Bayesian Models

2025-02-06T18:38:33Z

Planning under Uncertainty using Nonparametric Bayesian Models Campbell, Trevor; Ponda, Sameera; Chowdhary, Girish; How, Jonathan

Airline alliances : the airline perspective

2019-04-10T23:33:02Z

Airline alliances : the airline perspective Fernandez de la Torre, Pablo E. Airline alliances are one of the critical issues faced by the airline industry in the 1990s. In this thesis, an overview of the most significant impacts that the formation of alliances have brought to the industry-especially to airline management-is presented. Part I presents several frameworks to help understand why alliances have become so critical for the participating airlines. A definition of airline alliances, different typologies to classify them, the main motivations for their formation, and the recent trends in the industry are presented. The alliances' main objective is the increase of market coverage, though the strengthening of market position on certain routes and the reduction of costs are additional sources of competitive advantage they provide to the participating airlines. Alliances can also bring many benefits to customers in terms of improved service, although they represent a threat for sustainable competition. Part II analyzes two critical problems faced by airline management. First, it is analyzed the effect of the network connectivity through an alliance hub-to-hub linkage scheme on the increase in market share. The analysis shows that the alliance hub-to-hub link represents a significant source of additional traffic for the alliance. Accessibility, a measure developed for network connectivity, has proven to be a critical factor in increasing market share on the alliance hub-to-hub link. Scheduling coordination within alliances, therefore, should consider the maximization of accessibility as a critical driver of demand. The second problem analyzed is the introduction of codesharing into revenue management systems. There are four different problems associated with it, which are interrelated in practice. One of them, the valuation and seat inventory control process for codeshare traffic is analyzed in detail. Two main revenue management approaches to handle codesharing are presented: The proration approach and the fully integrated approach. The latter aims to maximize the combined revenue and implies higher complexity in its implementation, while the former has easier implementation. Under the proration approach, there is a significant source of revenue loss due to an incorrect valuation of the revenue contribution brought by codeshare traffic. Although a solution is proposed to solve this problem, a final answer should include a redefinition of the way codesharing agreements are currently established. Includes bibliographical references (p. 211-214)

Regionalism in international air transportation--cooperation and competition : papers from an international conference organized by the Massachusetts Institute of Technology, held at the Amman Chamber of Commerce, Amman, Jordan, April 19-21, 1983, under the auspices of Alia, the Royal Jordanian Airline.

2019-04-10T21:23:14Z

Regionalism in international air transportation--cooperation and competition : papers from an international conference organized by the Massachusetts Institute of Technology, held at the Amman Chamber of Commerce, Amman, Jordan, April 19-21, 1983, under the auspices of Alia, the Royal Jordanian Airline. Preface: Alia: The Royal Jordanian Airline is very pleased to present this collectiont of papers originally presented at the international conference entitled, "Regionalism in International Air Transportation: Cooperation and Competition", held in Amman, Jordan during April 19-21, 1983. Regionalism, a method which ideally, allows groups of nations and airlines to work together efficiently in air transport operations, while competing with other similar groups, has been proposed as a means to help solve many of the problems currently plaguing the airline industry. Regionalism has been practised in the past, with some difficulty and some success, but its many possibilities have yet to be fully explored. Thus, Alia, a commercial air carrier with a long commitment to regional cooperation and progressive thinking, and the Massachusetts Institute of Technology (MIT), an academic institution with an international reputation for excellence in the ideas and practical applications relating to modern technologies, decided to cooperate in organizing an international forum for discussion of this important concept. As a result of long and dedicated cooperation between the MIT's Department of Aeronautics & Astronautics, its Center for Advanced Engineering Study Seminar Office, Alia staff members and a wide range of local institutions in Amman, the conference was a great success. It was a unique opportunity for senior airline personnel and civil aviation authorities to address the potential of regionalism in commercial, operational and technical areas. As a quick scanning of the list of authors whose papers are published herein demonstrates, the participants, representing 25 different countries, were exposed to past experiences, current activities and conceptual approaches to regionalism by some of the aviation community's most respected thinkers and practitioners. Not reflected within the covers of this book are the equally valuable exchanges of ideas which followed each presentation and the high spirit of exploration which characterised the three-day conference. We were fortunate to have welcomed also eleven journalists representing some of the most prestigious journals in the aviation industry, who produced extensive and thoughtful reports which reached a much wider audience of air transportation professionals. Conference participant evaluations reflected their high satisfaction with program format, content, organization and services. Some 84 percent of those attending the Amman conference expressed interest in a follow-up program on the subject of regionalism. It was most gratifying for Alia to sponsor and host this meeting in Amman, the capital of a small but historic Arab country which has become an important regional commercial and aviation center. Alia has played a crucial role in Jordan's development during the past 20 years, as anticipated by the vision of His Majesty King Hussein, whose interest in aviation and the potential for regional cooperation was demonstrated by his contributions to the conference as both speaker and participant. The regional activities already undertaken by Alia have benefitted from his counsel and encouragement, and we remain committed to seeking new cooperative opportunities. With appreciation for the contributions of all program speakers, for the enthusiastic participation of the registrants, the hard work of the MIT and Alia staff members and the cooperation of many Jordanian institutions, this publication is dedicated to a brighter future for the international aviation industry, in the hope that the potential of regionalism - especially in its coo perative form - will be considered and tested in practice as an idea whose time has come. Cover title; Deceomber, 1994"--Preface; Includes bibliographical references

A systems analysis of short haul air transportation

2019-04-10T21:23:12Z

A systems analysis of short haul air transportation August 1965; This program [Project TRANSPORT; prepared for the U.S. Dept. of Commerce by the Massachusetts Institute of Technology; comprising pt. 3 of a 4 v. series] is concerned with the continuation of a study of short haul air transportation problems to establish the potential role of air travel using a systems approach in which all economic, operational and technical factors are examined"--p. [1] of a Continuation of A systems analysis of short haul air ground transportation (1965); Some technical reports issued with added cover: MIT Dept. of Aeronautics and Astronautics, Flight Transportation Laboratory; Includes bibliographical references

Competition between traditional and low-cost airlines for local hub traffic

2019-04-10T19:20:11Z

Competition between traditional and low-cost airlines for local hub traffic Nissenberg, James M. It is conventional wisdom among informed observers of the U.S. airline industry that the passengers who fly full-service, hub-and-spoke-style, "traditional" airlines like American, United and Delta are significantly different from those who fly so-called "low-cost" airlines Southwest, RenoAir and Valujet. The former supposedly value level-of-service attributes like frequent flights, frequent flyer program, pre-assigned seating and first class cabin, while the latter are mostly concerned with obtaining a low fare. In markets where traditional and low-cost airlines compete, one would expect that the number of passengers flying each airline has statistically different responses to changes in important airline transport supply and market socioeconomic variables. However, few studies have tried to quantify these differences. This thesis tests the idea that traditional and low-cost airline passengers belong to different market segments. A series of econometric demand models are developed separately for the traditional and low-cost airline for short-haul markets in which the two compete. The markets connect the traditional airline's hub airport with some of its "spoke" cities. Elasticities of demand are calculated for population, per capita income, average fare, nonstop frequency, flight time, cross-fare and cross-frequency. To determine if traditional and low-cost airline passenger elasticities also differ by level of competition, demand models are estimated for three separate hub airports. Estimated demand model elasticities strongly suggest that traditional and low-cost airline passengers have significantly different valuations of airline trip attributes. The values of exogenous market variables also appear to have a differential effect. Specifically, changes in average fare and flight time seem to have a stronger effect on the number of low-cost airline passengers, while changes in population and per capita income seem to have a stronger effect on the number of traditional airline passengers. Flight frequency seems to have an effect sensitive to the relative number of individual airline flights, but independent of carrier type. Cross-fare and cross-frequency elasticity estimates indicate that, in general, passengers perceive traditional and low-cost airlines as rather poor substitutes. June 1996; Includes bibliographical references (p. 133-134)

The Airline Operation Control Centre : an overview of Garuda's Operation Control (EM) at Cengkereng Jakarta, Indonesia : final report to PT Garuda Indonesia

2019-04-12T15:08:36Z

The Airline Operation Control Centre : an overview of Garuda's Operation Control (EM) at Cengkereng Jakarta, Indonesia : final report to PT Garuda Indonesia Clarke, Michael D. D.; Naryadi, Yudi. Introduction: Airline operations are generally handled in two phases, strategic and tactical. Strategic operations are concerned with schedule planning. Given the desired schedule of services to be offered to passengers (called the Schedule of Services) established by the Commercial/ Marketing department, the Operations group generates the Nominal Operational Schedule (NOS) for the airline's resources such aircraft rotations and crew rotations, and then assigns tail numbers, and individual crew members to a given flight. These activities constitute the schedule generation and resource allocation phases of the scheduling process. They are carried out by various groups which support the development of the planned schedule for all airline resources. Given these resource schedules, the tactical side of the Operations group is responsible for the final stage of the scheduling process: Execution Scheduling. Execution scheduling is the process of executing the system resource schedules on a daily basis. This involves three main activities: executing the pre-planned schedules, updating the schedules for minor operational deviations, and rerouting for irregular operations. The tactical operations of a regular scheduled air carrier is usually under the 24 hour/day control of a central organization often referred to as the Airline Operational Control Center AOCC. This chapter presents a summary of a typical AOCC, outlining its organization, primary activities within the airline, and operational facilities. The facilities and personnel of a particular AOCC will vary considerably depending on the type and size of the airline. AOCC centers can range from a single controller/dispatcher on duty to several dispatchers and hundreds of other personnel handling flights throughout the carrier's entire global network. During the process of operation control, the AOCC is supported by the Maintenance Operations Control Center (MOCC) which controls aircraft maintenance activities, and various Station Operations Control Centers (SOCC) which control station resources (gates, refuelers, catering, ramp handling, and passenger handling facilities). Operations Control Centers are usually linked to the Aeronautical Radio Inc. (ARINC) and the Societe International Telecommunications Aeronautiques (SITA) networks to send and receive teletype/telex messages. Communications with maintenance and engineering, customer service, and airport services are maintained to facilitate prompt contact with the appropriate personnel. Teletype, telex, facsimile, telephone, leased lines, and public data networks combine to provide an effective medium of collecting information and communicating revised operational plans developed by the AOCC center. In some cases, the AOCC has communications systems connected to VHF, HF and Satcom radio links, air traffic control centers, and other relevant locations, allowing them to effectively gather and disseminate information instantaneously. October 16, 1995; Includes bibliographical references

Forecasting for airline network revenue management : revenue and competitive impacts

2019-04-10T23:33:01Z

Forecasting for airline network revenue management : revenue and competitive impacts Zickus, Jeffrey S. Airline revenue management entails protecting enough seats for late-booking, high-fare passengers while still selling seats which would have otherwise gone empty at discounted fares to earlier-booking customers. In the evolution of revenue management to network origin-destination control, previous research has shown that revenue gains of some seat optimization algorithms can be much lower than others. One possible reason is the process by which demand estimates are generated; namely, forecasting and detruncation. Forecasting is used to estimate passenger demand based on historical flight data, while detruncation makes projections of what demand would have been in cases where the historical data has been constrained by a capacity limitation. This thesis explores the question of the interaction between forecasting methods, detruncation methods, and seat optimization algorithms on a simulated airline network, using the Passenger Origin-Destination Simulator (PODS) revenue management simulation tool, which models a network environment with two competing airlines. Changes in the forecasting and detruncation methods in combination with the seat optimization algorithms were tested in order to see what revenue impacts resulted. Additionally, passenger loads, forecasts, and fare class availability were examined to understand the reasons behind the observed revenue results. The simulations showed that seat optimizers which had relatively poor performance using a standard forecasting and detruncation method had substantial revenue increases when different forecasting and detruncation combinations were implemented. The results also indicate that the better combination of forecasting and detruncation causes higher revenues for all seat optimization methods tested, as a better passenger mix is realized due to higher levels of detruncation and more accurate forecasts. However, the sensitivity of the seat optimizers to the forecasting and detruncation methods remains mixed. Inferior detruncation (or forecasting) methods on a network can offset the revenue gains resulting from improvement to origin-destination control from leg-based control for some seat optimization algorithms. Includes bibliographical references (p. 137-138)

Network value concept in airline revenue management

2019-04-10T23:33:00Z

Network value concept in airline revenue management Bratu, Stephane A connecting passenger occupies a seat on each of the flight leg of his itinerary. Moreover, for a given fare class, the fare of a connecting passenger is lower than the sum of the fares of the local passengers on the traversed legs. If the demand is high, giving availability to a connecting passenger may displace local passengers and the airline would lose revenue. The objective of this thesis is to evaluate methods that airlines can use to better estimate the network revenue value of connecting passengers for the purpose of determining seat availability. In this thesis we analyze and compare two different ways of estimating the network revenue value of the connecting passengers. The first approach consists of estimating the displacement cost of the connecting passenger on all the traversed legs by the shadow prices associated with the capacity constraints of a network linear program (LP). The second one is a prorated fare convergence technique developed in this thesis. The fares of the connecting passengers are prorated on each of the traversed legs using an estimation of the expected marginal revenue of the last seat on the legs. The existence and uniqueness of the limit for each prorated fare sequence are also proven. We have compared the performance of different seat inventory control models that incorporate these two network revenue estimation techniques. The optimization/booking simulation uses demand forecasts from an airline's Yield Management historical database. The seat inventory control methods that use the network revenue value concepts perform up to 1.50% better than the existing fare class control approach at a high demand scenario (82% average load factor). Moreover, the prorated fare convergence technique performs better than the LP shadow price displacement cost approach especially if the demand is controlled by a bid price mechanism. Indeed, for a high demand scenario and a relatively high number of reoptimizations along the booking process, the prorated fare convergence method performs 0.12% better than the shadow price approach for a bid price control mechanism. Finally, the revenue difference between the two methods is both significant and robust with respect to demand variations. Includes bibliographical references (p. 114)

Presentations from the 1996 MIT/industry cooperative research program annual meeting.

2019-04-10T21:23:11Z

Presentations from the 1996 MIT/industry cooperative research program annual meeting. Belobaba, Peter.; Skwarek, Daniel Kew.; Simpson, R. W.; Nissenberg, James M.; Ferea, James D.; Mathaisel, Dennis F. X.; Clarke, Michael D. D.; Idris, Husni Rifat.; Wei, Yuanyuan Cover title

Investigation of competitive impacts of origin-destination control using PODS

2019-04-10T23:32:59Z

Investigation of competitive impacts of origin-destination control using PODS Lee Alex Yen Hung The Passenger Origin / Destination Simulator (PODS) was used to investigate the competitive impacts of Origin-Destination control airline Revenue Management (RM) methods. Experiments performed included revenue performance of O-D control RM methods versus EMSRb fare class control, impacts of passenger choice assumptions, competing airlines with co-located hub vs. separate hubs, and different implementations of the most promising R1M methods. First, the revenue results from several O-D control RM methods are compared to the revenue result from EMSRb fare class control. Of the four O-D methods investigated, Displacement Adjusted Virtual Nesting (DAVN) performed consistently the best, followed closely by Heuristic Bid-Price (HBP). Greedy Virtual Nesting (GVN) was the third best performer, with decreasing performance as demand increased. Network Bid- Price (Netbid) performed the worst because of the "small network effect", and due to its sensitivity to forecasting and detruncation methods. Next, the impacts of passenger choice assumptions were investigated. We found that with the inclusion of demand correlation and passenger choice in the simulations, DAVN and HBP performed better, while Netbid performed worse. The result for GVN was inconsistent. Under the new PODS maximum willingness-to-pay formulation with lower levels of sell-up, we saw lower passenger loads with more spill. We also noticed lower absolute revenue, as well as bigger revenue impact from O-D methods. For competing airlines with co-located hub vs. separate hubs, most RM methods performed better under the co-located hub scenario tested because the airlines have to compete for both local and connecting passengers, making passenger selection more critical. As to O-D methods used by airlines competing head to head, under HBP and GVN, the co-located hub network leads to more sell-up, leading to better revenue performance. Finally, different implementations of HBP and DAVN were investigated. For HBP, we found that the d-factor had a large effect on performance. For DAVN implementations, we noticed that different virtual class boundary methods had a large impact on performance, while frequent re-optimization might actually reduce performance. Includes bibliographical references (p. 123)

Airline O-D control using network displacement concepts

2019-04-12T15:08:36Z

Airline O-D control using network displacement concepts Wei, Yuanyuan In the airline industry, it is customary for carriers to offer a wide range of fares for any given seat in the same cabin on the same flight. In order to maximize the total network revenue, the airline practices so-called seat inventory control methods. In this thesis, we first examine several seat inventory control methods which are employed or are being developed by some airlines. Then, based on these methods, we propose three new models to control the seats: the Network Non-greedy Heuristic Bid Price model, the Leg Based Probability Non-greedy Bid Price Model, and the Convergence Model. These models are created in order to find a better way to evaluate the connecting fares, taking into consideration their displacement impacts. An integrated optimization / booking simulation tool is employed in this research to compare the new models with the other methods in terms of network performance under the same demand circumstances. Generally, all the three new models improve network performance. The revenue results obtained from the simulation show that using network displacement concepts can provide us with an average of 0.5% revenue gain over the methods that do not explicitly include the displacement impacts at a load factor of 93%. The simulation results also show that under the same demand circumstance and seat control strategies, using a better way to evaluate the displacement impacts can provide 0.05% revenue improvement. Cover title; Includes bibliographical references (p. 120)

A recommended course of action for upgrading Garduda Operations Control Systems

2019-04-08T07:30:06Z

A recommended course of action for upgrading Garduda Operations Control Systems Mathaisel, Dennis F. X. Introduction: The purpose of this document is to construct a recommended course of action in the next year for Garuda Operations Control in its efforts to upgrade its information systems technology. The process of installing new technologies is not one that can be done quickly or easily. It is also not one that can be accomplished by simply purchasing new software, even if that software were to exist. Rather, the process of upgrading technologies must follow a carefully planned and designed path. Among information systems specialists, the process is often referred to as the Systems Development Life Cycle (SDLC). The scope of an SDLC can vary. For airline operations control projects, the scope of the SDLC process is large. It involves many people, both internal and external to the organization. It requires the establishment of a Systems Development Team with membership from several units of the airline to direct the project and to resolve problems. It (ultimately) involves a substantial resource commitment, typically on the order of $2,000,000 to $3,000,000 in development funding. It involves a number of tasks that need to be performed as part of the development effort. And the project typically takes a number of years to implement. Failing to follow a proper Systems Development process may lead to a number of risks, such as: e The new system may not meet the user's needs. e The acquisition of unnecessary or inappropriate hardware. e The acquisition of insufficient software, or software that does not allow the airline to grow or handle future expansion. e Software that may be inadequately tested and may not meet requirements or expectations. One way to look at systems development is to divide it into six phases: Phase 1 - Analyze the current system Phase 2 - Define new system requirements Phase 3 - Design the new system Phase 4 - Develop the new system Phase 5 - Implement the new system Phase 6 - Test and evaluate the system's performance and its ability to meet the user's requirements During the last year, MIT/FTL staff have been working on Phase 1. The results of our analysis of GA's current system have been documented in a separate report by Michael Clarke and Yudi Naryadi entitled "The Airline Operation Control Centre: An Overview of Garuda's Operation Control (EM) at Cengkereng", which was recently submitted to GA. Perhaps more work needs to be done in Phase 1 by GA internal staff after GA has reviewed our report. For example, it might be wise to: a) Evaluate the sources of all data needed to support operations control. b) Document the flows of these data as EM goes about solving various operations problems, or resolving irregular operations. c) Document the information needs which are not currently available. d) Review current EM policies and procedures to obtain suggestions for improvement. However, it is the next two phases in the SDLC process (Phase 2 - defining the new system requirements, and Phase 3 - designing the new system) for which we now need to turn our attention. Within the next year of the cooperation between MIT and GA, there are a number of tasks that can be accomplished to complete these next two phases. What follows is our suggestion for what should be accomplished within the next year. 2. Suggested steps for the next year of cooperation between MIT and GA Operations Control Step 1 - Establish a Systems Development Team. The very first step that should be taken is the establishment of a team of individuals from both within GA and external to GA. The mission of this team would be to oversee the development effort: direct all activities; approve all decisions; make recommendations on the design of the new system; and resolve problems that occur along the way. The team should consist of personnel from: e Operations (EP, EM) e Flight Dispatch, Navigation (EA, ON) e Operations Control Center (OCC) e Maintenance (MCC, MP) * Crew Planning (OB) e Airport Operations (KO) e Information Systems (DX) The team should have a leader from within GA, and MIT/FTL staff would act as "consultants" to this team. Step 2 - Complete Phase 2 of the System Development Life Cycle. In the second phase of the SDLC, we need to scope out the requirements for the new system in enough detail so that both the computer systems developers and the users know exactly what the new system is going to do and how the system is going to do it. Needless to say, these requirements should solve the problems identified in Phase 1. The requirements should identify the user's needs (what the system will do) as well as the hardware, software, and data needs. This phase concludes with a system requirements report. Step 3 - Configure and install the computer hardware and networking technology that is necessary to allow personnel to electronically communicate and interact with one another, make good use of existing Operations Control systems, and to establish reliable access to all necessary information/data. The design of the hardware and network configuration is not a trivial task. Questions need to be answered: e What would be the underlying operating system: UNIX, Windows NT? e What hardware will the system run on: 80486 PC's or UNIX Workstations? e What client - server architecture is optimum? e What local area network is best: Ethernet, Token-Ring? * What media: Twisted-Pair, Co-ax? e How is the network to be connected to the mainframe and other systems? e What communications and network software is needed? It is planned that the installation of this hardware and software will be incremental and evolutionary. GA can initially procure just a few workstations and connect them up on a local area network. This "test cell" of computers will allow GA to gain some experience with the new hardware before making a more substantial commitment of resources. In addition, this step will allow EM personnel to become familiar with the new computer hardware before the application software is designed and installed. It will also allow EM personnel to communicate with each other through a local area network. In addition, the hardware and operating system software that is chosen should allow EM to continue to access and use current systems, even if those systems are on the mainframe computer or other workstations. At the same time, it should allow an evolutionary transition to better systems and software. Step 4 - Begin installation of a centralized Database Management System to hold the data items that are needed for effective Operations Control. Refer to the earlier proposal entitled "System Operations Control Database Development" written by Dennis Mathaisel in July 1995 for a more detailed discussion of this step. Configuring and installing an effective DBMS is not trivial. It is intended that an improved DBMS will be available on-line at EP/EM by transferring and updating data currently in other systems. Step 5 - Complete Phase 3 of the System Development Life Cycle. This third phase focuses on the design of the new system software before the software is procured or developed. The phase involves two main objectives: e To optimally design the new system. e To establish a sound framework of controls within which the new system should operate (basically, meeting the requirements). The completion of the design phase is marked by a couple of events: the team completes, organizes, and assembles the system design documentation; and a series of meetings/presentations are organized to present and review the design proposal. From an overall perspective, next year would be devoted to a year of assessment and design, combined with the installation of necessary hardware, operating systems, and local area networks. It would require a commitment from Garuda to purchase necessary hardware and LAN technology, as well as taking the first steps necessary to install a centralized DBMS. 3. Beyond next year... Once the above steps were completed, then GA can begin to acquire more advanced software to assist in planning and execution of Operations activities. The greatest mistake would be to acquire existing software packages before a thorough study and design was completed. A complete plan for developing a new operational system must be established first. Beyond next year, the basic steps would be as follows: a) Complete the construction of the centralized DBMS. b) Replace the ROC system currently in use in Operations Control with advanced computer-graphics displays on high-powered workstations that are connected on a local area network and connected with the mainframe computer. This step involves a transition to UNIX-based software. c) Then, and only after the above steps were taken, consider the introduction of automated decision-support models to solve specific problems that are encountered in irregular operations, etc. Cover title; 19 October 1995

Presentations from the MIT/Industry Cooperative Research Program Annual Meeting, 1991

2019-04-09T16:15:16Z

Presentations from the MIT/Industry Cooperative Research Program Annual Meeting, 1991 Belobaba, Peter.; Williamson, Elizabeth Louise.; Hazelton, Lyman R.; Acker, Jan Van.; Botimer, Theodore Charles.; Mak, Chung Yu.; Svrcek, Tom.; Simpson, R. W.; Mathaisel, Dennis F. X. Cover title; May 1991; Includes bibliographical references

A systems analysis of short haul air transportation

2019-04-10T21:23:10Z

Incorporating sell-up in airline revenue management

2019-04-12T15:08:35Z

Incorporating sell-up in airline revenue management Charania Aamer The decision to buy a fare that is higher than the desired fare, under the situation when the desired fare is not available, is known as sell-up. Passengers' willingness to sellup can have considerable impact on airline revenues. The extent of this impact is dependent upon the method used to control booking limits and other parameters associated with passenger demand and fare structure. In this thesis we demonstrate the importance of incorporating sell-up in airline revenue management. The improvement in revenue, under various scenarios, and under various seat inventory control algorithms, is discussed. We also analyze the influence of demand factor, spill, sell-up rate and fare ratio on these improvements. A modification of the EMSRb heuristic is proposed to capture the revenue potential associated with passenger sell-up. The proposed rule increases the protection levels, obtained from the EMSRb algorithm, as long as the expected gain, from every additional seat protected, is greater than the expected loss. Unlike the existing models, the proposed rule uses expected spill to determine the expected number of passengers that would sell-up at a given demand level and sell-up rate, and then adjusts the protection levels accordingly. This makes it robust to variations in demand levels. We have also developed a simulation to compare the performance of the existing rules with that of the proposed heuristic. The simulation has the ability to account for errors in sell-up estimation and variability in demands. It is shown that the revenue gains under the proposed rule may not exist under all situations. In the tests performed in this thesis, the improvements over the original EMSRb algorithm vary from 0% to over 2.5%. Although the gains are not consistent, the proposed rule does not cause any negative impact on overall revenues and hence is unlikely to pose any risk when implemented over the original EMSRb algorithm. Includes bibliographical references

Summary of required data for revenue forecasting and potential data sources available at the Bureau of Corporate Planning of PT Garuda Indonesia : final report to PT Garuda Indonesia

2019-04-08T08:17:35Z

Summary of required data for revenue forecasting and potential data sources available at the Bureau of Corporate Planning of PT Garuda Indonesia : final report to PT Garuda Indonesia Clarke, Michael D. D.; Wickham, Richard Robert. Introduction: One of the most important strategic planning capabilities for an airline is the development of a good working understanding of the markets it serves in its network. These capabilities will include extensive market share and trend analysis, route development and expansion analysis, and long-term fleet planning, just to name a few topics. The bureau of Corporate Planning at Garuda has identified the need to significantly improve its analytical abilities in the area of traffic forecasting, in order give Garuda an effective advantage in the increasingly competitive airline industry within Indonesia and in South East Asia. In an effort to establish a comprehensive set of computer databases for passenger traffic forecasting at Garuda, a team of researchers from the MIT Flight Transportation Laboratory and Garuda personnel from the bureau of Corporate Planning (DQ) has started the process of collecting data from several sources both within the Garuda airline organization, and also external entities to the company. At present, the initial database includes limited information from the Indonesian Airport Authorities, the Tourism Ministry, the OAA Orient Airline Association , the ICAO International Civil Aviation Organization, IATA International Air Transport Association, and Garuda's Information Systems (DX). The following list outlines the desirable data for passenger revenue and demand forecasting at Garuda. It incorporates data sources currently available in Corporate Planning, as well as sources that have been identified as being necessary for the successful development of robust demand and traffic forecasting methodologies at Garuda. The current status and progress in the data collection is then given, for each individual data source. Further action items are identified, and recommendations are made for future activity in the research program. October 16, 1995

Development of heuristic procedures for flight rescheduling in the aftermath of irregular airline operations

2019-04-10T23:32:57Z

Development of heuristic procedures for flight rescheduling in the aftermath of irregular airline operations Clarke, Michael D. D. Airlines are constantly faced with operational problems which develop from severe weather patterns and unexpected aircraft or personnel failures. However, very little research has been done on the problem of addressing the impact of irregular operations, and developing potential decision systems which could aid in aircraft re-scheduling. The primary goal of this research project has been to develop and validate algorithms, procedures and new methodologies to be used to reschedule planned activities (flights) in the event of irregular operations in large scale scheduled transportation systems, such as airline networks. A mathematical formulation of the Airline Schedule Recovery Problem is given, along with a decision framework which is used to develop efficient solution methodologies. These heuristic procedures and algorithms have been developed for potential use in a comprehensive real-time decision support systems (DSS), incorporating several aspects of the tactical operations of the transport system. These include yield management, vehicle routing, maintenance scheduling, and crew scheduling. The heuristic procedures developed will enable the carrier to recover from an irregular operation and maintain an efficient schedule for the remainder of a given resolution horizon. The algorithms are validated using real-world operational data from a major US domestic carrier, and data from an international carrier based in the Asia Pacific region. A comprehensive case study was conducted on historical operational data to compare the output of the algorithms to what actually occurred at the airline operation control center in the aftermath of an irregularity. Some of the issues considered include the percentage of flights delayed, percentage of flights cancelled, and the overall loss in operating revenue. From these analyses, it was possible to assess the potential benefits of such algorithms on the operations of an airline. Includes bibliographical references (p. [151]-158)

Competitive impacts of yield management system components : forecasting and sell-up models

2019-04-12T15:08:34Z

Competitive impacts of yield management system components : forecasting and sell-up models Skwarek, Daniel Kew The focus of revenue management research efforts has historically been on the development of seat optimizers which find revenue maximizing booking limits by fare class in a nested fare class structure. Significantly less attention has been devoted to the input methodologies which provide information to the seat optimization algorithm, which is then used to calculate booking limits. Among these inputs are a forecasting method and detruncation method. The forecaster provides the seat optimizer with estimated mean unconstrained bookings and standard deviation by fare class for a forecast flight. The detruncator adjusts data from historical flights used by the forecaster which have constrained booking information because they have reached booking limits. A third optional input methodology is an adjustment within the seat inventory control process (either to booking data or booking limits provided by the seat optimization algorithm) to account for the possibility of passenger sell-up to a higher fare class when the initially-desired class has been closed. This adjustment has the effect of inducing more sell-up. Using PODS (a comprehensive simulator of passenger behavior and seat inventory control in a fully competitive framework), this thesis compares pickup, regression, and "efficient" forecasting on a revenue basis. Similar comparisons are performed for no detruncation, booking curve detruncation with and without scaling, projection detruncation, and pickup detruncation. Finally, a modified booking limit strategy to induce sell-up introduced by Belobaba and Weatherford is tested. All tests are performed under a variety of environmental conditions. Forecasting results indicate that the efficient forecaster is nearly always revenue inferior to pickup forecasting. Neither regression nor pickup forecasting were unambiguously superior: The relative performance of these two forecasters is dependent on detruncation method choice and environmental conditions. Among detruncation methods, not detruncating or pickup detruncation is inferior. Scaling the booking curve used for detruncation yielded superior revenue results over not scaling, and projection detruncation always performed at least as well as booking curve detruncation without scaling. Sell-up tests indicate significant revenue gains to estimating sell-up probabilities. Revenue gains are limited if competitors cannot collude, many alternative flights exist, or passengers have low willingness to pay for higher-valued fare classes. Cover title; Includes bibliographical references (p. 192-195)

The sell up potential of airline demand

2019-04-10T23:32:56Z

The sell up potential of airline demand Bohutinsky, Catherine H. Differential pricing of air transportation plays an important role in the current theories of airline seat inventory management. The ability to recognize those passengers willing to "sell up". or pay more for a seat on a given flight is also important, yet it has received little research attention. The proper detection and booking management of these passenger types can allow air carriers to realize higher flight revenues. This dissertation begins with an overview of airline pricing policies and seat inventory control management practices. Current fare structures and fare class designations are described in detail. Airline demand and consumer utility measures are then presented. Consumer behavior during the booking process. particularly in relation to sell up behavior, is discussed. Price elasticities of demand also play an important role in the prediction of sell up behavior. An in-depth description of sell up and its measurement follow. Once specific flights have been identified as having sell up potential, a sell up strategy can be implemented. Methods of testing the revenue benefits/costs of a particular sell up strategy were developed and used in an actual airline environment. A study consisting of a preliminary sell up test followed by an expanded study incorporating different sell up strategies was performed. Revenue results of the sell up strategies are presented and the impacts of each policy are discussed. Price elasticities of demand were estimated for individual fare classes. In general, sell up was found to be flight specific and more prevalent in the highest two fare classes (in terms of fare values) while being almost non-existent in lower fare classes. 1990; Also issued as an M.S. thesis Massachusetts Institute of Technology, Dept. of Civil Engineering, 1990; Includes bibliographical references (p. 106-107)

Leg-based heuristic methods to network seat inventory control

2019-04-12T15:08:33Z

Leg-based heuristic methods to network seat inventory control Tan, Jin C. Driving the development of increasingly sophisticated methods of seat inventory control are the complex fare and route structures evident in airline operations today. Most control methods are currently based on an individual flight leg level. However, with the increased presence of multi-leg traffic flows, it becomes necessary to extend control methods beyond the flight leg level in order to maximize network revenues. While utilizing a full network optimization approach is not a suitable solution to satisfying airline desires for immediate revenue gains, the development of leg-based network seat inventory control algorithms is viewed as an applicable alternative approach. In this thesis, two distinct components of seat inventory control are addressed. First, control structures that recognize multi-leg traffic flows are introduced and incorporated into leg-based network seat inventory control algorithms. Secondly, the development of local displacement cost logic is made and implementation issues within existing and newly developed control algorithms are explored. In order to quantify the effectiveness of inventory control algorithms to provide incremental revenue gains over existing control methods, an optimization/booking simulation was utilized to test the performances of these algorithms under a variety of demand patterns. Extensive simulation results in addition to discussions on practical implementation issues of different control approaches are made within the thesis. June 1994; Includes bibliographical references (leaves 134-136)

Presentations from the 1992 MIT/industry cooperative research program annual meeting

2019-04-11T03:39:42Z

Presentations from the 1992 MIT/industry cooperative research program annual meeting Williamson, Elizabeth Louise.; Svrcek, Tom.; Simpson, R. W.; Waldman, Gary L.; Mathaisel, Dennis F. X.; Pararas, John Demetrios.; Elias, Antonio L.; Botimer, Theodore Charles. Cover title; May 1992; Includes bibliographical references

Competitive behavior of airlines at multiple airport systems

2019-04-10T23:32:55Z

Competitive behavior of airlines at multiple airport systems Chen, Edmund The way passenger traffic is distributed at multiple airport systems continues to intrigue air transportation planners, urban planners, and policy-makers as researchers attempt to unravel how airlines, air travelers and airports relate to each other. While previous research efforts have typically concentrated on the air travelers' choice of airports, the current thesis addresses how the competitive behavior of airlines operating in a deregulated environment influences the air traveler's choice of airports and the resulting distribution of passenger traffic in the multiple airport system. The methodology of the research first involves identifying four scenarios under which airlines compete in multiple airport environments, after which an anecdotal analysis of a select number of city-pair markets for each scenario was performed to solicit supporting evidence of competitive behavior of airlines. To keep the preliminary investigation simple, the author has chosen to study the dual-airport systems at Chicago and Houston. Owing to limitations of the data from O&DPlus and ONBOARD, the author used a strict set of criteria to identify 14 city-pair markets to analyze the response of passengers and airlines to challengers entering the city-pair markets between 1984 and 1993. The six quantitative indicators used in the anecdotal analyses include: average fares, average number of nonstop departures per day each way, quarterly origindestination traffic, quarterly non-origin-destination traffic, average quarterly load factors, and the quarterly total airport-to-airport origin-destination traffic. The results of the research indicate that while competition is evident, a general trend of competitive behavior of the airlines in the multiple airport environment is not discernible. The entry of a challenger typically elicits a variety of responses. Significant stimulation of the origin-destination traffic was observed in cases where low-fare carriers entered the market. The fact that the number of non-origin-destination passengers usually exceeds the number of origin-destination passengers may indicate that justification for the service in the airport-pairs examined goes beyond simply satisfying the demand for travel in the origin-destination market. Although quantitative modeling techniques were not used in this study, the author believes that future researchers should contend with the complex, multi-dimensional nature of airline competition before attempting to accurately model the competitive behavior of airlines at multiple airport systems. February 1995; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1995; Includes bibliographical references (p. 201-204)

Analysis of the altitude tracking performance of aircraft-autopilot systems in the presence of atmospheric disturbances

2019-04-10T23:32:54Z

Analysis of the altitude tracking performance of aircraft-autopilot systems in the presence of atmospheric disturbances Sturdy, James Luckett; Hansman, Robert John. The dynamic response of aircraft-autopilot systems to atmospheric disturbances was investigated by analyzing linearized models of aircraft dynamics and altitude hold autopilots. Four jet aircraft (Boeing 737-100, McDonald Douglas DC9-30, Lockheed L-10ll, and Cessna Citation III) were studied at three flight levels (FL290, FL330, and FL370). The models were analyzed to determine the extent to which pressure surface fluctuations, vertical gusts, and horizontal gusts cause assigned altitude deviations by coupling with the aircraft-autopilot dynamics. The results of this analysis were examined in light of meteorological data on disturbance magnitudes and wavelengths collected from observations of mountain wave activity. This examination revealed that atmospheric conditions do exist which can cause aircraft to exhibit assigned altitude deviations in excess of 1,000 ft. Pressure surface fluctuations were observed to be the dominant source of altitude errors in flights through extreme mountain wave activity. Based on the linear analysis the maximum tolerable pressure surface fluctuation amplitude was determined as a function of wavelength for an allowable altitude error margin of 300 ft. The results of this analysis provide guidance for the determination of vertical separation standards in the presence of atmospheric disturbances. Cover title; January 1988; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1988; Includes bibliographical references (p. 99)

Airline overbooking performance measurement

2019-04-10T23:32:53Z

Airline overbooking performance measurement Holm, Carsten Since the "product" of an airline cannot be stored, the value of every seat which is left empty upon departure is lost forever or "spoiled". In order to compensate for the economic effects of passengers holding a confirmed reservation who fail to show-up, airlines overbook, i.e. accept more reservations than physical seats are available under the assumption that sufficient no-shows will occur. Even though airlines have overbooked their flights intentionally for decades, very few efforts have been made to measure the economic success of overbooking. As revenue maximization becomes more critical to the profitability of an airline, it is even more important to review the balanced tradeoff between denied boardings and spoilage. This thesis outlines the major philosophies of the currently applied overbooking models and illustrates further the common overbooking performance measurement approaches. As all of these models demonstrate significant shortcomings, a new model, the Revenue Achievement Model, is introduced. This new approach is based on a purely economics driven philosophy. Along with the Revenue Achievement Model, the different definitions of spoilage, oversales and other key values for the overbooking performance evaluation are reviewed and defined anew in an attempt to standardize the terminology. It is shown that the Revenue Achievement Model is more consistent with today's overbooking models than other overbooking performance measurement models. It matches the economic objectives of the airlines and shows superior qualities in comparing flights on a single flight level as well as evaluating the aggregate performance for large samples. The proposed methodology enables also to obtain a target performance index which allows a quantification of the objectives of overbooking. Finally, the impact of system overrides by revenue management analysts is analyzed and methods are suggested to evaluate their actions. Cover title; May 1995; Submitted to the Department of Aeronautics and Astronautics on May 5, 1995 in partial fulfillment of the requirements for the Degree of Diplom Ingenieur in Luft- und Raumfahrttechnik"--P. 1; Includes bibliographical references (p. 115-117)

Assessment of the potential diversion of air passengers to high-speed rail in the northeast corridor

2019-04-10T23:32:52Z

Assessment of the potential diversion of air passengers to high-speed rail in the northeast corridor Clarke, Michael D. D. The high level of intercity passenger travel in the Northeast Corridor is supported by densely populated metropolitan city-centers, the suitable distance between the urban areas, and the extent to which economic and social activities in these urban areas complement each other. Within the region, automobile and air travel account for the majority of the passenger traffic. The majority of the air passengers travel on the air shuttles operating in the Northeast. However, since the deregulation of the airline industry, there has been consistent traffic growth on regional carriers. The development of transport modes in the Northeast has been governed by the high level of competition which exists. A passenger's modal choice is influenced by the purpose of the trip. The majority of air shuttle passengers are non-discretionary (business) travellers, who are price insensitive and rely more on air travel because of its convenience and travel time. In 1992, there were 2.41 million air passengers (including regional service) and 600,000 rail passengers travelling in the Boston-New York origin-destination market. The forecasted ridership for high speed rail in this O/D market (2010) is 2.15 to 2.25 million passengers. Of this number, 1.32 million passengers are expected to be diverted from air travel. Based on FAA forecasts for air travel between Boston and New York City in 2010, it is estimated that there will be a twenty-nine percent (29%) diversion of air passengers to high speed rail. Cover title; February 1994; Also issued as an M.S. thesis, Dept. of Aeronautics and Astronautics, MIT, 1994; Includes bibliographical references (p. 77-78)

A simulation of aircraft motion on the airport surface

2019-04-08T07:13:06Z

A simulation of aircraft motion on the airport surface Mathaisel, Dennis F. X.; Pararas, John Demetrios.; Idris, Husni Rifat. This paper describes the design and implementation of a real-time simulation of aircraft motion on the ground at airports. The aircraft Ground Motion Simulator (GMS) is designed to realistically simulate tower, ground, and apron aircraft control. The simulation includes high-fidelity graphic views, in color, of airport ground activity. It simulates air traffic operations in real time for all stages of flight from take-off to landing as well as all phases of ground movement of aircraft including landing roll, taxiing, yielding, platooning, parking, pushback, and takeoff roll. The capability to simulate aircraft movement on airport taxiways and runways provides a realistic environment for testing the planning processes regarding the management of departing traffic and its interactions with aircraft landing at an airport. The GMS simulates the environment at any arbitrary airport and interfaces through a fast, two way data communications link to an existing Air Traffic Control simulation facility. The GMS consists of a host computer workstation, an experimenter's station, one or more traffic controller stations, and one or more pseudopilot stations. The graphical user interface and the graphical displays were developed in object-oriented C on the X/Windows graphics system on UNIX workstations. Cover title; March 16, 1994; Series statement handwritten on cover; Includes bibliographical references (p. 40)

The value of revenue management innovation in a competitive airline industry

2019-04-12T15:08:32Z

The value of revenue management innovation in a competitive airline industry Wilson, John L. The value of revenue management to the airlines has been amply demonstrated, both by industry experience and in simulation studies of the reservation process. However, there have been no attempts to determine if the benefits of seat inventory control are specific to the competitive market setting in which it is instituted. Furthermore, previous theoretical research has not considered whether interactions of the control methods of rival carriers may affect both the total revenue improvement attainable in the market and how these gains are shared by individual carriers. This thesis uses a modeling approach created by the Boeing Commercial Airplane Group to address these questions. The Passenger Origin / Destination Simulator combines a demand model framework with a set of routines which implement the basic forecasting and inventory control functions of airline revenue management. The Boeing simulation system is implemented in the thesis through the development of a generic fare product structure, passenger behavioral attributes, and assumptions on demand composition. Within this Operational Competitive Simulation Environment, the effect of competition on the value of revenue management is explored in simulation experiments with three classes of scenarios. In these scenarios, the gains from leg-based inventory control are assessed under varying competitive conditions, including the magnitude and distribution of passenger demand, carrier frequency share, relative departure timing, and route network design. From the simulation results, it is apparent first that inventory control innovation always improves carrier and aggregate market revenues-competition along the dimension of revenue management is not a zero-sum game from the carriers' perspective. A signal contribution of the experimental research has been the finding that the revenue dividend from inventory control derives largely from the sale of higher-yield fare products to leisure and discretionary business passengers, and only marginally at the expense of those carriers with a less advanced control capability. Additionally, the relative changes in revenue due to different control methods are indeed influenced by other competitive forces operative in the market. May 1995; Includes bibliographical references (p. 129-130)

A critical review of world jet transport safety

2019-04-12T15:08:32Z

A critical review of world jet transport safety Achtmann, Eric D. This thesis is intended to serve as a comprehensive introduction to world jet transport safety and aviation fire safety. Divided into six sections, this thesis contains: 1) a statistical review of overall levels of safety and risk assessment in world jet transportation, 2) a statistical breakdown of jet accidents occurring between 1970 and 1992 by accident type and cause, 3) a case review of major jet accidents involving fire, 4) a review of fire prevention and fire hardening measures in jet transport aircraft, 5) a review of fire management practices in world jet transport aviation, and 6) a comprehensive chronological summary of all world jet transport accidents occurring between 1970 and 1992. Special emphasis is placed on fire safety, as statistics have shown that both in-flight and post-crash fires are among least survivable of all accident causes and are leaders in total fatalities. Included is an exhaustive review of aviation fire-fighting agents and equipment, as well as design parameters and equipment used for the fire hardening of jet aircraft. Finally, an economic analysis is included to illustrate the economic impact of fire safety measures. Cover title; May 1995; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1995; Includes bibliographical references (p. 116-122)

Routings in a schedule space map : an interactive graphics-based implementation

2019-04-08T07:30:06Z

Routings in a schedule space map : an interactive graphics-based implementation Chan, Wing Keong Methods used for scheduling aircraft itineraries to desired maintenance bases and similar methods for specifying delivery routings from any number of sources to any number of required locations have been developed. The algorithms used to generate these routings have been incorporated in a prototype graphics-based scheduling environment. This environment, implemented on the Texas Instruments Explorer Lisp Machine, allows creation of schedule maps on a graphics terminal and display of routings. A fleet reduction algorithm has also been incorporated in the scheduling environment, which attempts to optimize the schedule by shifting flight arcs in the schedule to improve aircraft utilization. The software can be expanded to include other algorithms. Cover title; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1987; August 1987; Includes bibliographical references (p. 93)

Papers from the MIT-industry Cooperative Research Program, 1989 : proceedings of the annual meeting held at MIT

2024-02-15T13:38:34Z

Papers from the MIT-industry Cooperative Research Program, 1989 : proceedings of the annual meeting held at MIT Zabat, Grace Lyn Buenaventura.; Williamson, Elizabeth Louise.; Lee, Anthony Owen.; Kolb, Mark A.; Karlsson, Joakim; Fujiwara, Tsuneo.; Belobaba, Peter. Cover title; May 25-26, 1989; Includes bibliographical references

An investigation of constraint-based component-modeling for knowledge representation in computer-aided conceptual design

2019-04-10T21:23:08Z

An investigation of constraint-based component-modeling for knowledge representation in computer-aided conceptual design Kolb, Mark A. The earliest computer programs used for engineering design focused on detailed geometric design. Subsequently, computer programs for algorithmically performing the preliminary design of specific well-defined classes of objects became commonplace. However, due to the need for extreme flexibility, it appears unlikely that conventional programming techniques will prove fruitful in developing computer aids for engineering conceptual design. The use of symbolic processing techniques, such as object-oriented programming and constraint propagation, facilitates such flexibility. Object-oriented programming allows programs to be organized around the objects and behavior to be simulated, rather than around fixed sequences of function- and subroutine-calls. Constraint propagation allows declarative statements to be understood as designating multi-directional mathematical relationships among all the variables of an equation, rather than as uni-directional assignment to the variable on the left-hand side of the equation, as in conventional computer programs. The research presented here has concentrated on applying object-oriented programming and constraint propagation to the development of a general-purpose computer aid for engineering conceptual design. Object-oriented programming techniques are utilized to implement a user-extensible database of design components. The mathematical relationships which model both the geometry and physics of these components are managed via constraint propagation. In addition to this component-based hierarchy, special-purpose data structures are provided for describing component interactions and supporting state- dependent parameters. In order to investigate the utility of this approach to conceptual design, three sample design problems from the field of aerospace engineering have been implemented using the prototype design tool, Rubber Airplane: a long-endurance surveillance aircraft, a subsonical transport aircraft, and a small-payload launch vehicle. The additional level of organizational structure obtained by representing design knowledge in terms of components is observed to provide greater convenience to the program user, and to result in a database of engineering information which is easier both to maintain and to extend. Also issued as a Ph. D. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990; January 1990; Includes bibliographical references (p. 231-234)

Presentations from the MIT/Industry Cooperative Research Program : annual meeting, 1990

2019-04-10T21:23:15Z

Presentations from the MIT/Industry Cooperative Research Program : annual meeting, 1990 Belobaba, Peter.; Bohutinsky, Catherine H.; Lee, Anthony Owen.; Williamson, Elizabeth Louise.; Odoni, Amedeo R.; Kolitz, Stephan E.; Terrab, Mostafa.; Pararas, John; Simpson, R. W.; Svrcek, Tom. Statement of responsibility reads: Peter P. Belobaba; Catherine H. Bohutinsky; Anthony 0. Lee; Elizabeth L. Williamson; Amedeo R. Odoni, Stephan Kolitz and Mostafa Terrab; John Pararas; Robert W. Simpson; Tom Svrcek and Peter P. Belobaba; June 1990

Presentations from the annual meeting of the MIT/Industry Cooperative research Program.

2019-04-10T07:33:41Z

Presentations from the annual meeting of the MIT/Industry Cooperative research Program. Belobaba, Peter; Botimer, Theodore Charles; Clarke, Michael D. D.; Cohas, Franc\0326ois; Grandeau, Seth C.; Simpson, R. W; Svrcek, Tom; Waldman, Gary L Caption title; May 1991

A dynamic approach for air traffic flow management of arriving aircraft at a congested airport

2019-04-10T23:32:51Z

A dynamic approach for air traffic flow management of arriving aircraft at a congested airport Fedida, Fabien Both the airline industry and air travelers have been pummeled by increased delays experienced at major airports and, as a result, rising operating costs. In this thesis, we focus on the dynamic Arrival Flow Management sub-process of the more general Congestion Management process at a given airport. We show the inefficiencies of a current approach, Miles-In-Trail, and present and evaluate a new approach which we have called Integrated Interactive Dynamic Flow Control (IIDFC). IIDFC produces a set of Traffic Flow Management Advisories which are dynamically updated. It integrates all types of Traffic Flow Advisories and is interactive in the sense that the set of advisories generated and actually issued can be modified by Traffic Flow Managers. Given the complexity of the overall flow management problem, a Traffic Flow Management Simulator was implemented as part of this thesis in order to evaluate various dynamic flow control strategies. Cover title; 1994; Also issued as an M.S. thesis, Dept. of Aeronautics and Astronautics, MIT, 1994; Includes bibliographical references (p. 105)

Presentations from the 1995 MIT/industry cooperative research program annual meeting.

2019-04-09T16:05:23Z

Presentations from the 1995 MIT/industry cooperative research program annual meeting. Wong, Keewah Gary.; Belobaba, Peter.; Farkas Andrs̀; Mathaisel, Dennis F. X; Wilson, John L.; Idris, Husni Rifat; Ausrotas, Raymond A; Clarke, Michael D. D. Cover title

Planning level decision support for the selection of robust configurations of airport passenger buildings

2019-04-10T21:23:07Z

Planning level decision support for the selection of robust configurations of airport passenger buildings Svrcek, Tom Prevalent in the current practice of airport design is the view of the airport as a "terminal", or beginning and ending point only of a traveler's journey. Such a perspective wrongly encourages the belief that airport performance can be measured with only a limited number of criteria over a narrow range of conditions. This dissertation adopts the view that performance should be considered in broad range, multiple criteria terms, in order to balance the (often conflicting) objectives of the different users of an airport's services. To accomplish this goal, we develop a series of prototype Passenger Building Configuration Evaluator (PBCE) tools, to help airport planners during the selection of an initial configuration concept. To study objectively the differences among dissimilar concepts, we identify a general airport configuration nomenclature and use it to represent several different concepts geometrically. From these characterizations, we obtain the absolute distances between any two points within the airport. Based on assumptions regarding the distribution of passengers, we then estimate the transition probabilities of traveling between any of these points. Using the PBCE tools and well-known results of geometrical probability, we show how we can estimate the potential performance of any given configuration and geometry. Using a representation of data called a "performance profile", we demonstrate how planners can select an initial configuration based on robustness, or performance over a broad range. Specifically, we illustrate the selection process faced with uncertainty in such parameters as the level and type of transfer traffic, industry structure, and size. Our analyses suggest that configurations most appropriate for minimizing expected walking distances may not be the most appropriate for minimizing the expected taxi distances (and required number of turns) for aircraft. We also address the issue of passenger congestion, both in pedestrian walkways and waiting areas. Included in our analysis is a discussion of the IATA level of service standards, and a survey of how current practitioners use these standards during the planning process. Finally, we show how simple, "back-of-the-envelope" type calculations can be used to obtain congestion estimates consistent with ones obtained from more detailed, data intensive methods. Cover title; May 1994; Also issued as an Ph.D. thesis, Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1995; Includes bibliographical references (p. 252-255)

Seasonality in air transportation demand

2019-04-12T15:08:30Z

Seasonality in air transportation demand Reichard Megwinoff, Hčtor Nicolas This thesis investigates the seasonality of demand in air transportation. It presents three methods for computing seasonal indices. One of these methods, the Periodic Average Method, is selected as the most appropriate for the limited sample of data supplied by Delta Air Lines. These indices are used to determine the existence of significant differences between the seasonality of demand between directions of a markets as well as differences among markets. Finally, using the results from this assessment the markets are categorized into four categories: Vacation - Low Business, Low Vacation - Strong Business, Busines & Vacation, and Distict Markets. The markets in each category can be represented by a set of seasonal indices. The overall conclusion is that the seasonality does not differ by direction in a market but it differs by market category March 1988; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Civil Engineering, 1988; Includes bibliographical references (p. 81)

Airline network seat inventory control : methodologies and revenue impacts

2019-04-12T15:08:29Z

Airline network seat inventory control : methodologies and revenue impacts Williamson, Elizabeth Louise In the airline industry, it is customary for carriers to offer a wide range of fares for any given seat in the same cabin on the same flight. In order to control the number of seats made available in each fare class, airlines practice what is called seat inventory control. Traditionally, airline seat inventory control has been the process of allocating seats among varies fare classes on a flight leg in order to maximize expected revenues. Reservations for travel on a flight leg are accepted based on the availability of a particular fare class on that flight leg. A passenger's ultimate destination, overall itinerary, or total revenue contribution to the airline is not taken into account. The typical route structure of a large airline, however, is built around a complex network of connecting flights. Maximizing revenues on individual flight legs is not the same as maximizing total network revenues. The objective of this dissertation is to address the seat inventory control problem at the network level, taking into account the interaction of flight legs and the flow of traffic across a network. Beginning with the traditional network formulation of the seat inventory control problem, practical approaches for actually controlling seat inventories at the origin-destination and fare class (ODF) level are first discussed. To avoid problems associated with forecasting ODF itinerary demand, network methods based on aggregated demand estimates are then presented. Taking the network seat inventory control problem one step closer to fit in with current reservations control capabilities, several leg-based heuristics are introduced. These heuristics take into account information about different ODF passenger demand and traffic flows while optimization and control of seat inventories remains at the flight leg level. In order to effectively measure the revenue potential of the different network seat inventory control methods introduced, an integrated optimization/booking process simulation was developed. Specific issues related to realistically modeling the booking process are discussed and the multi-period, computer-based, mathematical simulation described in detail. With the use of this integrated optimization/booking process simulation, the revenue impacts of the different network seat inventory control methodologies are then evaluated using real airline data for both a connecting hub network and multiple flight leg networks. Overall performance of each method is examined by comparing the revenue obtained with that of current leg-based control approaches and the maximum revenue potential given perfect information. The performance of the different methods evaluated varies with both the network and the actual demand patterns, however, significant revenue impacts over current seat inventory control approaches can be obtained. One approach which consistently performs well is a deterministic network approach in which ODF seat allocations are nested by shadow prices. Depending on the network structure, other leg-based OD control heuristics also perform well. The benefits of network seat inventory control are a function of the load factor across a network. Below an average load factor of about 85%, revenue impacts over effective leg-based control are non-existent. However, as the average load factor increases, revenue impacts on the order of 2-4% are obtainable. Cover title; June 1991; Also issued as an Ph.D. thesis, MIT Dept. of Aeronautics and Astronautics, 1992; June 1992; Includes bibliographical references (p. 254-256)

The integration of Automatic Speech Recognition into the Air Traffic Control system

2024-02-15T13:41:08Z

The integration of Automatic Speech Recognition into the Air Traffic Control system Karlsson, Joakim Today, the Air Traffic Control (ATC) system relies primarily on verbal communication between the air traffic controllers and the pilots of the aircraft in the controlled airspace. Although a computer system exists that processes primary radar, secondary radar, and flight plan information, the information contained within the verbal communications is not retained. The introduction of Automatic Speech Recognition (ASR) technology would allow this information to be captured for processing. The research presented in this paper examines the feasibility of using ASR technology in the Air Traffic Control environment. The current status of the technology is assessed. Problems that are unique to ATC applications of voice input are identified. Since ASR technology is inherently a part of the man-machine interface between the user and the system, emphasis is placed on the relevant human factors issues. A man-machine model is presented which demonstrates the use of mixed input modalities, automatic error detection and correction techniques, and the optimal use of feedback to the controller. Much of the potential benefit of introducing ASR technology into the Air Traffic Control system is a result of the highly constrained language used by air traffic controllers. Consequently, the information content of the ATC language must be determined, and methods must be designed to process the various levels of knowledge inherently available in ATC communications. The man machine model adopted in this paper demonstrates techniques to utilize syntactic, semantic, and pragmatic information to improve overall recognition accuracy. An intelligent, adaptive voice input parser is presented. January 1990; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990; Includes bibliographical references (p. 89-94)

Presentations from the 1994 MIT/industry cooperative research program annual meeting

2019-04-12T15:08:28Z

Presentations from the 1994 MIT/industry cooperative research program annual meeting Achtmann, Eric D.; Belobaba, Peter.; Tan, Jin C.; Fedida, Fabien.; Farkas Andrs̀; Clarke, Michael D. D.; Mathaisel, Dennis F. X; Simpson, R. W; Chen, Edmund; Mette, Matthias Cover title; May 1994

Some fleet routing and scheduling problems for air transportation systems

2019-04-12T15:08:27Z

Some fleet routing and scheduling problems for air transportation systems Levin, Amos The purpose of this work is to formulate and develop practicable solution methods to some important fleet routing, scheduling and fleet composition problems. These problems arise in the operation of air transportation systems like the operating domestic and international airlines. The problem of minimal fleet size to meet a variable schedule, which will be fixed when the system goes into operation, is formulated in several ways as Integer Linear Programs in 0-1 variables. The ILP's obtained are large scale programs and solved here by Land and Doig type Branch and Bound algorithms. The computational experiments with them, which were conducted with MPS/360, have been very sucessful and in the majority of cases, particularly when larger systems are solved, the algorithms terminated at the optimal integer solutions after a single iteration. The problem of scheduling and routing the minimal fleet is then formulated as an ILP which has exhibited equally successful computational results. The minimal single fleet-problem is extended to include some extraneous constraints on service frequencies between and at stations. Computational results with examples are provided. The problem of system design with and without a given fleet size is formulated. The problem of decomposition of the system into subsystems, each consisting of a single vehicle type is next formulated in several ways for several considerations. These formulations are also given as Integer Linear Programs. The first is proven to have at least one optimal integer solution. Computational experience with the application of the Land and Doig Branch and Bound algorithm to some of the other multi-fleet problems is also given. A computerized Airline Management Decision System which will use the models and solution methods developed in this work is briefly described in Appendix A. The Crew Scheduling Problem is also briefly discussed in this appendix since its solution procedures must be a part of such a Decision System. 1969; PB-174912; Includes bibliographical references (p. 124-125)

Airline pricing and fare product differentiation

2019-04-12T15:08:26Z

Airline pricing and fare product differentiation Botimer, Theodore Charles Airlines offer combinations of price level and purchase restrictions, or fare products, designed to best maximize revenues on their flights. This dissertation provides the first comprehensive examination of the differentiated fare product structure on the market today in terms of passenger demand, airline revenue, and societal welfare. The role of pricing in the airline revenue management function is established first. The types of price discrimination currently practiced by airlines, as defined in the economics literature, are then identified. Although the terms airline product differentiation and price discrimination have previously been used interchangeably, the two practices are shown to differ and exist simultaneously in the current industry environment. Next, airline revenue management techniques and, in particular, fare product differentiation are examined from the standpoint of economic efficiency. This dissertation concludes that both efficiency in exchange and Pareto optimality are unattainable under the current structure of airline fare product differentiation as a result of the costs incurred by passengers due to applied purchase restrictions. It is found, however, that a differentiated fare product structure with a wide range of price levels coupled with effective revenue management techniques can provide airline seats to those consumers who value them most when demand exceeds supply. Efficiency in allocation can thus be achieved in the current industry environment. Virtually every existing yield management seat allocation model assumes that consumers view differentiated airline fare products as separate products with; (cont.) uncorrelated demands that compete for space on a fixed capacity aircraft. Such formulations ignore the dependence of the demand for a given fare product on the price levels and characteristics of the other available (competing) fare products. In this dissertation, a model of product differentiation that considers the interrelationships of the available airline fare products as well as the cost incurred by consumers of accepting more restricted (and less flexible) products is presented. This generalized cost model of airline fare product differentiation explicitly incorporates the techniques of fare product differentiation and price discrimination currently used by airlines. The generalized cost model is extended to incorporate the "buy down" or diversion of passengers to lower-priced fare products as a result of their ability to meet the additional purchase restrictions imposed by airlines. Moreover, diverting passengers may be induced to "sell up" to higher-priced fare products when booking limits are applied to the lower-priced products. The generalized cost model contributes the first behavioral motivation of both passenger diversion and sell up. The dissertation demonstrates the use of booking limits as devices to control and limit the revenue dilution effects of passenger diversion. The effects of pricing and other fare product design decisions are quantified for any set of OD market conditions using the generalized cost model. The model provides insight into the underlying effects of the tradeoffs made by airlines when making pricing and marketing planning decisions. In summary, this research provides the first cohesive look at the relationships between price level, purchase restrictions, demand, and revenue in the context of airline product differentiation and yield management. October 20 1993"--P. 2; Cover title; Also issued as an Ph.D. thesis, MIT, Dept. of Civil and Environmental Engineering, 1994; Includes bibliographical references (p. 282-286)

A multi-regression analysis of airline indirect operating costs

2019-04-10T07:30:39Z

A multi-regression analysis of airline indirect operating costs Taneja, Nawal K.; Simpson, R. W. A multiple regression analysis of domestic and local airline indirect costs was carried out to formulate cost estimating equations for airline indirect costs. Data from CAB and FAA sources covering the years 1962-66 was used, and the costs were broken down into the classification of the uniform system of accounts Form 41, used by the airlines in reporting to the CAB. Thus regression equations were found for 1) annual system expenses in the categories such as Passenger Servicing, Traffic Servicing, Promotion and Sales, General and Administrative, etc. as well as an overall indirect operating cost; and 2) annual station expenses where the Aircraft and Traffic Servicing expenses for individual stations are examined. A stepwise regression technique is used to select the best combinations of independent variables for the equations. The independent variables were data such as revenue passenger miles, passengers enplaned, revenue aircraft miles, total revenue aircraft departures, etc. The results generally showed that a high degree of correlation could be found between the costs and some combination of these variables. June 1968; PB 183 012; N69-33854; Includes bibliographical references (p. 53-54)

The processes of airline operational control

2019-04-12T15:08:25Z

The processes of airline operational control Grandeau, Seth C. The airline industry has undergone many drastic changes in the way operations are conducted since the Airline Deregulation Act of 1978. The Federal Aviation Administration of the Department of Transportation, however, has not fully kept up with these changes. This has created tension between the airlines and the FAA, who, responsible for providing air traffic control and management, is using decades old technology and procedures to handle modern day problems. This thesis details the process of building and implementing an airline schedule. This is based on interviews with several major US airlines. Particular attention is paid to the day to day running of the airline at the Airline Operations Control Center. Several areas are identified where the FAA can provide better ATC service to the airlines, and to the traveling public. These areas include more lenient rules for swapping ground delay program slots, including slot sale, and new tools to make more efficient use of the national air space. January 1995; Includes bibliographical references (p. 97-98)

An adaptive Final Approach Spacing Advisory system : modeling, analysis and simulation

2019-04-10T23:32:50Z

An adaptive Final Approach Spacing Advisory system : modeling, analysis and simulation Chi, Zhihang As airline industry grows and air traffic increases drastically, terminal airspace around busy airports is becoming more and more crowded. To accommodate the soaring demand for use of airports, a plausible and profitable way is to improve the efficiency of existing airports. An automated final approach spacing system can improve the efficiency as well as alleviate the workload of air traffic controllers. In this thesis we develop an automated adaptive and interactive Final Approach Spacing Advisory (FASA) system to be used in future at busy airports. Our system is able to generate and update final approach paths for aircraft and guarantee that the aircraft land as scheduled and safely spaced. It prompts air traffic controllers for calls of turns. It can also detect errors in the execution of final approach paths and provide warning and correcting cues for the controllers. We will elaborate on the motivation for this thesis in Chapter 1. In Chapter 2, we will define the problem of Final Approach Spacing and describe the operations involved. We will introduce the key idea of our model - schedule box and sketch the framework of our system. In Chapter 3, we will establish a mathematical model for our proposed system, analyze it and obtain the solution to it. We will show that our model is capable of incorporating any constraints and that the whole problem can be reduced to finding feasible solutions to a linear system of two variables. In Chapter 4, we will develop a simulation program to implement our model in Chapter 3. We will describe in detail the algorithms and logics of our simulation program. Finally in Chapter 5, we give a summary of our achievements as well as the topics and directions of future research. May 1991; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Sloan School of Management, 1991; Includes bibliographical references (p. 75)

Interactive dynamic aircraft scheduling and fleet routing with the out-of-kilter algorithm

2019-04-09T18:34:53Z

Interactive dynamic aircraft scheduling and fleet routing with the out-of-kilter algorithm Van Cotthem, Jan A decision support system is introduced that automates dynamic aircraft scheduling and fleet routing. Interactive graphics-based schedule construction and modification tools automate the dynamic scheduling of aircraft of a single-type aircraft fleet and the out-of-kilter algorithm is employed to automate their routing. With the out-of-kilter algorithm, either the minimum fleet size required to serve a complete schedule or the routes that aircraft of a fleet of fixed size should serve in order to maximize fleet income can be determined. Since many scheduling scenarios can be easily constructed and evaluated, fleet routing solutions that achieve planning goals, while satisfying organizational constraints, can be quickly obtained. As a result, significant improvements in aircraft scheduling and fleet routing productivity and quality are possible. Cover title; Also issued as an M.S. thesis, Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics, 1986; Includes bibliographical references (p. 142-143)

A study of the practicality and profit enhancement potential of demand driven dispatch in airline hub operations

2019-04-12T15:08:24Z

A study of the practicality and profit enhancement potential of demand driven dispatch in airline hub operations Waldman, Gary L. This thesis explores the use of demand driven dispatch in the hub and spoke environment prevalent in the route networks of major airlines in the United States. Demand driven dispatch is an operational mode where aircraft assignments can be changed in response to variation in demand. A computer program simulated the functions of a revenue management system and an optimal aircraft assignment routine over the course of the passenger booking process. An isolated hub with service exclusively between the hub and 15 spoke cities was assumed. Two series of quantitative studies were done, one looking at the possible profit improvements at various demand levels with demand driven dispatch and the other examining the sensitivity of demand driven dispatch results to when the first and last optimal reassignment of hub aircraft was made in the booking process. In the first series, comparisons were made between results obtained from static aircraft assignments and fully dynamic demand driven dispatch assignments. Several scenarios were simulated. These involved various combinations of demand distribution, demand balance, and booking process assumptions. Booking process sensitivity studies were performed on a small subset of the scenario combinations. A discussion of practical issues which could affect implementation is also included. Results show that demand driven dispatch performance is fairly uniform regardless of the scenario with the best projected yearly profit increases for a major hub and spoke operator of $35-$40 million over the current fixed assignment practice. This occurred at load factors similar to airline historical levels of 65%. The profit increases at normal demand levels were achieved mostly through better aircraft utilization patterns (lower costs) and not revenue enhancement. At higher average load factors demand driven dispatch improvement was less significant but was always positive. Studies on when demand driven dispatch was applied during the booking process showed that major benefits could be gained by evaluating assignments even once as long as this assignment period preceded any significant level of high yield passenger booking requests. Cover title; June 1991; Also issued as an M.S. thesis, Dept. of Aeronautics and Astronautics, MIT, 1993; Includes bibliographical references (p. 93-94)

Human-centered automation of air traffic control operations in the terminal area

2019-04-10T23:32:49Z

Human-centered automation of air traffic control operations in the terminal area Idris, Husni Rifat Introduction: Air Traffic Control operations are described extensively in the ATC manuals such as the Airman's Information Manual [1] and the ATC Controller's Handbook [2]. Mathematical analysis has also been conducted for the ATC operations as evident in the many theses that have been published in ATC research [3, 4, 5]. A brief description is due here however in order to provide a background for the following document. There are six major ATC functions in the terminal area and a summary of their description in Sadoune's thesis [5] follows: Flow Management: The flow management purpose is to provide efficient transition between the en-route corridors and the terminal area through the metering fixes. The en-route corridors are the airways connecting the airports, the terminal area is the designated space around the airport, and the metering fixes are the points at which aircraft enter the terminal area under the flow control process called metering. The flow management system is capable of delivering the aircraft to the metering fix at predetermined time, altitude, and speed, minimizing fuel consumption and flight time. Beyond the metering fix however the concern in no longer fuel and cost, it is the separation between the aircraft and the landing schedule. Ground-based flight path generation is needed at that point. Runway Scheduling: The runway capacity is the limiting factor of the flow of traffic at congested airports. There are many reasons why runways are not used efficiently in the current tactical practice. These include the independent scheduling of landings and takeoffs, the ad hoc fashion in which takeoffs are inserted between landings, and the common use of the first-come-first-serve approach which is fair but not optimal. Runway scheduling is a queuing process and can be optimized for maximum throughput, long term service, and minimum delays of aircraft, taking into account fuel consumption, duration of flight, and other factors. The difficulty is in the dynamic nature of the schedule where modifications are needed as new entrants arrive or as environmental conditions change. The determination of the runway capacity and its improvement through the use of advanced technologies are discussed in Flow Control: Through traffic redistribution the flow control process helps smooth the demand fluctuations leading to a controlled number of aircraft simultaneously present in the terminal area. Two processes accomplish flow control: metering and holding. Metering divides the approach to the airport into successive stages between metering fixes. The flow management system delivers the aircraft to the metering fixes at the predetermined time, altitude, and speed. Holding points are assigned where holding aircraft are stacked and isolated from traffic. Holding aircraft circle in holding patterns awaiting landing clearance. Therefore, while metering moves the delays resulting from the runway capacity upstream, holding extends the flight path in time to accommodate arrival delays. These practices however can result in idle runway time in favor of more flow control leading to less efficient use of the runway. Flight Path Generation: There are standard routes both from the terminal area entry points to the runway for approach and from the runway to the en-route corridors for departure. These predefined routes can be used at low traffic flow rates, and add to the precision since automatic flight control systems are capable of flying along them automatically. However they are not optimal in using the space, or in exploiting the aircraft capabilities, or in maximizing the runway capacity. Automated flight path generation allows the incorporation of the space organization, the ATC separation criteria, the landing and takeoff schedule, the aircraft dynamics and performance limitations, and the maneuvering characteristics of the pilot in generating more optimal and flexible paths. This subject will be emphasized further in this document. Path Conformance Monitoring: In order to supervise the execution of the flight path plan, the radar surveillance system provides vague and non-precise measurement of the position of the aircraft. The controllers base their estimates of the conformance on 2-dimensional radar displays, and have to wait few intervals to estimate the direction of the aircraft. To adjust for the path conformance error the controllers issue heading, altitude, and speed clearances (vectors) to the pilots. Communication between controllers and pilots is done via radio transmission. Errors result from misunderstanding between the pilot and the controller, pilot response, as well as wind and unexpected atmospheric disturbances. Again new technologies and more automation are expected to improve the path conformance capabilities. These include better surveillance using satellites, digital data links for communication between the controller and the pilot, and display of the path to the pilot on board the aircraft. Questions of resolution and threshold of the conformance error become critical to the automation of the monitoring function. Hazard Monitoring: This includes detecting possible collisions between aircraft and with the ground. There is a trade off between false alarms and missed alarms in setting the threshold for the hazard alarm. Namely the more conservative the alarm threshold is set, the less is the risk of collision due to a missed alarm. But the disturbance to the traffic flow caused by the large number of false alarms is higher. Cover title; November 2, 1994; Series statement handwritten on cover; Proposal for the Interdepartmental Doctoral Program in Human Factors and Automation; Includes bibliographical references (p. 70-73)

Creating new operational concepts for global automated ATM systems

2019-04-08T07:30:06Z

Creating new operational concepts for global automated ATM systems Simpson, R. W.; Advanced Workshop on Air Traffic Management With the availability of new CNS technologies (Communications, Navigation and Guidance, Surveillance) as described by the ICAO FANS agreement and the potential of new tools for Automation at the ATC controller's console, the aviation world is once again in the same position as it was in 1945 when WW2 technologies in the form of radar and ground based radio-navigation aids were introduced to create the present forms of ATC operations. But instead of providing the tools and waiting to see how operational people will use them to create new ATC operating procedures, the introduction of automation and the size and global scope of the new investments make it necessary to do a proper, top down approach to engineering a new ATM system. This means pre-determining the set of new Operational Concepts and their Operational Procedures which are safe and economical, which allow compatible transitions under mixed old and new operations, and which provide a significant increase in capacity needed in certain high density traffic areas. This paper is concerned with establishing a framework for describing and analyzing new ATC Operational Concepts which will then allow the requisite systems engineering task to proceed. Proceedings of ATM 95, Advanced Workshop in Air Traffic Management, Capri, October 1995; Includes bibliographical references (p. 21)

System design for express airlines

2019-04-08T08:17:35Z

System design for express airlines Fisher, Michael R. In this thesis we investigate and analyze express airlines for the purpose of system design. Chapter 1 contains a taxonomy for express carriers that is built around elemental system components, distinguishable from one another with a two-variable classification scheme. We describe how overnight carriers operate, what their basic philosophy of operation is, and how they might choose to develop their networks to best serve that philosophy. In addition, we present mathematical formulations for several systems. Chapter 2 is a review of research into similar problems and of solution techniques that might be applicable to express system design problems. In Chapter 3 we focus on the simplest express network problem, the Single- Hub, Single-Turn System Design Problem, SHP. We develop several models for SHP, both to expose the structure of the problem and to find a tractable formulation. The emergent concept of the chapter is the route complex. Using this approach to route expression, we choose a formulation that is essentially a set partitioning problem with side constraints. In Chapter 4 we explore the dualization of the side constraints and develop a solution procedure. There are three types of complicating constraints: aircraft availability, placement (for ferry flights), and columnjoining (for transforming a pure set partitioning problem into a nonbipartite matching problem with side constraints). We use a minimum weight, nonbipartite matching problem as the core of our solution procedure for SHP, focusing on obtaining feasible solutions directly from a Lagrangian relaxation, rather than using branch-and-bound. In Chapter 5 we report our computational results and offer suggestions for further research. October 9, 1987"--Cover; Includes bibliographical references (leaves 187-191)

Modelling risk in ATC operations with ground intervention

2019-04-12T15:08:24Z

Modelling risk in ATC operations with ground intervention Simpson, R. W.; Ausrotas, Raymond A. Preface: It was part of a continuing series of research work aimed at creating models for estimating Collision Risk for ATC operations which can be used by the Federal Aviation Administration and ICAO to establish safe criteria for separations between aircraft.; Introduction: The purpose of this information paper is; a) to provide a document describing the problems of analyzing risk for ATC systems which have surveillance over air traffic and which allow ground controllers to intervene to avoid unsafe encounters; b) to propose a framework for future studies which attempt to solve these problems. The need for such methods of analyzing risk arises in justifying reduced ATC separation criteria which ensure safety for newer forms of ATC operations. The benefits of these new systems strongly depend on achieving a reduction in current ATC separations, and as a result, an increase in capacity and efficiency for aircraft operations. These benefits must be weighed against the costs of developing and operating the new ATC systems. Cover title; July 1991; Includes bibliographical references (leaves 17-18)

Solving the schedule transition problem using optimization techniques

2021-07-05T14:03:20Z

Solving the schedule transition problem using optimization techniques Fujiwara, Tsuneo A new algorithm is introduced for effectively solving the airline schedule transition problem, which involves efficiently re-routing aircraft in order to balance the number and the types of aircraft at each station at the beginning of a new schedule with minimum cost. An extensive study was performed on using "pre-switches" - changing aircraft types of certain flights on the last day of the current schedule - and "post-switches" - changing aircraft types of certain flights on the first day of the new schedule - to balance the types of aircraft at each station for a pair of aircraft types. Several possibilities for extension to fleets of more than two aircraft types were examined. Airlines may use this algorithm in order to transition smoothly to the new schedule instead of relying on instincts of schedule analysts. Cover title; May 1989; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Civil Engineering, 1989; Includes bibliographical references

Impacts of technology on the capacity needs of the U.S. national airspace system

2019-04-12T15:08:23Z

Impacts of technology on the capacity needs of the U.S. national airspace system Ausrotas, Raymond A.; Simpson, R. W. Introduction: Air passenger traffic in the United States showed remarkable growth during the economic expansion of the 1980's. Each day a million and a quarter passengers board commercial flights. The boom coincided with the advent of airline deregulation in 1978. This drastic change in the industry has inspired professional and newspaper articles, graduate student theses, and books which have discussed the causes, effects, costs, and benefits of deregulation with predictably mixed conclusions. Economists, who like to predict the future by exercising econometric models, are finding that conditions in air transportation have become too dynamic (chaotic?) for their models to cope. Certainly the future of the air transportation industry is unclear. There has been, however, an unmistakable trend toward oligopoly, or, as industry spokesmen describe it, "hardball competition among the major airlines." This trend has been accompanied by formations of hub fortresses owned by these survivors. Air traffic has always been concentrated in a few large cities; airplanes will go where there is a demand for them. But airline (rather than traffic) hubs have created artificial demand. Up to seventy percent of travellers boarding airplanes in the hub cities do not live anywhere near these cities - in fact, they may have no idea at which airport they are changing planes. Most passengers do not care, while travel cognoscenti soon learn to avoid certain airports (and airlines which frequent these airports). A hub airport is a frenzy of activity for short periods of time during the day, as complexes of airplanes descend, park and interchange passengers, and take off. Then the airport lies quietly. If observers were to arrive at a major hub between times of complexes, they would be perplexed to hear that "this is one of the most congested airports in the world." Thus congestion and its evil twin, delay, are not constants in the system. Rather, they appear only if a number of conditions conspire to manifest themselves simultaneously, or nearly so. First, the weather must deteriorate from visual flight conditions to instrument flight conditions. Then, this must occur near peak demand conditions at the airport. Of course, some airports in the Unites States are always near peak conditions, among them the so-called slot constrained airports: New York's La Guardia and Kennedy, Washington's National, and Chicago's O'Hare. When weather goes bad at these airports or other major hubs during complexes, ripple effects start nearly all over the country, because some airlines have now designed schedules to maximize utilization of their airplanes. Very little slack time is built into the schedules to account for potential delays, although "block-time creep" exists: the phenomenon that travellers discover when they arrive at their destinations ahead of schedule (if they happen to leave on time). This "creep" protects the airlines from being branded as laggards by the DOT's Consumer On-Time Performance Data hit list. Thus a combination of management practices by airlines (which place great demand on terminal airspace over a concentrated period of time) and mother nature (which provides currently unpredictable behavior of weather near the airport) conspire to limit the capabilities to handle arrivals and departures at various airports below the numbers that had been scheduled. Travellers complain that the schedules aren't being met, and if enough people complain to Congress, or if the travellers themselves happen to be members of Congress, a national problem appears. How much of a problem is this? In 1988 there were 21 airports, according to the FAA, which exceeded 20,000 hours of annual aircraft delay, perhaps 50,000 hours per year, or 140 hours per day. (One, Chicago's O'Hare, exceeded 100,000 hours.) These airports, in turn, averaged 1,000 operations (arrivals and departures) per day, so that each operation would have averaged about 8 minutes of delay. At O'Hare, for example, 6% of all operations experienced in excess of 15 minutes of delay. (In excess means just that - there is no knowledge of how much "in excess" is.) Conversely, this means that at that most congested airport in the United States, 94% of all airplanes arrive or depart with less than 15 minutes of delay. However, airline delay statistics may be similar to the apocryphal story of the Boy Scout troop which drowned wading across a creek which averaged two feet in depth. There are estimates that on a dollar basis, delay accounts for a $3 billion cost to airlines, or a net societal cost of $5 billion if travellers' wasted time is included. Since in their best years U.S. airlines make about $3 billion in profit, reducing delay is a sure-fire way for airlines to climb out of their all too frequent financial morasses, as well as diminishing their passenger frustrations. Even though all of the numbers mentioned in the paragraphs above are subject to substantial caveats, it is indisputable that on certain days during the year the air transportation system seems to come to a crawl, if not a halt. Travellers either find themselves sitting at airport lounges observing cancellation and delay notices appearing on the departure and arrival screens, or sitting in airplanes (on runways or at gates) being told that there is an "air traffic delay." Old-timers grumble that the only difference twenty years of technology improvements has made to the U.S. airspace system is that the wait is now on the ground instead of circling in the air near their destinations. To the casual observer, it would appear that a number of solutions exist to solve this problem. The most obvious is to pour more concrete: more airports, more and longer runways, more taxiways, more gates and terminals. This is analogous to widening highways and building more interstates for ground transportation congestion. The concrete solution, alas, runs into both financial and citizen roadblocks. It is very expensive - the latest airport coming off the drawing boards (Denver International) carries a tag of some $2 billion, with about $400 million of that in bonds being backed by a new funding creature, the Passenger Facility Charge (a head tax of up to 3 dollars assessed to every passenger enplaning at an airport - voluntary or not). The citizen roadblock is community objections to airport noisiness. The bill creating the PFC in 1990 also carried with it a mandate for the FAA to create a national noise policy so that individual airports would not wreak havoc with the whole system by creating their own local operational rules, such as curfews. The bill also attempted to pacify airport neighborhoods by setting a deadline for all U.S. aircraft to be quiet(er) - complying with Stage 3 regulations by the year 2000. More damaging than financial difficulties are the anti-noise sentiments, and the concomitant not-in-my-backyard syndrome, that are at the forefronts of protests of either an alert citizenry, or New Age Luddites, when any expansion plans are made public. Whatever one's view, it is a crowd vocal and seemingly powerful enough in local political circles to stop any large- scale progress to ground solutions of the congestion problem. That, then, leaves the air. It is intuitive that if airplanes were closer spaced than they are now, much more traffic would move through a given area in the same amount of time, and consequently airplanes would land (and take off) quicker, reducing any waiting (queue) time. This obviously increases airport noise levels. There are two problems with this approach. The first trick is to accomplish this safely. Safety has at least two dimensions: there is the physical, i.e., airplanes should not run into each other (or the ground, as a result of weather disturbances and wake vortices); and pilots (and controllers) should feel they are still in control of the situation, even after separation standards are reduced. The first aspect is mostly a matter of technology, the second mostly a matter of human factors. But if traffic moved quicker and noise of the aircraft is not reduced, the same citizens who had vehemently opposed the construction of additional ground facilities would once again rise in righteous anger and demand a stop to the more efficient techniques of flying airplanes which have caused an increase in the noise levels in their neighborhood. They, too, must be considered. This report will attempt to address some of the issues outlined above. The focus will be on technology and where it is best suited to provide an equitable and efficient expansion of capacity in the air transportation system. Ultimately, the discussion will be centered on NASA's potential contributions to solving the capacity problem. December 1991; Includes bibliographical references (leaf 57)

Airline market share modeling in originating city markets

2019-04-10T23:32:48Z

Airline market share modeling in originating city markets Davis, James E. The Airline Deregulation Act of 1978 has not only affected the way airlines compete with each other, it has also changed the distribution channels that were once rigidly controlled by the airlines, travel agents and Civil Aeronautics Board. In recent years, the cost to airlines of having travel agents distribute their tickets has increased significantly. Since a large portion of these costs stems from airlines paying "overrides" to travel agents who exceed a baseline market share, which has been set by airline management, the determination of a carrier's market share in an originating city market can have serious profit implications. The problem addressed in this thesis is how an airline might predict its share of the passenger market out of an originating city. In this thesis, six different mathematical models, relating a carrier's market share to a set of exogenous variables, are proposed. Using actual airline market share data, each of these models is calibrated and tested in fifteen selected test markets and a statistical determination of each model's accuracy is performed. Of the six models tested, a non-linear multivariable regression model, relating a carrier's market share to its: seat share; frequency share; proportion of non-stop flights; and proportion of total destinations served, out of an originating city, is preferred. The use of this market share model should help airlines predict their share of the originating city passenger market, and thus, provide them with a means of setting market share quotas based upon a known set of service variables. August 1989; Also issued as an M.S. thesis Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1989; Includes bibliographical references (p. 129-130)

Algorithmic approaches to circuit enumeration problems and applications

2019-04-11T03:47:44Z

Algorithmic approaches to circuit enumeration problems and applications Lee, Boon Chai A review of methods of enumerating elementary cycles and circuits is presented. For the directed planar graph, a geometric view of circuit generation is introduced making use of the properties of dual graphs. Given the set of elementary cycles or circuits, a particular algorithm is recommended to generate all simple circuits. A simple example accompanies each of the methods discussed. Some methods of reducing the size of the graph but maintaining all circuits are introduced. Worst-case bounds on computational time and space are also given. The problem of enumerating elementary circuits whose cost is less than a certain fixed cost is solved by modifying an existing algorithm. The cost of a circuit is the sum of the cost of the arcs forming the circuit where arc costs are not restricted to be positive. Applications of circuits with particular properties are suggested. June 1982; Also issued as an M.S. thesis, Dept. of Aeronautics and Astronautics, 1982; Includes bibliographical references (p. 129-132)

Revenue impacts of airline yield management

2019-04-10T23:32:46Z

Revenue impacts of airline yield management Mak, Chung Yu In the highly competitive airline industry today, Yield or Revenue Management is extremely important to the survival of any carrier. Since fares are generally matched by all carriers to be competitive, the ability of an airline to control its passenger mix and achieve higher overall revenue is essential. Therefore, the revenue impacts of airline yield management are very important. Although there has been much discussion among people in the industry about the revenue impacts of yield management, it has received little research attention. The focus of this research is to develop an understanding of the revenue impacts of several factors that contribute to the effectiveness of yield management. In this thesis we begin by discussing the issues involved with airline yield management and the existing relevant literature. Based on the knowledge and experience gained through these previous studies, we develop a method to study the revenue impacts of airline yield management. With the development of a single-leg booking simulation, we can isolate most of the external and indirect factors that influence an airline's overall revenue. We perform a number of simulations under different scenarios to estimate the real revenue impacts of airline yield management. The different scenarios tested include varying the number of fare classes, relaxing the demand distribution assumptions, comparing static vs. dynamic seat allocation, relaxing seat inventory control assumptions and incorporating different capacity constraints or demand factors. We then present and discuss the results from these simulations with respect to their revenue impacts. Finally, we use the Revenue Opportunity Model developed by American Airlines Decision Technologies to compare revenue opportunity achieved in a simulated environment, and suggest areas for future research. January 1991; Also issued as an M.S. thesis, Dept. of Civil Engineering, MIT, 1992; Includes bibliographical references

Impact of videoconferencing on the demand for air travel

2019-04-12T15:08:22Z

Impact of videoconferencing on the demand for air travel Mette, Matthias Videoconferencing is widely seen as the form of modern telecommunications having the largest potential to impact the growth of business air travel demand. Most existing studies focus on the substitutional effect of enhanced telecommunications on air travel and suggest different substitution estimates that diminish future business air travel growth rates. However, this research reveals that reasonable and convincing theoretical arguments exist supporting the complementary interaction of modern telecommunications and business travel. A critical assessment of previous studies in this field shows that most research lacks sound empirical evidence. Besides this major deficiency, the thesis also recognizes other areas in need of future research efforts and identifies the potential for the airline industry to minimize the adverse impacts of modern telecommunications on its business and to benefit from the capability of these technologies to complement air travel. In this study, the discussion and analysis of empirical data and observations are focused on the U.S. domestic and U.S. international market. Nevertheless, research findings regarding potential interactions between videoconferencing and business air travel, main implications of these relationships for the aviation industry, potential responses by airlines, and future research opportunities are applicable on a global basis. A key component of the thesis is an industry-wide field survey carried out primarily among companies of the "Fortune 500" industry group on the characteristics of videoconferencing use and the actual and expected impact on corporate travel needs. From assessments made by videoconferencing managers and individual users of videoconferencing in these companies, it was possible to identify (1) characteristic videoconferencing adoption patterns, (2) main user groups and business purposes, (3) the role of travel substitution in the investment justification, (4) actual and projected impacts on business air travel patterns, and (5) perceived benefits and limitations of videoconferencing for business applications in economical, technical, social and communicational terms. Together with previous research findings, the results of this survey are used to construct a coherent picture of the present state of research in this field, considering all potential and observed interactions between both modes. February, 1995; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1995; Includes bibliographical references (p. 260-266)

Man Vehicle Systems Research Facility : functional specification of the ATC subsystem.

2019-04-08T07:21:03Z

Man Vehicle Systems Research Facility : functional specification of the ATC subsystem. Pararas, John Demetrios; Simpson, R. W. The ATC subsystem will be designed to realistically simulate the present and future air traffic control environments in which the cabs will fly their experiments. Statement of responsibility on title-page reads "John Pararas and Robert W. Simpson; December 1980; Includes bibliographical references

Analysis of aircraft surface motion at Boston Logan International Airport

2019-04-12T15:08:21Z

Analysis of aircraft surface motion at Boston Logan International Airport Alhanatis, Robert Elias The purpose of this thesis is to examine the nature of aircraft surface motion on the airport surface during normal operations. Twelve hours of radar data, gathered by MIT Lincoln Laboratories from Logan airport in Boston, were made available for this study. Specifically, the data included target position reports from the ASDE-3 surface surveillance radar and the ASR-9 radar from the near terminal airspace information. This data covers a variety of runway configurations, weather conditions, traffic levels and high or low visibility conditions. The study is divided into three sections. The first one focuses on the runway, and examines occupancy times, exit velocities, exit usage and velocity profiles of the final approach and landing phase. The second section, analyzes fourteen runway-taxiway intersections. Results are presented for the crossing times and usage of these intersections. The analysis also focuses on relating crossing times and usage to crossing direction, runway configuration and aircraft size. Finally, average taxiway velocities and the overall taxiway usage is measured. Additionally, the role that the location of the taxiway segment as well as its length, plays in the variation of these velocities are examined. Where possible, this study includes means, standard deviations and sample sizes of the variables in question. September 1994; Includes bibliographical references (p. 126)

Evaluation of forecasting techniques for short-term demand of air transportation

2019-04-10T10:00:45Z

Evaluation of forecasting techniques for short-term demand of air transportation Wickham, Richard Robert Forecasting is arguably the most critical component of airline management. Essentially, airlines forecast demand to plan the supply of services to respond to that demand. Forecasts of short-term demand facilitate tactical decisions such as pricing and seat inventory control-the allocation of seats among the various booking classes. In this study, an evaluation was conducted of the relative performance of selected forecasting techniques used to predict short-term demand for air transportation. Short-term in this context is defined as intervals less than eight weeks prior to the date of departure. The selected techniques were representative of current practices in the airline industry including simple time series, linear regression, and booking pickup models. Two types of pickup models were analyzed: the classical model and an advanced model. The set of models was subjected to the same short-term forecasting environment where the historical data was restricted to ten weekly departures and the forecast horizon limited to seven weeks in the future. Eight scenarios were examined to study the effects of varying the size of the historical data set as well as the length of the forecast horizon. Performance was determined on the basis of the relative accuracy of the forecasts measured through the use of selected metrics. It will be shown that the booking pickup models consistently outperformed the time series and regression models and the advanced pickup model produced the best results. Furthermore, it was discovered that increasing the size of the historical data set beyond seven weekly departures did not have a significant impact on the performance of the various models and in most cases the performance of the models deteriorated as the size of the historical data set was increased. May 1995; Includes bibliographical references (p. [121]-124)

Airline reservations forecasting : probabilistic and statistical models of the booking process

2019-04-10T10:00:44Z

Airline reservations forecasting : probabilistic and statistical models of the booking process Lee, Anthony Owen In this thesis, we develop the necessary statistical framework to produce accurate forecasts of total bookings in a particular fare class on a specific flight number departing on a given date at various points before departure. After an introduction to the basic terminology of the airline booking process, a rigorous probabilistic model is developed. The booking process is modeled as a stochastic process with requests, reservations, and cancellations interspersed in the time before a flight departs. The key result of the probabilistic analysis is a censored Poisson model of the airline booking process. A comprehensive statistical framework views the booking process from a data analysis perspective. We describe models based on advance bookings (the traditional booking curve) and historical bookings (a traditional time series model). An important development is the combined model which features a potentially more accurate combination of the advance bookings and historical bookings models. Additionally, we extend the statistical framework to include booking limits, which constrain the observed number of reservations in each fare class. The result is a truncated-censored regression model with truncation from below at zero and censoring from above at the booking limit. We test the forecasting ability of the censored Poisson model and a combined statistical model with censored Normal errors using actual airline data provided by a major U.S. airline. When compared to industry standard models, the models developed in this thesis produce significant improvements in forecast accuracy. In the appendix, a Monte Carlo simulation is performed to determine the value of accurate forecasting for the airlines. The results demonstrate that each 10% improvement in forecast accuracy can bring about a 0.5% to 3.0% increase in expected revenues. September 1990; Includes bibliographical references (p. 232-236)

TWA reservations analysis : project update -- demand distribution patterns

2019-04-09T19:13:41Z

TWA reservations analysis : project update -- demand distribution patterns Belobaba, Peter Background: Research into airline capacity management and yield optimization at the Flight Transportation Laboratory is being performed with the support and funding of the Cooperative Research Program. The focus of this research over the past six months has been on patterns of demand for the different fare products available in airline markets. The objective of this work is to gain insight into the most complex component of the capacity management problem faced by airlines--variations in demand. Trans World Airlines, a participant in the Cooperative Research Program, has given us access to reservations data and booking histories from its domestic operations over the past several years. A preliminary analysis of final reservations totals by day and by fare class for a sample of two transcontinental flights was undertaken to explore the database and identify its potential uses. The results of this preliminary analysis are discussed in an FTL report completed in April 1984. The preliminary analysis examined trends in daily booking levels and their variability over the sample period. The reservations totals exhibited traditional seasonal and daily variations, except when disrupted by changes in product pricing and/or marketing. Of potential importance to the capacity management problem was the finding that the frequency distributions of demand over the sample period (and portions thereof) did not appear to be Normal (Gaussian) in shape, but rather were- positively skewed. An intuitive explanation of such a distribution shape was suggested in the paper, namely that some base level of demand can generally be expected and that extreme values are more likely to be high relative to the mean number of reservations. This issue of demand distribution patterns was pursued with further, more detailed, analysis of reservation data from a larger sample of TWA flights. This paper outlines the analysis that was undertaken and discusses the analysis results in the context of airline capacity management.

A planning tool for predicting en route ATC conflicts and designing ATC sectors

2021-07-05T14:03:20Z

A planning tool for predicting en route ATC conflicts and designing ATC sectors Loiederman, Eric S. The modernization of the Air Traffic Control system has led to a reevaluation of sector performance in order to design a safer and more efficient system for the future. There are, however, few available tools to aid in measuring and optimizing this performance. Existing safety models of air traffic lack the flexibility to represent the broad range of air traffic characteristics. In this thesis, we present a simulation model of en route air traffic which predicts conflict frequencies for a sector under any number of traffic assumptions. We then use the results of our mode! to formulate a sector optimization problem and present algorithms to solve the problem. The model we develop is a stochastic representation of sector traffic. That aircraft is, arrivals and speeds are represented as random processes. While aircraft are assumed to operate under straight line travel restrictions, the route network through which the travel is also stochastic. Thus, deviations in flight paths are easily represented. As our model is a simulation, we make few assumptions regarding the input distributions allowing for a great amount of flexibility. The model has been implemented on the VAXNMS system. While there is a limited amount of available conflict data from the field, initial comparisons show results of the model to agree with actual conflict frequencies. Further analysis of FAA supplied data should yield similar results. - Finally, we extend the usefulness of the model by formulating a center districting problem which uses the predicted conflict frequencies to divide an air center into optimal sectors. The formulation models controller-conflict interactions within the framework of a classic queuing system. With a number of simplifying assumptions, the problem reduces to a quadratic integer optimization and two algorithms are provided to solve such an optimization. Unfortunately, the simplifying assumptions are not necessarily supported by actual data so the usefulness of our presentation is more in providing an example of a mathematical programming approach then in providing a robust planning tool. August 1985"--Cover; Includes bibliographical references

Modeling airline group passenger demand for revenue optimization

2019-04-09T15:45:29Z

Modeling airline group passenger demand for revenue optimization Svrcek, Tom Many airlines currently use a variety of analytic techniques for seat inventory control as part of a larger revenue or "yield" management system. However, much of the this effort has emphasized decisions based on the individual passenger, and has neglected a significant segment of total airline passenger demand, namely that of group passengers. Group passenger demand differs in several important respects from individual passenger demand, and these differences have motivated the need for separate attention in booking procedures and future demand forecasting. In this thesis we begin by discussing the issues involved with trying to characterize the stochastic nature of airline group passenger demand, and identify the primary elements of variability associated with it. Later, we use these primary elements of demand to develop a mathematical model for the distribution of group passengers on a given flight(s). Armed with a well-defined distribution for group passenger demand, we enhance current mathematical programming approaches for solving the seat inventory control problem to include the control of group seat inventories. We then present a model for determining the minimum per passenger fare an airline should charge an ad hoc group request based on the displacement of individual passengers. Finally, we discuss the issues involved with overbooking in the group demand context, and suggest areas for further research. Cover title; May 1991; Also issued as an M.S. thesis, Dept. of Civil Engineering, MIT, 1991; Includes bibliographical references (p. 103-104)

International aeronautical user charges

2019-04-10T10:00:43Z

International aeronautical user charges Odoni, Amedeo R. Introduction: 1.1 BACKGROUND AND MOTIVATION Very few issues relating to the international air transportation industry are today as divisive as those pertaining to user charges imposed at international airports and enroute air navigation facilities. In recent years, this general subject has led to acrimonious arguments, heated confrontations and even legal proceedings involving airlines (and the entire airport user community), airport authorities and national and local governments. Moreover, the end is nowhere in sight: should the current economic difficulties of many of the world's international airlines persist -- as well they might -- it is possible that disputes related to user charges will intensify further and reach critical proportions at some future time. The general label 'user charges" comprises a variety of fees which are employed by providers of aeronautical facilities and services as a means of recovering (partially, fully, or more-than-fully) the costs that they incur. A listing of the various kinds of user charges in existence is given in Table 1.1. Any given Airport Authority or organization that offers air navigation and aeronautical services may impose some or all of these charges. It is possible to state several facts that help explain why the subject of user charges is such a controversial one. At the same time, these facts provide the motivation for studies such as the one reported here: Fact 1: User charges have gone through a period of rapid increases in absolute and, in many cases, relative terms as well, over the last decade. A confluence of factors have contributed to these increases. Perhaps the foremost among them is that, during the 1970's, the aviation industry Table 1.1 TYPES OF USER CHARGES AIRPORT CHARGES:- Aeronautical Charges: Landing and/or take-off charges, Parking and hangar charges, Passenger service charges, Security charges, Airport noise charges, Ground (ramp and traffic) handling charges, Concession fees for aviation fuel and oil, Rentals of air terminal space, premises and equipment, Non-Aeronautical Charges: Rentals of airport land, premises and equipment (for purposes other than servicing traffic), Concession fees for commercial concerns catering to the public, Fees derived from airport's own operation of shops and services, Fees charged for tours, admission to reserved areas, etc. ENROUTE CHARGES Air navigation charges * The International Civil Aviation Organization (ICAO) recommends that where fuel charges are imposed, they should be recognized by airport authorities as being concession charges of an aeronautical nature and that fuel concessionaires should not add them automatically to the price of fuel to aircraft operator [ICAO, 1981d]. began to be treated as a "mature" one, in most of the world. Until then, many countries were content to subsidize the industry through provision of aeronautical facilities and services at no cost or at much-below cost. (It is a remarkable fact, for instance, that no enroute air navigation charges were collected by someWest European nations until 1971, the year when Eurocontrol began collecting charges designed to recover only 15% of costs.) However, as the industry grew "above critical size" and stabilized during the 1960's and 1970's, government attitudes toward it generally changed and a "users-pay" principle was increasingly being applied to the setting of user charges by the 1970's. (By 1981, Eurocontrol was recovering 100% of enroute air navigation costs on behalf of its 11 member states.) A second factor is that, during this period, some new types of charges, notably security charges and noise charges, have been added for the first time to the array of other charges that airlines traditionally faced. The fact that many aeronautical services are labor-intensive ones -- notably ground handling, enroute and terminal-area air navigation and security -- was a third contributing factor, as labor costs are particularly sensitive to inflationary pressures such as those experienced worldwide during the period in question. Yet another factor is that since the mid-1960's many countries have been investing large amounts of capital toward improving their aeronautical infrastructures (new or improved airports, modernization of ATC systems). As these new or improved facilities came into service, the cost-base on which user charges are computed grew rapidly. While one can expand this list of factors considerably, the point is that airlines and users of aviation facilities have felt the impact of such rapid increases. This, moreover, happened at a time when many of them were experiencing significant economic pressures. For example, IATA contends that, during the period of the dramatic fuel-price increases (1973-1981), the only other component of their costs that grew nearly as rapidly as fuel costs were aeronautical user charges (see Table 1.2). Fact 2: There are large differences from country to country and from location to location in the ways user charges are computed and in the magnitude of user charges. This is amply demonstrated by Table 1.3, which shows the size of typical landing fees and passenger service charges in a number of selected countries for three important aircraft types. Similar or even larger differences exist in the magnitudes of other charges imposed (especially for ground handling and enroute air navigation services), as will be shown in many parts of this report. Such differences - coupled with the unfortunate tendency of many aeronautical authorities to provide inadequate or minimal documentation in explaining their user charges -- have led to accusations of "unfairness", "predatory behavior", or "discrimination" against several specific countries or airports' (e.g., London/Heathrow, Tokyo/Narita, Australia). It is not surprising that such accusations are usually directed toward those that impose the highest charges. However, locations that impose much-lower charges, but have the benefit of a lower cost-base as well, are just as susceptible to adopting such practices. Fact 3: In many cases, user charges may absorb a sizable fraction of an international commercial flight's gross revenues. This is illustrated in Tables 1.4 and 1.5 for the case of flights by a real, but anonymous, Airline X between its home base (XXX) and New York (JFK International), London/Heathrow and Amsterdam. Table 1.4 shows all the charges imposed for each route/equipment combination for load factors of 100%, 1We do not imply here that such accusations are necessarily justified. Landing Fee at destination includes parking charge 4-hour stay-over in NYC; 2-hour in LON, AMS Peak-hour use in summer ... The specific assumptions made are listed at the bottom of Table 1.4. Table 1.5 estimates what percentage of total revenues (true one-way yields on the routes were provided by Airline X) is absorbed by user charges. (For example, for a B747 flight to NYC at 100% load factor, the total user charges of $18,378 -- see Table 1.4 - amount to 5.74% of the round-trip revenues of $320,000). It can be seen that user charges in these examples vary from 6% to 22% of gross revenues, depending on destination, aircraft involved and load factor. It is also important to note that the total user charges (last line of Table 1.4) are largely determined by the type of aircraft flown on any given route and are quite insensitive to the load factor -- a characteristic that is quite vexing to the airlines. While this example is given for illustrative purposes only, the range of percentages it indicates in Table 1.5 is not atypical. IATA estimates that the sum of enroute charges and landing and other airport fees (not including ground handling charges and passenger service costs at airports) amount to approximately 6% of the total (direct and indirect) costs of the international scheduled services of its members. West European airlines contend that these same charges amount to 11.2% of their total costs for intra-European services and an even-higher percentage for airlines specializing in short-haul routes.; (cont.) The Association of European Airlines (AEA), in fact, often blames high user charges in Europe as one of the main reasons for the higher European operating costs and therefore higher fares per mile.2 Most of the recent complaints of AEA carriers have centered in particular on enroute air navigation charges collected through the Eurocontrol agency. Pan Am has reported that whereas user charges of various kinds accounted for 4% of its costs on international routes in 1970, they now account for 9%. For domestic trunk carriers in the 2This view is not necessarily endorsed here. United States, user fees account for 4.2% of their costs. However, this percentage does not include the 8% tax on domestic fares, which is collected on behalf of the Aviation Trust Fund and which can be viewed as an aeronautical user charge. Up to a few years ago, U.S. airlines were among those most vocal in protesting the magnitude of and lack of uniformity in international user charges. Partially as a result, the International Air Transportation Fair Competitve Practices Act that became law in the United States on January 3, 1975 directs the Secretary of Transportation to survey foreign user charges and to report to the Secretary of State and the Civil Aeronautics Board any charges that unreasonably exceed comparable U.S. charges or are otherwise discriminatory. The latter are then to negotiate with the foreign country involved to reduce such charges or eliminate such discrimination [Pogue and Davison, 1979]. The Act also gives to the Secretary of Transportation, in consultation with the Secretary of State, the right to impose compensatory charges on foreign carriers, should such negotiations fail. It should be noted that, as a result of the rapid increase of the exchange value of the U.S. dollar during the 1981-1984 period, U.S. international carriers have been protected, to a large extent, from "internalizing" the further increases in international user charges that have taken place during these years. (For example, although the costs, as computed in local currencies, of enroute air navigation in Western Europe (Eurocontrol) nearly doubled between 1980 and 1983, the cost to U.S. carriers when computed in U.S. dollars has not changed appreciably.) Should however, the current trend concerning exchange rates be reversed, it is likely that the international-user-charges issue will receive renewed prominence in the United States. Fact 4: Limited guidance on setting user charges is provided by multilateral or bilateral international agreements and by the International Civil Aviation Organization. The multilateral Convention on International Civil Aviation (Chicago, Decemer 7, 1944) which provides the legal framework for many aspects of international air transportation is vague on the subject of user charges. The relevant provision of the Convention is contained in Article 15 of Chapter II, which calls for non-discriminatory charges for international aviation, without being more specific on what this means. Bilateral agreements, e.g. Bermuda II, are equally non-specific, usually calling for: "just and reasonable" charges; equal treatment for the contracting states' carriers with regard to user charges; user charges that "may reflect, but should not exceed, the full cost" of providing facilities and services "including a reasonable rate of return on assets, after depreciation"; and continuing consultations and exchange of information between "the competent charging authorities" and airline representatives. The ICAO has also struggled repeatedly with the issue of user charges, notably in special conferences on the subject held in 1967, 1973 and 1981, all of which met with limited success. The principles and recommendations endorsed by the ICAO on the assessment and allocation of user charges are contained in ICAO Doc. 9082-C/1015 (Statements by the Council to Contracting States on Charges for Airports and Route Air Navigation Facilities). The ICAO Statements are not binding on member countries, but offer guidelines that charging authorities are encouraged to; (cont.) follow. The Statements are reproduced here as Appendix 1A, because they will be repeatedly referred to and discussed in Chapters 2-6. (The reader who is unfamiliar with them is encouraged to review them.) For now, two points need to be made: First, that the ICAO Statements do endorse the concept that, in principle, international users should bear the full and fair share of costs of the aeronautical facilities and services they use. And, second, that, as is natural for a document that attempts to establish a common ground among many conflicting views and interests, the Statements are often ambiguous, subject to conflicting interpretations and, in a number of instances, even self-contradictory, as will be pointed out later in this report. As noted earlier, Facts 1-4 in addition to providing a background on the problem of international user charges, also constitute motivations for this report. Indeed the aim here is to attempt to present a systematic and integrated discussion of relevant issues and to contribute to an improved understanding of the range of options and approaches that exist worldwide with regard to setting user charges. 1.2. OUTLINE OF THIS REPORT We now present an outline of the contents of Chapters 2-6. Chapter 2 contains a brief survey of most types of aeronautical charges: landing fees; parking and hangar charges; passenger service charges; fuel throughput charges; noise and nuisance charges; security charges; and enroute air navigation charges. Discussion of ground handling charges is left to Chapter 6. For each one of the types of charges covered, the following are addressed: (i) Ways in which the charges are specified, as well as typical magnitudes and ranges of the charges (ii) Principal issues concerning the charges, including the positions of users (mostly the airlines) (iii) Summaries of the findings of recent ICAO surveys on the charges, as well as tabulations of charges in individual countries based on information collected by these surveys. Chapter 3 deals with the approach needed to determine whether, in the context of the conditions under which an aeronautical service or facility is provided, the resulting user charges are reasonable and fair. The emphasis in the preceding sentence is intended to underscore the point that comparisons among user charges in different countries or locations should not be undertaken without a full understanding of the particular circumstances and assumptions that underlie each of the systems of charges being compared. In fact, it is believed here that such comparisons should normally be avoided and that user charges at international airports and enroute air navigation facilities should be reviewed individually on a case-by-case basis. Chapter 3 presents what could be described as a normative model* for conducting such a review. Specifically, on the basis of the insights gained during this research, we shall review the steps that must be carried out by a provider of aeronautical services in order to determine and specify a system of user charges. These steps include: (a) Postulating the policy guidelines that should be followed (b) Developing a cost base (c) Allocating costs in the cost base among the various cost and revenue centers of the aeronautical facility (d) Allocating costs associated with each center among the users of that center (e) Arriving at a methodology for computing charges to be paid by each specific user (f) Setting up a framework for interacting with users and soliciting user comments and general inputs. Each of the above steps is discussed in Chapter 3 in some detail, with emphasis on: (i) Identifying the range of; (cont.) practices that exist around the world with respect to each of these steps (ii) Discussing some of the principal options available at each step (iii) Highlighting a few important points that the prospective reviewer of user charges should be aware of, including common pitfalls (iv) Identifying certain areas where there may exist some room for improvement in prevailing international practices (v) Illustrating the discussion through a number of brief examples. In Chapter 4, four selected case studies are reviewed. Each of the cases has been selected for two reasons: (1) It helps illustrate one or more of the principal concepts that were discussed in Chapter 3 (2) In itself, the case offers one or more interesting aspects (important airport, innovative approach, controversy, etc.). The first example discussed is Boston's Logan International Airport. We examine in detail the procedure used to determine the unit-rate (charge per thousand pounds) for computing landing fees at this major United States airport. This, in turn, offers an opportunity to explain why airside user charges at U.S. international airports are usually considerably lower than those elsewhere in the world. The controversial case of Tokyo/Narita International Airport is brought up next. It illustrates how a combination of poor site and planning choices and of often-unreasonable cost-allocation practices has led to what seems to be a system of unfair and excessive user charges. A study aimed at helping the Board of Civil Aviation of Sweden ("Swedish CAA") determine an appropriate system of user charges is summarized next. This study is especially important, because of the several innovative concepts that it contains, principally regarding the practical application of shortand long-term marginal-cost approaches to the setting of user charges. Finally, cost allocation in the Commonwealth of Australia is reviewed. User charges in Australia have become a matter of considerable controversy in recent years. Moreover, the Australian cost-allocation approach is quite typical of the "traditional" kind of rationale and methodology generally used in efforts of this type. Chapter 5 deals in its entirety with the Eurocontrol system of user charges. This represents the principal case study reported herein. In its first part, Chapter 5 examines in detail the distribution of Eurocontrol charges among users. The second part concentrates on the cost-base which these charges are designed to cover. Some of the points which are addressed include: (a) The extent to which the Eurocontrol "formula" for computing user charges truly reflects the costs that individual users impose on facilities and services (b) The effects of changes in this formula on the distribution of costs among the various types of users: much quantitative evidence is provided in this respect (c) The composition of the cost-base and differences among memberstates in this respect (d) Possible explanations for the large differences in the unit rates that the eleven individual member-states specify for computing user charges. Chapter 6 represents a first attempt to examine in a systematic way the subject of costs of ground handling services at international airports. It is noted that, due (i) to vast differences among airports as to who the provider of these services is, and (ii) to lack of uniformity in the type and quality of services provided, it is difficult to develop general conclusions in this area. Nevertheless, several preliminary but highly-interesting observations are made on the basis of previously-unpublished data provided to the author by the International Civil Airports Association (ICAA) and by a major U.S. trunk carrier. The data in question deal with ground handling costs at many European and a few U.S. airports. An extensive list of references on the subjects of airport economics and of airport user charges is also provided at the end of this report. Finally, as already indicated in the Foreword, two companion reports, based on the thesis work of D. Lippera and E. Ch'ng, cover much related ground, especially with regard to a more-formal analysis of alternative costallocation methodologies. These two reports also include many additional examples, especially several concerning the British Airports Authority and the setting of user charges at London/Heathrow Airport. February 1985; Includes bibliographical references

Out-of-kilter flow (OKF) : user's guide

2019-04-09T16:47:51Z

Out-of-kilter flow (OKF) : user's guide Levin, Amos; Ford, L. R. Section 1: The following few pages are from the book, "Flows in Networks" by Ford and Fulkerson, which is referenced in this report. After these few pages, the report itself commences. -- Section 2: This writeup is intended for the user of the "Out of Kilter" program which has been written for the IBM system 360 model 65. The program has been successfully run at the MIT Computation Center. Both the program and the writeup are based on the SHARE routine RS OKFl and its corresponding writeup. The FORTRAN subprograms are written in FORTRAN IV ( G level ). The assembly language subprograms use the extended mnemonic branching instruction codes and the macros SAVE and RETURN. 1967; Includes bibliographical references

A multi-regression analysis of airline indirect operating costs

2019-04-12T15:08:20Z

Concentration in U.S. air transportation : an analysis of origin-destination markets since deregulation

2019-04-09T19:09:09Z

Concentration in U.S. air transportation : an analysis of origin-destination markets since deregulation Van Acker, Jan The thesis examined the effects on competition of deregulation in the airline industry by analyzing changes in concentration over the ten-year period 1979-1989 in two sets of origin-destination city-pair markets: the top 100 markets in which the most passengers traveled in 1989, and the top ten markets to and from each of fifteen dominated cities. Concentration levels were significantly lower in the top 100 markets in 1979 than in 1989. Average concentration levels in the 150 markets out of the dominated cities were only slightly lower in 1989 than in. 1979. In both sets of markets average concentration decreased from 1979 to 1985. From 1985 to 1989, it increased slightly in the top 100 markets, and it increased significantly in the 150 markets out of the dominated cities. The hub-and-spoke route structure developed by all major airlines was the primary cause for the decrease in concentration levels in most of the markets. In the markets out of the hub airports, the development of the hub by a single airline led to an increase in competition in the period 1979-1985, as this airline began to compete against incumbent carriers in those markets. After 1985, however, the hub airlines became gradually dominant in the markets out of their hub airports, prompting many to ask for re-regulation of some kind. This would probably not increase competition in the dominated cities' markets, however, and would very likely adversely affect competition in the overall air transportation system. May 1991; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, and Sloan School of Management, 1991; Includes bibliographical references (p. 131-132)

Terminal area flight path generation using parallel constraint propagation

2019-04-10T10:00:42Z

Terminal area flight path generation using parallel constraint propagation Sadoune, Michel A Flight Path Generator is defined as the module of an automated Air Traffic Control system which plans aircraft trajectories in the terminal area with respect to operational constraints. The flight path plans have to be feasible and must not violate separation criteria. The problem of terminal area trajectory planning is structured by putting the emphasis on knowledge representation and air-space organization. A welldefined and expressive semantics relying on the use of flexible patterns is designed to represent aircraft motion and flight paths. These patterns are defined so as to minimize the need for replanning and to smoothly accommodate operational deviations. Flight paths are specified by an accumulation of constraints. A parallel, asynchronous implementation of a computational model based on the propagation of constraints provides mechanisms to efficiently build feasible flight path plans. A methodology for a fast and robust conflict detection between flight path plans is introduced. It is based on a cascaded filtering of the stream of feasible flight paths and combines the benefits of a symbolic representation and of numerical computation with a high degree of parallelism. The Flight Path Generator is designed with the goal of implementing a portable and evolving tool which could be inserted in controllers' routine with minimum disruption of present procedures. Eventually, a model of aircraft interaction provides a framework to rethink the notion of Separation Standards. Cover title; May 1989; Also issued as an Ph.D. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1989; Includes bibliographical references (p. 175-181)

An expert system for temporal planning with an application to runway configuration management

2019-04-12T15:08:20Z

An expert system for temporal planning with an application to runway configuration management Hazelton, Lyman R. This thesis describes an expert system to aid in the management of operations in complex qualitative domains characterized by multiple parallel activities with time-critical relationships. An extension to "standard" temporal logic required for reasoning about inferred allocation of resources and a detailed representation of temporally dependent facts, including persistence, is presented. The non-linear planning paradigm commonly used in planning programs is extended into the temporal domain to facilitate scheduling as well as ordering of plan steps. This enhancement requires new structures and analytical methods for the detection and resolution of serendipitous interactions and conflicts between proposed schedules. A computer implementation of these concepts is discussed in detail. The expert system is organized into three modules: the time map manager or temporal database manager which stores, organizes, and retrieves time dependent knowledge; the temporal system analyzer which uses this knowledge to forecast and analyze domain dynamics; and the planner/scheduler which formulates and schedules activities in order to satisfy goals generated by the temporal system analyzer. Finally, Tower Chief, an application of the system to scheduling runway configuration changes and maintenance at large airports, is described. January 24, 1991; Also issued as a Ph. D. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991; Includes bibliographical references (p. 100-105)

Comparison of optimization techniques for origin-destination seat inventory control

2019-04-10T10:00:41Z

Comparison of optimization techniques for origin-destination seat inventory control Williamson, Elizabeth Louise Airlines have recently realized the importance of an effective seat inventory control system on revenues and profits. Yet, at the same time, there is a lack of practical optimization models for determining the number of seats to allocate to each origin-destination and fare class itinerary in an airline's network. In this thesis, several different mathematical models and optimization techniques for origin-destination seat inventory control are evaluated and compared. Each technique is applied to a small network with assumed demand levels and fares for each O-D/fare class combination. The techniques are then compared with respect to the differences in seat allocations and booking limits, fare class nesting order and total potential system revenue. The "optimal" seat allocation solution is found by the probabilistic linear programming technique, but actual use of such a method is impractical due to the size of its formulation and its distinct inventory solution, which is not compatible with the nested reservations systems of most major airlines today. The technique that seems to have the most potential as an efficient origin-destination seat inventory control method is a network based deterministic linear programming technique, with seat allocations nested according to shadow prices. Cover title; May 1988; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Civil Engineering, 1988; Includes bibliographical references (p. 125-126)

Management processes in U.S. air traffic management modernization : a study of global navigation satellite system development

2019-04-12T15:08:19Z

Management processes in U.S. air traffic management modernization : a study of global navigation satellite system development Sandvig, John H. This thesis investigates organization and management issues associated with the Federal Aviation Administration's (FAA) efforts to modernize the nation's Air Traffic Management (ATM) system. Focus is placed specifically on efforts by the FAA to implement a satellite-based navigation system in accord with the ICAO's definition of a Global Navigation Satellite System (GNSS). The US Global Positioning System (GPS) provides much of the capability desired in the GNSS, but enhancements are required to meet full capability required for civil aviation purposes. The research examined the working relationships and the management processes used in the course of major system development and acquisition. The research and analysis discovered a strong functional orientation in the FAA. The research also identified a significant difference in cultural attributes between the two major divisions in the agency: Systems Operations and Systems Development. The combination of these differences serves to impede communication and cooperation among development project participants at the agency and, therefore, to inhibit identification and development of new systems to satisfy airspace users needs. In addition recommendations are made for improvements to the agency's acquisition policy and to system development processes. Cover title; May 6, 1994; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Sloan School of Management, 1994; Includes bibliographical references (p. 114-116)

A microprocessor driven liquid crystal graphics display for aircraft use

2019-04-12T15:08:10Z

A microprocessor driven liquid crystal graphics display for aircraft use Marzke, Lee Howard A complete graphics system for use in modular avionics is built around a liquid crystal flat panel display. Screen refresh is handled by display controller that provides a bit mapped representation of the display in RAM. A 8085 based single board computer is programmed to allow user defined graphics symbols to be moved about easily, and a character generator is included to facilitate the display of ASCII strings. The computer uses a RS-232 interface to receive commands. A demonstration program is also included which demonstrates a simple instrument landing system (ILS) type display without the need for an external device. Cover title; June 1996; Also issued as an B.S. thesis, Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1984; Includes bibliographical references (p. 35)

IFA/1 : an interactive airline fleet assignment model

2019-04-10T10:00:23Z

IFA/1 : an interactive airline fleet assignment model Duchesne de Lamotte, Herve This thesis investigates the Airline Fleet Assignment models which have been designed during the past 10 years within MIT's Flight Transportation Laboratory. Emphasis is placed on developing an interactive computer system, called IFA/1, which simplifies the use of fleet assignment models and improves the insertion or modification of necessary data. The first section gives a general review of the mathematical models used for vehicle planning in air transportation, with special attention given to the Airline Fleet Assignment and Fleet Planning problem. The techniques used to solve these problems are discussed, and one model of particular interest, the FA4 model, is introduced. The second part describes how FA4 is used in practice and points out some of its major deficiencies. An improvement is proposed through the means of an interactive computer package available at the Flight Transportation Laboratory. Future modifications to this interactive system are also discussed. Finally, an alternative solution is suggested to one of the theoretical problems which underlies the Fleet Assignment model: the "phantom frequency problem". This issue is discussed and a new set of equations is proposed which improves the efficiency of the model. Cover title; Series statement hand-written on cover; May 1981; Includes bibliographical references (p. 105-108)

Computer program development specification for the air traffic control subsystem of the Man-Vehicle Systems Research Facility.

2019-04-12T15:08:10Z

Computer program development specification for the air traffic control subsystem of the Man-Vehicle Systems Research Facility. Functional summary: The Air Traffic Control (ATC) Subsystem of the Man-Vehicle System Research Facility (MVSRF) is a hardware/software complex which provides the MVSRF with the capability of simulating the multi-aircraft, multi-controller Air Traffic Control environment required to perform full-mission flight simulations. The ATCSIM CPCI is the software component of this complex. The ATCSIM operates in three modes: 1) Standalone, that is, without the required participation of the rest of the MVSRF. 2) Single-cab mode, with either the conventional (727) or advanced cab. 3) Dual-cab mode, with both simulated cabs. The ATCSIM is capable of simulating up to three simultaneous ATC radar positions and up to 40 aircraft (called "pseudo-aircraft" to differentiate them from the cab aircraft(s)). The ATC subsystem performs the following functions: 1) Simulates the movements of up to 40 pseudo-aircraft. 2) Simulates the navigational and surveillance equipment in the area. 3) When in the single or dual cab mode, it communicates with the host computer and the cab computer(s) to receive data concerning the cab positions as well as directives regarding the management and control of the ATC environment. 4) Drives up to three simulated ATC positions, each equipped with a calligraphic display scope and a keyboard. The human operator of each ATC position (called the air traffic controller) can monitor the aircraft movements on the calligraphic display and can control them through clearances communicated to the pseudo-pilots (see next item) via audio channels provided for this purpose. The keyboard can be used to enter aircraft clearances and to modify the information displayed on the radar screen. 5) Drives up to three pseudo-pilot positions, each equipped with a video terminal and a keyboard. The operator of each pseudo-pilot position (called the pseudo-pilot) will at any point be responsible for "piloting" up to 12 aircraft. He is responsible for responding to clearances received from the air traffic controller regarding any aircraft under his control. To accomplish this task, the pseudo-pilot will have complete status information on all the aircraft under his control displayed on the video screen at all times. To initiate the execution of the clearance received by the air traffic controller, a repertoire of piloting commands will be available to him. Those will have to be entered on the keyboard along with appropriate identification of the target aircraft. January 1982

Routing problem with service choices

2019-04-10T10:00:22Z

Routing problem with service choices Lee, Boon Chai This thesis finds solutions to the routing problem with service choices which is formulated as a capacitated minimum cost flow circulation problem with GUB constraints. The routing problem with service choices is solved using a specialized GUB branch and bound algorithm. Methods for node and GUB set selection are presented. A heuristic for finding good feasible solutions to initiate the branch and bound using vehicle size cuts is also derived. Furthermore, a network reduction scheme is formalized to reduce the size of the problem. This reduction is applied between pairs of nodes whose ground arcs have infinite upper-bounds. Initial experiments using the GUB branch and bound on several medium scale test problems appear promising. A variable tracking scheme which updates the status of the branching variables is included, which can be used to fully automate the branch and bound. This work supports the use of LP based GUB branch and bound for solving combinatorial problems with GUB constraints. Extensions to several related problems are also given. June 1986"--Cover; Also issued as an Ph.D. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1986; Includes bibliographical references (p. 97-100)

A review of extended-range operations by transport aircraft

2019-04-10T10:00:21Z

A review of extended-range operations by transport aircraft Simpson, R. W.; Ausrotas, Raymond A. Introduction: The safety of enroute operations of aircraft engaged in public transport has been a continuous concern since the early days of air transportation. There are a variety of inflight emergency situations which can create a need to land the aircraft as soon as safely possible: fire in cargo compartments or toilet areas, incapacitated crew members or a medical problem with a passenger, insufficient fuel or oil, failure of one or more engines, or failure of other major aircraft systems such as electrical or cabin pressurization systems. All of these occur frequently enough in public air transport to cause airline operators and airworthiness authorities to consider the time to reach airports suitable for enroute diversion as a factor in planning and approving the operation of any aircraft along its intended route. One of the inflight emergencies which does occur commonly in air transport is the failure or inflight shutdown (IFSD) of an engine. The shutdown of a single engine creates a situation where aircraft are exposed to the risk of an independent failure of a second engine, during the period of the flight to a diversion airport. For a twin-engine transport aircraft, this "double independent failure" case leaves the aircraft with no means of propulsion, and may be considered a catastrophic event since the probability of fatalities in the ensuing forced landing away from an airport is very high. The past five years have seen the introduction of operations by modern twin-engine turbofan transport aircraft on long-haul oceanic routes. These have been dubbed ETOPS (Extended-Range Twin-Engine Operations). This caused a review of the safety of enroute operations by twin-engine aircraft with an emphasis on the situation where there might be an inflight shutdown of one engine. Various airworthiness authorities around the world have established safety regulations to approve ETOPS operations by a specific operator and aircraft-engine combination on "extended range" (ER) routes. In 1986, ICAO amended Annex 6 of its International Standards and Recommended Practices to provide guidance on "extended range operations by aeroplanes with two power-units (ETOPS)" to its contracting states. In June 1985, the FAA issued its Advisory Circular AC 120-42 which "states an acceptable means, but not the only means for obtaining approval under FAR 121.161 for two-engine airplanes to operate over a route that contains a point farther than one hour flying time at the normal one-engine inoperative cruise speed (in still air) from an adequate airport." By the end of 1986, there had been a few years of experience with ETOPS activity by several US and foreign carriers on the North Atlantic routes and in other areas of the world. This study is a review of the current ETOPS situation, carried out for the Transportation Systems Center and the Office of Aviation Safety, FAA, at the request of the FAA Administrator. While the activity of the past five years has focused on extended-range operations of twin-engine transport aircraft, there now seems to be general agreement that some of the regulatory actions should be extended to cover ER operations by all transport aircraft. April 1987; Includes bibliographical references

Airline competition analysis

2019-04-10T10:00:21Z

Airline competition analysis Taneja, Nawal K. Introduction: The purpose of this study is to investigate how airlines share the passengers, attracted to air transportation. The percentage of these passengers, that one airline will carry in any given market, where it is in competition with other airlines, depends mostly on the frequency it operates, number of competitors in the market, stage length number of daily non-stop and one-stop flights, type of aircraft and the connecting flights. Market share furthermore depends on variables such as passenger service, the image of the airline, the amount of money spent on advertising in the given market. These variables are called behavioral variables and are impossible to be included in the models because of the inavailability of data on them. In this study investigation was restricted to the variables on which data can be fairly easily obtained. Until recently it was assumed that market share depends mostly on frequency share and furthermore that the relation between these is linear. This implies that if for example one airline operates 70% of the flights in any given market, it will carry 70% of the passengers in that market. The models presented in this study investigate this hypothesis as well as the effects that some of the other variables have on the market share. Model 1 investigates the effects of varying stage length and frequency share. Model 2 brings in additional explanatory variables including the second most important variable, number of competitors in the market. At this stage of investigation it was recognized that market share depends almost completely on frequency share. However the form of the relationship was not yet clear. Models 3 to 6 are an attempt to determine this relationship. Models 7 and 8 investigate the effects of times of flight through the day and the quality of service offered. Cover title; September, 1968; Includes bibliographical references (leaf 40)

Potential use of artificial intelligence techniques in air traffic control

2019-04-10T10:00:20Z

Potential use of artificial intelligence techniques in air traffic control Elias, Antonio L. A.I., or Artificial Intelligence, is a vast field that includes more than the so-called "Expert Systems" that the public seems to identify with A.I. In particular, research in A.I. has created an entirely new mode of operating with computers which raises the level of abstraction at which the computer user (and the programmer) interfaces with the computer, enabling systematic and economical handling of high-complexity problems. These techniques are particularly applicable to Air Traffic Control automation problems which exhibit a high degree of complexity, such as system-wide simulation experiments, flow control procedures, and tactical control supervision. In addition, specific A.I. techniques- such as Expert Systems - have unique specific applications in ATC, for example Airport Runway Configuration planning, passive visual radar, and others. October 1985

Interactive dynamic aircraft scheduling

2019-04-10T10:00:19Z

Interactive dynamic aircraft scheduling Deckwitz, Thomas Anthony Introducing recent advances in computer technology to improve aircraft scheduling is investigated. Incorporating interactive graphics, modern database manipulation techniques, and decision support algorithms, the computer is proposed as a tool for the schedule development process, replacing present manual methods. A detailed set of graphics representations of schedule data are presented based on the sequence chart and station activity chart. The interactive manipulation of these displays by the scheduler results in an immediate appropriate update of the schedule database. Quick graphics response and automatic constraint violation alerts speed the search for feasible schedules. The execution of complex aircraft scheduling operations by the proposed system is presented. Schedule display and database structures are designed for implementation on computers with modern high resolution graphics and pointer directed list capabilities. June 1984; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1984; Bibliography: leaf 138; Includes bibliographical references (leaf 138)

Rule-based implementation of automation aids for ATC controllers

2019-04-12T15:08:09Z

Rule-based implementation of automation aids for ATC controllers Elias, Antonio L. Development of Air Traffic Controller automation aids is frequently hampered by the mathematical nature of the algorithms they are based upon. These limitations are: lack of adaptability to local conditions; high development, testing, and modification costs; and low end-user confidence on the algorithm's behavior. Research in Artificial Intelligence has produced systems whose logic is implemented by means of rules which may be defined by the end-user without explicit programming. Such rule-based systems may provide a flexible, low-cost alternative to mathematical algorithms. Since the end-user can exercise significant control over the behavior of such logic, automation aids built using these methods can be tailored to the user's environment, preferences, and experience more readily than if built around a classical mathematical algorithm. While this is theoretically possible, present rule-based systems technology is insufficient to allow practical implementation of an ATC aid today. An experimental new rule-based core system has been developed which overcomes some of these obstacles, but a number of problems, including that of poor hardware performance, remain outstanding as topic for continuing research. March 1985; Includes bibliographical references (leaf 9)

Congestion delays at hub airports

2019-04-12T15:08:09Z

Congestion delays at hub airports St. George, Martin J. A deterministic model was developed to study the effects of inefficient scheduling on flight delays at hub airports. The model bases the delay calculation on published schedule data and on user-defined airport capacities. Data from the Official Airline Guide of May, 1977 and May, 1985 was used for the analysis. Twelve large airports were studied in the hopes of finding a correlation between airport delay due to congestion and hubs. Data for both time periods was analyzed for the twelve airports in order to find historical trends in the growth of hubbing. Among the airports studied, those that were hubs had significantly more delays due to inefficient scheduling than the non-hubs, even for an equivalent number of operations. Also, these relative inefficiencies were shown to exist from hub to hub. Delays at hubs of similar size differed by up to 200 percent. Cover title; June 1986; Includes bibliographical references (p. 146)

An air traffic control simulator for the evaluation of flow management strategies

2019-04-12T15:08:08Z

An air traffic control simulator for the evaluation of flow management strategies Butler, James Franklin An air traffic-control (ATC) simulator for the evaluation of flow management strategies was designed and implemented in Lisp. The ATC system is modeled as a network of queueing systems. Flights are generated from a flight schedule, a text file created by the simulation scenario designer. The simulator supports the following flow control actions: ground holds, airborne holds, speed control, and rerouting. Tools are included for schedule generation and statistical analysis. The design of a scenario requires a working knowledge of Lisp. This thesis includes an overview of the flow management problem, a discussion of modeling issues and design considerations, a description of the implementation of the simulator in moderate detail, results from a sample simulation scenario which includes a simple flow management strategy, and suggestions for possible improvements to the simulator. Cover title; February 1987; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1987; Includes bibliographical references (p. 55)

Air travel demand and airline seat inventory management

2019-04-10T10:00:18Z

Air travel demand and airline seat inventory management Belobaba, Peter Many airlines practice differential pricing of fare products that share a common inventory of available seats on an aircraft. Seat inventory management is the process of limiting the number of seats made available to each fare class. The objective of both strategies is to maximize the total revenues generated by the mix of fare products sold for a flight. This dissertation first examines the evolution of airline marketing and seat inventory management practices. A demand segmentation model is developed to help explain current airline fare structures. A conceptual model of the consumer choice process for air travel is then presented, and extended to describe the airline reservations process and the probabilistic elements that can affect seat inventory control. A survey of current airline practice in this area revealed that seat inventory control is an ad-hoc process which depends heavily on human judgement. Past work on quantitative approaches has focused on large-scale optimization models that solve simple representations of the problem. A primary objective of this research was the development of a quantitative approach based on the practical constraints faced by airlines. The Expected Marginal Seat Revenue (EMSR) model developed in this thesis is a decision framework for maximizing flight leg revenues which can be applied to multiple nested fare class inventories. It is applied to a dynamic process of booking limit revision for future flight departures, and overbooking factors as well as fare class upgrade probabilities are incorporated. Examples of EMSR model results are presented, and a critical analysis of the demand assumptions and sensitivity of the model is performed. The EMSR model was implemented as part of an automated seat inventory control system at Western Airlines and tested on a sample of actual flights. Compared to flights managed by existing manual methods, flights for which fare class booking limits were set and revised automatically on the basis of the EMSR decision model carried more passengers at a lower yield, and generated higher total revenues. May, 1987; Also issued as a Ph. D. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1987; Includes bibliographical references (leaves 211-214)

An advanced situation display for air traffic control

2019-04-10T10:00:18Z

An advanced situation display for air traffic control Ezekiel, Solly A new approach to presenting Air Traffic Control (ATC) situation information to controllers has been devised and implemented. The approach allows the controller to spend more time analyzing traffic trends by decreasing the effort required to issue flight vectors; increases the amount of information available to the controller through the situation display; improves the presentation of altitude information; and interfaces the controller with an improved ground-to-air communication system. These objectives necessitated the use of a raster display device; the particular hardware used for the implementation was a Digital Equipment Corporation (DEC) VAXstation-100 display. Although the VAXstation- 100 machine was adequate for the task, the effort identified shortcomings of raster display technology that must be rectified before raster machines may be used for ATC applications. In particular, the window management system should handle non-rectangular bitmaps. The use of a positional entry device (PED) was found to be beneficial in accessing the functions of the advanced display, and in alleviating controller workload by reducing the amount of verbal controller-pilot communication. It was found that the functions specified above can be implemented on existing hardware, but that the functions require large computational resources to operate in real time. More data are needed before the benefits of the functions can be quantified. June, 1985; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1985; Includes bibliographical references (leaf 63)

Summary and recommendations for the NASA/MIT Workshop on Short Haul Air Transport, Waterville Valley, New Hampshire, August 1971

2019-04-10T10:00:17Z

Summary and recommendations for the NASA/MIT Workshop on Short Haul Air Transport, Waterville Valley, New Hampshire, August 1971 Simpson, R. W. Executive summary: A review is given of the material covered by the MIT/NASA Waterville Valley workshop which dealt with the institutional, socio-economic, operational, and technological problems associated with introducing new forms of short haul domestic air transportation. It was found that future air systems hold great potential in satisfying society's needs for a low noise, low landspace, high access, high speed, large network system for public travel over distances between 5 and 500 miles. Technology recommendations supported further development in each of the areas because of their importance to future short haul air systems. A recommendation was made for developing improved guidance and control systems for STOL and VTOL vehicles, and for a review of research and development needs in non-vehicle areas such as air traffic control, and metroport operations. The crucial issue for introducing new forms of short haul air transport was identified by the workshop as community acceptance of new airport/metroport ground facilities. An environmental statement and hearing are now required for federal investment in such facilities. It was concluded that quiet air systems were necessary (but not sufficient) for obtaining community approval. October 1971; Workshop ran from Mon., 2 Aug. to Fri., 27 Aug 1971

Cell fleet planning : an industry case study

2019-04-10T10:00:16Z

Cell fleet planning : an industry case study Silva, Armando C. The objective of this thesis is to demonstrate the practical use of the Cell Fleet Planning Model in planning the fleet for the U.S. airline industry. The Cell Model is a cell theory, linear programming approach to fleet planning. Four scenarios of the Model are presented: three with a nine-cell representation of the system and a test case using a thirty-cell representation. A detailed analysis of the results for each case has been performed. A comparison between the cases, with other forecasts, and with recent historical data which has also been .analyzed is shown. The Cell Model has produced realistic results. It has proven to be efficient regarding computer time and labor intensity given the size of the problem, and to be viable for industry use. Should no dramatic changes in the airline route system structure occur in the next ten years, results obtained show a greater need for small-capacity, short-range aircraft (e.g. B737's, B757's, and DC9's) than for other aircraft types. May 1984; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1984; Includes bibliographical references (p. 279-280)

The interaction of radio frequency electromagnetic fields with atmospheric water droplets and application to aircraft ice prevention

2019-04-10T10:00:15Z

The interaction of radio frequency electromagnetic fields with atmospheric water droplets and application to aircraft ice prevention Hansman, Robert John In this work the physics of advanced microwave anti-icing systems, which pre-heat impinging supercooled water droplets prior to impact, is studied by means of a computer simulation and is found to be feasible. In order to create a physically realistic simulation, theoretical and experimental work was necessary and the results are presented in this thesis. The behavior of the absorption cross-section for melting ice particles is measured by a resonant cavity technique and is found to agree with theoretical predictions. Values of the dielectric parameters of supercooled water are measured by a similar technique at X = 2.82 cm down to -17 0 C. The hydrodynamic behavior of accelerated water droplets is studied photographically in a wind tunnel. Droplets are found to initially deform as oblate spheroids and to eventually become unstable and break up in Bessel function modes for large values of acceleration or droplet size. This confirms the theory as to the maximum stable droplet size in the atmosphere. A computer code which predicts droplet trajectories in an arbitrary flow field is written and confirmed experimentally. Finally, the above results are consolidated into a simulation to study the heating by electromagnetic fields of droplets impinging onto an object such as an airfoil. Results indicate that there is sufficient time to heat droplets prior to impact for typical parameter values and design curves for such a system are presented in the study. June 1982; Also issued as an Ph.D. thesis, Massachusetts Institute of Technology, Dept. of Physics, 1982; Includes bibliographical references (p. 188-191)

Aircraft collision models

2019-04-10T10:00:14Z

Aircraft collision models Endoh, Shinsuke Introduction: The threat of midair collisions is one of the most serious problems facing the air traffic control system and has been studied by many researchers. The gas model is one of the models which describe the expected frequency of midair collisions. In this paper, the gas model which has been used, so far, to deal only with simple cases is extended to a generalized form, and some special types of collision models, such as the overtaking model, are deduced from this generalized model. The effects of the probability distributions of aircraft direction and altitude on the frequency of collisions are also analyzed. The results in this paper can be applied to evaluate the frequency of conflicts as well as that of collisions. In this paper, an aircraft is represented as a circular cylinder, and a collision is described as an overlap of two cylinders. If the size of the cylinder is expanded to the volume of the protected airspace of an aircraft, an overlap of two cylinders means a conflict. Therefore, with a slight modification, the results can be used to analyze the frequency of conflicts. This flexibility gives the models of this paper an important potential for application to a future air traffic control system. The FAA is currently developing a new type of air traffic control system called AERA (automated en route air traffic control). AERA is expected to reduce the workload of human controllers and expand the capacity of airspace using new computer systems and better communication links. When this system is fully implemented, aircraft will be able to fly under fewer restrictions. However, if many aircraft are flying on random routes, the frequency of potential conflicts the computer system should handle becomes high. Therefore, the frequency of potential conflicts under various circumstances should be calculated in order to estimate the computer workload before full implementation of the system. The models developed in this paper may be helpful in this evaluation. The consequences of actual collisions are, of course, grave. Fortunately, the average number of such collisions per year has remained relatively small. According to an FAA Report (Report of the FAA Task Force on Aircraft Separation Assurance, Jan. 1979), the average number of midair collisions reported to NTSB from 1974 through 1978 was 33 per year. Most midair collisions have occurred between small general aviation aircraft operating under VFR. However, the report also states that there were 227 near midair collision reports in 1975 alone, and that air carriers were involved in 68 of these cases. (According to the report, a near midair collision is an incident which would probably have resulted in a collision if no action had been taken by either pilot. Closest proximity of less than 500 ft would usually be required for a near midair collision report.) Although the number of conflicts is not available in the report, it is clearly far greater than the number of near midair collisions considering the difference of airspace volumes involved. The outline of this thesis is as follows. In Chapter 2, we present an overview of two aircraft collision models, the Reich model and the gas model, which have been the most important ones in this field. In Chapter 3, we develop some extensions of the gas model including a generalized two-dimensional gas model, an overtaking model and a three dimensional gas model. In Chapter 4, we develop an aircraft collision model which does not assume the uniformity of aircraft distribution. The conclusions of this thesis are summarized in Chapter 5. Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1982; May 1982; Includes bibliographical references (leaves 86-87)

Ground facilities for a VTOL intercity air transportation system

2019-04-10T10:00:13Z

Ground facilities for a VTOL intercity air transportation system Allen Edward; Simpson, R. W. Introduction: This study covers the design of ground facilities, or metroports, for a future form of short haul intercity air transportation, the VTOL Airbus system as described by previous M.I.T. Flight Transportation Laboratory reports. This system will use VTOL aircraft, such as compound helicopters or tilt wings, which will operate from metroports sited throughout a metropolitan region, and will provide frequent service between the regions which make up an urban corridor, or megalopolis. The metroports are conceived as relatively compact installations placed in city center areas and at major roadway junctions throughout the surrounding suburban region. By providing shorter access and egress times for short haul passengers, and by avoiding airport taxi times and delays due to congestion, the Airbus service will offer substantially improved megalopolitan travel times at total costs comparable to those of the present air system. The service will be all weather, night and day, using its own airspace at the metroports, and a segregated airspace when the metroport is co-located with an airport. The trip lengths will vary between 30-300 miles, which would include travel generated by business commuters in the corridor region, and the travel arising from collecting and distributing the long haul air passenger to and from the major airports in the corridor. Previous systems engineering studies discovered that the ground facilities for such a VTOL system are easily the most important component. The usual predominance of the design and operation of the air vehicle did not hold for this new system, since the ground operations costs were projected to be much higher, and at least twice as much investment was expected to be required for new ground facilities as for new vehicles. Additionally, the time savings offered by the system were far more sensitive to the number and distribution of metroports than to vehicle speed. May 1969; Includes bibliographical references (p. 133-136)

A proposed system for aviation noise measurement and control

2019-04-12T15:08:07Z

A proposed system for aviation noise measurement and control Simpson, R. W.; Hays, Anthony P. This report reviews previous work on various measures for aviation noise, and proposes a completely new system for aviation noise measurement and control compatible with real time, operational noise monitoring hardware. This new system allows new methods of control and regulation to be introduced and is designed to cover problems arising from future CTOL, RTOL, STOL, and VTOL aviation systems operating from current airports as well as new urban sites. New measures are proposed for aircraft flyover noise, airport noise exposure, and community noise impact. January 1973; Includes bibliographical references (p. 61-64)

Final approach guidance using an altimeter-aided Loran-C display system

2019-04-10T10:00:12Z

Final approach guidance using an altimeter-aided Loran-C display system Dogan, Norry Introduction: The goal of this thesis is to test the flyability of a display system that uses a King Radio KEAO-346 altimeter and Micrologic ML-3000 LORAN-C receiver for final approach guidance and to model the dynamics of the altimeter and the Micrologic ML-3000 LORAN-C tracking loop. The altimeter and LORAN-C receiver provide position information that provides navigation in the vertical and horizontal planes, respectively, and that is displayed as glideslope deviation and XTK deviation to the pilot. The display system will be subject to flight tests that will have the twofold purpose of testing the flyability of the display system and of determining the dynamics of the navigation equipment. The flight tests will be a set of missed approaches to a runway with an ILS. The testing of the flyability of the display system will be a qualitative analysis of a pilot's reaction to the display form. The analysis will consist of comments from the pilot who flies the flight tests. The flight tests will be simply a set of missed approaches to a runway with an ILS. The system dynamics will be determined by comparing the recorded altimeter and LORAN-C navigation data with the simultaneously-recorded ILS navigation data. The glideslope angle from the ILS data will be compared to that of the arctangent of the altitude divided by the range. The localizer angle from the ILS data will be compared to that of the arctangent of the XTK error divided by the range. By also modeling the altimeter and Micrologic LORAN-C receiver dynamics, the data comparisons will provide information on not only system dynamics but also individual component dynamics. The flight tests will have the aim to excite the dynamics of the LORAN-C receiver by doing zig-zag patterns during the approach. The comparisons between the ILS and display system data will be done under the assumption that ILS dynamics are negligible with respect to the system dynamics. LORAN-C is a hyperbolic line-of-position (LOP) system by which a receiver can be located at the intersection of two hyperbolas. This is accomplished by measuring the difference in arrival times between two pairs of pulses emitted from three fixed transmitting sites as ground waves. The transmitting stations may be designated as Master M, Slave X, and Slave Y. One hyperbola is determined by the X minus M pair of stations, the other hyperbola by the Y minus M pair of stations. Through the use of cesium clocks, each station transmits precisely-timed, pulsed RF signals. A pulse transmitted by the Master is received by Slave X, which will synchronize itself to the Master and then transmit its own pulse a fixed time later. The Slave Y station, also synchronized to the Master, will transmit a fixed time after it receives the Slave X signal, in order to avoid ambiguities. LORAN-C pulses are transmitted on a 100 kHz carrier in groups of eight pulses and with a group repetition (Master-Slave X-Slave Y) rate ranging from 10 groups per second to 25 groups per second. The pulses in a group are spaced 1000pus apart. A LORAN-C chain, which is a group of stations with one master and at least two slave stations, is distinguished from others by its group repetition interval (GRI), which is the time (in tens of microseconds) that the chain cycles through its master-slave transmission sequence. Currently, there are sixteen LORAN-C chains throughout the world. For the New England area, the common LORAN-C chain is the 9960 chain or the chain that has the GRI of 99600pis. In practice, there are a number of ways that are used to locate oneself using LORAN-C. One method is to locate the actual time differences (TD's) given by a LORAN-C receiver on a special LORAN-C map. For modern receivers, the TD's can be displayed as latitude and longitude so that a special LORAN-C map is not required. Other methods that come as options on most modern receivers are to have the receiver display numerically the receiver's range and bearing to a recorded waypoint or to have the receiver display graphically cross-track error from a path determined by two waypoints (starting point and destination). Since LORAN-C can only provide navigation in the local horizontal plane because pulses are transmitted as ground waves, other means such as a barometric altimeter are necessary to provide vertical navigation data for final approach guidance. Over the past two decades, because of the increase in processing power and the corresponding decrease in cost, LORAN-C has become a viable option for aircraft navigation. The increase in processing power has increased the speed by which LORAN-C signals can be locked onto and has decreased the volume of the receiver so that it can be considered as an optional piece of equipment for the cockpit panel. Airborne units can be purchased for as little as $400 per unit, exclusive of antenna and installation costs. Errors in TD measurement are set by the signal-to-noise ratio (SNR) and by the dynamic response of the tracking loop of the user's receiver. Errors in position determination can result from warpage in the local line-of-position (LOP) or from coordinate conversions such as from TD's to lat-long. Reference 9 shows that for static tests, the repeatability accuracy in over 90% of the average area in the Northeast and Southeast United States is better than 80 meters, and that in 50% of the same coverage area, the accuracy is better than 40 meters. The dynamic response of LORAN-C is limited by the response of the receiver's tracking loops to noise and vehicle accelerations. Studies by the Department of Transportation and the State of Vermont showed that LORAN-C accuracy met FAA AC90-45A specifications (Reference 3: 'Approval of Area Navigation Systems for Use in the US National Airspace System ') for enroute, terminal area,and non-precision approach use. Non-precision approaches using LORAN-C have become more acceptable to FAA approval, as exemplified by their approvals in the recent past for LORANC non-precision approaches at Burlington, Vt. airport and at Hanscom Field in Bedford, Massachusetts. The thesis will follow the methodology of the following outline. Chapter 2 will introduce the display form and the manner in which it displays the navigation information. Chapter 3 will look in detail at the flight test data-taking equipment and methodology. Chapter 4 will explain how the altimeter and LORAN-C tracking loop were modeled. Chapter 5 will show the flight test results and the analysis that was done on the results using the modeling from Chapter 4. Chapter 6 will then provide a discussion of the display's flyability and the data analysis. Appendix A will explain an experiment that was used to test the static accuracy of the altimeter; Appendix B will explain in detail the construction and certification of the flight test pallet; and Appendix C will provide the computer documentation for the computer programs used in the display and for data analysis. Cover title; May 1986; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1986; Includes bibliographical references (p. 116-117)

Probabilistic modelling of LORAN-C for non-precision approaches

2019-04-12T15:08:06Z

Probabilistic modelling of LORAN-C for non-precision approaches Einhorn, John Kenneth A mathematical model of the expected position errors encountered from LORAN-C during a non precision approach was formulated. From this, position error ellipses were generated that corresponded to two time difference correction schemes. One involved relaying corrections to the pilot just before he initiated the approach, and the other involved publishing time difference corrections in the instrument approach plates. It was found that the errors associated with both update scenarios were well within FAA AC90-45A accuracy standards for non precision approaches. The former scenario showed a significant improvement over the latter. Flight tests were conducted in a general aviation airplane carrying an equipment test bed designed to take data from a LORAN-C receiver and an ILS localizer receiver. The results of the flight tests show that the LORAN-C had a maximum error (average plus one standard deviation) of 1.276 degrees deviation from the localizer path, and an average error (average plus one standard deviation) of .648 degrees. It is concluded that LORAN-C is a suitable navigation system for non precision approaches and that time difference corrections made every eight weeks in the instrument approach plates will produce acceptable errors. June 1985; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1985; Includes bibliographical references (p. 272)

Integration of engineering models in computer-aided preliminary design

2019-04-12T15:08:05Z

Integration of engineering models in computer-aided preliminary design Lajoie, Ronnie M. The problems of the integration of engineering models in computer-aided preliminary design are reviewed. This paper details the research, development, and testing of modifications to Paper Airplane, a LISP-based computer program, designed to address these integration problems. Paper Airplane integrates engineering models by treating them like a set of simultaneous non-linear functions and numerically solving for them as such. The original version of Paper Airplane could only handle engineering models represented by single equations and simple LISP functions; that is, multiple-input single-output (MISO) functions. The modifications to Paper Airplane were to allow it to handle engineering models represented as complex LISP functions and external computer programs as well; that is, multiple-input multiple-output (MIMO) functions. The research was divided into three tasks: (1) to get Paper Airplane to communicate with an external computer program (without changing the computer program), (2) to get Paper Airplane to numerically solve a non-linear MIMO function, and (3) to get Paper Airplane to numerically solve a set of simultaneous non-linear functions made up of MISO and MIMO functions. (Formally 'Multi-valued Output and External Code Interface Capability'); This report reproduces a thesis submitted on January 16, 1987, to the Department of Aeronautics and Astronautics of the Massachusetts Institute of Technology in partial fulfillment of the requirements for the degree of Master of Science; Includes bibliographical references (p. 143-[144])

The U.S. aviation system to the year 2000

2019-04-09T18:44:45Z

The U.S. aviation system to the year 2000 Ausrotas, Raymond A. Introduction: 1.1 The Future of the Aviation System. It is nothing if not presumptuous to look ahead twenty years in any phase of human activity. This seems particularly true in civil aviation where the certificated airlines are in the throes of transition from economic regulation to a free market system. Furthermore, while in the past forecasters could count on the number of players in the game remaining constant (subject to elimination by merger), currently new airlines are born every day, at least on paper. The friendly old aviation gang has broken up, with the rules of the game constantly changing. Thus at first glance an attempt now to predict what will happen in the future appears whimsical, if not downright foolish. However, this inquiry concerns not just the airlines, but aviation. Here that much-misused and maligned word, system, is justified. Airlines depend on many other parts: manufacturers build their aircraft, airports provide space to land them, and the air traffic control system keeps them apart. Then-there is general aviation, by some measures the largest part of the system. The flying farmer in Kansas views the big jets which occasionally appear high overhead as simply faster and more expensive Greyhounds; looking at clear and empty skies over his homestead, talk about the aviation system straining at capacity appears ludicrous. One possible approach to the future is to dissect the system and look at the components. The objection to this tack is the interrelationship of the parts if one part moves, then it affects most, if not all, of the other parts.-- The problem is equivalent to solving a set of simultaneous equations (with possibly time-varying coefficients). For example, if some airports reach saturation, the effects on the system will appear in both the short term and the long term. In the short term, traffic may shift to other (nearby) airports; general aviation aircraft may be banned; larger aircraft may replace smaller aircraft, keeping operations almost constant while providing extra lift; or operations may simply remain at the saturation level. In the long term, more or longer runways may be added to the airports; larger and more sophisticated aircraft may be designed by the manufacturers; technological improvements in the ATC system may provide more airport and airway capacity. Furthermore, the outside world is interacting with the system and affecting its behavior. A slump in the economy leads to a downturn in travel, as fewer businessmen fly as well as fewer vacationers even the deepest discounts cannot attract the public when consumer confidence is down.-- And in the long run, changes in lifestyles, population make-up, telecommunications, etc., alter travel patterns as well. Since the aviation system has reacted to internal and external forces over time, a plausible approach to the future is to look back and search for potential cause-effect relationships. Then, if long term trends exist inside and outside the system. and links between them are identified, pictures of the future can be drawn. These certainly will not be predictions, but rather possible evolutions of the system. Many alternative futures are possible, depending on the action taken by different persons both inside and outside the aviation system. With some luck the futures that will be presented here will seem credible, even if not highly probable, given the nature of the task. At the least, they are intended to stimulate thought about the likelihood of the outcomes they portray. Consequently, to planners concerned with aviation, they may provide guidelines for possible initiatives in research and technology.* The author would like to acknowledge the guidance and assistance of the contract monitors, Messrs Robert Letchworth and Matt Winston of NASA Langley Research Center. 1.2 The Aviation System: Definitions and Measures The aviation system is sufficiently complex so that no single statistic can provide a comprehensive overview. However, there are measures of activity which indicate how fast the system is changing and some key variables which explain how the system functions. There are also constraints (or potential constraints) on the system (or various subsystems), and linkages between constraints and key variables. These constraints may or may not be quantifiable, such as regulatory changes, aircraft noise limitations, and airport curfews. It is possible to classify the subsystems of aviation in many ways the exact designation is not important if no major components are lost.-- Most simply, the system can be split into the users of the system and the providers of the service. The users are general aviation and public-for-hire carriers (scheduled and unscheduled, a distinction which is gradually being blurred). The suppliers of the service are airports, airways, the ATC system, and the aerospace industry which builds the vehicles which flow over the system. More detail is provided in Figure 1.1. Different classifications are possible. One used often (Schriever and Seifert, 1967) splits the system into air vehicle; air traffic control; and airports and terminals. Another widely used breakdown (FAA, 1967) is into air carriers, GA, fuel consumption, aircraft technology, air cargo, aviation safety and complementary and competing modes. Yet another way (CARD, 1971) is to look at the system from a mission point of view (commercial passenger service, air cargo, GA) and a system element point of view (air vehicles, ATC, airports, complementary surface transporta- tion). It is apparent that classifications and their concomitant emphases depend to a large degree on who is looking at the system and for what reason. Figure 1.1 shows the complete system. Some parts of it will receive little analysis in this study: military components (since the emphasis is on civil aviation) and non-transportation-related GA activity. Table 1.1 shows the key measures of activity which will be used throughout the study. Public Service General Aviation Passei Cargo The Aviation System A. User Subsystems Schedld ~Trunks, Regionals, etc (jet equipment) LCommuters (propeller equipment) Supplemental (large aircraft) Charters EAir Taxi (small aircraft) Corporate Transportation Private Recreational Industrial (Agricultural, etc) Military B. Supply Subsystems Large hubs Other hubs Airport Commuter GA Military/joint use Surveillance and Data Acquisition Airways and ATC System Navigation Communication Landing Aids Airframe Aerospace Manufacturers Engine Avionics Fuel Key Measures of Activity of the Aviation System A. User Subsystems Measures 1. Public Service la. Passenger Scheduled Trunk, etc Revenue passenger miles, aircraft revenue hours, average stage length Airborne speed, available seats/aircraft, number of aircraft Yield (t/RPM), net profit, DOC, IOC Commuter Charters Supplemental Air Taxi RPM, average stage length RPM Number of operations lb. Cargo 2. General Aviation 2a. Transportation Corporate Private Number of operations (IFR/VFR), number of aircraft, hours flown Number of operations (IFR/VFR), number of aircraft, hours flown Number of operations, number of aircraft Number of operations, number of aircraft Number of operations 2b. Recreational 2c. Industrial 3. Military B. Supply Subsystems 1. Airports la. Large Hubs lb. Other Hubs Ic. Id. Commuter GA le. Military/Joint Use 2. Airways and ATC System Measures Total number, enplaned passengers, number of operations Enplaned passengers, number of operations (scheduled/GA) Enplaned passengers, number of operations (schedul ed/GA) Number of operations Number of operations, number of airports Number of operations Number of IFR operations, (airports, ARTCC), total number of operations, number of towered airports, flight service operations, delay measures Aerospace Manufacturers Fuel Fuel consumption (jet and avgas gallons/year) 1.3 1960 Revisited In 1960 there was an exciting presidential campaign in the United States as Richard Nixon and Jack Kennedy debated on television and radio. Kennedy won the debates (although this was disputed by some listeners) and the election (although some questions were raised about the decisive ballots in Chicago). The value of manned space exploration was being heatedly discussed, even as NASA (the National Aeronautics and Space Administration , which itself had only been established in 1958, replacing NACA, the National Advisory Committee for Aeronautics) tentatively selected 1970 as the year for a manned lunar landing. In the air transport system, it had been over a year since the first turbo jet had been introduced in domestic service (B707-12C, December 10, 1958), followed quickly by two other turbine-powered aircraft, the turboprop Electra (January 23, 1959) and the DC-8 (September 18, 1959). The transition to the jet age was well under way.; (cont.) By the end of 1960 the domestic airlines had in their inventory 470 turbine-powered aircraft (246 turboprops and 224 turbojets) out of a total of 1980 aircraft. The total investment by the domestic passenger carriers reached $1.66 billion. For the first time DC-3's carried less than half of local service airline traffic. The airlines had not yet passed the combined bus-railroad intercity common carrier passenger mile total (38.8 billion RPM, 49.3% of the total RPMs). In fact, in domestic travel passenger miles flown in coach were still fewer than in first-class (47.2% compared to 52.8%), but,increasingly, faster trips as well as 25% discounts were making coach ever more attractive. However, the new era was not without its problems. In 1960, there were 0.93 fatalities per 100 million rpm in domestic passenger service, notably the second in-flight Electra crash (which led to severe speed restrictions on the aircraft, but no grounding) and the mid-air collision between a TWA Super Constellation and a UAL DC-8 over Brooklyn, New York. 1960 was the worst year for accidents since 1951. As a result, questions were raised about the efficiency of the FAA (Federal Aviation Agency), which had been established in 1958, almost coincidentally with the introduction of the jets. The higher speeds of the turbine-powered aircraft required faster reaction times from the ATC system if safety was not to be compromised. Additionally, flight delays, diversions, and weather cancellations were estimated to have cost the airlines $25-50 million for the year. In the economic regulation area, 1960 saw the conclusion of the four-year-old General Passenger Fare Investigation (GPFI), in which the CAB (Civil Aeronautics Board) decided that a 10.5% return on investment would be proper for the trunks. However, a 5% fare increase granted in June 1960 did not help the industry achieve this profit; rather, for the year profit shrank to $4 million (a 3.4% return), although gross revenues rose to $2 billion. Air cargo reached 920 million ton-miles, up from 350 million in 1950. While the air transport industry and general aviation were undergoing tremendous growth by practically any operational measure, complaints and apparent problems were abundant. In fact, President Kennedy established a task force ("Project Horizon") to "redefine and affirm" national aviation goals for the 1960's. Alan Boyd, then the new Chairman of the CAB, was well aware of one of the objectives of the Board -to nurture the industry -when he reflected on the findings of the GPFI (which had noted that,while revenue growth proceeded unimpeded, profits trended downward since mid-1955 and that the "transition to jet equipment which the industry is now undergoing has presented financial and other problems of a magnitude never before faced." [ATA 1961]) "Today's low (airline) earnings focus attention on another of our immediate problems. Mach 3 (supersonic) is staring us in the face ... Carrier earnings are the only hope for a substantial private enterprise contribution to supersonic development and the nation must develop one.-- Carrier earnings in the years immediately ahead are the only hope that a private enterprise air transport system can absorb the next equipment transition." SST's, the need for improved earnings, and modernization of the ATC System aside, observers of the airline industry noted these additional problems facing air transportation in 1960: 1. Overcapacity and the concomitant need for traffic to fill the seats; 2. Rising cost levels, in particular high wage costs which took up 42% of total expenses, compared to 23% for materials and services, 12% for fuel and oil, and 11% for amortization and depreciation; 3. Nascent noise problems; 4. Rising subsidy needs by local service carriers (from $15 million in 1950 to $37 million). Given all these difficulties, how did the industry survive? July 1996; NASA Contractor Report 166010"--Cover; Includes bibliographical references (p. 116-118)

Airline crew scheduling : a group theoretic approach

2019-04-10T10:00:12Z

Airline crew scheduling : a group theoretic approach Thiriez, Herv The problem of airline crew scheduling is studied, the different problems composing it are formulated and solution techniques are offered. Special emphasis is given to the set covering problem appearing in the rotation selection phase. An approach is presented, based on the group theoretic method, which allows the fast solution of problems with large sizes Also issued as a Ph. D. thesis in the Dept. of Civil Engineering, Massachusetts Institute of Technology, 1970; October 1969; Includes a [4] p. FTL memo no. M69-3, dated December 1969 with title: Set covering problems solved by group theory computational experience, by Herve Thiriez; Errata inserted after title-page; Includes bibliographical references (p. 105-108)

The choice of V/STOL transportation for the Northeast Corridor

2019-04-12T15:08:18Z

The choice of V/STOL transportation for the Northeast Corridor Swan, William M. Aircraft type, aircraft size, number of terminals, and degree of nonstop routing for a V/STOL transportation system in the Northeast Corridor are chosen by exploring a wide range of combinations. Helicopter and STOL aircraft from 20 to 200 seats are considered. From 15 to 20 total terminals were considered. Nonstop, one stop and two stop routings were used. A market model explores the response of a typical route to variations in these parameters. Demand response to the total trip cost, trip time, and frequency of service is measured by a modal split model. It is found that land costs and manoeuver times make STOL operations less attractive than VTOL. The system is found to be sensitive to indirect operating costs associated with ticketing and boarding. A small number of terminals is required. A 16 port system serving 10 cities using a 60 seat helicopter can carry 16% of the 1985 intercity traffic while charging the full costs to the user. The results were confirmed by a market by market analysis for the corridor. June 1972; Also issued as an E.A.A. thesis in the Dept. of Aeronautics and Astronautics, 1971; Includes bibliographical references (p. 80-81)

Some fleet routing and scheduling problems for air transportation systems

2019-04-10T10:00:40Z

Automation of airlift scheduling for the upgraded command and control system of military airlift command

2019-04-12T15:08:17Z

Automation of airlift scheduling for the upgraded command and control system of military airlift command Simpson, R. W.; Mathaisel, Dennis F. X. This report describes a conceptual design for automation of the scheduling of airlift activities as part of the current upgrade of the MAC C2 System. It defines the airlift scheduling problem in generic terms before reviewing the current procedures used by MAC; and then a new scheduling system aimed at handling a very busy and dynamic wartime scenario, is introduced. The new system proposes "Airlift Scheduling Workstations" where MAC Airlift Schedulers would be able to manipulate symbolic information on a computer display to create and quickly modify schedules for aircraft, crews, and stations. For certain sub-problems in generating schedules, automated decision support algorithms would be used interactively to speed the search for feasible and efficient solutions. Airlift Scheduling Workstations are proposed to exist at each "Scheduling Cell", a conceptual organizational unit which has been given sole and complete responsibility for developing the schedule of activities for a specific set of airlift resources-aircraft by tail number, aircrew by name, and stations by location. A Mission Scheduling Database is located at each cell to support the Airlift Scheduling Workstation, and requires information communicated by Airlift Task Planners, and, Airlift Operators at many other locations. These locations would have smaller workstations with local databases, and database management software to assist Task Planners and Operators in viewing current committed and planned schedule information of particular interest to them, and to allow them to send information to the Mission Scheduling Database. The Command and Control processes for Airlift have been structured into a three level hierarchy in this report: Task Planning, Mission Scheduling, and Schedule Execution. Task Planners deal with Airlift Users and Mission Schedulers, but not Airlift Operators. Task Planning has three sub-processes: Processing User Requests; Assigning Requirements and Resources; and Monitoring Task Status. Task planning does not create missions, schedule the missions, or route aircraft. Mission Schedulers deal with Task Planners and Airlift Operators, but not Airlift Users. Mission Scheduling combines several sub-processes to allow efficient schedules to be quickly generated at the ASW (Airlift Scheduling Workstation). These sub-processes are: Mission Generation, Schedule Map Generation (for each type of aircraft), Crew Mission Sequence Generation, Station Schedule Generation, Management of Schedule Status, and Monitoring Schedule Execution and Resource Status. It is important that all these processes be co-located and processed by the Airlift Scheduling Cell. Schedule Execution is performed by Airlift Operators assigned by the scheduling process. It has three sub-processes: Monitor Assigned Schedules, Report Resources Assigned to Schedule, Report Local Capability Status. The assignment of local resources such as aircraft by tail, and crew by name is actually another scheduling process, but has not been studied in this report. Airlift Operators do not deal with Task Planners, but may deal with Airlift Users to finalize details of the scheduled operations. This three level hierarchy is compatible with the current organizational structures of MAC Command and Control. However, it is clear that both the current organizational structures and procedures of MAC Command and Control for both tactical and strategic airlift will be significantly affected by the introduction of the automated scheduling systems envisioned here. These changes will occur in an evolutionary manner after the upgraded MAC C2 system is introduced. April 1984

A generalized model for the prediction of controller intervention rates in the en route air traffic control system

2019-04-08T08:17:34Z

A generalized model for the prediction of controller intervention rates in the en route air traffic control system MacDonald, Bruce A. A generalized model of the domestic en route air traffic control system is constructed, which can be used to predict the rate at which controllers will need to intervene in the flow of radar-controlled traffic to prevent the violation of minimum horizontal separation standards. The model considers both crossing and overtaking conflicts, and includes both on- and off-airway traffic. Further, the model is able to incorporate complex airway intersections, including those involving more than two crossing airways, as well as those which permit aircraft to change airways at the intersection. A delayed negative exponential distribution on aircraft interarrival distances is used to reflect the traffic separation efforts of controllers in neighboring sectors. The model is initially presented in a two-dimensional form and then extended to three dimensions by the use of traffic "sources" and "sinks" to represent climbing/descending aircraft which appear and then disappear in successive flight levels. The three-dimensional version is not extended to Terminal Control Areas, due to the decidedly non-random-traffic flow into and out of large airports. Monte Carlo simulations of simple airway intersections and single airway segment overtaking situations are used to confirm the expected intervention rates predicted by the analytic model. The simulations also serve to illustrate the significant variation to be expected about the mean intervention rate. An expression for the variance about the mean intervention rate at simple intersections is derived by conditioning on the actual (as opposed to expected) traffic density and then using well known results for the variance of binomial random variables. An extensive sensitivity analysis is performed on several of the model's key assumptions. The model is found to be particularly sensitive to assumptions about steady state behavior in mean traffic flow rates and somewhat less sensitive to errors in aircraft velocity distributions. October 1986; Also issued as a Ph. D. thesis, Massachusetts Institute of Technology, Sloan School of Management, 1987; Includes bibliographical references (p. 247-250)

Aviation safety analysis

2019-04-10T10:00:39Z

Aviation safety analysis Ausrotas, Raymond A.; Hansman, Robert John. Introduction: Just as the aviation system is complex and interrelated, so is aviation safety. Aviation safety involves design of aircraft and airports, training of ground personnel and flight crew members' maintenance of aircraft, airfields, en route and terminal area navigation and communication facilities definition and implementation of Federal Aviation Regulations (FARs)l air traffic control procedures and much more. Ultimately, every part of aviation has a safety aspect. No other transportation mode has its safety record so rigorously scrutinized. In part this is due to the general societal (and media) fascination with infrequent large disasters in part because U.S. legislators have a personal interest in air safety, as they rely upon aircraft for their seasonal commutes to Washington, and in part because people in the industry are aware that their paychecks ultimately depend on their customers' perception that travel by air is as safe as possible. (Various airlines still conduct aircraft familiarity classes for travelers who have a fear of flying, although as the younger generation of Americans gains experience with airlines, this particular phobia should become less prevalent.) Aside from the industry's self-enforcement attempts, the Federal government tries to assure safety of the traveling public through regulation. The National Transportation Safety Board (NISB) investigates all major air carrier accidents and subsequently makes safety recommendations to the Federal Aviation Administration (FAA) - which the FAA may or may not choose to accept. One of the long lasting standoffs in aviation safety is between the NPSB (backed by Congressional committees), whose sole concern is safety,and the FAA, which must also take the economics of safety regulations into account-unless it wishes to run into a buzzsaw of industry reaction every time it changes (or issues) a FAR. On the international side, the International Civil Aviation Organization (ICAO) issues technical rules affecting aviation safety, although such decisions as its upcoming ruling on twinjet aircraft over-water flights may be tinged with economic considerations as well. But for safety regulations, whether external or internal to the aerospace industry, to make any sense, they must be grounded, to some degree, in reality, i.e. they must be backed up by some technical, statistical, or economic factors which people can address on their own merits. The more quantitative the supporting data are for rule justifications or changes, the greater the likelihood is that the regulations will be successfully promulgated and accepted by industry. Thus aviation safety analysis came into existence. Most broadly stated, the purpose of safety analysis is to improve safety. The spectrum of analysis ranges from the investigative to the predictive. At one end of the spectrum is the after-the-fact investigation of accidents and a search for causes at the other end is the attempt to seek out likely causes (or, more typically, combination of causes) of system failure before the system is put into operation. However, the great quandary of aviation system analysis is the lack of sufficient data to make probabilistic statements - even while the goal of this analysis is the elimination of the very accidents that provide the data. Practitioners of classical statistics, who have grown up considering probability as the likely outcome of an event based on a large number of repeated trials, face a mental hurdle when asked to accept the concept that an event which has never taken place can nevertheless be assigned a 0.95 probability of success. This is essentially the dichotomy between the investigative and the predictive ends of safety analysis - one is based on few accidents (but real accidents nonetheless), the other is based on more subjective probabilities of system (and subsystem) failures.; (cont.) But safety analysts cannot throw up their hands and say that there is insufficient data after only one accident occurs and simply wait for the next one to happen. They must combine forces with their predictive brethren and attempt to head off the next accident. Only when this becomes the rule will aviation safety analysis rest on a sound base. Until this millennium, however, much remains to be done to improve safety analysis at each end of the analysis continuum, and also where the two occasionally intersect by chance. The investigative techniques depend on data: of incidents, accidents, near misses, and the like. The FAA, NASA, NSB, ICAO, aircraft manufacturers, airlines, etc., all maintain various types of data bases, most of which are incompatible (in the sense that they keep track of slightly different variables). A further complication is that some bases are computerized (different data base management systems are usually involved) and some are manual. The safety analyst, attempting to establish broad trends, is immediately faced with this incompatibility problem. Still, if the focus of the investigation is narrow enough (for example, a failure of a mechanical part on a specific aircraft), it may be possible to extract enough information from the various data bases to find a definitive cause. This is especially true when the cause of the incident is, in fact, mechanical - it is here that repeated failures should be noticed, isolated, and corrective action taken. Flight International (1984) provides a typical example that an alert safety analyst (or system) should have anticipated and caught: "Mis-rigging of the baggage door operating mechanism and the failure of the door warning arrangements to give adequate warning of door safety led to the fatal crash of a Dan-Air BAe 748-2A in June 1981, according to the official report. The baggage door at the rear end of the cabin, blew out and became fixed on the tailplane, thus making the aircraft uncontrollable. Subsequently, the wings were overstressed and suffered structural failure. The condition of the door operating mechanism, says the report, made it impossible to lock the door fully using the outside handle. But it was probably by the outside handle that the door had last been closed. Crew checks failed to discover the fault because of "a combination of shortcomings in the design, construction, and maintenance of the door warning systems and the appearance of the visual indications". The report notes that there have been 35 instances of the 748 baggage door malfunction reported in the past". Very rarely do accidents have such obvious design-induced crew error precursors. Most accidents result from interactive causes, rather than one specific factor, and one of the causes is, invariably, a human being - the pilot, the air traffic controller, or the maintenance worker. These acts of human beings do not fit readily into data banks, there to be identified by a specific parts number, and the safety analyst must now switch to the other end of the spectrum and try to isolate the sequence of events that lead to "pilot error". These accidents involving human performance usually turn out to be oneof- a-kind events - and it should be the aim of the safety analyst to ensure that they remain so. Data unavailability and incompleteness, however, are always present and it is up to the skill (and luck) of the analyst to uncover the sequence of events leading to the accident. If a procedural error is found, it can be immediately correctedy more difficult are those amorphous incidents where it is not at all clear why there was human error. (If it were possible to obtain quantitative estimates of human performance, such as human error rates per task, it would be a simple matter to incorporate them into operational reliability equations to determine system reliability.) Just as the role of analysis of incident and defect reporting systems should be to find mechanical failures before they become accidents, the human incident reporting systems should be designed to cause humans to "confess" their incidents so that the analyst can isolate potentially dangerous trends and practices before they too become accidents. (The Aviation Safety Reporting System (ASRS) managed by NASA is a step in the right direction.) It is the purpose of this report is to discuss various aspects of aviation safety analysis, ranging from general aviation to the public transportation system, and then to make some recommendations for improving the methodology of safety analysis.* April 1984; Includes bibliographical references

An experimental and theoretical study of the ice accretion process during artificial and natural icing conditions

2019-04-09T15:37:27Z

An experimental and theoretical study of the ice accretion process during artificial and natural icing conditions Kirby, Mark Samuel; Hansman, Robert John Real-time measurements of ice growth during artificial and natural icing conditions were conducted using an ultrasonic pulse-echo technique. This technique allows ice thickness to be measured with an accuracy of ł0.5 mm; in addition, the ultrasonic signal characteristics may be used to detect the presence of liquid on the ice surface and hence discern wet and dry ice growth behaviour. Ice growth was measured on the stagnation line of a cylinder exposed to artificial icing conditions in the NASA Lewis Icing Research Tunnel, and similarly for a cylinder exposed in flight to natural icing conditions. Ice thickness was observed to increase approximately linearly with exposure time during the initial icing period. The ice accretion rate was found to vary with cloud temperature during wet ice growth, and liquid runback from the stagnation region was inferred. A steady-state energy balance model for the icing surface was used to compare heat transfer characteristics for icing wind tunnel and natural icing conditions. Ultrasonic measurements of wet and dry ice growth observed in the Icing Research Tunnel and in flight were compared with icing regimes predicted by a series of heat transfer coefficients. The heat transfer magnitude was generally inferred to be higher for the icing wind tunnel tests than for the natural icing conditions encountered in flight. An apparent variation in the heat transfer magnitude was also observed for flights conducted through different natural icing cloud formations May 1986; Also issued as an M.S. thesis, Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics, 1986; Includes bibliographical references (p. 128-129)

Reservations forecasting in airline yield management

2019-04-12T15:08:17Z

Reservations forecasting in airline yield management Sa, Joao This report shows the application of Regression Analysis in reservations forecasting in airline yield management. The first three chapters highlight the need for yield management and the automation of seat inventory control. The seat inventory control problem is related to the determination of an optimal allocation of seats among the various fare classes being offered in a flight so as to maximize revenues. In order to determine such optimal seat allocation, forecasts of final bookings need to be made. Forecasting alternatives are presented in this report. An example of application of Time Series Analysis is given as an alternative in providing such forecasts. Results obtained via Time Series Analysis were not encouraging enough in providing acceptable estimates. Regression Analysis is also presented as a forecasting tool. Although regression models were developed for each market, a generalized model structure was thought to be preferable in view of the reduction of modeling efforts, data handling and model specification, that are needed for forecasting final bookings for all markets/flights/classes. A general structure model is presented in this thesis as the result of the search for structural behavior across markets and flights. Regression Analysis results are presented for a set of five citypairs, one flight in each directional market, i.e. ten flights in total. These results evidenced that a general structure model via regression analysis can indeed be used in the forecasting module of an automated seat inventory control system, and thus provide better estimates of final bookings when compared to Time Series Analysis or historical averages. February 1987; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1987; Includes bibliographical references (p. 116-117)

Decision support systems for automated terminal area air traffic control

2019-04-10T10:00:38Z

Decision support systems for automated terminal area air traffic control Pararas, John Demetrios This work studies the automation of the terminal area Air Traffic Management and Control (ATM/C) system. The ATM/C decision-making process is analyzed and broken down into a number of "automation functions". Each of these functions is described with particular emphasis on its role in the overall system and its interactions with the other ATM/C automation functions. Runway Scheduling and Traffic Flight Plan Generation are identified as the two functions with the greatest potential for providing efficiency improvements over the current terminal area ATC system and are studied in detail. A very general Mixed Integer Linear Programming (MILP) formulation of the Runway Scheduling problem is developed. Less general formulations and algorithms which have appeared in the literature are reviewed and evaluated. A heuristic algorithm is developed. The algorithm is based on the work of Dear and adopts the Maximum Position Shifting methodology proposed by him [DEA 76]. It extends Dear's work in several ways: (1) it is applicable to multiple runway configurations. (2) it is designed to operate in a real-time simulation environment, and (3) it is designed to accept arbitrary constraints imposed by the ATM/C controller. The methodology for generating flight plans is developed. Flight plans are based on a specified route structure. They are 4-dimensional and conflict-free. To allow maximum runway scheduling flexibility, a .specific route structure is proposed. It is designed to allow easy modification of flight plans to adapt to the dynamically changing schedule. To allow algorithmic development and testing of this (as well as other) ATM/C automation concepts, a real-time terminal area simulation facility (called TASIM) is designed and implemented. The facility has a number of characteristics which make it a good general purpose tool for terminal area ATM/C research: (1) Highly modular design which allows addition, removal and modification of functions with relative ease. (2) Realistic modelling of the aircraft dynamics of motion and the aircraft guidance system. Errors introduced by the navigation equipment (onboard and on the ground) and by the surveillance radars are also modelled. -3- (3) Capability to simulate multiple controller positions (4) Flexible controller interface which allows easy implementation of alternative displays and alternative protocols for man machine interaction. The simulation is fully operational in the conventional (manual) ATC mode. In addition, it is currently interfaced with an implementation of the runway scheduling heuristic, and with a special purpose final vectoring display designed to aid the controller in precisely timing the delivery of landing aircraft at the outer marker. Also issued as a Ph. D. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1982; September 1982; Includes bibliographical references (p. 233-237)

A method for governing spacecraft evasive maneuvering

2019-04-10T10:00:37Z

A method for governing spacecraft evasive maneuvering Keller, Keith Richard A computer program is developed to govern the evasive maneuvering of a spacecraft in response to an anti-spacecraft missile threat in regions of space where drag is not significant. With a view to circumventing the need to numerically integrate the equations of motion for both vehicles to predict future position and velocity along their trajectories, the methods of astrodynamics are used to determine the unissile's orbit from two vector position fixes over time so it can be compared -to the spacecraft's orbit, determined from a position and velocity vector. The transfer time required for the missile to reach the spacecraft's altitude is determined and the future position of the missile is predicted so that a future relative position vector between the spacecraft and missile can be found. If it is found that the missile will intercept the spacecraft at the future time, appropriate evasive action is initiated for the spacecraft. A maneuver to any point in three-dimensional space can be targeted by specifying the magnitude and direction of the miss-distance desired, and velocityto- be-gained calculations are done as an aid to making maneuvering decisions. To test the assumptions of the astrodynamic techniques in the program, a fourth-order Runga-Kutta numerical integration technique was implemented in the program and is used to update all current trajectory data points. Spacecraft engine thrust, if an impulsive maneuver is not selected, atmospheric drag, and higher order gravitational harmonics are modelled and included in the integration of the equations of motion for both vehicles. When the trajectories of the vehicles were fully integrated to the predicted intercept time, the integrated data points could then be compared to those generated through the astrodynamic techniques. It was found that agreement between integrated and astrodynamic data points could typically be obtained to the third or fourth decimal place in kilometers in scenarios where drag was not significant. The astrodynamic techniques were found to be able to predict intercept and provide information for maneuvering the spacecraft in real-time for simulations run on a VAX 11/750, while the integration techniques experienced a time lag in updating trajectories which was dependent on the integration step size used. May 1986; Also issued as an M.S. thesis, Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics, 1986; Includes bibliographical references (p. 249-251)

Parallel parametric combinatorial search : its application to runway scheduling

2019-04-10T10:00:36Z

Parallel parametric combinatorial search : its application to runway scheduling Trivizas, Dionyssios Anastasios The Runway Scheduling Problem (RSP) addresses the fundamental issues of airport congestion and energy conservation. It is a variation of the Traveling Salesman Problem (TSP) from which it differs in three basic points: the maximum position shift (MPS) constraints, the requirement to enforce the triangular in its cost structure and the multiplicity of runways (corresponding to multiple salesmen in TSP). The RSP is dynamic, requiring fast and frequent schedule updates. The MPS constraints, designed to prevent inequitable treatment of aircraft, define a combinatorial neighborhood of tours around a base tour, determined by the arrival sequence of aircraft in RSP. The neighborhood contains all tours in which the position of an object (aircraft, city etc.) in the new tour is within MPS positions of its position in the base tour. The parameter MPS controls the radius of the neighborhood, which covers the full solution space when MPS equals half the number of aircraft. We first describe the RSP and then develop a parallel processor (PPMPS) that finds the optimal solution in the MPS-neighborhood in time linear to the number of objects, using up to 4MPS processors in parallel. Subsequently, PPM'S is applied to the general RSP and a case study is presented to justify simplifying assumptions in the scheduling of mixed traffic on multiple runways. The case study shows substantial improvements in the capacity of a system of three runways. Suggestions are made on how to use the PPMPS to create fast heuristic procedures for the TSP, based on divide and conquer and node insertion strategies. Cover title; February 1987; Also issued as a Ph. D. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1987; Includes bibliographical references (p. 167-171)

Flight tests of a digital data acquisition system for analysis of ultrasonic pulse-echo signals used to measure ice accretion

2019-04-12T15:08:16Z

Flight tests of a digital data acquisition system for analysis of ultrasonic pulse-echo signals used to measure ice accretion Ryan, Justin Mark; Hansman, Robert John. A number of signal processing algorithms were developed for analyzing ultrasonic signals used to measure aircraft ice accretion in flight. A high speed digital signal acquisition system was designed and constructed to acquire the signals. The ultrasonic signals were acquired during a series of flight tests in actual icing conditions. This digital data was used to evaluate various algorithms for determining the ice thickness. An analog data acquisition system provided data for comparison with the digital data. A gated peak detector, employing low signal to noise ratio filtering and derivative preprocessing, was developed. This algorithm correctly determined the ice thickness for all tested flight data. Icing rate algorithms were also developed. The measured icing rate correlated reasonable well with the liquid water content of the cloud. May 1986; Also issued as an M.S. thesis, Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics, 1986; Includes bibliographical references (p. 76)

Paper Airplane user's manual : version four

2019-04-12T15:08:15Z

Paper Airplane user's manual : version four Lajoie, Ronnie M. Preface: This document provides the user with a step-by-step guide to using Paper Airplane, Version IV. Although this program can be used to design any system (once given the proper set of design equations), this manual will use as a running example the design of an executive transport jet, the AM410-Laser. This design was originally done by the author using manual calculations; where appropriate, comparisons will be made between the two methods. This manual contains the following conventions for displaying examples: * Bold sans-serif text such as this will represent user input requirements or options that you should enter exactly as shown - including upper and lower case. o Italic sans-serif text such as this will represent user input requirements or options that you need to specify. o Thin curly-brackets surrounding a list of user input separated by commas: {. } will represent a choice of requirements. "Thin square-brackets surrounding user input: [...] will represent optional input." Thin square-brackets surrounding a list of user input separated by commas: [......] will represent a choice of options. " Typewriter-style text such as this will represent the response from Paper Airplane or the system. Paper Airplane Version IV runs under NIL release 329 or above on the DEC VAX family of processors under the VMS operating system. The NIL Lisp language system is available from M.I.T.'s Laboratory for Computer Science, 545 Technology Square, Cambridge MA 02139. Paper Airplane also runs under Zeta LISP on the Texas Instruments Explorer. Paper Airplane requires a VT100-compatible terminal, equipped with a keyboard containing arrow keys and a programmable keypad with PF-keys as well as numbers. Version IV of Paper Airplane contains a substantial number of improvements over the last documented release. In particular: 1. Much faster convergence on design point solutions. 2. Capability to use multiple-input multiple-output design functions along with multiple input single-output design functions. 3. Capability to use non-LISP based external computer programs as design functions (on VAX only). 4. An enhanced Design Function Exerciser. 5. Pre-defined table-lookup auxiliary functions. 6. Addition of a Library to store design variables and design functions from which design sets can be made. Paper Airplane is distributed with the understanding that no claims are made as to the use or performance of this system. Paper Airplane is released for evaluation, stimulation, and exchange of ideas only. The Massachusetts Institute of Technology authorizes the use and distribution of this program and associated manuals as long as the copies are not made for sale or other commercial purposes, either in its original form or in an enhanced form, and that the copyright notice on each source file also be copied. The Massachusetts Institute of Technology retains the copyright to the Paper Airplane code and manuals, and all enhancements, developments, or results obtained using Paper Airplane must be reported in writing and sent to the following address: Paper Airplane CAPD Project Flight Tansportation Laboratory, Room 33-412 Department of Aeronautics and Astronautics Massachusetts Institute of Technology Cambridge, MA 02139 March 26, 1987; Includes bibliographical references

An expert system for generating terminal area flight paths for arriving aircraft

2019-04-08T08:17:34Z

An expert system for generating terminal area flight paths for arriving aircraft Sadoune, Michel Air-traffic congestion and frequent saturation of major airports require improved Air Traffic Control procedures to make the flow of traffic more uniform and increase system capacity. Advanced technologies allow an increased aircraft controllability that makes trajectory planning feasible. A computerized Flight Path Generator for Air Traffic Control has been designed and is described herein. This tool is intended to aid controllers in their decision-making process for guiding aircraft to the runway before landing. The flight path generation program has been developed in the form of an Expert System in a Prolog and Lisp environment. A computationally tractable symbolic representation framework for aircraft motion in space is introduced. Several Artificial Intelligence techniques are combined to design a planner, based on partially predefined sequences of actions involving mathematical descriptions, such as movement in space with a time requirement. The adequacy of an Expert System to develop new flight approach procedures and adaptive separation criteria is highlighted. Symbolic conflict detection and resolution are presented as an extension to the Flight Path Generator in an Expert System environment. July 1987; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1987; Includes bibliographical references (p. 145-150)

The impact of airline-airport relations on airport management decisions

2019-04-10T16:32:09Z

The impact of airline-airport relations on airport management decisions Cohen, Dayl Arlene Airlines, in the past, have had an important influence on airport operations through privileges granted them by the airport lease agreements. Airport administrators and sponsoring agencies have agreed to grant these privileges because much of airport capital investment has been amortized with airline money. This has been accomplished through the mechanism of the long-term lease. This paper examines the working relationships which have been developing between airlines and airports in recent years. These relations have been influenced by deregulation and by inadequate airport capacity--both actual and anticipated--for growing passenger demand. Through an examination of the current role that airlines play in obtaining capital financing for airports, and an analysis of the leases and use agreements between airlines and three U.S. airports, a consideration of the diverging priorities of airports and airlines is presented. June 1985; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1985; Includes bibliographical references (p. 149-152)

Potential impacts on advanced technologies on the ATC capacity of high-density terminal areas

2019-04-08T08:17:34Z

Potential impacts on advanced technologies on the ATC capacity of high-density terminal areas Simpson, R. W.; Odoni, Amedeo R.; Salas Roche, Francisco Javier. Advanced technologies for airborne systems (automatic flight control, flight displays, navigation) and for ground ATC systems (digital communications, improved surveillance and tracking, automated decision-making) create the possibility of advanced ATC operations and procedures which can bring increased capacity for runway systems. A systematic analysis is carried out in this report to identify certain such advanced ATC operations, and then to evaluate the potential benefits accruing over time at typical US high-density airports (Denver and Boston). The study is divided into three parts: Part 1, "A Critical Examination of Factors Which Determine Operational Capacity of Runway Systems at Major Airports", is an intensive review of current US separation criteria and terminal area ATC operations. It identifies 11 new methods to increase the capacity of landings and takeoffs for runway systems; Part 2 - "Development of Risk Based Separation Criteria", is the development of a rational structure for establishing reduced ATC separation criteria which meet a consistent Target Level of Safety using advanced technology and operational procedures; Part 3 - "Estimation of Capacity Benefits from Advanced Terminal Area Operations - Denver and Boston", provides an estimate of the overall annual improvement in runway capacity which might be expected at Denver and Boston from using some of the advanced ATC procedures developed in Part 1. Whereas Boston achieved a substantial 37% increase, Denver only achieved a 4.7% increase in its overall annual capacity. June 1986; Includes bibliographical references (leaves 135-136)

Simulator evaluation of manually flown curved instrument approaches

2019-04-12T15:08:14Z

Simulator evaluation of manually flown curved instrument approaches Sager, Dennis Wayne Pilot performance in flying horizontally curved instrument approaches was analyzed by having nine test subjects fly curved approaches in a fixed-base simulator. Approaches were flown without an autopilot and without a flight director. Evaluations were based on deviation measurements made at a number of points along the curved approach path and on subject questionnaires. Results indicate that pilots can fly curved approaches, though less accurately than straight-in approaches; that a moderate wind does not affect curve flying performance; and that there is no performance difference between 600 and 90 turns. A tradeoff of curved path parameters and a paper analysis of wind compensation were also made. January 1973; Also issued as an M.S. thesis in the Dept. of Aeronautics and Astronautics, MIT, 1973; Includes bibliographical references (p. 122)

Freight mode choice : air transport versus ocean transport in the 1990's

2019-04-12T15:08:14Z

Freight mode choice : air transport versus ocean transport in the 1990's Lewis, Dale B. Value density is often considered when considering the choice whether to ship cargo by air or by water. However, although cargo value is directly linked to the overall cost of shipment, it is the deciding factor in mode choice only for those cargoes with either an extremely high or extremely low value per pound. For cargo in some middle range other criteria, such as density of stowage, perishability, reliability of service, or the need for more accurate demand forecasting must be considered. The characteristics of international cargoes shipped by both modes in 1992 are examined and a logistics cost for the distribution of representative goods is calculated. A schedule of premiums is developed, which shows the transportation premium arrange of cargo value densities and stowage densities could support if transit time were reduced from the longer times associated with water transport to the shorter times found in air travel. The volume of mode-converted cargo is projected for the year 2030 and the number of aircraft required to transport the cargo is estimated. Cover title; December 1994; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1995; Includes bibliographical references (p. 137-139)

A survey of approaches to the airport slot allocation problem

2019-04-10T10:00:35Z

A survey of approaches to the airport slot allocation problem Cohen, Dayl Arlene; Odoni, Amedeo R. Introduction: The allocation of slots at congested major commercial airports is one of the most difficult problems facing the aviation community today. The stakes involved are very large and the controversy generated by the various proposed approaches to the problem is heated. This report is an attempt to provide a concise summary of the various proposed approaches and to discuss briefly the advantages and disadvantages of each. Four important airports (JFK International and LaGuardia in New York City, O'Hare International in Chicago and National in Washington) are now and have been since 1969 - designated as "high density terminal area" (HDTA) airports.-- Runway access to these airports is allocated among airline users through scheduling committees which meet twice a year. Access to these airports by commuter/air taxi operators and by general aviation aircraft is also rationed. At the same time, several other important airports now experience (or are on the verge of experiencing) habitually-high levels of congestion during the peak traffic hours of the day. The costs associated with this state of affairs are high. Although no particularly-reliable data exist, there is little doubt that the additional direct operating costs to the airlines due to airport congestion run in the hundreds of millions of dollars a year (and, possibly, may even exceed the one-billion-dollar mark). Indirect costs (loss of passenger time, disruption of airline schedules, missed appointments or missed flight connections, anguish and aggravation, etc.) may be just as large or larger. A successful slot-allocation system would accomplish two things simultaneously: it would "alleviate" the congestion problems just referred to until that time, if'ever, when increased airport capacity becomes available, and it would provide access to the congested airports to those aircraft 2 operators whose use of the facility offers the highest "social benefits". Unfortunately, underlying such lofty statements there are two difficult questions to be addressed, namely, "what is the optimum level of delay/congestion?" and "how does one identify the flights that offer the highest social benefits?" While the presence of a market economy provides considerable assistance in answering these questions at the theoretical level, implementation of a successful slot-allocation system is made difficult by a number of complicating factors, as will be seen later in this report. It is appropriate to classify approaches to the slot-allocation problem into two broad categories and several sub-categories: 1, Administrative Approaches a) Historically-based (or "current-use-based") allocation b) Allocation on the basis of optimization c) Allocation by lottery d) Scheduling committees 2, Economic Approaches a) Time-dependent user charges b) Auctions As suggested by this classification scheme, the main distinguishing feature that we could identify in comparing alternative approaches is whether or not an economic mechanism is explicitly used in the allocation process. The rest of this report is organized as follows: Section 2 summarizes the disadvantages of the "do nothing" strategy concerning slot allocation. Section 3 covers the administrative slot-allocation approaches and Section 4 the economic approaches. Section 5 presents a review of several important questions in this area which are yet unresolved. Finally, Section 6 presents a quite-thorough annotated bibliography of the existing literature. May 1985; Includes bibliographical references (leaves 46-55)

Automated Speech Recognition in air traffic control

2019-04-10T10:00:34Z

Automated Speech Recognition in air traffic control Trikas, Thanassis Over the past few years, the technology and performance of Automated Speech Recognition (ASR) systems has been improving steadily. This has resulted in their successful use in a number of industrial applications. Motivated by this success, a look was taken at the application of ASR to Air Traffic Control, a task whose primary means of communication is verbal. In particular, ASR, and audio playback was incorporated into an Air Traffic Control Simulation task in order to replace blip-drivers, people responsible for manually keying in verbal commands and simulating pilot responses. This was done through the use of a VOTAN VPC2000 ASR continuous speech recognition system which also possessed a digital recording capability. Parsing systems were designed that utilized the syntax of ATC commands, as defined in the controller's handbook, in order to detect and correct recognition errors. As well, techniques whereby the user could correct any recognition errors himself were included. Finally, some desirable features of ASR systems to be used in this environment were formulated based on the experience gained in the ATC simulation task and parser design. These predominantly include continuous speech recognition, a simple training procedure, and an open architecture to allow for the customization of the speech recognition to the particular task at hand required by the parser. Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1987; January 1987; Includes bibliographical references (leaf 54)

Solving large-scale dial-a-ride vehicle routing and scheduling problems

2019-04-10T10:00:33Z

Solving large-scale dial-a-ride vehicle routing and scheduling problems Jaw, Jang-Jei In this thesis we develop two heuristic algorithms for large-scale multi-vehicle advance-request version of the dial-a-ride problem. This problem is concerned with developing a set of routes for a fleet of vehicles serving customers who have to be picked up from specified origins and be delivered to specified destinations. In this thesis it is assumed that each customer has specified either a desired pick-up time or a desired delivery time and that customer requests for service as well as the number of available vehicles throughout the time period of interest are known well in advance of the time of actual vehicle dispatching. The first heuristic approach consists of three successive and distinct steps: "grouping", "clustering" and "routing". Grouping divides customers into "time groups" on the basis of their desired pick-up and delivery times. Clustering separates customers in each time group into "clusters" and assigns vehicles to serve each cluster. Finally routing generates routes for each individual vehicle to serve every cluster in turn and for every time group. The second algorithm, Advanced Dial-A-Ride with Time Windows (ADARTW), treats customers' desired service times as strict constraints and can guarantee prespecified standards of service quality. The service quality constraints refer to guarantees that (i) customer's ride time will not exceed a pre-specified maximum and (ii) the service time will not deviate from the most desired time by more than a pre-specified amount ("the time windows"). The algorithm builds up vehicle tours through sequential insertion of customers and uses a nonlinear objective function to guide such insertions. Variations of this basic approach are also discussed. We have tested the two algorithms on many simulated cases using computer-generated data. Computational experience with a large-scale real world dial-a-ride problem (2617 customers and 30 simultaneously operating vehicles) is also presented. June 1984; Also issued as a Ph. D. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1984; Includes bibliographical references (p. 221-224)

Recommendations (Phase I) DOT/CAB/MIT air freight data study

2019-04-10T10:00:32Z

Recommendations (Phase I) DOT/CAB/MIT air freight data study Simpson, R. W.; Taneja, Nawal K. Introduction: On January 15, 1971 the Department of Transportation and the Civil Aeronautics Board announced a joint research project in conjunction with the Department of Transportation's contractor, the Massachusetts Institute of Technology. The purpose of the project is the development of a domestic and international air freight traffic data base. Although both agencies recognize a continuing need for regularly reported statistics on air freight movements, their individual needs are not compatible. Furthermore, it was not obvious that the industry's needs would automatically be fulfilled even if these two agencies were to settle on a common set of data requirements. The first part of the study involved establishing the statistical needs of the DOT, CAB and the industry. Although the initial DOT requirements included the CAB needs, there remained the need to review the data desired by the industry. MIT, in conjunction with the DOT and CAB representatives, initially interviewed selected US air carriers and cargo data users to analyze the air freight data systems operations and determine whether the data requirements developed in the DOT/CAB specifications were in fact useful and practical from an industry point of view. Based on preliminary industry needs and DOT/CAB needs, MIT's task was to determine a feasible initial data specification in light of the information presently available from air bill sampling (or the information which might be reasonably expected on a new air bill). In case of conflicts, MIT was to recommend priorities. As required for completion of Phase I of the Air Freight Data Study, the following are our recommendations for the continuation into Phase II based on the informal survey of the data-gathering activities and capabilities of the industry and specific needs of the DOT and the CAB. Throughout February and March a survey of eleven airlines and three airframe manufacturers was made to determine the industry's data needs and ability to provide such data. The atmosphere throughout the attendant meetings was one of interest and cooperation with much constructive criticism. The airlines and manufacturers surveyed included: Allegheny Airlines, Inc., American Airlines, Inc., Continental Air Lines, Inc., Delta Air Lines, Inc., Eastern Air Lines, Inc., North Central Airlines, Inc., Northwest Airlines, Inc., Pan American World Airways, The Flying Tiger Line, Inc., Trans World Airlines, Inc., United Air Lines, Inc., The Boeing Company, McDonnell-Douglas Corporation, Lochkeed-California Company, Lockheed-Georgia Company. October 1971

A.I.S.E. : a hybrid scheduling system

2019-04-10T10:00:32Z

A.I.S.E. : a hybrid scheduling system Duchesne de Lamotte, Herve A.I.S.E. (Advanced Interactive Scheduling Environment) is an interactive computer system designed to schedule efficiently a fleet of vehicles accordingly to a set of requests made in advance or at the last minute. The system consists of both an electronic drawing-board with which the schedule can be manipulated visually, and a support algorithm that helps the user to build the schedule efficiently. This thesis begins by discussing-the evolution that lead to the design of the A.I.S.E. planning tool together with the environment in which A.I.S.E. will be used. It then gives a general analysis of the support algorithm used in A.I.S.E.. The analysis describes the "insertion heuristic" that is being used, and shows how it can generate an efficient schedule from a list of requests, or insert an individual request into an already existing schedule with minimum disruptions. Since the heuristic was initially designed to solve the "Dial-a-Ride" problem, necessary modifications are also reviewed. The various aspects of the schedule electronic drawing-board are then presented. The description is based on the version of A.I.S.E. that will be delivered to the U.S. Air Force Operational Support Airlift. Graphics displays are reviewed; the links between the support heuristic and the graphic interface are analysed. This presentation is followed by a review of other areas in which such a scheduling tool can be used. May 1985; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Sloan School of Management, 1985; Includes bibliographical references (leaves 97-98)

Policy alternatives for the U.S. commuter airline industry after four years of airline deregulation

2019-04-10T10:00:30Z

Policy alternatives for the U.S. commuter airline industry after four years of airline deregulation Molloy, James F. Beginning with the passage of the Airline Deregulation Act of 1978, the dramatic changes in the passenger commuter airline segment of the U.S. aviation industry are identified and evaluated. The results of this evaluation provide a background for judging the future course for government policies in this segment of the U.S. airline industry. Since airline deregulation, there has been accelerated growth in this segment of aviation, frequently without regard to available resources. Unanticipated increases in fuel prices, the strike of air traffic controllers, and a general business slowdown in the United States, have adversely impacted the commuter airline industry and their basic constituency, the small communities. The performance, and perhaps the survival, of the approximate 150 passenger commuter airlines, and the air service to small communities will depend on governmental policy adjustments in the areas of: essential air service standards, subsidy goals and standards, airport access priorities, joint fares, commuter aircraft development, and FAA commuter loan guarantees. Sound planning, and more realistic allocation of resources for the commuter management, small community air service advocates, and governmental policy makers are required. This means there is a need for enlightened regulatory policies, and improved and strengthened management. May 1983; Includes bibliographical references

A method for determination of optimum vehicle size and frequency of service for a short haul V/STOL air transport system

2019-04-12T15:08:13Z

A method for determination of optimum vehicle size and frequency of service for a short haul V/STOL air transport system Simpson, R. W.; Neuve Eglise, Michel J. To compete successfully in short haul markets under 200 miles, an air transport system must offer a high daily frequency of service, N, as well as short air travel times. In a given market, N can be increased by using vehicles of smaller seat capacity, C, which are more expensive per seat to operate. A method of determining optimal values of N and C for assumed market behavior in terms of fare and time elasticities is presented. By defining total trip time to include the average wait for service, and using a demand model developed for the Northeast Corridor, the air share of total demand in any market can be calculated as a function of N and the competing fares. Plotting daily passengers versus N, and relating this to the maximum and breakeven load factors for a family of vehicles of different seating capacities, determines the values of N and C which maximize return to the operator. May 1968; Includes bibliographical references (p. 39)

An application of advanced statistical techniques to forecast the demand for air transportation

2019-04-09T16:17:33Z

An application of advanced statistical techniques to forecast the demand for air transportation Mathaisel, Dennis F. X.; Taneja, Nawal K. Introduction and objectives: For some time now regression models, often calibrated using the ordinary least-squares (OLS) estimation procedure, have become common tools for forecasting the demand for air transportation. However, in recent years more and more decision makers have begun to use these models not only to forecast traffic, but also for analyzing alternative policies and strategies. Despite this increase in scope for the use of these models for policy analysis, few analysts have investigated in depth the validity and precision of these models with respect to their expanded use. In order to use these models properly and effectively it is essential not only to understand the underlying assumptions and their implications which lead to the estimation procedure, but also to subject these assumptions to rigorous scrutiny. For example, one of the assumptions that is built into the ordinary least-squares estimation technique is that the explanatory variables should not be correlated among themselves. If the variables are fairly collinear, then the sample variance of the coefficient estimators increases significantly, which results in inaccurate estimation of the coefficients and uncertain specification of the model with respect to inclusion of those explanatory variables. As a corrective procedure, it is a common practice among demand analysts to drop those explanatory variables out of the model for which the t-statistic is insignificant. This is not a valid procedure since if collinearity is present the increase in variance of the coefficients will result in lower values of the t-statistic and rejection from the demand model of those explanatory variables which in theory do explain the variation in the dependent variable. Thus, if one or more of the assumptions underlying the OLS estimation procedure are violated, the analyst must either use appropriate correction procedures or use alternative estimation techniques. The purpose of the study herein is three-fold: (1) develop a "good" simple regression model to forecast as well as analyze the demand for air transportation; (2) using this model, demonstrate the application of various statistical tests to evaluate the validity of each of the major assumptions underlying the OLS estimation procedure with respect to its expanded use of policy analysis; and, (3) demonstrate the application of some advanced and relatively new statistical estimation procedures which are not only appropriate but essential in eliminating the common problems encountered in regression models when some of the underlying assumptions in the OLS procedure are violated. The incentive for the first objective, to develop a relatively simple single equation regression model to forecast as well as analyze the demand for air transportation (as measured by revenue passenger miles in U.S. Domestic trunk operations), stemmed from a recently published study by the U.S. Civil Aeronautics Board [CAB, 1976]. In the CAB study a five explanatory variable regression equation was formulated which had two undesirable features. The first was the inclusion of time as an explanatory variable. The use of time is undesirable since, from a policy analysis point of view, the analyst has no "control" over this variable, and it is usually only included to act as a proxy for other, perhaps significant, variables inadvertently omitted from the equation. The second undesirable feature of the CAB model is the "delta log" form of the equation (the first difference in the logs of the variables),which allowed a forecasting interval of only one year into the future. This form was the result of the application of a standard correction procedure for collinearity among some of the explanatory variables. In view of these two undesirable features, it was decided to attempt to improve on the CAB model. In addition to the explanatory variables considered in the CAB study a number of other variables were analyzed to determine their appropriateness in the model. Sections II and III of this report describe the total set of variables investigated as well as a method for searching for the "best" subset. Then, Section IV outlines the decisions involved in selecting the appropriate form of the equation. The second objective of this study is to describe a battery of statistical tests, some common and some not so common, which evaluate the validity of each of the major assumptions underlying the OLS estimation procedure with respect to single equation regression models. The major assumptions assessed in Section V of this report are homoscedasticity, normality, autocorrelation, and multicollinearity. The intent here is not to present all of the statistical tests that are available, for to do so would be the purpose of regression textbooks, but to scrutinize these four major assumptions enough to remind the analyst that it is essential to investigate in depth the validity and precision of the model with respect to its expanded use of policy analysis. It is hopeful that the procedure outlined in this report sets an example to demand modeling analysts of the essential elements used in the development of reliable forecasting tools. The third and ultimate objective of this work is to demonstrate the use of some advanced corrective procedures in the event that any of the four above mentioned assumptions have been violated. For example, the problem of autocorrelation can be resolved by the use of generalized least-squares(GLS), which is demonstrated in Section VI of this report; and the problem of multicollinearity , usually corrected by employing the cumbersome and restrictive delta log form of equation, has been eliminated by using Ridge regression (detailed in Section VII). Finally, in Section VIII an attempt is made to determine the "robustness" of a model by first performing an examination of the residuals using such techniques as the "hat matrix", and second by the application of the recently developed estimation procedures of Robust regression. Although the techniques of Ridge and Robust regression are still in the experimental stages, sufficient research has been performed to warrant their application to significantly improve the currently operational regression models. August 1977; Includes bibliographical references (p. 76-78)

A flexible scheduling environment using dynamic exception handling

2019-04-09T17:16:39Z

A flexible scheduling environment using dynamic exception handling Appel Peter H. A generalized environment which facilities the development of various types of schedules has been developed. This environment includes an extensive user interface in which a graphics terminal and a mouse is used to display and manipulate schedules. A common data structure is used for representing schedules; this data structure is flexible enough to allow for the different amounts of information required by different scheduling problems. In developing algorithms to be used in conjunction with this scheduling environment, an attempt has been made to address the situation that has faced automated airline scheduling systems in the past - that there are such a large number of pieces of information specific to each scheduling situation that it is hard to incorporate this "knowledge" into a deterministic algorithm. The solution that is proposed can be called dynamic exception handling. This system will allow an individual to communicate these specific piece of information to the automated system in a way that will allow the special cases to be handled with a minimum los of efficiency. May 1987; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1987; Includes bibliographical references (p. 89)

Blown flap noise

2019-04-12T15:08:12Z

Blown flap noise Haas Martin This report is concerned with the noise generated by blown flaps of the type currently being developed for the short take off and landing aircraft. The majority of the report is an experimental study of the sound-radiation produced by a small scale externally blown double-slotted flap model. Tests were carried out with and without a forward velocity of 60 MPH for a basic engine-wing configuration and for a modified (Engine moved inboard) configuration. Noise radiation patterns and sound pressure level spectra were obtained for nozzle exhaust velocities between 100 and 500 ft/sec. In addition all model data was extrapolated to five fictional full scale STOL aircrafts. The noise generated by the impingement of the jet on the externally blown flap is highly dependent on the jet velocity and the flap position. As the flap angle is increased the noise generated increases. At the 45* - 70* flap position the noise is more than 25db over that caused by the model jet alone. It is especially louder below the wing. The sound power level generated by the externally blown flap (at all positions) increased with the sixth power of the jet's blowing velocity. As the nozzle jet velocity is increased, the sound power level of the noise from the nozzle alone generally increased with the expected eighth power of the jet velocity. Therefore, the difference between the impingement noise and the noise of the nozzle alone decreased with increasing velocity. The noise radiation pattern becomes more directed below the wing as the flaps are lowered. The effect of forward velocity on the noise generated was neglible for a ratio of jet to forward velocity greater than 4.5. Results on tests made on the modified engine-wing configurations were similar to that of the basic configuration except for a slight reduction in overall sound pressure level (2 to 4 db) over all positions measured. An extrapolation to full scale indicated that the externally blown flap noise must be suppressed to meet STOL aircraft noise goals. June 1972; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1972; Includes bibliographical references (p. 91)

An assessment of lighter than air technology : the report of the Multi-agency Workshop on Lighter Than Air : Monterey California, September 9-13, 1974

2019-04-10T10:00:29Z

An assessment of lighter than air technology : the report of the Multi-agency Workshop on Lighter Than Air : Monterey California, September 9-13, 1974 Vittek, Joseph F. Summary: This document is a draft report of the Workshops' output - The Working Group Reports. It is for your review and comment which should be returned to me by January 1, 1975. With those comments and criticisms in hand, I will make any needed revisions, add sections on background, history, etc. and print significant comments or minority views if they exist. The revised final report will be issued in the spring of 1975. With this draft report completed, I will turn my attention to the proceedings. A preliminary review indicates that there is more work to be done on the papers than expected, but I still plan to mail the papers in early 1975. I am pleased to announce that the AIAA has approved its' LTA subcommittee's plan to hold a followup conference in Snowmass-at- Aspen, Colorado, July 15-17, 1975. Details will be in the December issue of Aeronautics and Astronautics. Hope to see you there! To help us improve that program, could you take a few minutes to complete and return the questionnaire on the reverse side of this page? It would be very helpful. The major issues addressed were: 1. Should the United States Government, undertake development of a Lighter Than Air vehicle. 2. Should the United States sponsor research and technology efforts in the area of Lighter Than Air including the construction of an experimental LTA research vehicle? Due to unknown economic risks, the group concluded that it was premature to stress government development of an LTA vehicle at this time. Rather, appropriate agencies, particularly NASA, should sponsor appropriate studies in LTA to better define the technical unknowns. only after some of the general uncertainties are resolved did the group feel that it would be beneficial to construct an experimental LTA vehicle. However, the working group did feel that a positive policy statement was needed, which is set out starting on page 3 of this report. Cover title; October 1974; Draft Copy."--Stamped on every page

On the numerical solution of simultaneous, non-linear equations in computer-aided preliminary design

2019-04-10T10:00:28Z

On the numerical solution of simultaneous, non-linear equations in computer-aided preliminary design Kolb, Mark A. In the solution of problems in preliminary design, it often becomes necessary to solve systems of equations. An immediate example from aeronautical design is the frequent need to perform several iterations around the gross takeoff weight in order to determine a consistent value for this design variable. The Paper Airplane program is the result of research by the MIT Flight Transportation Laboratory into automating the computational aspects of preliminary design, with the object of freeing the designer to concentrate on the more creative aspects of the design process. Paper Airplane is written in Common LISP (augmented by the object-oriented programming "f lavor" construct, supported by NIL and ZetaLisp), and implemented on both a VAX-11/750 and a Texas Instruments EXPLORER Lisp Machine. In its original form, Paper Airplane possessed the capability of transforming declarative knowledge about design relationships into imperative form; i.e., the declarative statement, w = fi(X, y, z), could be understood to imply that z = f 2(w, y, z), y = fs(w, z, z), and z = f 4 (w, z, y), as well. Understanding of this concept was simulated by applying the Newton-Raphson method to numerically invert design relationships. This capability enabled Paper Airplane to solve design problems which could be reduced to sets of single, independent equations. However, no techniques were available for cases in which iteration was required to solve the design relationships-i.e., when the system could only be reduced to two or more simultaneous equations. Towards the end of providing this additional capability, three numerical techniques for solving sets of two equations in two unknowns were examined. In the course of investigating these approaches, the need for explicit representation of the steps by which design relationships were to be used to calculate values for design variables was recognized, and appropriate software representations were developed. The first of these techniques, the so-called "fixed-point" method, involves assuming a value for one variable, based upon which the equations are solved, enabling calculation of a new value for the variable whose value was assumed. This calculated value is used as the assumed value for the next iteration, repeating this 3rocess until, if possible, the value calculated at the end of an iteration is sufficiently close to the value assumed at the beginning of the iteration. In the "simultaneous Newton-Raphson" method, a value is again assumed for one variable, and design relationships are chained together in such a way as to make it possible to calculate two values for a second variable. The assumed value is updated by calculating the intersection of tangent lines determined by the derivatives of the two chains of design relationships, until the values calculated by both chains are identical. Upon establishing that the two former methods rely upon invalid assumptions concerning the linearity of design relationships, a third method, the "logarithmic distribution" method was examined. In setting up the problem, an approach parallel to that used in the "simultaneous Newton-Raphson" method is taken, but the solution to the system of equations is determined by testing logarithmically distributed values over progressively smaller search intervals. Due to difficulties associated with design relationships which are multi-valued in certain directions, this technique required modification to the procedure whereby design relationships are numerically inverted, using the Newton-Raphson method. It was found that by making the selection of the initial guess value for the Newton-Raphson procedure stochastic, multi-valued relationships could be prompted to use the appropriate branches, when necessary. To more effectively deal with multi-valued branches, application of symbolic algebra techniques and further modifications to the Newton-Raphson procedure are proposed. January 1986"--Cover; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1986; Includes bibliographical references (p. 89-91)

ATCLAB : a laboratory environment for research in advanced ATC automation conceptual design

2019-04-10T10:00:27Z

ATCLAB : a laboratory environment for research in advanced ATC automation conceptual design Elias, Antonio L.; Pararas, John Demetrios. Introduction: A large number of ideas and schemes have been proposed and are constantly being suggested to enhance the Air Traffic Control system's safety, reliability, and efficiency by means of automation. The capability of the Federal Aviation Administration to properly specify and procure advanced automation systems depends critically on its capability to evaluate these ideas from a number of viewpoints: 1. Functional: i.e., is the proposed idea of any value, assuming it could be implemented? 2. Procedural: i.e., can the proposed idea be implemented in conjunction with existing and/or new ATC procedures? 3. Implementability: i.e., can the proposed functionality and/or procedures be implemented, with sufficient accuracy, reliability, data requirements, etc? 4. Cost/benefit: i.e., are the benefits expected from the proposed functionality sufficient to offset the expected costs and risks? 5. Requirements definition: i.e., is the proposed scheme or system sufficiently well defined to allow the development of meaningful and supportable requirements? There are two conventional approaches available to answer these questions: analysis and simulation. The effectiveness of analysis to evaluate an automation proposal usually depends on the degree to which the proposed function interacts with other elements of the ATC system. In general, the more isolated and self-contained the function, the more amenable it is to analytical evaluation. Functions that interact with many different elements of the system generally require dynamic simulation for effective evaluation. Traditionally, this has required the development of an ad-hoc simulator to evaluate the proposed automation scheme, or the adaptation of an existing simulation. Both approaches are expensive and risk intensive; attempts at building all-inclusive, general purpose simulations are even more expensive and not entirely risk free. As an alternative, a mid-ground solution would be the establishment of a flexible computer-based laboratory environment to perform combined analysis and simulation evaluation on an ad-hoc basis in response to the specific automation scheme being evaluated. To be more effective than traditional analysis and simulation techniques alone, this environment must reduce the cost of building prototype code by two orders of magnitude, both in terms of labor and of calendar time, over traditional environments, such as the ones used to develop existing simulators and prototype systems. Recent developments in computer hardware and software have drastically altered the process of developing software, particularly in the systems simulation area. Symbolic computation and object-oriented languages, along with hardware specialized to execute this type of code, have been shown to produce the two orders of magnitude improvement suggested in the previous paragraph. This report analyzes the feasibility of establishing such a laboratory environment, including identification of the required technology, a possible architecture that would fulfill these requirements, a tentative implementation plan, and two sample pathfinder projects to show how the proposed environment could be used to evaluate two specific advanced automation proposals. To facilitate references to this environment, it will be referred to in this report as ATCLAB; this is not an official FAA-approved name. Cover title; June 1986; Includes bibliographical references (p. 42)

A model for forecasting future air travel demand on the North Atlantic

2019-04-10T10:00:26Z

A model for forecasting future air travel demand on the North Atlantic Taneja, Nawal K. Introduction: One of the key problems in the analysis and planning of any transport properties and facilities is estimating the future volume of traffic that may be expected to use these properties and facilities. Estimates of this kind are now being made regularly as the transport system continues to expand. The future planning, implementation and operation of a successful transportation system requires accurate and realistic forecasts of traffic volumes. To achieve optimal policies, the planner needs to be able to predict the effect of alternate decisions. Although the planning process involves much more than a forecast of the future traffic statistics, these statistics provide the essential quantitative dimensions for the planning process. Forecasts of expected traffic are an essential prerequisite to long-range planning. The link between planning and forecasting lies in recognizing that in order to bring an expected situation under control, the planner must be provided with the entire spectrum of situations that could be anticipated and, hence, could be planned for. The reasonableness and reliability of these traffic statistics is, therefore, of vital importance to the planner. This study investigates the North Atlantic passenger travel demand. The final goal is to make a forecast of the passenger traffic on this route. It is believed that such a forecast would prove to be a critical tool for long-range planning of transport properties and facilities on both sides of the Atlantic. For this reason, it is important to be well informed about the technical and economic factors which will determine and limit the travel volume, especially for manufacturers of aircraft, domestic and international airlines, and the government. Governments, for example, must be provided with traffic forecasts if they are to provide adequate ground facilities and air traffic control systems. April 1970; Includes bibliographical references (p. 125-128)

The development of a wind tunnel facility for the study of V/STOL noise

2019-04-10T10:00:25Z

The development of a wind tunnel facility for the study of V/STOL noise Widnall, S. E.; Bauer Paul E. An open-jet wind tunnel operating within an anechoic chamber was developed for the purpose of the study of V/STOL noise mechanisms. An existing low-speed conventional hard-walled wind tunnel was modified to operate as an open-jet tunnel; an anechoic chamber was then constructed around the test section. The resulting aerodynamic and acoustic characteristics of the tunnel are discussed. August 1972; Includes bibliographical references (leaf 12)

Concept development and evaluation of airborne traffic displays

2019-04-10T10:00:25Z

Concept development and evaluation of airborne traffic displays Imrich, Thomas A system concept for a cockpit traffic situation display (TSD) was developed and a preliminary evaluation was undertaken to investigate the effect of a TSD on safety, efficiency, and capacity in the 3rd generation NAS/ARTS ATC system environment. The optimum display configuration, examples of procedural changes, benefits to the pilot and benefits to ATC are discussed. The test program was conducted in three phases: 1. Basic tracking tests 2. ATC procedural tests 3. Spacing tests using position command data Both quantitative and qualitative measures were used for determining safety, pilot and controller workload, and task performance. A comparison was made between operations conducted with and without a TSD. Results of the test program were quite promising. Pilot response to the TSD as a safety device was strongly favorable. In tasks which involved limited pilot participation in the ATC control process, improvements in spacing accuracy and a decrease in communications at satisfactory pilot workload levels were demonstrated. Initial results indicate that additional research to fully explore the potential of TSD's should be undertaken at the earliest opportunity. June 1971; Also issued as a M.S. thesis in the Dept. of Aeronautics and Astronautics, MIT, 1971; Includes bibliographical references (p. 104-105)

A programmable pilot oriented display system for GA aircraft

2019-04-10T10:00:24Z

A programmable pilot oriented display system for GA aircraft Littlefield, James A. This report presents a complete description of a digital flight data processing platform designed to support a range of airborne or flight simulator based experiments requiring the acquisition, processing, and display of information. The Programmable Pilot Oriented Display (PPOD) is based on IEEE S-100 bus standard equipment and readily available software utilities. The design philosophy and techniques used to achieve project objectives with a minimum of hardware/software customization are discussed. System resources include three Z80 processors, intelligent 10, complete interprocessor communications firmware, and RS-170 composite video output. Discussion of both PPOD capabilities and the steps required to employ PPOD in future experimental setups are presented in the context of a mobile test run. May 1982; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Dept. of Aeronautics and Astronautics, 1982; Includes bibliographical references (p. 87-90)

An economic analysis of the determination of congestion tolls at commercial airports

2019-04-08T07:29:55Z

An economic analysis of the determination of congestion tolls at commercial airports Odier, Edouard Christian This report examines the problem of determining runway fees at major commercial airports when the objective is the maximization of social benefits. Unlike most of the analytical work that has been performed to date, the economic model used here takes into consideration time variations in airport demand and extends earlier results to this more realistic case. As with earlier models, the one used here demonstrates clearly the differences in the optimal tolls that result from assuming different regulatory environments. An alternative model, based on the concept of Pareto optimality, not only leads to the same results as the traditional approach, but also allows consideration of some additional factors such as frequency of service and average load factors. In particular, it is shown that when low load factors are sufficiently valued by passengers, optimality does not require that aircraft fly full, even in the presence of sizable delays. An example is worked out in detail, illustrating many of these points and especially how an appropriately determined peak hour surcharge can reduce substantially congestion and result in increased social benefits from the airport facility. Finally, the experience of the Port of New York Authority in New York airports and that of the British Airports Authority at Heathrow is discussed briefly and compared with the conclusions of this report. Originally presented as the author's thesis, (Ph. D.) in the M.I.T. Dept. of Aeronautics and Astronautics, 1976; September 1976; Includes bibliographical references (p. 90)

An assessment of deregulation and its effect on the international air transportation community : a 1981 update

2019-04-10T10:00:10Z

An assessment of deregulation and its effect on the international air transportation community : a 1981 update Gray, Robert Reed July 13, 1981; Lecture delivered July 13, 1981, by Robert Reed Gray, Esq. to the "Air Transportation -- Management, Economics, and Planning" course, organized by the Center for Advanced Engineering Study, Flight Transportation Laboratory, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology. Mr. Gray is a Senior Partner of the New York and Washington law firm of Hale Russell & Gray"--p. [1]

The multilateral agency : the approach, the perspective and the means

2019-04-10T10:00:09Z

The multilateral agency : the approach, the perspective and the means Kotaite, Assad Cover title; Lecture by Dr. Assad Kotaite, President of the Council of the International Civil Aviation Organization (ICAO), at the Massachusetts Institute of Technology (MIT) (Cambridge, Massachusetts - 14 July 1981)"--p. [1]; July 1981

Concepts studies for future intracity air transportation systems

2019-04-10T10:00:09Z

Concepts studies for future intracity air transportation systems Summary: This report is concerned with describing the possible application of future air transportation systems within urban areas of the United States. The planning horizon extends to 1995 and the report focuses on the period 1980-85 for introduction of urban air systems. The general conclusion of the study is that urban air systems will be technically and operationally feasible, but that economic viability remains inextricably linked to future governmental policies on urban development, and consequently policies for development of urban transportation. In view of the uncertainties in these policies, it becomes difficult to be definitive about the forms of future urban air systems and the research and development needs to develop these systems. The marketing section of the report identifies the kinds of urban travel markets, and attempts to apply a modal split model to show the share of the travel market which an air system would capture in competition with automobile or new forms of rapid transit. The results indicated the need for a high frequency of air service, and low values of access and egress times and costs, and reasonably competitive fares. The air system did not gain any appreciable share of the travel until trip distances were over 20 miles. Since most of the trips in an urban area are under this distance, the overall penetration of the urban travel market was less than one per cent. Application of the modal split model to data for a 1980 case study of the Boston area indicated that the loads were much too low to justify a large scale urban system. Although the modal split model results can be questioned and more work on such models is indicated, the general nature of these marketing conclusions is unlikely to change. There were two concepts for urban air systems described in this study: a "metrobus" concept which used 40-80 passenger vehicles as a public carrier in the urban area and a "metrotaxi" concept which used 4-5 passenger VTOL air taxis as a private-for-hire carrier. The components of these systems (vehicles, metroports, air traffic control system) were described as they might exist for the 1980-85 period. Appendix B describes an analysis for any public urban transportation system which demonstrates that a large number of stopping points are required of a large scale urban system in order to reduce the access and egress times and therefore the total trip time. Its conclusion is that a public urban system can never compete with a private system like the automobile for the total mass market, but must attract a much reduced travel volume consisting of trips between local areas surrounding its stopping points. This result led to access plus egress times for the air urban system on the order of 30 minutes by automobile or taxi which greatly reduced its speed advantage particularly for the shorter trips. The dominant problem in implementing an urban air system is community acceptance of the metroport, and the prime factor would be the noise of the air vehicles. A peak noise level of 85 EPndb at 500 feet is suggested as acceptable based on experience with 70 heliports in the Boston area. However, there is a need for establishing a community noise criteria based on factors other than peak noise such as frequency of service, background noise levels, number of listeners, etc. and using it to establish noise categories for metroport operation. This would give the community some assurance that the volume of noise pollution from the site can be controlled. Planning for a future urban air system is linked to planning for both future airport development and future intercity V /STOL systems. Land side congestion problems at major airports can be relieved through the provision of remote check in facilities which have an air link to the airport. The construction of new airports at sites somewhat removed from urban areas may become reasonable if urban air service exists. Similar factors affect the problems of passengers transferring from airports to metroports for intercity V/STOL service. The metroports are a ground facility common to the metrobus concept for urban air systems and intercity V/STOL, and as such link the development of these two systems. December 1970; Includes bibliographical references (p. 63-66)

Scheduling and routing models for airline systems

2019-04-12T15:08:04Z

Scheduling and routing models for airline systems Simpson, R. W. Foreword: This report attempts to put together all of the optimal computer models concerned with scheduling and routing problems for passenger transportation systems. By placing them in one place, classifying them, and using a consistent notation, it is hoped that the models' relationships to each other can be seen, and that a clear picture of the state of the art in model building and solving can be shown. The emphasis of the report is on optimal models which use well-known optimization techniques from mathematical programming. Work which uses heuristic computer methods in this area is quite extensive, but is not described here. The models are oriented towards public transportation systems operati-ng on a short haul network. Generally a cyclic or repetitive schedule of services is assumed, and a single vehicle rather than a train of vehicles is being dispatched. Within those assumptions, the models can find applicability to schedule planning for a wide range of public transportation systems, not necessarily just airline systems. The research is supported in part by the Office of High Speed Ground Transportation, Department of Transportation, and is pointed towards producing schedules for both high speed trains and future V/STOL aircraft. The models are useful to planners and regulators in studying problems in corporate planning, in transportation systems planning, and in regulation of transportation industries. An extensive bibliography accompanies each class of models in this report. If it is not complete (with respect to optimal models), I would appreciate receiving additional references from interested readers. One of the reasons for writing this report is to give a good bibliography for various groups of present researchers who seem to be unaware of segments of the literature, or of each other's activities. Much of the content of this report has been taken from lecture notes prepared by the author for an MIT graduate course, "Flight Transportation Operations Analysis", given by the author for the past few years. Students from that course will recognize the examples as being homework problems involving "Tech Airways", and I am indebted to them since some of their computer solutions are used as examples in the report. As well, the report gives an overview of current research activity in this area in the MIT Flight Transportation Laboratory. A previous report, FTL R68-5 by Professor Amos Levin describes some of the Fleet Routing models and computational methods for solving them. Other reports and theses from the laboratory are referenced where appropriate. I must also recognize the work performed by Dave Benbasset, Norm Clerman, and Thor Paalson in providing computer runs for several of the examples. iv December 1969; PB 196 528; Includes bibliographical references

Time dependent estimates of delays and delay costs at major airports

2019-04-10T10:00:08Z

Time dependent estimates of delays and delay costs at major airports Hengsbach, Gerd; Odoni, Amedeo R. Two queuing models appropriate for estimating time dependent delays and delay costs at major airports are reviewed. The models use the demand and capacity profiles at any given airport as well as the number of runways there to compute bounds on queuing statistics. The bounds are obtained through the iterative solution of systems of equations describing the two models. This computational procedure is highly efficient and inexpensive. The assumptions and limitations of the models are discussed. Common characteristics and properties of delay profiles at major airport are illustrated through a detailed example. Potential applications to the exploration of the effect of air traffic control innovations on congestion and to the estimation of marginal delay costs are also described. January 1975; Includes bibliographical references (p. 35)

A scheduling model for the aerial relay system

2019-04-08T08:17:26Z

A scheduling model for the aerial relay system Ausrotas, Raymond A.; Liu, Elliott Wu-Hsun. Introduction: The growth of air travel in the United States during the last 40 years has been caused by a fusion of technology and economics. Aircraft design improvements, resulting-in higher speed and larger size, have increased the efficiency and productivity of airplanes. Airlines have passed on these savings to the public through ever-lower ticket prices. At the same time, the U.S. economy has had substantial growth in per capita GNP (and per capita disposable income), thus compounding the consumer's ability to purchase travel. One million passengers flew in the U.S. in 1938; 240 million flew in 1978. As travel grew, the infrastructure grew with it. Old airports expanded and new airfields and terminals were built; the air traffic control system was modernized to keep pace with the jets; airlines took advantage of the computer and communications explosions and adapted them to their own needs. But eventually air travel created its own set of problems. Increased operations of jets caused the once-curious and proud residents near airports to clamor for relief from incessant noise. Improved engines and a leveling of operations due to the introduction of wide-body aircraft have abated complaints somewhat, but any plans for airport expansion are automatically resisted. Similarly, unless airports are placed far away from population areas (Kansas City, Mirabelle, Fort Worth-Dallas) and contain sufficient acreage to effectively hide the noise within the airport boundaries, they will not be built. Thus, capacity at large hubs is running out and no relief seems possible through airport expansion due to political and environmental reasons. With rapidly rising fuel costs, congestion at airports is also diminishing the productivity gains of fuel-efficient aircraft and causing the price of air travel to increase. Future technological innovations (metering and spacing of aircraft, wake vortex reduction, etc.) promise to increase airport capacity. However, the gambit of substituting ever larger aircraft for smaller ones will eventually transfer the congestion to the ground side of the airport (already Los Angeles International Airport prefers to have a wide-body operation replaced by a narrow-body -2- because of access problems). Thus, if the system of air transportation remains as currently constituted, further growth in air travel will be stymied by a combination of energy (costs and availability) and congestion (air and land) in the not-too-distant future. Such considerations have led some observers of the aviation scene to conclude that the air transportation mode is simply maturing, just as other transportation modes have in the past. Other analysts, more optimistically, note that some fundamental changes to the existing system of transporting people and cargo by air could allow growth to continue. One of the more imaginative and radical departures is the Aerial Relay System (Kyser, 1979). Briefly, in the Aerial Relay System a series of "liners", made up of "liner modules", continuously cruise over the United States at a set altitude and on a predetermined schedule. These liners are met by a fleet of "feeders" carrying aloft passengers bound for cities along the liners' routes and accepting passengers destined for their own base. The basic elements of the system are shown in Figure 1. A fully-developed Relay system could provide frequent non-stop service between practically any two cities in the United States. The advantages of the Relay system are many. The elements of the system can be tailored for their own function leading to efficiency of operation: the liners for cruise conditions; the feeders optimized for short haul take-off and climb. But the basic attraction lies in the Relay system's ability to unload the major hubs' airports by utilizing secondary (or satellite) airports and smaller city airports for the feeders' operations; since one of the major functions of airports, especially those at large hubs, is the interchange of connecting passengers between airplanes, this transfer is now performed onboard the liners. The feeder from a smaller city or secondary airport takes up passengers bound for many destinations downstream (and accepts diverse passengers for the downward journey) bypassing the hub and relieving the hub of these operations. The Relay system would thus supplement and not replace the existing airline networks; the hub-to-hub origin-destination (O-D) traffic could continue to be served by dedicated aircraft at the major airports. Alternatively, the Relay system could serve as the major O-D link between large hubs while utilizing satellite airports and thus relieving the major airports of this type of traffic. Thus the Aerial Relay System has intrinsic appeal, as it could both relieve congestion and decrease energy consumption while allowing continued growth by the air mode. Clearly, substantial engineering and design work is required before the system can be implemented. However, some questions regarding its operational feasibility can be addressed to insure that there are no fundamental drawbacks to the general concept. The scheduling of liners, i.e. the ability to calculate their position during the course of the day, and the estimation of the passenger flow in response to this service, is one such consideration. This report describes an interactive computer scheduling model to perform these functions for the Aerial Relay System. September 1979; Includes bibliographical references (p. 21)

Predicting the impact of new technology aircraft on international air transportation demand

2019-04-08T07:29:55Z

Predicting the impact of new technology aircraft on international air transportation demand Ausrotas, Raymond A. Introduction: A desire to see new places, meet different people, and perhaps conduct some business on the side has been an enduring feature of civilization. However, international travel remained largely the province of the adventuresome or the very rich until the advent of modern aircraft. The second half of this century has seen a steady expansion of the jet set as international air travel to and from the United States has risen from 1.1 million passengers (1950) to 32.8 million (1978). While in 1950 half the overseas visitors went by ship, by 1978 the ocean liner customers had decreased to less than five percent of the total travelling public. International travel is still small compared to the domestic air travel market. In 1938, when domestic trunks carried 1.2 million passengers, the airlines had two percent of the 27 billion intercity common carrier passenger miles. In 1950 airlines had increased their share to 14% (of 56 billion) and by 1978 the air share had risen to 84% (of 218 billion). In 1978, 120 million round trips by air were taken in the U.S., compared to 7.8 million U.S. citizen departures for an overseas destination. Both domestic and international traffic statistics clearly surpass growth in population from 1950 to 1980 (152 million to 223 million) and Gross National Product ($534 billion to $1,481 billion, 1972 dollars). What was responsible for this surge of travel? First of all, a reasonably safe and convenient vehicle was needed. "Most of the people who traveled on planes in the early 1930s 'had damn good reason to travel,' said C. R. Smith [President of American Airlines]. 'Their son fell off a horse, or they had to go to Mayo's --that kind of thing. There wasn't much discretionary about that kind of travel.' "The well-to-do flew. Since flying cost more, air travel was elite travel all through the 1930s. And of these, only the brave flew. A few might take a trip 'to see what it was like.' Others flew for the exaltation earthlings were still discovering in the sky. "But the dominating motive for the 474,000 passenger-flights taken in 1932 was speed. It could not have been anything else, Fortune said, because planes were not as safe as trains, and far less comfortable. One in every 2,200 who travelled that year was involved in a flying accident. Still, in 1932 a $5,000 insurance policy for a plane trip cost $2; for a train journey, twenty-five cents. Wives were still a powerful influence--they swayed men to stay off airplanes after every crash. "Manufacturers' representatives were the backbone of air travel in the 1930s. These were men who had to travel to sell, and the airlines sought their patronage." (Solberg, 1979: 220-221) In the U.S., the DC-3 revolutionized airline travel. On the Atlantic, it was the DC6-B and DC-7 and the introduction of tourist class. When growth in 1951 had fallen to only 8%, it appeared that the limit of people who were willing to pay $711 for a round-trip ticket had been reached, and Pan Am introduced tourist flights--followed shortly by planes that were operated in part as first class and in (large) part as tourist. "...tourist class brought a fantastic upsurge in Atlantic air traffic --up 17% by 1953, 9% more by 1954, then up 19% in 1955, and 20% more in 1956. By 1958 low-fare air travel constituted two-thirds of the North Atlantic business, and Pan Am found that between 67 and 77% of those flying tourist had never been in the air before." (Solberg, 1979: 347-348) In fact, Juan Trippe, Pan Am's president, said later "that the introduction of air coach ranks after Lindbergh's flight and the onset of the jetliner as the third major milestone of airline history." "The importance of that change, which preceded the arrival of jets, was that for the first time the ordinary man began to fly with us," Trippe said. (Solberg, 1979: 345) "The increase in population, in the moneyed class, in overall income played its part in this swift growth.... Tremendous promotion by the airlines and travel agents of economy fares and package vacations also had their effect." (Solberg, 1979: 406) The arrival of the jets, starting with the Boeing 707 -in October 1958 from New York to Paris and ending witwide bodiesbodies, did indeed result in a tremendous increase in travel. At last airplanes were able to fly-over the weather and, combined with dependable fan jet engine power, the reputation of air travel for reliability, comfort, and safety became firmly established. Able to purchase economy class tickets, the public rushed in to fill the seats. By 1972, according to Gallup, half the people in the United States had flown at least once. But even in the early days of jet travel, it was the business traveller who was the dominant passenger. The PANYNJ estimated in 1969 that 5% of the passengers took 40% of all air trips. Across the Atlantic, as late as 1965, the full-fare paying passenger still exceeded the discount and promotional passenger. By 1972 this percentage had decreased to 16%, as the total of all air passengers went from 3 million to 13 million. (The International Air Transport Association [IATA] surveys indicate that 70% of business passengers pay full fare, compared to 20% of vacationers.) Thus, the big upswing in international travel has been in the pleasure travel class, while business travel has increased only slightly in the last decade. The industry is still relatively young and dynamic. Across the North Atlantic, the primary international travel market, going through the air surpassed travelling on water only in 1957. Even in this relatively well established market, trends are subject to rapid change. Growth had been positive from year to year (averaging 18% from 1957 to 1973, with annual increases ranging from 9% to 27%) until 1973, when the total traffic topped out at 14 million passengers. It was 1977 before 1973 levels were reached again. Did the factors that caused growth reverse themselves, or did new factors appear and overwhelm past causes? Do the aggregate numbers hide differing cause and effect relationships? This report is an attempt to explore questions of this nature. January 1981; Includes bibliographical references (p. 45-47)

The cost of noise reduction for powered-lift S.T.O.L. aircraft

2019-04-10T10:00:07Z

The cost of noise reduction for powered-lift S.T.O.L. aircraft Moore, Wesley F. The direct operating costs and noise impacts of a wide variety of Externally Blown Flap and Augmentor Wing STOL short haul transport aircraft designs were evaluated to study the costs of noise reduction for these types of aircraft. The "two-stream" Augmentor Wing designs were found to be capable of the greatest noise reductions, and to have the lowest direct operating costs at all levels of noise impact. Sideline noise levels of 81 PNdB at 500 feet were attainable for an 80 seat aircraft with an 8 to 15 percent increase in direct operating cost over an aircraft designed with no constraints on noise. February 1973; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1973; Includes bibliographical references (p. 69-71)

General aviation Omega navigation in the national airspace system

2019-04-09T17:16:03Z

General aviation Omega navigation in the national airspace system Wischmeyer, Carl Edward Introduction: Omega navigation has great potential as a navigation sensor for general aviation aircraft. Advantages of Omega navigation include signal availability at all altitudes, and no need for overflying of various stations. Also, because Omega coverage is not localized to small geographic areas, area navigation is an implicit capability of airborne Omega receivers. For use in the National Airspace System, several questions arise: How accurate is Omega navigation? How do you use the measurements made to give navigation information? What are the noise sources? How can these noise sources be eliminated or minimized? How do you use Omega in the National Airspace System? This thesis attempts to answer these questions based upon a 70-hour flight test program, mathematical models, analysis of the literature, and the author's experience as a commercially licensed, instrument-rated pilot. The thesis rather naturally divides into two parts: the first, Chapters II through VIII, attempts to answer the questions of Omega accuracy and operational characteristics. The second part of the thesis, Chapters IX through XVI, considers the questions of Omega implementation, including regulatory aspects and details required by good operating practice. The first part of the thesis, Chapters II through VIII, concerns Omega accuracies and the results of a 70-hour flight test program. Omega noise sources discussed in the literature were used for mathematical models, and a noise source not considered in the literature is discussed and measured. This is "short-term Omega noise", which is the noise in phase between successive measurements. For long time constant receivers, this noise is not important, but for light aircraft navigation, this is an important noise source. Analysis of the Weibull distribution showed little applicability of this distribution to Omega navigation errors, based upon the experience acquired in this program with a low-cost, commercially available Omega receiver. This flight test is also discussed in Refs. 16 and 17. In addition, four approaches were flown using Omega navigation, with surprisingly good results. Based upon the flight test data and the short-term noise measurements, mathematical models were made to determine RMS error of differential Omega with variations in update rate, and path-following accuracies available using Omega. The second part of the thesis concerns Omega implementation. The various configurations of Omega receivers are discussed. These configurations differ in what information is processed and how this information is used to give position information. Present regulations for Omega receivers are discussed, and future requirements for airborne Omega receivers, such as self-test and fail-soft capabilities, are discussed. Problems of waypoint setting errors with area navigation systems are discussed, and an easy method of error detection is shown which is compatible with Omega way point definition and which will allow use of standard aeronautical charts with minimal changes. Differential Omega is discussed in terms of message content and uplink medium. The results of the thesis are boiled down into the last chapter, the Conclusions. All of the meaty points are discussed briefly. Appendices include data on the approaches flown with the Omega receiver; the data collection and reduction for the flight evaluation program; and copyright agreement restrictions on reproduction of certain figures in the thesis based upon copyrighted approach plates. June 1976; Originally presented as the author's thesis (Ph. D.), M.I.T. Dept. of Aeronautics and Astronautics, 1975; Vita; Includes bibliographical references (p. 208-210)

A multi-regression analysis of airline indirect operating costs

2019-04-12T15:08:03Z

A multi-regression analysis of airline indirect operating costs Taneja, Nawal K.; Simpson, R. W. Issued as a M.S. thesis in the Dept. of Aeronautics and Astronautics, 1967; Bibliography: p. 53-54

The ASNA formula : a new concept -- cost per passenger mile (kilometer)

2019-04-12T15:08:02Z

The ASNA formula : a new concept -- cost per passenger mile (kilometer) Nasr, Asad The demand for air transport is affected by the usual extraneous factors, demographic, social and economic, as well as those falling properly within the sphere of the industry itself such as the quality of service, safety, .reliability, punctuality, speed, frequency comfort, price. But whatever the overall volume of the demand thus determined, it will not be evenly distributed. There will always be fluctuations in the demand for the individual flights. This emphasis on the individual flight is simply a reflection of the nature of scheduled air transport and of the indivisibility of the air transport vehicle. Obviously, the use of averages would reduce the magnitude of demand fluctuations and would therefore make any analysis correspondingly less meaningful. The fluctuations in individual flight demand have wide ranging effects on several aspects of the Air Transport Industry such as scheduling, optimum size of aircraft, frequency and capacity, price elasticity and the determination of fares, etc. It will thus be observed that airlines tend to offer a level of capacity falling between the extreme values of demand, high and low. They almost never choose to operate an aircraft with a capacity sufficient to satisfy the demand for each and every flight. Equally, they are most unlikely to operate, continuously, on the basis of a virtually full aircraft. In the first case, i.e. if the airline were to operate an aircraft sufficiently large as to cater for the highest demand levels, then it would be offering excessive capacity on most remaining flights. This would mean lower average load factors and lower profitability. Such consequences are not only harmful to the airline itself but, also, to the public, as lower load factors and lower profitability will necessarily mean that fares will be maintained at a higher level than would have been possible otherwise. In the second case, i.e. where the airline is aiming at a continuous operation with a very high load factor, (say above 90%), there will be very few flights in respect of which the demand is totally satisfied by the capacity offered. On all the remaining flights, and they are the vast majority, there will be more passengers than seats, which means that certain numbers of passengers will be turned away, i.e. there will be frequent flights with overflows, some of substantial proportions. These will cause public dissatisfaction and outcry of such intensity as to harm the development of the industry and, probably, bring 3 about the intervention of regulatory authorities. Furthermore, the airline would not be maximizing its profits, since, at such load factors, as will be shown later, total profits can be increased by operating an aircraft with a greater seating capacity. Airline managements are therefore required to determine that level of capacity which, given the specific volume and fluctuations of demand on a particular route or segment, produces the optimum compromise between the above constraints. Another consequence of the fluctuations in the demand for individual flights relates to price elasticity and the determination of fares. On the basis that the demand for air transport is price elastic, the increase in demand, resulting from a given reduction in price, cannot be fully satisfied by the airline because of the fluctuations in individual flight.demand. Also, the airline itself cannot achieve the full increase in revenue indicated by the price elasticity. March 1978

Analysis of VSTOL aircraft configurations for short haul air transportation systems

2019-04-09T17:44:04Z

Analysis of VSTOL aircraft configurations for short haul air transportation systems Gallant, Robert A.; Scully, M.; Lange, William Richard. Introduction: The potential of air transportation as a means of filling the growing need for a mass short haul transportation system was investigated in Ref. 1 where all aspects of short haul air transportation systems were examined in some detail. It was concluded that air transportation could provide a promising means of relieving the congestion associated with the heavy vehicular ground traffic encountered on our urban access routes and at a cost which could well be competitive in the 1970 period with surface transportation systems. This conclusion was postulated on the basis of existing developments in the aircraft industry not yet put into practice on operating airlines but whose feasibility has been well demonstrated with experimental units. Among the many aspects of the total system which must be examined in arriving at such a conclusion are the flight vehicle characteristics. The direct operating costs (DOC) of these vehicles was chosen as a measure of their effectiveness. In short haul operations the direct costs are frequently less important than indirect costs in determining total transportation costs and hence ticket price. However the DOC is a convenient measure for estimating the relative performance of different vehicle configurations and of the penalties associated with operation off optimum conditions. Furthermore, the previous study (Ref. 1) had quantified the almost obvious need in short haul transportation for a vehicle capable of operating from highly congested areas and requiring a minimum in take-off, landing or cleared approach areas. This need directed attention to the newer concepts of vertical take-off and landing (VTOL) aircraft which would not have the speed limitation of present day helicopters, the only VTOL aircraft currently in commercial operations. Because present day experience with these aircraft indicates their direct operating costs to be several times that of comparable fixed wing aircraft, there has been a natural reluctance to predict future operating costs for these vehicles at a level which would make them effective other than in a high-priced specialized operation such as an airline feeder system. Consequently, in Ref. (1), a study of the costs and operating procedures of the existing helicopter airlines was conducted in some depth and by this means the predicted direct operating costs were removed from the realm of discussion and opinion and reduced to a matter of statistics and analysis. Maintenance costs and lost time in air and ground maneuvering were, as expected, important aspects of the cost problem and these were therefore analyzed on a quantitative basis. While there may still be room for disagreement on the predicted DOC for the various vehicles considered in this study, the quantitative information on which these are based have been carefully documented in Ref. (1) and are further substantiated in Ref. (2) for the maintenance aspects and in this report for the vehicle characteristics such as weight, fuel burned and block speeds. This additional documentation has been considered desirable not only to confirm the previous results and to explore other promising configurations, but also to provide a basis for rational discussion of the relative merits and potentials of different vehicle configurations which all too often in the past has been conducted on a subjective rather than an objective basis. -3- It may be well to reiterate the conclusion of Ref. (1) that, in face of the high indirect costs inherent in short haul systems, the actual vehicle configuration is not a dominant factor in determining total operating costs. Any well engineered configuration capable of safe all weather operations would probably prove satisfactory. However the need for direct access to city centers with a minimum of land taking does indicate the desirability of VTOL. These vehicles have the potential for appreciably reducing block times, and hence costs, in the shorter legs, below 50 miles, of interest in intra urban or suburban travel, providing present concepts of control and navigation currently under intensive development for military applications can be reduced to practice in the more legalistic environment of commercial operations. November 1966; PB-174912; Includes bibliographical references

Airport quotas and peak hour pricing : theory and practice

2019-04-10T10:00:07Z

Airport quotas and peak hour pricing : theory and practice Odoni, Amedeo R.; Vittek, Joseph F. This report examines the leading theoretical studies not only of airport peak-hour pricing but also of the congestion costs associated with airport delays and presents a consistent formulation of both. The report also considers purely administrative measures, such as quotas, and hybrid systems which combine administrative and economic control techniques. These are all compared to the real-world situation and problems of implementation discussed. The actual experiences of the Port Authority of New York and New Jersey at the three major New York area airports and the British Airports Authority at Heathrow are then presented. Both organizations administer hybrid quota/ peak-hour pricing systems in conjunction with their respective air traffic control authorities. Their experience is compared with the theoretical analyses. Work performed by the Flight Transportation Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts; and sponsored the Office of Aviation Policy, Federal Aviation Administration, Department of Transportation, Washington, D.C; May 1976; Includes bibliographical references

Application of the calculus of variations in determining optimum flight profiles for commercial short haul aircraft

2019-04-10T10:00:06Z

Application of the calculus of variations in determining optimum flight profiles for commercial short haul aircraft Gallant, Robert Alfred The method of steepest descent of the calculus of variations is used to determine the optimal flight profile of a hypothetical tilt wing aircraft travelling a distance of 50 miles. Direct operating cost, (as derived from the ATA formulation) is minimized using aircraft lift coefficient and power as control variables each with upper and lower limits. Only the portion of the flight from the end of transition to the beginning of retransition was considered, with both initial and final values of velocity, flight path angle, and altitude specified. The results show that full power is used to accelerate and to climb at a speed about twice the value for maximum rate of climb. At 12000 feet, power is reduced to flight idle and a high speed, power off glide is made to destination. A rapid deceleration is made at low altitude to achieve the specified conditions for retransition. While the optimal profiles for velocity, altitude, and power are greatly different from the nominal profiles chosen to design the aircraft (Ref. 5), the optimal trip cost of $30.54 is only slightly less than the nominal trip cost of $31.60. December 1966; Includes bibliographical references (p. 52-53)

Modeling of wind and radar for simulation in four-dimensional navigation environment

2019-04-12T15:08:02Z

Modeling of wind and radar for simulation in four-dimensional navigation environment Malherbe, Gerard Andre Disturbances affecting time control precision in four-dimension navigation are modeled. Several models of wind and turbulence from the ground to ten thousand feet are developed. A distinction is made between wind mean and turbulence and between the different layers of the troposphere. These models can be used for most cases of flight simulations. A selection of simple wind and radar models is made. Real-time computer programs using a mathematical model of a Boeing 707-320B are developed Originally presented as the author's thesis, (M.S.) in the M.I.T. Dept. of Aeronautics and Astronautics, 1976; September 1976; Includes bibliographical references (p. 97-100)

Maintenance cost studies of present aircraft subsystems

2019-04-12T15:08:01Z

Maintenance cost studies of present aircraft subsystems Pearlman, Chaim Herman Shalom; Simpson, R. W. This report describes two detailed studies of actual maintenance costs for present transport aircraft. The first part describes maintenance costs for jet transport aircraft broken down into subsystem costs according to an ATA classification. From 90 airlines polled, only four were able to supply costs in this breakdown.- Despite the lack of data, multiple regression techniques were then used to demonstrate the construction of cost estimating formulae for both subsystems and a total aircraft system. The results indicate the possibility of improving present methods of estimating maintenance costs. The second part of this report briefly describes the results of an extremely detailed study of actual maintenance costs for the rotor and transmission systems of present commercial helicopters.. The background information concerning each item of maintenance cost was examined to determine if it would be avoidable in the context of a mature airline operation with a full scale modification program for vehicle deficiencies. Muh, The results show that if only "normal" maintenance on rotor and transmission systems were performed, the potential maintenance costs for present helicopters are roughly 1.3 times the standard ATA estimate for fixed wing aircraft. November 1966; PB-174914; Includes bibliographical references (p. 64-65)

Estimates of capacity and delay for proposed runway systems : Schiphol Airport, Amsterdam, final report

2019-04-08T07:29:55Z

Estimates of capacity and delay for proposed runway systems : Schiphol Airport, Amsterdam, final report Odoni, Amedeo R.; Simpson, R. W. 1. The addition of the fifth runway at Schiphol increases the airport hourly capacity for landings by almost 100%, and the capacity for takeoffs by more than 40%. 2. The current runway system will provide good levels of service (average delays less than 4 minutes, % aircraft delayed more than 20 minutes less than 2%) until aircraft traffic reaches a level of approximately 200,000 annual operations. The current level of annual operations is 130,000. 3. The addition of the fifth runway creates a runway system which provides good levels of service until the annual traffic reaches a level of approximately 270,000 annual operations, or more than double the current level. 4. With the addition of the fifth runway, the center runway (which presently has noise problems) would not be used at current levels of traffic. If it is used only at peak times, the percentage of annual operations on this runway remains very small until an annual level of over 200,000 operations is reached. 5. The crossing problem (caused by aircraft which use the fifth runway having to cross the center runway) is not severe, and has been successfully handled at busy U.S. airports. At peak times when all three runways are used, the average wait for a crossing is less than 1 minute with the average number of waiting aircraft less than one half. The maximum number of aircraft waiting to cross ever observed will be less than four during the peaks of these busy periods. December 1976; Includes bibliographical references (p. 110)

A systems analysis of short haul air transportation

2019-04-12T15:08:00Z

Minimax network location : theory and algorithms

2019-04-12T15:07:59Z

Minimax network location : theory and algorithms Handler, Gabriel Y. For a given network let P and N denote the set of all points and the set of all nodes respectively. Let G and T denote a cyclic network and a tree network respectively and let m denote the number of centers available. The categorization scheme P N/P N/m/G T, where the first and second cells refer to the possible locations of centers and demand generating points respectively, provides for compact identification of a variety of minimax network location problems. This dissertation presents algorithms which efficiently solve all problems in this class--for example, P/P/m/G-for virtually any size of network. Moreover, tree problems can usually be solved manually. Methodologically, the tree-based results are graph-theoretic while the general case, formulated in a mathematical programming framework, leads to a highly efficient strategy for a class of massive generalized set covering problems. Originally presented as the author's Ph. D. thesis, M.I.T. Dept. of Aeronautics and Astronautics, 1974; August 1974; Includes bibliographical references (leaves 122-126)

The state-of-the-art in air transportation demand and systems analysis : a report on the proceedings of a workshop sponsored by the Civil Aeronautics Board, Department of Transportation, and National Aeronautics and Space Administration (June 1975)

2019-04-10T10:00:05Z

The state-of-the-art in air transportation demand and systems analysis : a report on the proceedings of a workshop sponsored by the Civil Aeronautics Board, Department of Transportation, and National Aeronautics and Space Administration (June 1975) Taneja, Nawal K.; Kneafsey, James T.; Workshop on Air Transportation Demand and System Analysis Introduction and summary: Forecasting air transportation demand has indeed become a complex and risky business in recent years, especially in view of unpredictable fuel prices, high inflation rates, a declining rate of aggregate population growth, and an uncertainty with respect to the regulatory structure in the aviation industry. Since the stakes are very high, the need for accurate forecasting and for a more complete understanding of the total system of air transportation continues to grow. Past forecasting methods have become inadequate for at least two reasons. First, the trend extrapolation method of forecasting is no longer appropriate due to the significant changes in both the economic and the operating environments in recent years. Second, the more sophisticated econometric forecasting models are only as good as our understanding of the total air transportation system on the one hand, and the availability of data on the other. In light of these deficiencies, the dual needs for improving forecasting methods and for increasing the reliability of data are more critical now than ever before. In short, there is a compelling need to perform basic research to improve both the forecasting methods and the data in the aviation industry. Among the various types of forecasts of aviation activity desired by the government agencies, the air carriers, the airframe and engine manufacturers, the airport authorities, and the financial community, one component that plays a critical role in long-range planning pertains to the future fleet requirements for the aviation industry. Forecast items needed with respect to future fleet requirements include types, configuration, ranges, and technologies of new aircraft so that the industry and government can coordinate their resources to maximize the interests of the producers, regulators and consumers of future air service. The National Aeronautics and Space Administration (NASA), with its twin missions of both aeronautics and astronautics, has been focusing its attention on the aeronautics component in recent years. In this overall responsibility, the Systems Study Division of NASA-Ames Research Center has as one of its main objectives the development of a better understanding of the civil air transportation system in the United States, with emphasis placed on the proper and timely application of new technology. In order to fulfill this objective, the division has a critical need for projections of the growth of demand and for the determination of the role of technology in the future growth of air transportation. Before undertaking an extensive research effort in the area of air transportation demand analysis and forecasting, NASA-Ames attempted to solicit the views of the industry and other government agencies at a one day informal meeting in San Francisco in December 1974. The meeting was attended by about twenty experts from the carriers, airframe and engine manufacturers, U.S. Department of Transportation, universities and NASA. The goals of this mini-workshop were three-fold: the first objective was to determine the ways in which the NASA-Ames Systems Study Division could play a supportive role in this area; second, it was essential to receive an informal endorsement from the industry and other government agencies; and third, it was necessary to determine the direction for the proposed research. This meeting concluded with a general agreement on a definite need for future research, with the belief that not only could NASA-Ames play a supportive role but, more important, that it could play a catalytic role. However, due to the limited participation in this one-day meeting and the assistance that the proposed research could have provided to a wide variety of users, a more extensive workshop was proposed at that time, possibly to be co-sponsored by other government agencies. Subsequent to the December 1974 meeting, further discussions with the U.S. Civil Aeronautics Board (CAB) and the U.S. Department of Transportation (DOT) resulted in a three-day workshop co-sponsored by the CAB, DOT and NASA. The reasons for the joint sponsorship by the CAB and DOT reflected a desire from these agencies to participate in the search for methodologies and information on the long-range benefits, problems and issues of technological advances in aviation and to assist NASA in deploying its funds on these matters in the most productive and efficient ways. The overall objectives of this workshop were four-fold: first, to investigate the state-of-the-art in air transportation demand forecasting; second, to determine the needs of the various government agencies and the industry; third, to assess the possibility of long-term government sponsorship of basic research to improve the forecasting of air transportation activity; and fourth, to determine the most promising areas of research in air transportation and systems analysis. This workshop was organized by the Flight Transportation Laboratory of the Massachusetts Institute of Technology and the Transportation Center at Northwestern University and was held at the Mayflower Hotel in Washington, D.C. on June 2-4, 1975. The meeting was attended by one hundred experts, thirty-three of whom made extensive presentations. This report then is a summary of the highlights of the presentations delivered at the workshop, with appropriate interjections and editorial comments as perceived by its authors. August 1975

The dynamic scheduling of aircraft in the near terminal area

2019-04-12T15:07:58Z

The dynamic scheduling of aircraft in the near terminal area Dear, Roger George Aircraft arrive in a random fashion into a terminal area seeking to land at a given runway. The aircraft are differentiated by their landing velocities. All aircraft are required to maintain a prespecified minimum horizontal separation distance and also fly on a common final approach. As a consequence, the minimum interarrival time separation is interactive, i.e., a function of the landing velocities of the preceding and following aircraft as well as the separation minimum and final approach length. The controller's decision-making problem in sequencing the aircraft, termed dynamic scheduling, is formulated in this dynamic environment. It is observed that the first-come, first-serve discipline is inefficient and the system properties employing optimality objectives of maximum throughput and minimum delay are investigated. The solutions must be updated with each new arrival and, as a result, the solutions employing these optimality objectives are shown to have undesirable properties, including 1) a priority structure with the potential for indefinite delay; 2) non-implementable updating assignments; 3) computationally intractable solutions in real time. As a consequence of this analysis, a decision methodology termed Constrained Position Shifting (CPS) is proposed to eliminate these undesirable properties. CPS prohibits an aircraft from being shifted more than a given number of positions from its first-come, first-serve position. The CPS methodology is then shown via simulation to be practical, efficient and extremely flexible, with the following properties: 1. increases the runway throughput rate; 2. treats individual aircraft equitably; 3. treats aircraft velocity classes equitably; 4. particularly successful during peak periods; 5. well within the capabilities of today's computers. The simulation is designed to compare identical arrival streams under various strategies. The simulation-aided analysis is then extended to include "heavy" jets (with aircraft dependent separation minima) and also mixed operations (arrivals and departures). Even greater improvements in terminal area levels of service are demonstrated for these extensions. Originally presented as the author's thesis, (Ph. D.) in the M.I.T. Dept. of Electrical Engineering and Computer Science, 1976; September 1976; Includes bibliographical references (p. 316-318)

A methodology for determining the relationship between air transportation demand and the level of service

2019-04-10T10:00:04Z

A methodology for determining the relationship between air transportation demand and the level of service Eriksen, Steven Edward; Scalea, John; Taneja, Nawal K. Introduction: Within the last ten years significant advances in the state-of-the art in air travel demand analysis stimulated researchers in the domestic air transportation field. Among these advances, researchers in academia, industry, and government have investigated the relationship between observed demand and general level of economic activity such as GNP on the one hand and general passenger-perceived characteristics such as fare on the other hand. Advanced econometric techniques have been used to develop these relationships. However, to date very little effort has been devoted to investigating the impact of a change in the supply of air transportation service on the demand for air transportation. Thus, for all practical purposes, there are no analytical economic models which show the complex interrelationship between the supply of and the demand for air transportation. This research report is an attempt to begin to understand these complex interrelationships. During the sixties the demand for air transportation services experienced substantial growth rates due to the fact that fares (in constant dollars) were continually declining (because of increasing productivity of transport aircraft) and partly due to the fact that the level of service offered was continuously increasing, again the result of improvements in technology. However, at the beginning of the current decade the growth in the demand for air transportation services began to exhibit radical and unforeseen changes. These changes were caused by a reversal of the impact of the two factors mentioned earlier, namely that the fares were now increasing (due to rapidly increasing costs, particularly with respect to the price of fuel) and the level of service was decreasing, particularly evidenced by fewer total flights and fewer direct flights. The demand models developed in the sixties were adequate to caution airline managers on the impact of changes in the general state of the economy and changes in fare level. However, since these models did not adequately incorporate the factors relating to the supply of air transportation services, very few analysts were able to predict the impact of a change in the level of service. As a result, the industry was quite surprised to observe suppressed traffic growth rates when the level of service offered was changed as a result of a general recession in the economy and shortage of fuel. Due to the deterioration in the financial position, the carriers began to cut costs by reducing further the level of service offered. However, instead of improving the profitability of the carriers, this strategy further suppressed traffic and hence revenue, resulting in even lower profits. On the basis of evidence from the above discussion, there is now a critical need for the development of economic models that simultaneously incorporate the factors effecting both the demand and the supply of air transportation services. In order to begin to fulfill this need, the Aeronautical Systems Office of Ames Research Center at NASA funded a research project to investigate how the supply related variables (particularly those related directly to technology) contribute to the determination of the demand for air transportation. The research was divided into two parts. The first part, mostly exploratory in nature, was designed to determine whether sophisticated economic models incorporating supply and demand factors can be developed given the state-of-the-art in econometric modeling and the limitations of the existing data. During this phase the thrust of the research effort was first to analyze the existing data, second to analyze the components of the levels of service and third to develop simple models which serve merely to generate avenues of pursuit for further research in the second phase. This report presents the results of the initial exploratory phase of the research project and contains directions for research in the second phase to be carried out in 1976. During the first phase, research efforts were directed at investigating single equation models incorporating a level of service index in addition to the usual fare and socioeconomic terms. The models were calibrated using data from fifty-eight region pairs over a sixteen year period. The level of service index developed in this report represents an improvement over the one incorporated in past models (namely flight frequency). The new level of service index is a nondimensional generalized trip time scaled from zero to one, which takes into account not only the number of flights, but also number of intermediate stops, direct or connecting service, speed of aircraft and most important, the matching of the departure schedules to time variability of demand. Based upon the preliminary results, it appears that the level of service is a more appropriate explanatory variable in the demand model than just frequency. The significant results of the demand models developed in this exploratory stage of the research will be discussed in the following sections of this report. Section 2 describes the reasons for calibrating the models based upon region pair data rather than city pair data. Section 3 differentiates between the supply and demand components of air travel and elaborates upon the development of the level of service index. Section 4 discusses the sampling procedures used in determining the region pairs. Section 5 contains the specification of the single equation models and presents the empirical results. The final section of this report outlines the plans for future research in Phase II of this project. January 1976; Includes bibliographical references

Changes in air transport policy : the problem of regulating a market in transition

2019-04-10T10:00:04Z

Changes in air transport policy : the problem of regulating a market in transition Rabň, Hans A lecture given for the summer course "Air Transportation -- Management, Economics and Planning" presented under the auspices of the Flight Transportation Laboratory and the Center for Advanced Engineering Study of the Massachusetts Institute of Technology Cambridge, Massachusetts; July 1, 1981; Includes bibliographical references (p. 10)

Proceedings of the NASA/MIT Workshop on Airline Systems Analysis, Waterville Valley, New Hampshire, July 10-21, 1972

2019-04-10T16:40:47Z

Proceedings of the NASA/MIT Workshop on Airline Systems Analysis, Waterville Valley, New Hampshire, July 10-21, 1972 Vittek, Joseph F. Introduction: The recent renaming of the NASA Office of Advanced Research band Technology as the Office of Aeronautics and Space Technology emphasizes the new stress being placed on aeronautical research by the Federal government in general, and NASA in particular. Aeronautical research at NASA now engages 5,300 people with an annual budget of $110 million dollars and addresses such problems as: - Major reductions in aircraft noise, particularly by developing a very quiet short-haul aircraft. - Improved automated air traffic control - Encouragement of development of vehicles for both high- and low density short-haul markets. - Development of an experimental approach to test and verify not only technical concepts, but also market characteristics, social benefits and the like. Research and development are essential to the solution of current problems, as they always have been. They are also essential if the full potential of civil aviation is to be realized. However, it must be recognized that neither today's nor tomorrow's problems are solely technological. Solutions will involve not only traditional applications of the physical sciences but also the techniques of economic analysis and the social sciences. Technological advances are subject to a variety of institutional constraints which can be categorized as regulatory, legal, financial, social, attitudinal and the like. All of these factors must be examined and are an essential part of both the problems and their solutions. Although it is realized that NASA's role in seeking solutions to these problems is essentially technical, it is imperative that the technologist be familiar with the additional constraints that the social and legal systems impose on technical designs. As an example, future aircraft engines must not only provide more thrust, but they must do so economically and quietly. The purpose of the summer workshop was to provide a background and insight into these non-technical areas for NASA personnel who will be involved in both the direction and implementation of the technical programs to ensure end products that are acceptable to the market place and the public in general. As was stated in the CARD study: ... the scope of civil aviation research and development should be expanded to increase emphasis on nonphysical sciences such as economics and sociology." The workshop consisted of a two-week series of lectures and discussions by leading academic government and industry personnel in the field of flight transportation, covering the interface between technology and the remaining aspects of the air system. The workshop was held at Waterville Valley, New Hampshire. This site was chosen, because it is away from the normal business setting, thus freeing participants from the daily interruptions of their office routines and offering them a fresh setting in which to immerse themselves in the subject material. The presentations, as reported here, are not compiled chronologically but rather they are grouped according to major topic and also from the more basic to the more advanced within each topic. This is done so as to give the reader the proper background and continuity. November 1972; Includes bibliographical references

A computer simulation of Tampa International Airport's landside terminal and shuttles

2019-04-12T15:07:57Z

A computer simulation of Tampa International Airport's landside terminal and shuttles Blumer, Terry P.; Simpson, R. W.; Wiley, John R. TOPSIM, a terminal simulation package developed at M.I.T., was used to simulate Tampa's landside terminal and to study its capacity-congestion characteristics as traffic levels increase. Tampa has no congestion problems at present, processing 5 million passengers per year, but may in the future. TOPSIM indicates that congestion arises at the ticket counters and on the critical segments of the elevator cycle when annual traffic volumes reach 14+ million passengers. TOPSIM's modular design has sufficient flexibility to handle a variety of airport layouts without major reprogramming effort. The package was previously used to simulate passenger flows for hypothetical "Metroport" terminals (handling passenger volumes similar to LaGuardia) and for Eastern Airlines' terminal at Logan. It produces performance statistics on passenger movements (such as total distance walked and time spent standing in queues), and on facilities (such as utilization of ticket booths). TOPSIM's application to Tampa demonstrates its ability to handle other than "shuttle" oriented terminals. In fact, it can theoretically simulate any terminal regardless of trip type or mode, since the passenger processing routine is similar for most terminals. Cover title; April 1976

An analytical study of advanced terminal area air traffic management and control

2019-04-08T07:29:55Z

An analytical study of advanced terminal area air traffic management and control Hsin, Chen-Chung This dissertation gives a comprehensive study of the theory and practice of the advanced terminal area air traffic management and control. The entire terminal area ATM/C system has been formulated as a feedback control system, with individual subsystems identified and described. The ground control system, which is one of the two major control elements in the system, has been studied in detail. Definitions, purposes, input, output, and the processing steps of the control functions in the ground control system have been discussed. Automation of these functions has been recommended. One of the control functions, namely, the path generation function has been presented to demonstrate the automation implementation. Formulated as a two point boundary values problem (TPBVP) of optimal control, solution techniques and numerical examples of the path generation problem have been presented. A Newton-Raphson method on trajectory optimization has been used to carry on the computer simulation. Finally, a one-degree-of-freedom, speed control final approach problem has been presented to demonstrate the application of parametric error analysis to ATM/C system performance evaluation. Originally presented as the author's thesis, (Ph. D.) in the M.I.T. Dept. of Aeronautics and Astronautics, 1976; September 1976; Includes bibliographical references

Vehicle routing and scheduling for the ultra short haul transportation system

2019-04-12T15:07:56Z

Vehicle routing and scheduling for the ultra short haul transportation system Smith, Barry C. A method of vehicle routing and scheduling for an air based intraurban transportation system is developed. The maximization of level of service to passengers in a system operating under time varying demand is considered on both the optimal and heuristic levels. It is shown that while the determination of an optimal schedule is mathematically feasible, it is computationally impractical. Heuristic vehicle control algorithms are developed and tested using computer simulation. It is shown that, as compared to fixed routing strategies, dynamic vehicle routing strategies provide a greater level of service to passengers while substantially reducing the direct operating costs of the system. July 1979; Includes bibliographical references (p.195-196)

Feasibility of New York Airways expansion to Nassau County : progress report

2019-04-12T15:07:56Z

Feasibility of New York Airways expansion to Nassau County : progress report Mann Robert Wellesley A short-haul helicopter service demand analysis on journey to work trips between Nassau and Suffolk counties and the New York central business district was performed over several operational policy/scenario combinations. Results indicated that there was sufficient demand to support multiple rotorcraft additions to the New York Airways Fleet. Market penetrations ranged from 1.9% to 6.0% over the policies/scenarios envisioned. Sensitivity analyses were performed on level of service parameters including fare, frequency, service patterns, and heliport location indicating a high degree of flexibility to be possible in any demonstration program. Fleet requirements were calculated as a function of overall level of service and a sample fleet assignment and schedule proposed. The proposal - to handle the mean demand forecast - consists of three 25 passenger helicopters, 150 flight segments, 2100 route miles/day and a utilization approaching 8.5 hours/aircraft/day. System averages are 13.8 mile stage lengths and 9 minute block times. Sixteen peak hour round trip frequencies flown to Wall Street from three suburban heliport locations include twelve nonstop and four one-stop services. Eight peak hour round trip frequencies are offered to 59th Street (Vic. Central Park), LaGuardia and Kennedy. Load building multi-stop routes were flown between the outer suburban heliports and the innermost transfer point location in western Nassau County. System planning for off peak use was not examined, but will add to flight utilization and latent demand stimulation in the non-business sector. The overall utility of the proposed addition to the NYA route structure could be maximized by careful interfacing with the currently operated routes. April 1976; Includes bibliographical references

Energy and U.S. airline traffic

2019-04-12T15:07:55Z

Energy and U.S. airline traffic Higginbottom, Samuel L.; Burgess, E. H. Introduction: THE U.S. AIRLINE INDUSTRY HAS BEEN EXPOSED TO A PERIOD OF MAJOR SURGERY DURING THE PAST THREE YEARS AND HAS SURVIVED. VIEWED FROM THE STANDPOINT OF THE CAB, IT WAS NATURAL THAT THE GREAT IMPROVEMENT IN PROFITABILITY WHICH OCCURRED IN THE FIRST TWO YEARS BE DIRECTLY ATTRIBUTED TO THE SURGERY WHILST THE DOWNTURN THIS YEAR WAS CAUSED BY THE CYCLICAL NATURE OF THE BUSINESS. OTHERS BELIEVE THAT THE UPTURN IN PROFIT WOULD HAVE BEEN EVEN MORE DRAMATIC HAD IT NOT BEEN FOR THE ACTIVITIES OF THE CAB AND THAT THE DOWNTURN WAS GENERATED BY FARCICAL TARIFF STRUCTURES. WHATEVER THE POSTMORTEM ON THE LATE 1970'S REVEALS, DEREGULATION IS NOW INEVITABLE ALTHOUGH ITS TOTALITY REMAINS IN DOUBT; CYNICS TEND TO BELIEVE THAT CONGRESS AND THE ADMINISTRATION WILL SHY AWAY FROM THE FINAL ACT OF COMPLETELY DEMOLISHING THE CAB. THE 1979 Iranian COUP GENERATED ONE MORE ENERGY CRISIS WITHIN THE UNITED STATES. IT, AND SUBSEQUENT FEDERAL ACTIONS, ARE UNLIKELY TO CREATE AN EXTENDED SHORTAGE OF PETROLEUM PRODUCTS IN THE UNITED STATES BUT HAVE PRODUCED A SIGNIFICANT INCREASE IN ENERGY COSTS WHICH WILL CONTINUE TO INCREASE, THE AIRLINE INDUSTRY IS ONLY A MINOR USER OF LIQUID HYDROCARBONS BUT IS NONETHELESS HIGHLY VISIBLE. ITS USE OF ABOUT 4 TO 5 PERCENT OF THE U.S. TOTAL CONSUMPTION OF OIL LEADS TO MORE CONTROVERSY THAN IS THE CASE IN ALMOST ANY OTHER CONSUMER SEGMENT; AS ONE POLITICAL COMMENTATOR PUT IT, "AIRLINES DON'T HAVE MANY VOTES." IN CONSEQUENCE, THE INDUSTRY'S LONG-TERM PLANS TEND TO SUFFER PERTURBATIONS DEPENDENT UPON BOTH THE FUEL SITUATION AND POLITICAL ACTIVITY RESULTING THEREFROM, THERE IS HEIGHTENED CONCERN IN THE UNITED STATES THAT THE DETERIORATION IN Iranian OIL SUPPLY, THE PRESENT GLUT, AND THE DOWNTURN IN THE ECONOMY MAY RESULT IN AN EXTENDED SHORTAGE AS MORE OPEC SUPPLIERS CURTAIL PRODUCTION IN THE INTERESTS OF INCREASING PRICES.AND CONSERVING THEIR RESOURCES. SOME OF THE RECENT U.S. GOVERNMENTAL DECISIONS ARE AIMED AT REPLACING IMPORTED OIL WITH ADDITIONAL DOMESTIC PRODUCTION; OTHERS ARE DIRECTED AT REDUCING DOMESTIC DEMAND. WHILST REDUCTION IN SUPPLY, EVEN OF A TEMPORARY NATURE, WOULD OBVIOUSLY SEVERELY AFFECT THE AIRLINE INDUSTRY, A REAL GASOLINE SHORTAGE WOULD HAVE A MORE PERVASIVE EFFECT ON THE WHOLE ECONOMY AND WOULD GENERATE SECOND-ORDER CHANGES IN MANY ASPECTS OF U.S. LIFE. THE OBJECT OF THIS LECTURE IS TO REVIEW THE LIKELY EFFECTS OF CHANGING U.S. OIL POLICIES ON THE U.S. AIRLINE INDUSTRY. Seminar, July 1, 1980, to Summer Course 'Air Transportation -- Management, Economics and Planning' sponsored by Flight Transportation Laboratory/ Center for Advanced Engineering Study Massachusetts Institute of Technology; July 1980

Aircraft requirements for low/medium density markets

2019-04-10T10:00:03Z

Aircraft requirements for low/medium density markets Ausrotas, Raymond A.; Dodge, Steven Malcolm.; Faulkner, Henry B.; Glendinning, I.; Hays, Anthony P.; Simpson, R.; Swan, William M.; Taneja, Nawal K.; Vittek, Joseph F. Introduction: In 1971, the joint Department of Transportation, National Aeronautics and Space Administrations, Civil Aviation Research and Development Policy Study (CARD) Report, identified the problems of providing air service to low density, short haul markets, as the third most pressing difficulty facing the United States' aviation industry. In the words of the report, "Low-Density Short Haul: While lower in priority than noise and congestion, solutions to the problems of low-density, short-haul service will be important to the future of civil aviation and to its ability to contribute to the goals of the Nation. This service of civil aviation can be a positive force in future regional development. In order to obtain a better definition of the problems and potential of low-density, short-haul service, a program should be established to determine accurately market sensitivities to changes in service, fare, frequency, and equipment. A government-sponsored market demonstration is required for this purpose. Concurrent and integrated with this demonstration, the Government should fund studies for the conceptual design and analysis of economical vehicles for the low-density, short-haul market." (Emphasis Added, p. 2-6) In response to this policy statement, NASA has undertaken a number of technical and systems studies as outlined by Mr. George Cherry, Deputy Associate Administrator for Aeronautics and Space Technology (Programs) in his 1972 testimony before the U.S. House of Representatives' Subcommittee on Aeronautics and Space Technology of the Committee on Science and Astronautics. "1 In FY 73, NASA programs relating specifically to low-density, short-haul will fall into three main categories: a. Continuing an effort begun in FY 72 which is identifying technology problems associated with providing economical air service to sparsely settled regions. b. Continuing an effort begun in FY 72 which will investigate and develop very-low-frequency navigation techniques for en route and terminal area navigation for civil aviation, especially low-density, short-haul service. c. Increasing knowledge of economic and operational factors which bear upon technology and aircraft requirements. Studies will be undertaken to fit existing and hypothetical aircraft into realistic low-density, short-haul arenas and to identify where and why economic short-comings appear. Those that can be improved by technology will be identified. In addition, programs will be undertaken to investigate: ride-quality improvement as it influences aircraft design and passenger acceptance, crosswind landing characteristics, and operational techniques." This study attempts to answer some of the questions in Item C. Statement of responsibility on title-page reads: R. Ausrotas, S. Dodge, H. Faulkner, I. Glendinning, A. Hays, R. Simpson, W. Swan, N. Taneja and J. Vittek; September 1973; Includes bibliographical references (p. [197]-[199])

New directions for forecasting air travel passenger demand

2019-04-10T10:00:02Z

New directions for forecasting air travel passenger demand Garvett, Donald Stephen; Taneja, Nawal K. While few will disagree that sound forecasts are an essential prerequisite to rational transportation planning and analysis, the making of these forecasts has become a complex problem with the broadening of the scope and variety of transportation decisions. Until recently, the forecasting methods available addressed the issues which were important a couple of decades ago. These methods attempted to predict the amount and in some cases character of travel to be used in designing major highways, transit facilities, seaport facilities, and airports. However, today's issues to be addressed in transportation are much broader and more complex. For example, in the modern process of transportation planning, the decision-maker is concerned with the broad range of social, economic and environmental effects, equity issues, wider range of options including not building major facilities, resource constraints such as energy, and increased public participation in the planning process in general. The complexity of the problem has necessitated the planner's developing improved methods of forecasting the demand for transportation at all levels and by all modes. While significant contributions have been made recently to the development of improved methods in forecasting, we are still a long way from possessing tools which provide our decision-makers with more effective, that is, more useful, accurate and timely information. The purpose of this report is to present a very brief overview of the current and emerging air transportation forecasting methods with the aim of identifying areas which need further research. Throughout the report, the object is to indicate future directions for research into transportation forecasting methods which are more responsive to today's issues. For example, it is clear from reviewing the literature that tremendous improvements in travel forecasting methods can be achieved through deeper understanding of the traveler's behavior, under a range of conditions, development of models which are more policy-responsive and development of improved data bases. Peculiarities of the airline industry and aviation in general cause many standard techniques of economic and managerial analyses to break down. Air travel demand is unique in that even the sophisticated techniques developed by urban transportation analysts are often not directly applicable to modelling the demand for air transportation. Econometricians usually do not have specific training in air transportation. Airline managers, on the other hand, quite often do not have the technical background necessary to fully understand many highly detailed and complex models. In order to develop sophisticated yet user-oriented models, an analyst must have background in several areas. It is hoped that the material presented in this report will help bridge the gap between managerial and technical personnel and provide some new directions for air travel demand modelling. Generally speaking, there are two broad categories of forecasting methods. The quantitative group is composed of techniques which rely on the existence of historical data, and which assume that the historical trend will be expected to continue in the future. This group is further divided into two classes, time-series methods and causal methods. The quantitative techniques are by far the most widely used and contain such popular methodologies as moving averages, classical decomposition analysis, spectral analysis, adaptive filtering and Box-Jenkins methods under the category of time-series analysis. The causal methods contain such favorites as modelling classical consumer behavior through regression models and more recent applications in transportation demand analysis of Bayesian analysis, Markov chains, input-output analysis, simulation methods and control theory models. The second group of forecasting methods is qualitative in nature. The techniques in this group are used when none or very little historical data exists, or when the underlying trend of the historical data is expected to change. Qualitative techniques have in general been applied to project future technological developments and their impacts are described in literature as "technological forecasting methods." The group is further divided into two classes, exploratory and normative methods. The exploratory methods start with today's knowledge and its orientation and trends and seek to predict what will happen in the future and when. On the other hand, normative methods seek first to assess the organization's goals and objectives and then work backwards to identify new developments which will most likely lead to the achievement of these goals. Familiar examples of exploratory methods are the envelope, logistic or S-curve, the Delphi technique and morphological analysis. Examples of methods used to perform normative forecasting are relevance trees and cross impact analysis. Although this classification scheme is consistent with the way that many forecasters might differentiate models, it is by no means unique. Other and perhaps better classification schemes exist. For the purposes of this report we will not attempt to define a particular classification but present five broad areas which show the greatest potential for improving our capabilities of modelling the demand for air transportation. These areas are: technological forecasting, time-series models, control theory models, econometric models and simulation models. Each of the general techniques are reviewed, and specific examples are presented where relevant. Excessive mathematical detail was avoided in order to make this work easily understandable by managers and others who might not have a rigorous analytical background. Since a number of models discussed in the report require extensive computer modelling, we have included a few computer programs in the appendices to make the report more user-oriented. July 1974; Includes bibliographical references (p. 160-163)

Air service to small communities-directions for the future : final report of the Workshop on Low/Medium Density Air Transportation

2019-04-12T15:07:55Z

Air service to small communities-directions for the future : final report of the Workshop on Low/Medium Density Air Transportation Vittek, Joseph F. Introduction: In the decade between 1962 and 1972, certificated air service was deleted at about 250 points in the United States. In some of these cases, the service was no longer needed because of improved highway access to communities of interest. In other cases, the rapidly emerging commuter carrier industry replaced certificated carriers at marginal points However, in many cases, the cities were left without adequate transportation In addition, many cities that have never received air service now face a similar plight. The federal government, through the creation of the local service air carriers in the mid-1940s and their subsequent subsidy, has attempted to provide better air service to the nation's smaller towns. But the questions persist Is the federal subsidy program effective? Should federal regulation and/or subsidy be extended to commuter carriers? Indeed, should the federal government subsidize this type of service at all? What national goals does subsidy support? Perhaps most important, who should be formulating the answers to these questions?. February 1974; Includes bibliographical references

The development of an operational game for the U.S. domestic airline industry

2019-04-12T15:07:54Z

The development of an operational game for the U.S. domestic airline industry Elias, Antonio L. Introduction: The use of computer simulations to analyze large complex systems is now a well-established technique. By combining detailed numerical models of each component of the system, the behavior of the entire system can be simulated, observed, and analyzed; some examples of systems that have been successfully designed and analyzed by means of computer simulations are communications networks, the Microwave Landing Systems (MLS) that competed for the ICAO standard, and many aircraft and spacecraft, such as Apollo and the Space Transportation System ("Space Shuttle"). Attempts to simulate systems that involve human decisionmaking (principally economic and economy-related systems) have not been so successful. The difficulty in modeling an individual's decision-making process: leads to the impossibility of fully modeling such systems, short of including a human element in the simulation itself. This is precisely the essence of the gaming approach to system simulation a number of "players" (properly called "game participants") drive, with their decisions, numerical models of the other components of the system under consideration. This effort is motivated by the author's belief that research on domestic air transportation may benefit from the use of such a game for the following reasons: a) There is a significant number of mathematical models developed or in development about elements of its operations, which have not been integrated. b) The industry is reaching a turning point, namely deregulation, which increases the relative importance of the human decision-making element over a wider range of options. The effort undertaken in past years to develop and refine mathematical models for the airline industry, was made possible in part by the wealth of numerical data available. In their unique position between private industry and the public utilities, the airlines have been forced to keep and make public a staggering amount of data. The high technology environment that permeates the industry has enhanced both the quantity and quality of this data gathering effort, and the uses of this data for model-building (and analytical) purposes. These models are highly interrelated, but in general are used individually by making simple assumptions about other elements of the system. Thus, sophisticated demand models assume simple statistical supply functions, supply models assume non-competitive environments, etc. A computer simulation, such as the one required for this game, seems to be the ideal way of integrating many of these models in a coherent fashion, while the gaming dimension acts as a surrogate for the unmodelable human decision-making component. One of the consequences of the current trend towards deregulation in the air transportation industry is an increase in the freedom and range of management decisions. This in turn increases the relative importance of the human decision-making element in the total environmental uncertainty in which the industry must operate. The difficulty in modeling the individual decision-making process indicates a gaming approach to systems analysis. Also issued as a Ph. D. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1979; February 1979; Includes bibliographical references (p. 199-202)

Air transportation in the 1980's, and the role of IATA : address :

2019-04-09T19:26:58Z

Air transportation in the 1980's, and the role of IATA : address : Hammarskjl̲d, Knut "(Ladies &) Gentlemen, I am grateful for this opportunity to talk to you about the developing scene in the civil air transport industry. And to take a look at the evolving role of IATA - the International Air Transport Association - in the 1980s. It is particularly gratifying to me that some of you are from younger countries where airlines are growing and preparing themselves to play their part in international commerce as an instrument for national development. About two-thirds of present ICAO members did not exist at the time when ICAO and IATA were created or re-created in the mid 40s. If anything, this is indicative of the major changes which have taken place since in world aviation. It may be helpful if I start by giving a brief description of IATA and its activities. The organization is the trade association for scheduled international and domestic airlines. There are currently more than 100 member airlines from some 85 nations. An additional 137 airlines are our interline partners as signatories to the multilateral IATA standard interline agreements. It is a voluntary, non-exclusive, non-political organization which follows democratic decision-making procedures. I emphasize that it is non-political. This means that the airline representatives from nations with differing economies and political philosophies can and do come together to discuss matters of mutual interest in a friendly and cooperative manner. This is to the benefit not only of the airlines themselves but of their all-important customers - the passengers and cargo shippers worldwide. Furthermore, their governments - which for political reasons sometimes simply cannot talk to each other - greatly benefit from this neutral forum and instrument for the solution of aviation problems. Here, I should add sometimes there are also other problems with heavier political overtones ... July 9, 1980

The marketing of international air transportation in the USA

2019-04-10T10:00:01Z

The marketing of international air transportation in the USA Meredith, John D'A Introduction: I am very honoured to have been invited to talk to you today at such a distinguished place of learning as the Massachusetts Institute of Technology. I understand that you have already had talks from several far more distinguished members of the aviation community, including the Chairman of the Civil Aeronautics Board and the Director General of the International Air Transport Association, so by now you are certainly well aware that international aviation has reached a critical, and some would say, crucial stage in its development. In spite of all the talk of deregulation which you will have heard within the last few years, there is nevertheless no doubt that in international aviation airlines remain at the mercy of decisions by governments, and indeed cannot operate unless the governments of the countries between which they wish to fly permit them to do so. There is not time in this lecture to discuss this subject in detail, but you can do no better than read Professor Taneja's excellent book on U.S. international aviation policy* if you wish to obtain a clear understanding of the implications of government policy for international aviation to and from the USA.. July 1980; Seminar, July 15, 1980, to Summer Course, "Air Transportation -- Management, Economics and Planning" sponsored by Flight Transportation Laboratory/ Center for Advanced Engineering Study Massachusetts Institute of Technology Cambridge, Massachusetts 02139; Includes bibliographical references

An advanced time-dependent queueing model for airport delay analysis

2019-04-12T15:07:53Z

An advanced time-dependent queueing model for airport delay analysis Roth, Emily Jane Introduction: In the past several years many attempts have been made to model the probabilistic nature of airport runway operations using a queueing-theoretic approach to runway modeling. Early studies were limited by computational considerations to examination of systems only once they reached "steady state". These models were unable to reflect the characteristic hourly "rises" and "falls" of demand for runway use at major airports. Koopman was the first to include time-varying demand in a queueing model of a runway. He examined simple M(t)/M/l and M(t)/D/1 models with planes awaiting landing or takeoff placed in a single common queue. By using advanced numerical techniques he showed that the airport system equations can be solved recursively through the computer to exhibit the system behavior as a function of time. A later study by Hengsbach and Odoni extended these models to include the case of k independent runways. This study also resulted in a set of computer programs which increased tremendously the computational efficiency of this approach. In this report we explore, for the first time, time-dependent queueing-theoretic models in which landing and departing aircraft are kept in separate queues. This allows explicit acknowledgement of various sequencing strategies by air traffic controllers and computation of separate statistics for delays to landings and to takeoffs. The report is organized into several basic sections. Expanding on an idea introduced by Koopman, we begin with the development of a basic two-queue runway model under time-varying demand. We then present an extended model which more realistically reflects actual airport runway situations. Third, results from an experimental investigation with these models are presented, including comparisons with the earlier single-queue model. Section 4 is a discussion of the expected delay to aircraft in these two-queue systems. Finally, we mention some simple extensions and suggest directions for further study. October 1979; Includes bibliographical references (p. 61)

Proceedings of the Workshop : Air transportation Demand and System Analysis.

2019-04-12T15:07:52Z

Proceedings of the Workshop : Air transportation Demand and System Analysis. The Workshop was jointly sponsored by the Civil Aeronautics Board, Dept. of Transportation, and National Aeronautics and Space Administration; August 1975"--Cover. -- "September 1975"--t.p; Includes bibliographical references

Effect of fare and travel time on the demand for domestic air transportation

2019-04-12T15:05:47Z

Effect of fare and travel time on the demand for domestic air transportation Eriksen, Steven Edward; Liu, Elliott Wu-Hsun. Introduction: One of the axioms in the air transportation industry is that advances in technology have led to a greater amount of passenger travel by air. Improvements in airframe and engine design have increased range, speed and payload and have decreased seat-mile costs (in constant dollars), while simultaneously introducing more comfortable and safer travel. The resultant lower ticket prices have made pleasure travel steadily more attractive in the competition for the consumer's disposable income, while the availability of comfortable, high speed travel has increased the air mode's share of business travel. However, it has not been a trivial matter to determine the magnitude of travel that can be attributed to advanced aircraft technology. NASA, as the U.S. government agency responsible for research and technology in commercial aviation, has a natural interest in the applications of the technological improvements it has helped to create. Thus NASA has sponsored research analyzing the economic and operational impact of technological innovations; some of these studies have attempted to quantify the demand for air transportation that improvements in technology have brought about. This report presents the final results of an econometric demand model developed by the MIT Flight Transportation Laboratory under NASA sponsorship over the course of the last three years. During the first two years the conceptual framework for the model was developed and the initial calibration was undertaken.* Preliminary results were encouraging and validation and refinement of the model continued under Langley sponsorship during 1978. The model that was finally developed is useful for analyzing long haul domestic passenger markets in the United States. Specifically, it was used to show the sensitivities of passenger demand to changes in fares and speed reflecting technology through more efficient designs of aircraft; and to analyze, through the year 2000, the impact of selected changes in fares, speeds, and frequencies on passenger demand. April 1979; Includes bibliographical references (p. 80)

A comparative analysis of area navigation systems for general aviation

2019-04-12T15:05:46Z

A comparative analysis of area navigation systems for general aviation Dodge, Steven Malcolm Within the next decade area navigation is to become the primary method of air navigation within the United States. There are numerous radio navigation systems that offer the capabilities of area navigation to general aviation operations. In this analysis the author investigates three such systems: (1) the VORTAC system; (2) the Loran-C system; and (3) the Differential Omega system. The initial analyses are directed toward a comparison of the systems with respect to their compliance to specified performance parameters and to the cost-effectiveness of each system in relation to those specifications. Further analyses lead to the development of system cost sensitivity charts, and the employment of these charts allows conclusions to be drawn relative to the cost-effectiveness of the candidate navigation systems. Cover title; June 1973; Includes bibliographical references (p. 174-191)

Demand models for U.S. domestic air passenger markets

2019-04-12T15:05:45Z

Demand models for U.S. domestic air passenger markets Eriksen, Steven Edward; Eriksen, Steven Edward. The airline industry in recent years has suffered from the adverse effects of top level planning decisions based upon inaccurate demand forecasts. The air carriers have recognized the immediate need to develop their forecasting abilities and have applied considerable talent to this area. However, their forecasting methodologies still are far below the level of sophistication of their other planning tools. The purpose of this thesis is to develop a set of demand models which are sufficiently sensitive to measure the effects upon demand of policy decisions with respect to such variables as fare and technological and quality of service factors. A brief overview of transportation demand theory and a survey of recently published research in air passenger demand modeling are presented. Following these is a discussion of the economic nature of domestic air transportation passenger service indicating the demand and service attributes and how they interact in equilibrium. Based upon this background information a multi-equation econometric model is developed. The model is calibrated over subsets of a base of historical data from 180 markets over a six year time frame. The subsets are cross classifications of markets with respect to length of haul and market size. Recently developed techniques in model sensitivity analysis are applied to ensure statistical robustness, and principal components regression is employed to combat the problem of multicollinearity. Numerical examples of applications of the model are provided. The results indicate that the model performs very well in the analysis of long and medium haul markets. It is particularly effective in the higher density markets. The model is not equipped to account for the impacts upon air transportation passenger demand of competing modes, and therefore does not perform well in the analysis of short haul (less than 400 miles) markets. Originally presented as the author's thesis, (Ph. D.), "Policy oriented multi-equation models of U.S. domestic air passenger markets", in the M.I.T. Alfred P. Sloan School of Management, 1977; June 1978; Includes bibliographical references (p. 291-295)

Ground access to major airports in the United States : summary of present characteristics and evaluation of future requirements

2019-04-10T10:00:00Z

Ground access to major airports in the United States : summary of present characteristics and evaluation of future requirements Munds, Allan J. Synopsis: The ground access problem at United States airports will be discussed in general terms. Those characteristics of airport users relative to ground transportation will be analyzed to provide a clear picture of the potential users of any transportation system to serve airports. The requirements of any total system to serve airport users will be defined and, based on projections of future ground traffic, the suitability of various technological options will be discussed. January 1969; Includes bibliographical references (p. 59)

The cost of noise reduction in commercial tilt rotor aircraft

2019-04-10T10:00:00Z

The cost of noise reduction in commercial tilt rotor aircraft Faulkner, Henry B. The relationship between direct operating cost and departure noise annoyance was developed for commercial tilt rotor aircraft. This was accomplished by generating a series of tilt rotor aircraft designs to meet various noise goals at minimum DOC. These vehicles were spaced across the spectrum of possible noise levels from completely unconstrained to the quietest vehicle that could be designed within the study ground rules. A group of optimization parameters were varied to find the minimum DOC while other inputs were held constant and some external constraints were met. This basic variation was then extended to different aircraft sizes and technology time frames. It was concluded that reducing noise annoyance by designing for lower rotor tip speeds is a very promising avenue for future research and development. It appears that the cost of halving the annoyance compared to an unconstrained design is insignificant and the cost of halving the annoyance again is small. August 1974; Includes bibliographical references (p. 48-50)

Theoretical study of network design methodologies for the aerial relay system

2019-04-08T07:29:55Z

Theoretical study of network design methodologies for the aerial relay system Rivera, Jorge M.; Simpson, R. W. Growth of the United States air transportation system is currently facing two major barriers: energy and congestion. While the price of fuel has gone up by approximately an order of magnitude in the last 10 years, there is no assurance that fuel will continue to be available at the levels desired by the airlines. At the same time, lack of capacity at the major airports is causing delays to increase, both in number and duration. Both of these factors are causing the price of air transportation to reverse a 40-year-old trend and to increase in real terms, negating gains in aircraft productivity and engine efficiency. These considerations have led some observers of the aviation scene to conclude that the air travel mode is reaching maturity, although various regulatory, economic, and technological options have been suggested which offer incremental improvements to the existing system. For substantial growth to continue, however, major structural changes may be necessary. One imaginative and radical departure is the Aerial Relay System (Albert C. Kyser, "The Aerial Relay System: An Energy Efficient Solution to the Airport Congestion Problem," NASA Technical Memorandum 80208, January 1980). Briefly, in the Aerial Relay System a series of "liners", made up of "line modules", continuously cruise over the United States at a set altitude and on a predetermined schedule. These liners are met by a fleet of "feeders" carrying aloft passengers bound for cities along the liners' routes and accepting passengers destined for their own base. The basic elements of the system are shown in Figure I. A fully-developed Relay system could provide frequent non-stop service between practically any two cities in the United States. The advantages of the Relay system are many. The elements of the system can be tailored for their own function leading to efficiency of operation: the liners for cruise conditions, the feeders optimized for short-haul takeoff and climb. But the basic attraction lies in the Relay system's ability to unload the major hubs' airports by utilizing secondary (or satellite) airports and smaller city airports for the feeder's operations; since one of the major functions of airports, especially those at large hubs, is the interchange of connecting passengers between airplanes, this transfer is now performed onboard the liners. The feeder from a smaller city or secondary airport takes up passengers bound for many destinations downstream (and accepts diverse passengers for the downward journey), bypassing the hub and relieving the hub of these operations. The Relay system would thus supplement and not replace the existing airline networks; the hub-to-hub origin-destination traffic could continue to be served by dedicated aircraft at the major airports. Alternatively, the Relay system could serve as the major link between large hubs while utilizing satellite airports and thus relieving the major airports of this type of traffic. Thus the Aerial Relay System has intrinsic appeal, as it could both relieve congestion and decrease energy consumption of the air mode. Clearly, substantial engineering and design work is required before the system can be implemented. However, some questions regarding the fundamental mathematical network properties of the Relay system can be addressed to insure that no basic drawbacks to the general concept exist. This report presents the derivation of a generalized algorithm which can be used for basic design studies of networks for the Aerial Relay System. Contract NAS 1-15268; June 1980; Includes bibliographical references (p. 160-163)

The cost of noise reduction in helicopters

2019-04-12T15:05:44Z

The cost of noise reduction in helicopters Faulkner, Henry B. The relationship between noise reduction and direct operating cost was studied for transport helicopters. A large number of helicopter preliminary designs was generated with the help of a computer program. Vehicles were selected to meet certain noise goals with minimum direct operating cast. this was repeated for several payloads and technology time frames. The effect of changes in the assumed mission profile was studied. November 1971; Includes bibliographical references (p. 52)

Estimation of the economic relationship of an airport to the regional economy : a critical analysis

2019-04-10T09:59:59Z

Estimation of the economic relationship of an airport to the regional economy : a critical analysis Fortune, Stephen James In the past decade many major U.S. airports have encountered extensive opposition to plans for future growth and expansion from environmentalists and community groups who cite the noise and air pollution created and the use of increasingly scarce land resources. In an effort to counterbalance these criticisms and highlight the regional benefits the airport provides, several airport authorities have completed economic impact studies which attempt to define the airport's role in the regional economy. In reviewing the airport economic impact studies which have been completed in the past twenty years, it is obvious that a wide range of methodologies have been developed to accomplish the common task of estimating the different elements of airport economic impact. This thesis provides an overview and critical evaluation of the techniques used in past studies to define what is the airport economic impact and how is the impact estimated in the absence of primary data. Three major economic impact categories, primary, direct and induced, provide the framework for analysis. An economic impact case study of Boston's Logan International Airport is presented to provide insight into problems common to all airport economic impact studies and the solutions to these problems in a specific situation. The need for and direction of future research to clarify and define the quantification of the airport/community economic relationships is also recognized and discussed. September 1981; Includes bibliographical references (leaves 122-124)

A study of signal to noise ratio, lane counting, and position accuracy using the Omega navigation system

2019-04-08T08:17:26Z

A study of signal to noise ratio, lane counting, and position accuracy using the Omega navigation system Francisco, Glen Leif A forty-hour flight program was completed to study signal to noise ratio, lane counting and position accuracy using a low cost Omega navigation system in a general aviation aircraft. Specific test objectives were developed to investigate signals both on the bench and in the air. Signal to noise ratio and lane counting characteristics were investigated in a single frequency, uncorrected mode and in a pseudo-differential mode. It was learned that the received signal to noise ratio is highly correlated with lane counting characteristics and receiver navigability. The relationship between system accuracy and reliability was also examined. The Omega navigation system's bias and position accuracy were investigated with the aid of the Discrete Address Beacon System (DABS). A circular probable error of 3500 feet was observed. It was also determined that certain necessary hardware and system improvements must be implemented before a completely usable Omega navigation system can be offered to the general aviation user. Prepared under National Aeronautics and Space Administration Contract no. NGL-22-009-640; Originally presented as the author's thesis, (M.S.) in the M.I.T. Dept. of Aeronautics and Astronautics, 1977; December 1976; Includes bibliographical references (p. 162-164)

Massachusetts state airport system plan forecasts.

2019-04-10T09:59:58Z

Massachusetts state airport system plan forecasts. Mathaisel, Dennis F. X. This report is a first step toward updating the forecasts contained in the 1973 Massachusetts State System Plan. It begins with a presentation of the forecasting techniques currently available; it surveys and appraises the methodology used in prior aviation forecasts; it reviews the techniques used in the master plan forecasts for Massachusetts' airports; it lists factors which have an influence on aviation activity; and it makes some conclusions designed to help in arriving at revised forecasts for the Massachusetts System Plan. February 1978; Includes bibliographical references (p. 57-59)

Deregulation : an update

2019-04-10T20:39:01Z

Deregulation : an update Maurer, R. S. Cover title; October 1981; Includes bibliographical references

Maintenance cost studies of rotary wing commercial transport aircraft

2019-04-09T18:14:14Z

Maintenance cost studies of rotary wing commercial transport aircraft Ausrotas, Raymond A.; Hsin, Chen-Chung.; Taneja, Nawal K. Introduction: The vertical take-off and landing (VTOL) aircraft market has had substantial growth in the period of the last ten years when one considers the overall number of aircraft in use. The military fleet has continued to increase, as have such operators as natural resource (petroleum and lumber) companies, and law enforcement agencies. (See Table 1.) In scheduled passenger service, however, the VTOL- market has not enjoyed sustained growth. Consider Table 2, the type and number of helicopters in passenger service during 1962-1972. Following the cessation of federal subsidies to helicopter operators in 1966 the number of aircraft (and total available seats) has been steadily declining. Table 3 shows the composition of the fleets of the certificated carriers since 1966. Los Angeles Airways has been in bankruptcy since 1969; Chicago Helicopter is now largely a charter operator, although retaining its certificate; New York Airways, after a period of experimentation with the fixed wing Twin Otter (DHC-6) in 1968-1969, finally made it into the black in 1973, flying Sikorsky S-61's; and SFO Helicopter has retrenched its passenger services severely, but is not yet profitable. Why is the state of scheduled passenger operations so bleak? Many answers to this question have been given. For example, it has been said that the aircraft used by the operators have been inadequate: that they have been designed for military use and are ill suited for civilians who have been used to a higher comfort level (especially since most flights taken on a helicopter are in conjunction with a ride on a large, comfortable jet transport). Alternatively, it has been said that the high cost of operating the current helicopter fleet has caused the ticket price to be too high to be attractive to the traveler. Sometimes the operators have been fingered as the culprits -- that they have not priced their product adequately and have structured their networks poorly, i.e., that the failure has been one of management and marketing. And from the purely technology minded, the answer has been that once the properly designed rotary wing aircraft arrives on the scene -- one designed for civilian use and having the proper payload-range configuration -- the market will boom as VTOL aircraft enter city-center to city-center service. Doubtless there is a kernel -of truth in all these explanations, and examples to sustain most of them can be found in the history of helicopter operations in the United States. The intent of the work described in this report was to explore one frequently cited cause of the problem of high operating costs of helicopters in scheduled service - to wit, high maintenance costs of rotary wing aircraft. This attempt was made to allow a look ahead and to predict trends in maintenance costs of future rotary wing aircraft. December 1974; Includes bibliographical references (p. 121-123)

The cost of noise reduction for departure and arrival operations of commercial tilt rotor aircraft

2019-04-12T15:05:43Z

The cost of noise reduction for departure and arrival operations of commercial tilt rotor aircraft Faulkner, Henry B.; Swan, William M. The relationship between direct operating cost (DOC) and noise annoyance due to a departure and an arrival operation was developed for commercial tilt rotor aircraft. This was accomplished by generating a series of tilt rotor aircraft designs to meet various noise goals at minimum DOC. These vehicles ranged across the spectrum of possible noise levels from completely unconstrained to the quietest vehicles that could be designed within the study ground rules. Optimization parameters were varied to find the minimum DOC. This basic variation was then extended to different aircraft sizes and technology time frames. It was concluded that reducing noise annoyance by designing for lower rotor tip speeds is a very promising avenue for future research and development. It appears that the cost of halving the annoyance compared to an unconstrained design is insignificant and the cost of halving the annoyance again is small. February 1976; Includes bibliographical references (p. 50-51)

Ground controlled precision landing delivery in the presence of radar disturbances

2019-04-12T15:05:42Z

Ground controlled precision landing delivery in the presence of radar disturbances Durocher, Cort Louis Introduction: The purpose of Air Traffic Control is to ensure separation of aircraft in the most efficient manner possible. The need for efficiency is becoming more important as air traffic continues to increase at a high rate. Terminal area traffic control is the area in which the greatest amount of effort is expended since this tends to be the limiting factor in airspace congestion. The current Automated Radar Terminal System provides a monitoring function which was unheard of with previous systems. However, this is not sufficient in view of the increasing air traffic. More improvements are needed in the exchange of information between the ground controller and the aircraft. The proposed upgraded Air Traffic Control system will provide better data acquisition, communications service, and increased automation. Future systems should be capable of providing more complete automation in terms of command generation and delivery. These systems are called Strategic Navigation or Four-Dimensional Navigation. The principle of these systems is to assign a route-time profile to each aircraft thus providing good management of energy, space, and runways. This method utilizes a fixed airspace structure with a variable flight path to de-randomize aircraft runway arrival time. The method favored by the Federal Aviation Administration consists of ground computation of heading, altitude, and airspeed commands which are broadcast to the aircraft via digital data-link. These commands can be either visually displayed for manual operation by the pilot or at some future time directly tied into the aircraft auto-pilot. The purpose of this study is to simulate the flight of an aircraft on a terminal approach in a Four-Dimensional Navigation environment using discrete control commands. During the flight, position information is estimated from noisy radar observations. Speed is estimated from these observations and is used in a timed delivery algorithm to determine when to issue commands to the aircraft. Time control precision will be experimentally determined in the presence of the radar disturbance and accuracy of the Four-Dimensional Navigation task in the presence of this uncertainty will be quantified. A number of studies have previously been conducted to determine fix-to-fix and runway arrival time accuracy. These studies neglected the effect of wind and assumed perfect radar position information. For this reason a comprehensive model for these two effects was developed. Originally presented as the author's thesis, (M.S.) in the M.I.T. Dept. of Aeronautics and Astronautics, 1977; May 1977; Includes bibliographical references (p. 51)

Some measures of aircraft performance on the airport surface

2019-04-12T15:05:42Z

Some measures of aircraft performance on the airport surface Swedish, William J. During the month of January, a survey was conducted at Boston and Atlanta Airports to obtain input data for an interactive computer simulation of runway and taxiway traffic being developed by Lincoln Laboratory. Data was collected for landings, takeoffs, and taxiing; included were such items as runway occupancy times, touchdown distances and times, liftoff distances and times, time over a given taxiway stretch, taxiway intersection delays and pre-takeoff delays. This thesis presents the results of the analysis of that data. Sample means and deviations of various parameters are given. The results of further analysis, intended to disclose inherent patterns in the data, are also discussed. First, it was found that there were few statistically significant differences in the speeds of different aircraft over the same taxiway stretch, regardless of the aircraft type or direction of travel. Also, length of the segment did not seem to have a uniform effect on speed. It is felt, though, that the location of the segment does have a substantial influence on taxiing speed. Secondly, touchdown distance was not significantly different on runways equipped with VASI (Visual Approach Slope Indicator) systems, when compared with non-VASI runways. Both exhibit substantial variance in the distribution of touchdown points. - 3 - However, the distribution for VASI-runways presents a double peaking not otherwise noticed, which may indicate a difference between a VASI-assisted and an unguided landing. Third, in analyzing runway occupancy times, it was found that the time to a given exit did not statistically vary, in general, regardless of the aircraft type involved. Overall differences between types were noted, with average occupancy times increasing with weight, but this is seen as being caused mainly by different patterns of exit use. On takeoffs, very few differences in occupancy times were found, regardless of type or runway. Lastly, other analyses which could be performed on the collected data are discussed, and suggestions are made for the planning of future surveys. In particular, a more automated data gathering system, involving remote sensors on the runway, is strongly recommended for greater accuracy. May 1972; Based upon a survey conducted at Boston and Atlanta airports; Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1972; Includes bibliographical references

Definition of the problems associated with air traffic control of closely spaced helicopter traffic performing instrument approaches

2019-04-08T07:29:55Z

Definition of the problems associated with air traffic control of closely spaced helicopter traffic performing instrument approaches Simpson, R. W. This study reviews the requirements for a modern, high performance all weather Air Traffic Management and Control System designed for U.S. Army airfields. A strawman ATM/C system is created to illustrate problems, and to identify research and development needs in surveillance, communications, and computer display and automation. December 1980; Includes bibliographical references

Computerized schedule construction for an airbus transportation system

2019-04-10T09:59:57Z

Computerized schedule construction for an airbus transportation system Simpson, R. W. As part of a continuing study of the application of V/STOL aircraft to the transportation problems of the Northeast Corridor, the U.S. Department of Commerce has requested that detailed data be developed on schedules, travel times, and fares which might be expected for a V/STOL system operating in the year 1980. This section deals with the computer methods used to construct such schedules. A schedule (or more properly a schedule plan) is a complete description of a transportation system. It details the services to be offered in the dimensions of time and geography, gives the routings followed by vehicles, and indicates the loadings to be placed upon terminals. A complete statistical summary of the operation of the transportation system can be obtained once the schedule is completed. The number of vehicles and crews, their daily utilization, the expected load factors, the required number of loading gates, the average length of vehicle hop, etc. are all implicitly determined by the schedule plan. Constructing and maintaining an efficient schedule is the main problem of transportation system managements. It is both their production plan and their product to be marketed, and the economic success of the plan is gauged by the management's ability to produce a low cost production which will be saleable to the travelling public. The use of computers in scheduling is not widespread at this time, and if they are used, it is generally for data processing as distinct from decision making or problem solving. The reasons for this are clear. There has not been in the past, sufficient capability either in the hardware, or the software to handle problems of the size and complexity associated with even such relatively small transportation systems.as the airline systems. This situation has been changing in the last few years, to the point where we can now begin to handle fairly large scale scheduling problems, introducing optimization at several points, and constructing fairly quickly and easily full system schedules and their statistical summaries. Parametric investigations of the effects of restricting fleet size, terminal size, etc. can be quickly carried out. Various strategies or policy decisions are similarly easily investigated. The construction of computer programs for the scheduling process immediately points out the need for detailed accurate data concerning demand. This is now becoming available to the airlines through their reservation systems and the management information systems evolving from them. We need to know, for example, detailed information on the number of people travelling from A to B throughout the day, by day of week and month of year, with an accuracy much greater than our present estimates. We would like to know the demand elasticity, e.g. the change in the number of people travelling as services are changed in time or quality for every service pair in the system. The character of the available data (as distinct from opinion) determines the type of problem that operations research and the computer will be able to successfully solve. Various large scale econometric models are conceivable, if revenue and cost data are available. This section will describe the work which has been carried out for a hypothetical Airbus short haul V/STOL system in the Northeast Corridor. It is only a beginning as valuable extensions are yet to come. December 1966; PB174913; Includes bibliographical references (p. 75)

Some observations on the first half year of passenger deregulation

2019-04-10T09:59:57Z

Some observations on the first half year of passenger deregulation Brenner, Melvin A. This report is the text of a seminar given by Mr. Brenner for the course "Air Transportation -- Economics, Management and Planning." The course was presented by MIT's Flight Transportation Laboratory in cooperation with the Technical Assistance Bureau of the International Civil Aviation Organization. The course is part of the Advanced Study Program in Air Transportation, given under the auspices of the Center for Advanced Engineering Study, July 1979

The impact of high inflation rates on the demand for air passenger transportation

2019-04-09T18:49:34Z

The impact of high inflation rates on the demand for air passenger transportation Vitek, Richard Leo; Taneja, Nawal K. The impact of high inflation rates on the demand for domestic air passenger transportation is tested in a demand model using time-series data and linear and non-linear least squares regressions with Revenue Passenger Miles as the dependent variable, and measures of cost, income and inflation as the explanatory variables. The investigation begins with an extensive survey of the past and current air transportation demand models. The model selected uses linear and non-linear log specifications to account for the secular trend and detrended variables to account for the cyclical variations. These transformations allow determination of the coefficients comparable to delta log models and simultaneously retain the forecasting ability of linear log models. Forecasts are provided to 1990 for both the linear and non-linear secular trends. Results show that the price is the most stable and significant determinant of demand. Income and the rate of inflation are both significant but are more variable and highly dependent on the type of secular trend and the time period used in the regression. The non-linear secular trend model provided the best overall fit and explained 96% of the variation in demand. Originally written as the first author's M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1975; May 1975; Includes bibliographical references (p. 116-117)

The development of an operational game for the U.S. domestic airline industry

2019-04-12T15:05:41Z

Ground facilities for a VTOL intercity air transportation system

2019-04-10T09:59:56Z

Ground facilities for a VTOL intercity air transportation system Allen Edward; Simpson, R. W. Bibliography: p. 133-136

Controller and computer display interface in an advanced terminal area ATC system

2019-04-10T09:59:55Z

Controller and computer display interface in an advanced terminal area ATC system Dopart, Kevin Peter Controller and display interactions and information requirements in an advanced Air Traffic Control (ATC) system are investigated. A description of the present ATC system and of some proposed developments for the future is presented. Suggestions are made for interfacing and modifying these present system concepts for implementation in an advanced system. Emphasis is on tower controllers and their display/data entry requirements (using the Terminal Information Processing System, TIPS). June 1980; Includes bibliographical references (leaves 89-91)

Pilot workload in the air transport environment : measurement, theory, and the influence of air traffic control

2019-04-10T09:59:54Z

Pilot workload in the air transport environment : measurement, theory, and the influence of air traffic control Katz, Jeffrey G. The operating environment of an air transport crew is characterized by multiple interrupting tasks, these tasks being composed of a mixture of purely physical control and purely mental planning processes. Measurement of crew workload is thus d difficult undertaking due to the necessity to resolve workload contributions imposed by several sources. These sources include physical efforts, mental efforts, random task interruptions, and emotional disturbances. A multiattribute, subjective opinion rating scale is presented for usa as an effective measure for this air transport cockpit environment. An analysis is performed which indicates that a major component of workload is induced by the federal air traffic control system. Mechanizations of this loading inClude speed and altitude restrictions imposed by regulation, confinement and restraint imposed by the structure of the National Airspace System, and loads induced by a stochastic interruption process associated with ATC voice communications, In fact, the analysis of a routine transport arrival into Boston's Logan airport indicates that the (primarily system induced) workload levels in the terminal area, may be higher than the (primarily aircraft induced) workload levels on final approach. A fixed base, Boeing 707 simulator was employed to investigate the consistency, sensitivity, and acceptability- of the 31, subjective rating scale. Four airline pilots and four general aviation, IFH pilots flew a series of routine, MI2 arrivals from high altitude cruise into Boston's Logan airport, each arrival terminating with a standard instrument approach. Consistent ratings were achieved across the airline subjects for all segments of the arrivals. In general, all subjects seemed receptive to the subjective assessment methodology. May 1980; Includes bibliographical references (p. 185-188)

Commuter airlines at Boston Logan International Airport: 1973-1981

2019-04-10T09:59:53Z

Commuter airlines at Boston Logan International Airport: 1973-1981 Ausrotas, Raymond A.; Godly, Martin A. Introduction: The adequacy of air transportation in New England has been the subject of intermittent debate-over the last twenty years-, culminating in the Civil Aeronautics Board's 1970-1974 "New England Service Investigation" (Docket 22973). Spurred on by Senate hearings on the "Adequacy of Northern New England Air Service" (1971) in particular and by Senator Norris Cotton of New Hampshire in general, in 1974 the Board certificated Air New England as a local service carrier. It was the first certification of a commuter airline by the Board. The certification contradicted the advice of the Board's own Bureau of Operating Rights and the U.S. Department of Transportation and overturned the initial (1973) decision of Administrative Law Judge Greer M. Murphy, who held that existing commuter airlines could provide adequate service in New England without certification. A potentially successful commuter ("Air New England 1970-1974 ," MIT-FTL Report R75-9), millions of subsidy dollars later, Air New England is struggling financially and operationally and is now giving up many subsidized points to replacement commuter carriers. Logan Airport, the major hub of New England, has one of the largest concentrations of commuter carriers in the U.S. During the last seven years, it has ranked in the top three. Some twenty commuters (including all cargo carriers) land at Logan, serving over fifty markets. However, of the passenger-carrying commuters, only four (including Air New England) have remained steady customers since 1973. The others are Command, Pilgrim, and Provincetown-Boston Airlines. This report is an attempt - 2 - to analyze the pattern of commuter airlines operations at Logan. Since the events prior to 1973 are well documented, the emphasis is on the years 1973-1981. In Section 2, the theoretical background to analyze the commuter industry Is provided. Section 3 gives the Boston market analysis. In Section 4, a brief description of the aircraft used by commuters is provided as well as a look ahead to the aircraft that will be available to the commuter industry in the 1980s. Finally, in Section 5 some recommendations are made to monitor the commuter activities at Logan airport. January 1981

Review and evaluation of national airspace system models

2019-04-09T19:03:30Z

Review and evaluation of national airspace system models Odoni, Amedeo R.; Simpson, R. W. Abstract from Technical Report Documentation Page: This report is intended to serve as a guide to the availability and capability of state-of-the-art analytical and simulation models of the National Airspace System (NAS). An extensive literature search produced a listing of 230 reports potentially containing technical descriptions of models developed during the last decade. These reports are classified into primary categories based on applicability of the model to various aspects of the NAS. Capacity/delay models are classified as capacity-oriented runway, delay-oriented runway, complete airport, terminal airspace. air route traffic (including communications), controller workload and performance, and models of major segments of the NAS. Reports describing models primarily concerned with safety-related measures and noise-related measures are categorized separately. Reports were initially screened to eliminate those known to have been superseded by a subsequent report, and those containing inadequate or inconsequential technical information concerning models. The remaining reports (approximately 180) were subjected to a detailed review. The results of this review are documented for each of the 50 distinct models described by the selected reports. Information contained in each model review includes report ID, abstract, input/output parameters, computer-related characteristics, assumptions, quality of documentation, extent of validation, and an evaluation of the model's usefulness and limitations. Another part of the report contains a comparative evaluation of models in the same primary category. These evaluations present an overview of the models contained in each category, summarize the main features of the best models, and document the conclusions and recommendations regarding the models best suited for specific applications. Cover title; October 1979; Includes bibliographical references (p. B1-B32)

Flight test and evaluation of Omega navigation for general aviation

2019-04-12T15:05:40Z

Flight test and evaluation of Omega navigation for general aviation Hwoschinsky, Peter V. A seventy hour flight test program was accomplished to determine the suitability and accuracy of a low cost Omega navigation receiver in a general aviation aircraft. An analysis was made of signal availability in two widely separated geographic areas. Comparison was made of the results of these flights with previous work focused on VOR/ DME. Conclusions are drawn from the test experience that indicate developmental system improvement is necessary before a competent fail safe or fail soft area navigation system is offered to general aviation. Cover title; Originally presented as the author's thesis (E.A.A.), M.I.T. Dept. of Aeronautics and Astronautics, 1975; NASA CR- 132677"--stamped on cover. -- "R75-5"--handwritten on cover; Includes bibliographical references (p. 263-266)

An assessment of deregulation and its effect on the international air transportation community

2019-04-11T03:51:35Z

An assessment of deregulation and its effect on the international air transportation community Gray, Robert Reed "Multiple entry is now the norm for U.S. international air transportation, except in cases in which the bilateral aviation relations between the United States and the foreign country concerned call for a different approach. This basic policy is founded on broad economic considerations which have been thoroughly evaluated in Congress and in the Board's adjudicatory processes. It was recently given explicit Congressional sanction by the International Air Transportation Competition Act. Objectors to multiple entry now have a heavy burden of proof to show that application of the policy would be inconsistent with the public convenience and necessity"--p. [1]. June 1980; Lecture delivered June 19, 1980, by Robert Reed Gray, Esq. to the "Air Transportation -- Management, Economics, and Planning" course, organized by the Center for Advanced Engineering Study, Flight Transportation Laboratory, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology. Mr. Gray is a Senior Partner of the New York and Washington law firm of Hale Russell Gray Seaman & Birkett."--p. [1]

Wide-body aircraft demand potential at metropolitan Washington airports

2019-04-10T09:59:53Z

Wide-body aircraft demand potential at metropolitan Washington airports Ausrotas, Raymond A.; Taylor, Morais Anthony. Introduction: At present there is concern regarding the feasibility and future impact of allowing service by wide-body aircraft into National Airport in Washington. Some of the important issues are: (i) To what extent would the air carrier traffic change at Dulles and National Airports if wide-bodies were allowed at National? In addition, would this reduction in the quality of service (i.e. trip convenience and time) result in diversion of passengers to other modes of transportation in short-range markets? (ii) Could airlines maintain a high level of service to Metropolitan Washington and still make a profit serving their Washington markets? (iii) What would be the effect of changing the existing quota of 40 operations per hour at National Airport? FA-7, an air transportation simulation model developed in the Flight Transportation Laboratory at M.I.T. is well suited for analysis of these policy-oriented questions and was used to obtain answers to a series of hypothetical scenarios regarding wide-body aircraft use at the two Metropolitan Washington airports.. May 1976; Includes bibliographical references (leaf 24)

Intermodal air-surface movement of cargo John H. Mahoney.

2019-04-12T15:05:39Z

Intermodal air-surface movement of cargo John H. Mahoney. Mahoney, John H. Someone who told me he was a friend asked me to talk to you about "any single important aspect of air cargo" and the booby trap I suddenly stumbled into was the difficulty of sticking to a single subject from the many delectable debates currently raging in the airline industry. I would be delighted to loose a torrent of thoughts on a pallet load of air cargo topics such as a participant's critique of air cargo deregulation, a swimmer's eye-view of the cargo wave of the future, and a dirty-picture candid-camera snapshot of the love-hate relationship of those strange bedfellows, cargo wholesalers and retailers.-- It also would be fun to turn over rocks in the snake-infested field of air cargo marketing, and bounce around among the various rubbery definitions of market elasticity. But, unfortunately, time won't permit the pleasure of serving up a melange of these tidbits, because each ought to be stewed separately in its own juice over a slow fire and presented to you with the proper condiments in order to be savored fully, in justice to it, and to you. So, I'm forced to select a single subject in spite of the great temptation to wander these various enticing realms, mixing metaphors as I go. The single subject I've selected is intermodal air-surface movement of cargo. The major question involved is whether it is economically efficient to utilize special 8x8x20-ft intermodal containers in the airplane and over the road. You may say, "how dull can you get! ", because this may sound to you like a pretty dull subject. But, I trust you'll find such is not the case. This subject involves plenty of controversy and strong opinions. Furthermore, it will give you a real live air cargo problem that is still being worked out in the field, to which you can apply your own judgment. The inputs to its economic analysis, such as labor, fuel costs, and customer perceptions, are constantly changing and assuming differing proportions in the equation, so your analysis and recommendation can be just as valid and effective as one being done by someone who gets paid for doing it. If you begin to get the feeling that I'm about to present you with a "case history", eschew the thought. The boys in the Business School up the street at Harvard Yard have a patent on the "case history method" upon which they deeply meditate to the exclusion of all else. By contrast, this is a live and throbbing issue, not a timeworn fossil. Seminar, July 14, 1980, to Summer Course, 'Air Transportation -- Management, Economics and Planning,' sponsored by Flight Transportation Laboratory / Center for Advanced Engineering Study Massachusetts Institute of Technology; July 1980; Includes bibliographical references

User charges in international air transportation

2019-04-08T07:29:55Z

User charges in international air transportation Seagrave, Norman P. The charges dealt with here are those paid by international airline operators for the use of airports and airways. At airports, there are charges for landings and takeoffs and various fees or rentals for other facilities and services required for the conduct of airline operations and business. Airway charges may cover enroute navigation aids, air traffic control, the supply of information on weather conditions, and the provision of ground-based communications services required in the identification and separation of air traffic. Cover title; October 1979; This report is the text of a seminar given by Mr. Norman P. Seagrave, Counselor, International and Regulatory Services, Pan American World Airways. The seminar was given at MIT on October 4, 1979, for the course "Air Transportation Analysis and Planning."--Pref

Air freight : the problems of airport restrictions : final report on the Conference of Air Cargo Industry Considerations of Airport Curfews

2019-04-12T15:05:38Z

Air freight : the problems of airport restrictions : final report on the Conference of Air Cargo Industry Considerations of Airport Curfews Ausrotas, Raymond A.; Taneja, Nawal K. Noise due to aircraft was considered to be a potential problem as far back as 1952, when the Doolittle Commission established by President Truman urged that a major effort be made to reduce aircraft noise. With the 'advent of the jet age in the late 1950's and the concomitant spread of suburbs towards airports in major cities such as New York, Denver, and Minneapolis-St. Paul, many more people became exposed to noise, and concern and anger intensified. Although only a small percentage (estimated at about 2-3%) of the total population of the U.S. is affected by high noise levels, these people and their representatives have been quite vocal about their dissatisfaction with noise abatement progress, even though technological advances have reduced the noise emanating from aircraft engines. As a result, the airports, the communities, and the federal government are seeking additional measures that will further diminish the noise impact of aircraft and airport operations. The dilemma is to decrease noise with the minimum economic disruptions to commerce, the community, and the aviation industry. Since very few people like to travel during the night hours (approximately 10 p.m. - 7 a.m.), and indeed very few aircraft operations take place (less than 5% of total operations at most airports), an environmentally and politically appealing option to diminish the effect of aircraft noise is to ban airplane operations during nighttime hours. However, a disproportionate number of operations at night are dedicated to cargo (about 50% of scheduled domestic all-cargo flights), and it is upon the air cargo industry and those users dependent upon nighttime flights that the major burden of a curfew would fall. The benefits of curfews are apparent; the economic penalties associated with them are not. To address this issue, the Flight Transportation Laboratory of the Massachusetts Institute of Technology hosted a week-long conference at Jupiter, Florida, in January, 1979, on the impact of airport use restrictions on air freight. This conference was sponsored by the Federal Aviation Administration and the Port Authority of New York and New Jersey. More than 70 participants, including some 50 panelists and speakers, represented various viewpoints of the air cargo industry: the users, the airlines, the airports, the communities, and various governmental agencies. April 1979; Conference held in Jupiter, Fla. in January 1979; Includes bibliographical references (p. 36)

A systems analysis of scheduled air transportation networks

2019-04-09T18:10:14Z

A systems analysis of scheduled air transportation networks Swan, William M. This work establishes the conditions for airline system design building from submodels of smaller aspects of air transportation. The first three sections develop submodels which then are combined in extensive numerical studies of singles market services. The final section discusses the changes to this problem that occur due to network effects. The first section develops a simple model of the cost of providing scheduled transportation on a link. The cost of aircraft of various capacities are divided into a per-frequency cost and a per-capacity cost for conventional subsonic turbojet designs. This cost structure implies that the more capacity provided in conjunction with a fixed schedule of departures the lower the average cost per seat. It is suggested that such aircraft scale economies create a trend toward monopoly or at least oligopoly services. The second section develops a model for demand. The market for transportation is argued to be the city pair. Demand for scheduled service is expressed in terms of fare, frequency and load factor. Fare, frequency, and load factor are combined into total perceived price for the service. This price depends on the consumer's personal value of time. With only a few competitors in such a market, only a few of the technically possible qualities of service will be offered. The services available will be suited better to some tastes than to others. Distributional effects influence the politics of regulation and have been neglected in the past. In this light it is shown that competitive firms are likely to design their services for the same value of time. Product matching increases costs without improving the distribution of benefits. Chapter 4 develops in detail the statistical model used to estimate denied boarding rates from long run design load factors. The development raises doubts about the viability of competition in this dimension. Chapter 5 develops the optimal service for a single carrier on a single city pair market. Optima defined by maximum traffic at zero loss show the importance of the flexibility in aircraft capacity for long run system design. Both algebraic solutions and extensive numerical studies suggest that optimal designs depend on traffic and distance. Changes in frequency and capacity are large; load factor and fare are more stable. Optima are shallow for U.S. domestic cost structures. The final section brings to the discussion issues associated with networks of services. Most U.S. domestic city pairs have amounts of traffic of only modest size compared to the efficient aircraft capacities. Networks overcome these limitations by sharing vehicles among markets. This is done at the expense of extra departure costs. The network design tradeoff in its simplest form is shown to be between larger aircraft capacities and longer stage lengths. The corresponding routing patterns emphasize stops and connections or direct flights. Network design adds another degree of flexibility to the design of transport services: the number of intermediate stops per passenger trip. This affects both cost and service quality. Originally presented as the author's Ph. D. thesis, M.I.T. Dept. of Aeronautics and Astronautics, 1979; June 1979; Includes bibliographical references (p. 231-234)

Economics and finance in the management of U.S. airports

2019-04-08T07:29:55Z

Economics and finance in the management of U.S. airports Lim, Liang Poh Using actual data gathered from field surveys and an extensive literature survey, this work examines and evaluates the economic and financial performance of the U.S. airports. A detailed analysis of the economics of airport ownership is also given. The impact of the airline deregulation act on airport capital financing and access to airport facilities is examined. In addition to a review of 16 airport-air carrier lease agreements, the financial and pricing policies adopted by the air carrier airports are also discussed. Originally presented as the author's Thesis (M.S.) in the M.I.T. Dept. of Aeronautics and Astronautics, 1980; September 1980; Includes bibliographical references (p. 205-208)

Use of Loran-C for general aviation aircraft navigation

2019-04-10T09:59:52Z

Use of Loran-C for general aviation aircraft navigation Natarajan, Krishnan This report describes an extensive evaluation of Loran-C for use by general aviation. Flight, ground, and antenna tests were done. Flight tests measured the accuracy and the ability to make approaches. Receiver reliability and susceptibility to atmospheric noise were also studied. Ground tests looked into grid stability and grid war page. Antenna tests were done to evaluate three antenna configurations -- ADF, vertical whip, and trailing wire antennas. The measured accuracy met FAA AC 90-45A requirements for all phases of flight. Loran-C was found to be satisfactory for approaches within AC 90-45A specifications. Reliability was 99.7%, the receiver was insensitive to atmospheric noise. The time difference grid was stable in the long run. Antenna tests showed the ADF and vertical whip antennas to be suitable for airborne use. It is concluded that Loran-C is suitable for navigation as an alternative to VHF RNAV. This navigation system is suitable for use in general aviation aircraft. Originally presented as the author's thesis (M.S.), M.I.T., Dept. of Aeronautics and Astronautics, 1981; February 1981; Includes bibliographical references (p. 102-104)

Can airline deregulation work in international air transportation?

2019-04-10T09:59:51Z

Can airline deregulation work in international air transportation? Cohen Marvin S. "I AM PLEASED TO BE ABLE TO JOIN YOU TODAY TO TALK ABOUT THE DEVELOPMENT OF A MORE COMPETITIVE INTERNATIONAL AIR TRANSPORT SYSTEM -- A TOPIC THAT HAS GENERATED SUBSTANTIAL DEBATE WORLDWIDE OVER THE LAST SEVERAL YEARS- IN THE COURSE OF THIS INTERNATIONAL DIALOGUE, THE UNITED STATES WHICH HAS ACTIVELY PROMOTED MORE COMPETITION, HAS BEEN ACCUSED NOT ONLY OF A VARIETY OF HEINOUS DIPLOMATIC CRIMES BUT ALSO OF TRYING TO SUBVERT THE CONTINUING DEVELOPMENT OF THE INTERNATIONAL AIR TRANSPORT System in MY PRESENTATION I WILL FIRST ADDRESS THE SPECIFIC CHARGES THAT HAVE BEEN MADE AGAINST THE UNITED STATES AND THEN DISCUSS MORE BROADLY THE REASONS WHY THE UNITED STATES FAVORS A MORE COMPETITIVE REGIME"--p. 1. Marvin S. Cohen is the Chairman of the Civil Aeronautics Board; June 1980; Seminar, June 25, 1980, to Summer Course "Air Transportation -- Management, Economics and Planning," sponsored by Center for Advanced Engineering Study/ Flight Transportation Laboratory Massachusetts Institute of Technology; Includes bibliographical references

International civil air transport : transition following WW II

2019-04-09T19:03:22Z

International civil air transport : transition following WW II Pogue, L. Welch International air transport, like many 20th Century marvels which are taken so much for granted today, broke out from its cocoon, so to speak, shortly after the end of World War II (WW II), took wing, and soared. Theretofore, its growth had been retarded by fear of flying, by restrictive policies in granting civil air rights based upon narrow views about the sovereignty of nations over their air space and by the inevitable "bugs" that plague the early phases of most innovative technologies. his paper will undertake to trace the high points in that post-WW II metamorphosis. June 1979; Lecture Delivered on June 15, 1979 in Cambridge, Massachusetts, in the Course Given by Massachusetts Institute of Technology in Cooperation with the International Civil Aviation Organization on "Air Transportation--Economics, Management, and Planning"--p. [1]; Includes bibliographical references

Proceedings of the NASA/MIT Workshop on Airline Systems Analysis, Waterville Valley, New Hampshire, July 10-21, 1972

2019-04-10T09:59:48Z

A comprehensive assessment of air transportation in Mainland China

2019-04-12T15:05:37Z

A comprehensive assessment of air transportation in Mainland China Tam, Koon-Ho Joseph This study attempts to obtain an overall picture of air transportation in Mainland China, domestic and international, past and present, so as to lay the ground for further studies. A brief history of early aviation development in China is described from limited available sources: the first sign of aviation in 1919, the starting of commercial aviation in 1929, general development under the Nationalists before 1949, and the establishment and growth of CAAC under the Communists. Then, the present situations of airline operations, CAAC and foreign, are discussed. As for domestic operations, flight schedules and timetables, a complete route map showing the important air hubs in the network, the direct service networks and summaries of the connections, fares, frequencies, non-stop distances etc. of 22 major cities are detailed to give a general view of CAAC's scheduled services. Internationally, an account of all foreign airlines serving China, their schedules and timetables, summaries of their present operations are tabulated. Next, CAAC's fares and rate structure, aircraft equipments and a comparison of CAAC with other airlines are touched upon. A brief description of airports and navigation aids in China is included. Maps are drawn showing their locations. Finally, the development of China's aviation relationships with her foreign partners is presented. Major partners like the U.S.S.R., Pakistan, France, Ethiopia and Japan are discussed in details. Cover title; Originally presented as the author's thesis (M.S.), M.I.T. Dept. of Aeronautics and Astronautics, 1975; February 1975; Includes bibliographical references (p. 301-305)

A simulation study of dynamic scheduling of a VTOL airport feeder system

2019-04-10T09:59:46Z

A simulation study of dynamic scheduling of a VTOL airport feeder system Taneja, Nawal K.; Simpson, R. W. Introduction: In considering ultra short haul, high density transportation systems, it may become feasible to use short term, real time decision making in operating the system. Here the dispatch of vehicles would be based upon actual traffic demands, the passenger waiting times for service, with perhaps some consideration given to expected future demands at the originating and downstream stations. This is called dynamic scheduling, or demand scheduling to differentiate it from the scheduling planning process which uses as input the expected or average demands for the system over some extended period. An example of pure dynamic scheduling is present taxi service in most urban areas. A fleet of roving or dispersed taxis is controlled by a centralized dispatcher who receives all demands by phone, and assigns a vehicle to a service using a radio communication system. The other extreme is typified by present domestic airline schedules where services, vehicle and crew assignments, etc. are ordained at least a month in advance, and the schedule is followed as closely as possible. Most transportation systems fall in between these extremes with trains adding extra cars or bus carriers making extra sections available at short notice, etc. The EAL shuttle service is partially dynamic in that the guarantee of a seat may force an unplanned extra section, and is partially planned since a continuing study of the patterns of demand allows planning for most extra sections. The published shuttle timetable remains fixed although departures occur before, on, and perhaps after the scheduled time. By having a fixed operating plan, the job to be performed becomes deterministic, and adequate planning can ensure good operating efficiencies over the system as measured by load factor, vehicle and crew utilization, ground facility utilizations, etc. With an uncertain operating plan, the system must have above average resources in order to be able to call them into service at peak or above average times. This implies lower load factors and lower utilizations on the average. The higher efficiencies mean lower costs, and presumably lower fares. The lower efficiencies of the dynamic system may mean higher costs, but will be accompanied, presumably, by better service for the traveller. A number of questions are thereby raised: How much will the traveller pay for an improved service? What sort of service improvements can we provide by being responsive to actual real time demands, and what will they mean in operating costs? What type of market will allow most effective use of dynamic scheduling? What kinds of dynamic scheduling strategies can be employed? How do we discover efficient strategies, and how do we test them? There does not seem to be any clear or well defined set of answers to such questions. This is a report on some preliminary investigations into the problems of dynamic scheduling in very short haul markets which exist in collecting and distributing passengers from a major transportation center.; (cont.) The decision making process by which the system operates -3- is called a scheduling strategy. Given the present system state in terms of accurate real time information concerning demands, passenger waiting time, vehicle availabilities, etc. and some short term expectations of future system states, a set of operating rules is established which determine the transportation system response. This set of rules, (or strategy always exists, either explicitly in the form of management policy directives, or implicitly in the form of the experience and intelligence used by a taxi dispatcher. Whether complex or simple, there are a wide variety of strategies which can be selected far testing in various markets. Each strategy will use certain information about the system state, which assumes that such information will be made readily available. One of the first problems is to discover strategies which allow efficient operation of the system with an economical use of data about the present and projected system states. This report describes the operation of a final strategy which has evolved from reference 1, and further testing during this study.; (cont.) The classical aim of airline managements is to maximize short term profits. It could easily be minimization of costs, maximization of revenues or aircraft utilization. From the public service point of view or longer term management objectives, it could be minimization of passenger waiting time. It could be some weighted combination of any of these factors. Different situations will dictate deferent objectives, and it is not clear which objectives are preferable, or what type of strategies are most effective in achieving any chosen objective.; (cont.) Simulation models of operations systems have benefited management in the decision making process and in comparing basic alternatives of operating policy. Computer simulation is a technique which provides management with means of testing and evaluating a proposed system under various conditions. In our study the system's behavior is modeled by a computer program which reacts to various scheduling strategies in a manner very similar to the system itself. With the use of the simulation model, management can thus determine the effects of many alternate strategies without tampering with the actual physical system. The result is that we do not risk upsetting the existing physical system without prior assurance to some degree of confidence that the proposed changes in strategies will be beneficial. Computer simulation thus produces a system which is efficient and fulfills the system operational objectives. Use of simulation can save cost and time. In this study for example, five days of airline operation have been simulated in less than three minutes of computer time using the General Purpose System Simulator on IBM 7094. The simulation allows us to follow through the system and observe the effects of blocking caused either by the need of time-share facilities or caused by limited capacity of parts of the system. Outputs of the program give information on: 1. The amount of traffic through the system, or parts of the system. 2. The average time and the time distribution for traffic to pass through the system, or between selective points on the system. 3. The extent to which elements of the system are loaded. 4. Queues in the system. 5. A departure schedule. 6. Miscellaneous parameters of interest in the system. With our simulation model a number of different dynamic scheduling strategies have been examined. The final decision rules are described in chapter 2. The effects of variations in these final decision rules are shown in chapter 3. January 1969; Includes bibliographical references (leaf 44)

A linear programming solution to the gate assignment problem at airport terminals

2019-04-10T09:59:45Z

A linear programming solution to the gate assignment problem at airport terminals Mangoubi, Rami This research solves the flight-to-gate assignment problem at airports in such a way as to minimize, or at least reduce, walking distances for passengers inside terminals. Two solution methods are suggested. The first is a heuristic algorithm which assigns the "most crowded" aircraft (i.e., most on-board passengers) to the best gate, while the second consists of formulating the problem as a linear program. A flight schedule of one day at Terminal No. 2 of Toronto International Airport is used to test and compare the two methods. The algorithm offers an assignment solution with a 27% reduction in the expected walking distance when compared to the original assignment at the airport. The linear program's assignment gives a 32% reduction. The heuristic algorithm is, therefore, only 5% suboptimal for the sample problem. In addition, its associated computational expenses, less than $10 per run, are by far cheaper than those of the linear program with expenses as high as $400 per run. Such excellent, or even acceptable, performance by the algorithm cannot be guaranteed for all problems. A strategy which helps decide when to use which approach is therefore suggested. June 1980; Includes bibliographical references (p. 110)

Air New England (1970-1974) : a case study of a commuter air carrier

2019-04-12T15:05:36Z

Air New England (1970-1974) : a case study of a commuter air carrier Ausrotas, Raymond A.; Blumer, Terry P. This is a brief account of research by CAB staff. The success of Air New England from the beginning of its corporate life to the summer of 1974, when it was offered a certificate of public convenience and necessity by the CAB, can be attributed to a number of factors. The foremost was capable management. The management team at Air New England had previous experience operating commuter airlines in the New England area and was aware of the two major pitfalls that would undermine profitability, excess capacity and high corporate overhead, and was careful to avoid them. Further, the regulatory environment in which the commuters operated was such as to allow various competitive marketing strategies to be tried by management, such as modifying fare structures, flying different routings, and changing frequencies on routes. Additionally, the area chosen for initial market penetration, the Cape and Islands, was dense enough to support a number of airlines during the peak season, and allowed Air New England to minimize its start-up losses. Air New England's management was, of course, aware of the financial situation at Executive, its major established competitor. Air New England realized that if it was able to control its own costs, the financial difficulties that had existed at Executive during previous years would eventually lead to the disappearance of that particular competitor. (Of course, the possibility always existed that new commuters could also appear.) Thus, the emergence of Air New England as the dominant commuter air carrier in New England was a combination of management skills in all areas of airline operations combined with mismanagement on the part of their competitors. In the summer of 1974 Air New England's future was bright. October 1975; On cover, series statement "R75-9" is the correct numbering; t.p. has "75-7" and has been corrected to "75-9" by hand; Includes bibliographical references

Route network improvement in air transportation schedule planning

2019-04-12T15:05:29Z

Route network improvement in air transportation schedule planning Chan, Yupo One of the routing and scheduling problems faced by an airline is to configure a route network. It seeks to answer the following two questions: First, should scheduled service be provided for a city pair market? Second, if market entry is warranted, should the city pair be served by a non-stop, multi-stop, or connect routing? A profit maximizing airline, in trying to answer these questions, has to abide by the route regulations imposed by the Civil Aeronautics Board. The airline has to take into account the inter carrier route competition. It has to recognize that its share of the passenger demand is a function of the level of service offered, and that passengers usually want to reach their destination in the most convenient routing for themselves. An optimization model is formulated for the route network configuration problem. Because of the huge combinatorial dimensionality inherent in the problem, a special solution method has to be devised. Only a handful of the most promising, feasible route candidates are identified at a time. An optimal choice is immediately made out of the few candidates. These route candidates are generated "as needed" by graph theoretic schemes, while route selection is performed by solving an integer program characterized by an ill-behaved objective function. At each generation/selection step, route network improvement is made by the optimal selection of the route candidate (i) to add to an existing network, (ii) to replace an unprofitable route, or simply (iii) to be deleted from the route network. The solution algorithm is based on the method of successive approximation in dynamic programming. Primal feasibility is maintained at all times. If the algorithm is stopped prematurely, due to limited computational resources, an improved (but not necessarily optimal) solution is always available. A 40-routine computer software package for the algorithm has been developed. It was successfully used to analyze a case study from American Airlines. Our limited computational experience showed that execution time is at least seven times faster than a comparable algorithm. Cover title; June 1972; Includes bibliographical references

Toward the definition and measurement of the mental workload of transport pilots

2019-04-11T04:03:16Z

Toward the definition and measurement of the mental workload of transport pilots Sheridan, Thomas B.; Simpson, R. W. This report describes work performed in the first year of a continuing research project aimed at developing useful methods for measuring the workload of pilots operating aircraft in the ATC system. Good methods of measuring mental workload of human operators are needed to evaluate the introduction of new technology and new procedures in the man-machine environment. The present research is concentrating on developing subjective assessment methods for any phase of an IFR (Instrument Flight Rules) flight and any crew station on the flight deck. One of the results achieved in the first year is an expanded conceptual structure which allows a more precise definition of terms and assumptions in defining pilot mental workload in a multi-task environment. A second area of research has concentrated on reviewing the alternative approaches to developing a measurement scheme for workload, with some emphasis on the subjective assessment approach. A tentative result in this area is the generation of a prototype subjective rating method for IFR pilot workload modeled closely on the Cooper-Harper rating developed in 1969 to evaluate aircraft handling qualities. This scheme and others will be tested in a transport aircraft simulation during the coming year. If successful, it will be used in a variety of cockpit simulators at NASA research centers (Ames and Langley) and FAA NAFEC as part of a joint research program to evaluate cockpit display of traffic information. January 1979; Includes bibliographical references (p. 69-72)

Dynamic scheduling in airline operations

2019-04-12T15:05:28Z

Dynamic scheduling in airline operations Akel, Ollie James Introduction: Although air transportation has been characterized by rapid development in vehicle design and performance, methods of airline management in the area of vehicle scheduling and control have advanced at a much slower pace. Because of high costs of operation and the pressures of current competition and government controls, effective and efficient use of aircraft is becoming an increasingly essential objective. The goal is to achieve an optimal balance between net revenue to the airline and improved level of service to the customer. Improved return implies higher load factors and air - craft utilization whereas improved passenger service necessitates reduced waits and increased frequencies. These are often conflicting aims. New techniques must be mobilized to give management more useful and adaptive methods of operating and controlling an air transportation system. Perhaps the particular requirements -1- of a very short-haul high density transportation system will lead to more demand responsive approaches. It is with this motivation that this study of dynamic dispatching strategy is undertaken. December 1967; Includes bibliographical references (leaves 129-130)

A Dynamic Programming approach to the Aircraft Sequencing problem

2019-04-09T18:58:45Z

A Dynamic Programming approach to the Aircraft Sequencing problem Psaraftis, Harilaos Nicholas; Psaraftis, Harilaos Nicholas. In this report, a number of Dynamic Programming algorithms for three versions of the Aircraft Sequencing problem are developed. In these, two alternative objectives are considered: How to land all of a prescribed set of airplanes as soon as possible, or alternatively, how to minimize the total passenger waiting time. All these three versions are "static", namely, no intermediate aircraft arrivals are accepted until our initial set of airplanes land. The versions examined are (a) The single runway-unconstrained case, (b) The single runway-Constrained Position Shifting (CPS) case and (c) The two-runway-unconstrained case. In the unconstrained case, no priority considerations exist for the airplanes of our system. By contrast, CPS prohibits the shifting of any particular airplane by more than a prespecified number of positions (MPS) from its initial position in the queue. All three algorithms exploit the fact that the airplanes in our system can be classified into a relatively small number of distinct categories and thus, realize drastic savings in computational effort, which is shown to be a polynomially bounded function of the number of airplanes per category. The CPS problem is formulated in (b) in a recursive way, so that for any value of MPS, the computational effort remains polynomially bounded as described above. All algorithms of this work are tested by various examples and the results are discussed. Implementation issues are considered and suggestions on how this work can be extended are made. This report is excerpted from the author's Ph. D. dissertation 'Dynamic programming algorithms for specially structured sequencing and routing problems in transportation' (Dept. of Ocean Engineering, M.I.T., September, 1978.)"; October 1978; Includes bibliographical references (p. 123-126)

Weather conditions affecting VTOL airbus operations in the Northeast Corridor

2019-04-12T15:05:27Z

Weather conditions affecting VTOL airbus operations in the Northeast Corridor Simpson, R. W. A detailed study of hourly weather observations in the Northeast Corridor during the periods 0600-2400 for a ten year period 1944-1958 was made to study the implications of weather affecting the operations of a VSTOL Airbus transportation system. As a result, specifications for an automatic approach to a hover ending at 75 feet above ground, and within 350 feet visibility were determined to achieve weather reliable operations of over 99.5% throughout the year. Examination of high temperatures indicated that a criterion of operation at 950 F at 1000 feet elevation should be used to ensure 99.5% reliability through the summer months over the corrider. The frequency of high winds indicated that a step gust of 30 mph could be used for specifying the aircraft's displacement from a hover position while under an inertially stabilized automatic control system. As a by product, this study indicates that Category II all weather operations occur about 0.9% of the time, and Category III about 1.3% of the time in the Northeast Corridor. These percentages were lower at major stations like New York, Boston, Philadelphia, and Washington. December 1966; PB-174915; Includes bibliographical references (p. 28)

On Dual-Weighted Residual Error Estimates for p-Dependent Discretizations

2019-04-12T15:00:29Z

On Dual-Weighted Residual Error Estimates for p-Dependent Discretizations Yano, Masayuki; Darmofal, David L. This report analyzes the behavior of three variants of the dual-weighted residual (DWR) error estimates applied to the p-dependent discretization that results from the BR2 discretization of a second-order PDE. Three error estimates are assessed using two metrics: local effectivities and global effectivity. A priori error analysis is carried out to study the convergence behavior of the local and global effectivities of the three estimates. Numerical results verify the a priori error analysis.

Threat Assessment Design for Driver Assistance System at Intersections: Experiment Video

2019-04-08T08:11:36Z

Threat Assessment Design for Driver Assistance System at Intersections: Experiment Video Aoude, Georges S.; Luders, Brandon D.; Lee, Kenneth K. H.; Levine, Daniel S.; How, Jonathan P.

Probabilistically Safe Avoidance of Dynamic Obstacles with Uncertain Motion Patterns

2019-04-12T07:21:19Z

Probabilistically Safe Avoidance of Dynamic Obstacles with Uncertain Motion Patterns Luders, Brandon D.; Aoude, Georges S.; Joseph, Joshua M.; Roy, Nicholas; How, Jonathan P. This paper presents a real-time path planning algorithm which can guarantee probabilistic feasibility for autonomous robots subject to process noise and an uncertain environment, including dynamic obstacles with uncertain motion patterns. The key contribution of the work is the integration of a novel method for modeling dynamic obstacles with uncertain future trajectories. The method, denoted as RR-GP, uses a learned motion pattern model of the dynamic obstacles to make long-term predictions of their future paths. This is done by combining the flexibility of Gaussian processes (GP) with the efficiency of RRT-Reach, a sampling-based reachability computation method which ensures dynamic feasibility. This prediction model is then utilized within chance-constrained rapidly-exploring random trees (CC-RRT), which uses chance constraints to explicitly achieve probabilistic constraint satisfaction while maintaining the computational benefits of sampling-based algorithms. With RR-GP embedded in the CC-RRT framework, theoretical guarantees can be demonstrated for linear systems subject to Gaussian uncertainty, though the extension to nonlinear systems is also considered. Simulation results show that the resulting approach can be used in real-time to efficiently and accurately execute safe paths.

Threat-aware Path Planning in Uncertain Urban Environments [Attached Video]

2019-04-08T07:26:39Z

Threat-aware Path Planning in Uncertain Urban Environments [Attached Video] Aoude, Georges S.; Luders, Brandon D.; Levine, Daniel S.; How, Jonathan P. This paper considers the path planning problem for an autonomous vehicle in an urban environment populated with static obstacles and moving vehicles with uncertain intents. We propose a novel threat assessment module, consisting of an intention predictor and a threat assessor, which augments the host vehicle's path planner with a real-time threat value representing the risks posed by the estimated intentions of other vehicles. This new threat-aware planning approach is applied to the CL-RRT path planning framework, used by the MIT team in the 2007 DARPA Grand Challenge. The strengths of this approach are demonstrated through simulation and experiments performed in the RAVEN testbed facilities.

An Arnoldi Approach for Generation of Reduced Order Models for Turbomachinery

2019-04-13T00:05:20Z

An Arnoldi Approach for Generation of Reduced Order Models for Turbomachinery Willcox, Karen; Peraire, Jaime; White, Jacob A linear reduced-order aerodynamic model is developed for aeroelastic analysis of turbo-machines. The basis vectors are constructed using a block Arnoldi method. Although the model is cast in the time domain in state-space form, the spatial periodicity of the problem is exploited in the frequency domain to obtain these vectors efficiently. The frequency domain proper orthogonal decomposition is identified as a special case of the Arnoldi method. The aerodynamic model is coupled with a simple structural model that has two degrees of freedom for each blade. The technique is applicable to viscous and three-dimensional problems as well as multi-stage problems with inlet and exit disturbance flows, although here results are presented for two-dimensional, inviscid flow through a twenty-blade single-stage rotor. In this case, the number of states of the model is on the order of ten per blade passage, making it appropriate for control applications.

Measurement of the Mass Flow and Tangential Momentum Accommodation Coefficient in Silicon Micromachined Channels

2019-04-10T10:25:06Z

Measurement of the Mass Flow and Tangential Momentum Accommodation Coefficient in Silicon Micromachined Channels Arkilic, Errol B. An analytic and experimental investigation into gaseous flow with slight rarefaction through long microchannels is undertaken in an attempt to obtain values of the Tangential Momentum Accommodation Coefficient (TMAC) for a common MicroElectroMechanical Systems (MEMS) surface. A set of analytic expressions is developed from the slip- flow solutions of the Navier Stokes equations which can be used to interpret the results of flow in micromachined channels and to extract TMAC values from these results. In addition to the theoretical framework, a robust microchannel fabrication procedure and a dedicated high-resolution mass flow measurement technique is developed. These are used in conjunction to obtain TMAC values for single-crystal silicon upon which a native oxide resides for gas flows of argon, nitrogen and carbon dioxide. It is shown that the TMAC for this common MEMS surface can possess a value less than unity (0.75-0.85) for the conditions which are expected to be encountered with state-of-the-art MEMS.

Massively Parallel Solver for the High-Order Galerkin Least-Squares Method

2019-04-10T10:25:23Z

Massively Parallel Solver for the High-Order Galerkin Least-Squares Method Yano, Masayuki A high-order Galerkin Least-Squares (GLS) finite element discretization is combined with massively parallel implicit solvers. The stabilization parameter of the GLS discretization is modified to improve the resolution characteristics and the condition number for the high-order interpolation. The Balancing Domain Decomposition by Constraints (BDDC) algorithm is applied to the linear systems arising from the two-dimensional, high-order discretization of the Poisson equation, the advectiondiffusion equation, and the Euler equation. The Robin-Robin interface condition is extended to the Euler equation using the entropy-symmetrized variables. The BDDC method maintains scalability for the high-order discretization for the diffusiondominated flows. The Robin-Robin interface condition improves the performance of the method significantly for the advection-diffusion equation and the Euler equation. The BDDC method based on the inexact local solvers with incomplete factorization maintains the scalability of the exact counterpart with a proper reordering.

Solution of Fluid-Structure Interaction Problems using a Discontinuous Galerkin Technique

2019-04-13T00:05:31Z

Solution of Fluid-Structure Interaction Problems using a Discontinuous Galerkin Technique Mohnot, Anshul The present work aims to address the problem of fluid-structure interaction using a discontinuous Galerkin approach. Starting from the Navier-Stokes equations on a fixed domain, an arbitrary Lagrangian Eulerian (ALE) approach is used to derive the equations for the deforming domain. A geometric conservation law (GCL) is then introduced, which guarantees freestream preservation of the numerical scheme. The space discretization is performed using a discontinuous Galerkin method and time integration is performed using either an explicit four stage Runge-Kutta scheme or an implicit BDF2 scheme. The mapping parameters for the ALE formulation are then obtained using algorithms based on radial basis functions (RBF) or linear elasticity. These strategies are robust and can be applied to bodies with arbitrary shapes and undergoing arbitrary motions. The robustnesss and accuracy of the ALE scheme coupled with these mapping strategies is then demonstrated by solving some model problems. The ability of the scheme to handle complex flow problems is demonstrated by analyzing the low Reynolds number flow over an oscillating circular cylinder.

Development of Astronaut Reorientation Methods: A Computational and Experimental Study

2019-04-13T00:05:32Z

Development of Astronaut Reorientation Methods: A Computational and Experimental Study Stirling, Leia Abigail Past spaceflight missions have shown that astronauts adapt their motor-control strategies to the microgravity environment. Even though astronauts undergo hundreds of training hours, the strategies for locomotion and orientation are not specifically prescribed. The majority of an astronaut’s motion-control strategies are developed underwater. While underwater training can be beneficial in certain aspects, such as learning which orientations an astronaut will encounter and becoming familiar with task timelines, it is not effective for self-learned motor-control strategies. Further, the development of unfamiliar tasks, such as reorienting without external forces, will most likely not occur naturally. Self-rotations—human-body rotations without external torques—are not only helpful for reducing adaptation time, but can be a crucial safety countermeasure during extravehicular activity. In this thesis, computational and experimental methods are developed to create and analyze astronaut reorientation methods. The computational development of control methods for human motion planning offers a novel way to provide astronauts with maneuvers that are difficult to obtain experimentally in Earth gravity (1-G). Control of human-body dynamics can be posed as a motion-planning problem for which many different solution methods exist. This research considers two different frameworks—quantized control and optimal control. The quantized control method permits the development of complete maneuvers that are appropriate for humans to perform in high-stress situations by defining a set of specific finite-time trajectories called motion primitives. The implementation of an optimal control method allows for the refinement and further understanding of maneuver characteristics with an emphasis on how the central nervous system controls motion. Human rotation experiments provide further insight into the complexity of self-rotation techniques and a way to study the effects of training in a rigorous and realistic manner.

Analysis of Dual Consistency for Discontinuous Galerkin Discretizations of Source Terms

2019-04-10T10:25:23Z

Analysis of Dual Consistency for Discontinuous Galerkin Discretizations of Source Terms Oliver, Todd A.; Darmofal, David L. The effects of dual consistency on discontinuous Galerkin (DG) discretizations of solution and solution gradient dependent source terms are examined. Two common discretizations are analyzed: the standard weighting technique for source terms and the mixed formulation. It is shown that if the source term depends on the first derivative of the solution, the standard weighting technique leads to a dual inconsistent scheme. A straightforward procedure for correcting this dual inconsistency and arriving at a dual consistent discretization is demonstrated. The mixed formulation, where the solution gradient in the source term is replaced by an additional variable that is solved for simultaneously with the state, leads to an asymptotically dual consistent discretization. A priori error estimates are derived to reveal the effect of dual inconsistent discretization on computed functional outputs. Combined with bounds on the dual consistency error, these estimates show that for a dual consistent discretization or the asymptotically dual consistent discretization resulting from the mixed formulation, O(h2p) convergence can be shown for linear problems and linear outputs. For similar but dual inconsistent schemes, only O(hp) can be shown. Numerical results for a one-dimensional test problem confirm that the dual consistent and asymptotically dual consistent schemes achieve higher asymptotic convergence rates with grid refinement than a similar dual inconsistent scheme for both the primal and adjoint solutions as well as a simple functional output.

Shock Capturing with PDE-Based Artificial Viscosity for an Adaptive, Higher-Order Discontinuous Galerkin Finite Element Method

2019-04-13T00:05:32Z

Shock Capturing with PDE-Based Artificial Viscosity for an Adaptive, Higher-Order Discontinuous Galerkin Finite Element Method Barter, Garrett Ehud The accurate simulation of supersonic and hypersonic flows is well suited to higher-order (p > 1), adaptive computational fluid dynamics (CFD). Since these cases involve flow velocities greater than the speed of sound, an appropriate shock capturing for higher-order, adaptive methods is necessary. Artificial viscosity can be combined with a higher-order discontinuous Galerkin finite element discretization to resolve a shock layer within a single cell. However, when a non-smooth artificial viscosity model is employed with an otherwise higher-order approximation, element-to-element variations induce oscillations in state gradients and pollute the downstream flow. To alleviate these difficulties, this work proposes a new, higher-order, state-based artificial viscosity with an associated governing partial differential equation (PDE).In the governing PDE, the shock sensor acts as a forcing term, driving the artificial viscosity to a non-zero value where it is necessary. The decay rate of the higher-order solution modes and edge-based jumps are both shown to be reliable shock indicators. This new approach leads to a smooth, higher-order representation of the artificial viscosity that evolves in time with the solution. For applications involving the Navier-Stokes equations, an artificial dissipation operator that preserves total enthalpy is introduced. The combination of higher-order, PDE-based artificial viscosity and enthalpy-preserving dissipation operator is shown to overcome the disadvantages of the non-smooth artificial viscosity. The PDE-based artificial viscosity can be used in conjunction with an automated grid adaptation framework that minimizes the error of an output functional. Higher-order solutions are shown to reach strict engineering tolerances with fewer degrees of freedom. The benefit in computational efficiency for higher-order solutions is less dramatic in the vicinity of the shock where errors scale with O(h/p). This includes the near-field pressure signals necessary for sonic boom prediction. When applied to heat transfer prediction on unstructured meshes in hypersonic flows, the PDE-based artificial viscosity is less susceptible to errors introduced by poor shock-grid alignment. Surface heating can also drive the output-based grid adaptation framework to arrive at the same heat transfer distribution as a well-designed structured mesh.

Small-Scale Forcing of a Turbulent Boundary Layer

2019-04-10T10:25:05Z

Small-Scale Forcing of a Turbulent Boundary Layer Lorkowski, Thomas In order to understand the effect of small scale forcing on turbulent flows and its implications on control, an experimental investigation is made into the forcing of the inertial scales in the wall region of a turbulent boundary layer. A wall-mounted resonant actuator is used to produce a local vortical structure in the streamwise direction which is convected downstream by the boundary layer flow. The frequency associated with this structure is governed by the resonant frequency of the device and falls in the range of the inertial scales at the Reynolds number of the experiment (Re[theta] [is approximately equal to] 1200). Single and multiple point measurements have been made to determine mean and fluctuating statistics as well as dual-point correlations. These data can be used to infer changes in the structure of the near wall region of the boundary layer that are due to the actuator forcing and subsequently, to construct transfer functions between the actuator and the fluid necessary for active control.

Analysis and design of axisymmetric transonic flow with linearized three-dimensional flow prediction

2019-04-10T10:25:05Z

Analysis and design of axisymmetric transonic flow with linearized three-dimensional flow prediction Ahn, Jon The primary goal of this thesis is the application of the proven stream-surface based Newton method to analysis/design of an axisymmetric nacelle with the actuator disk modeling of a fan. And to further utilize the benefits of the Newton method, full attention is given to the linearized prediction of three-dimensional flow from a base axisymmetric solution, with an aim at replacing costly three-dimensional flow computations during initial nacelle design stages. The resulting code is to be called AMIS (Axisymmetric Multiple-passage Interacting Stream_surface Euler solver) to denote the lineage of Newton solver family pioneered by Drela and Giles, although AMIS has been built from scratch and share a few code lines.

System Identification and Active Control of a Turbulent Boundary Layer

2019-04-13T00:05:22Z

System Identification and Active Control of a Turbulent Boundary Layer Rathnasingham, Ruben An experimental investigation is made into the active control of the near-wall region of a turbulent boundary layer using a linear control scheme. System identification in the boundary layer provides optimal transfer functions that predict the downstream characteristics of the streamwise velocity and wall pressure fluctuation using an array of upstream flush-mounted sensors that are sensitive to spanwise shear. Enhanced detection techniques isolated the large scale turbulent motion and improved the downstream correlations resulting in greater controllability. The techniques were based on the conditioned spectral analysis between adjacent sensors to extract the most correlated flow structures that span the distance between them. The control is applied using a spanwise array of resonant actuators that introduce a pair of streamwise vortices into the flow. Control experiments were carried out for single and multiple input/output configurations. The single output results show that a maximum reduction of 34% is achieved in the streamwise velocity fluctuation. This reduction is greatest at the point of optimization but spans over a few hundred viscous lengths downstream of the actuator and about 50 viscous lengths in the spanwise and wall-normal directions. The wall pressure fluctuation and the mean wall shear stress (measured approximately using mean velocity profiles near the wall) was reduced by 17% and7% respectively. The multiple-input/single-output configuration resulted in a wider spatial influence of the control while maintaining the maximum reductions in the fluctuations. The multiple-input/multiple-output configuration showed a marked increase in the spatial extent of the control (primarily in the spanwise direction), at the expense of a lower reduction in the fluctuations (maximum of 30% and 15% for the streamwise velocity and wall pressure respectively). The bursting frequency was computed from a VITA algorithm applied to the streamwise velocity fluctuation. The bursting frequency was reduced at all threshold levels examined but the maximum reduction of 23% occurred at a threshold level of 3. The span-wise spatial correlation was measured at different streamwise locations downstream of the actuator array. This result suggests that the reduction in turbulent fluctuations obtained using the current control scheme was achieved by reducing the strength of the most coherent flow structures and to inhibit their ability to interact with each other by increasing their average spanwise separation by more than 25% (from ≈ 90l* to 120l*).

Aerodynamic Optimization Based on the Euler and Navier-Stokes Equations using Unstructured Grids

2019-04-10T10:25:23Z

Aerodynamic Optimization Based on the Euler and Navier-Stokes Equations using Unstructured Grids Elliott, Jonathan Kindred The overall problem area addressed is that of efficient aerodynamic shape design through the use of computational fluid dynamics (CFD). A method is presented for performing optimization including modal inverse design and lift-constrained drag minimization -- based on the 2D and 3D Euler equations and the 2D and 3D laminar Navier-Stokes equations. The discrete adjoint approach was taken and the adjoint solvers developed were based on flow solvers developed for use with unstructured grids. Optimization exercises are presented which demonstrate the effectiveness and practicality of the optimization system in finding credible optimal geometries.

Analysis, Fabrication and Testing of a MEMS-based Micropropulsion System

2019-04-09T18:37:12Z

Analysis, Fabrication and Testing of a MEMS-based Micropropulsion System Bayt, Robert L. Various trends in the spacecraft industry are driving the development of low-thrust propulsion systems. These may be needed for fine attitude control, or to reduce the mass of the propulsion system through the use of small lightweight components. The nozzle converts the stored energy in a pressurized gas into kinetic energy through an expansion. The nozzle efficiency is characterized by the amount of kinetic energy leaving the nozzle, and is governed by the exit velocity. Because of the increase in viscous losses as scale is reduced, it was feared that high Mach number supersonic flows could not be generated in micro devices. However, a scaling analysis indicates that the reduction in throat area can be offset by an increase in operating pressure to maintain a constant Reynolds number. Therefore, thrust can be decreased by reducing the nozzle scale, and viscous losses mitigated by running at higher chamber pressures. In order to operate a supersonic nozzle efficiently, the geometry must be contoured to guard against flow separation and reduce the boundary layer thickness at the throat. Deep Reactive Ion Etching enables extruded flow channels of arbitrary in-plane geometry to be created at scales an order of magnitude smaller than conventional machining. These channels are encapsulated by anodically bonding glass to the upper and lower surfaces. Testing indicates that 11.3 milliNewtons of thrust is generated for a nozzle with a 37micron throat width, 308 microns deep, and a 16.9:1 expansion ratio. The exit velocity was 650 m/s, which corresponds to an exit Mach number of 4.2, and an Isp of 66 seconds. This is 100 m/s higher than previously achieved in a micromachined device and demonstrates that supersonic flows can be generated at this scale. The performance of the system is increased by electrothermal augmentation. By resistively heating fins present in the chamber, a thruster temperature of 700◦C has been achieved. This will increase the theoretical Isp to 145 seconds. However, the reduction in Reynolds number with increased chamber temperature causes viscous dissipation to increase and thruster efficiencies to decline. The efficiencies vary with Reynolds number in the same fashion as their unheated counterparts, which confirms that Reynolds number is the governing similarity parameter. The thruster was operated at a temperature of 420◦C, and demonstrated an Isp of 83seconds. This represents an Isp efficiency of 79% for an 8.25:1 area ratio nozzle. These results suggest that MEMS-based micropropulsion systems offer higher performance at lower mass, when operated at Reynolds numbers above 2500 for both heated and unheated thrusters.

Silicon micromachined sensors and sensor arrays for shear-stress measurements in aerodynamic flows

2019-04-13T00:05:31Z

Silicon micromachined sensors and sensor arrays for shear-stress measurements in aerodynamic flows Padmanabhan, Aravind In this thesis we report on a new micromachined floating-element shear-stress sensor for turbulent boundary layer research. Applications in low shear-stress environments such as turbulent boundary layers require extremely high sensitivity to detect the small forces (O(nN)) and correspondingly small displacements (O(A)) of the floating-element. In addition, unsteady measurements in turbulent flows require sensors with high operating bandwidth (~20 kHz). These requirements render most of the existing shear-stress measurement techniques inadequate for this application. In response to the limitations of the existing devices, we have developed a sensor based on a new transduction scheme (optical position sensing by integrated photodiodes). The sensors developed in this thesis have a measured resolution of 0.003 Pa, with a measured range of 133 Pa and the dynamic response of the sensor has been measured to 10 kHz. The new sensor comprises of a floating-element which is suspended by four support tethers. The element displaces in the plane of the sensor chip under the action of the wall shear stress. The displacement of the element causes a ‘shuttering’ of the photodiodes which are placed symmetrically underneath the element on the leading and trailing edge. Under uniform illumination from above, the differential photocurrent (normalized by the average current) from the photodiodes is directly proportional to the magnitude and sign of the shear stress. A set of analytical expressions were developed to predict the static and dynamic response characteristics of the sensor. Based on these estimates, sensors of two different floating-element sizes - 120 [mu]m x 120 [mu]m x 7 [mu]m and 500 [mu]m x500 [mu]m x 7 [mu]m - were fabricated. The devices were statically-calibrated in a laminar flow. The static calibration was performed in a custom-designed laminar-calibration flow cell. The sensors have been calibrated over a range of four orders of wall shear stress (0.003 Pa - 10 Pa) and have demonstrated a linear response over the entire regime (the measured non-linearity was 1% (or better) over the four orders of wall shear stress). In addition, the sensors have shown excellent repeatability, long-term stability and minimal drift. The lowest measured shear stress of 0.003 Pa is three orders of magnitude lower than that has been measured before using micromachined floating-element sensors. The dynamic response of the sensors has also been experimentally verified to 10 kHz. This measurement was performed in a custom-designed plane wave tube (PWT) which was capable of generating oscillating shear stresses of known magnitudes and frequencies, via acoustic plane wave excitation. The measured shear stress showed a square-root of frequency dependence, as predicted by the theoretical relationship. This is the first time that the dynamic response of a floating-element sensor has been experimentally verified using a direct scheme. The sensors have been tested in both laminar and turbulent boundary layers in the low-speed, low-turbulence wind tunnel at MIT. The response in the laminar boundary layer was found to be linear with the same sensitivity as measured in the laminar-calibration flow cell. The sensor was able to transduce shear stresses of 0.01 Pa and lower, in the laminar boundary layer. The same device also demonstrated a linear response during measurements in a turbulent boundary layer. We have made design improvements in the second-generation of floating-element sensors. The first-generation sensors employed a two-photodiode differential sensing scheme. This design was sensitive to non-uniformities in the incident illumination. In order to minimize this we have developed a new three-photodiode scheme. The new scheme was designed to null out any linear gradients in the intensity and has demonstrated 94% reduction in sensitivity to intensity variations when compared to the earlier design. The new photodiode design was implemented in the fabrication of one-dimensional arrays of sensors. The sensor arrays have been calibrated in a laminar flow environment. They exhibited a linear response with a measured sensitivity which was in good agreement with the theoretically predicted value.

The effects of manufacturing variability on turbine vane performance

2019-04-10T10:25:22Z

The effects of manufacturing variability on turbine vane performance Duffner, John D. Gas turbine vanes have airfoil shapes optimized to deliver specific flow conditions to turbine rotors. The limitations of the manufacturing process with regards to accuracy and precision mean that no vane will exactly match the design intent. This research effort is an investigation of the effects of manufacturing-induced geometry variability on the performance of a transonic turbine vane. Variability is characterized by performing Principal Components Analysis (PCA) on a set of measured vanes and then applied to a different vane design. The performance scatter of that design is estimated through Monte Carlo analysis. The effect of a single PCA mode on performance is estimated and it is found that some modes with lower geometric variability can have greater impact on performance metrics. Linear sensitivity analysis, both viscous and inviscid, is carried out to survey performance sensitivity to localized surface perturbations, and tolerances are evaluated using these results. The flow field is seen to be practically insensitive to shape changes upstream of the throat. Especially sensitive locations like the throat and trailing edge are investigated further through nonlinear sensitivity analysis.

Anisotropic Grid Adaptation for Multiple Aerodynamic Outputs

2019-04-10T10:25:06Z

Anisotropic Grid Adaptation for Multiple Aerodynamic Outputs Venditti, David A.; Darmofal, David L. Anisotropic grid–adaptive strategies are presented for viscous flow simulations in which the accurate prediction of multiple aerodynamic outputs (such as the lift, drag, and moment coefficients) is required from a single adaptive solution. The underlying adaptive procedure is based on a merging of adjoint error estimation and Hessian-based anisotropic grid adaptation. Airfoil test cases are presented to demonstrate the various adaptive strategies including a single element airfoil at cruise conditions and a multi-element airfoil in high-lift configuration with flow separation. Numerical results indicate that the lift, drag and moment coefficients are accurately predicted by all of the output–based strategies considered, although slightly better accuracy is obtained in the output(s) for which a particular strategy is specifically designed. Furthermore, the output-based strategies are all shown to be significantly more efficient than pure Hessian-based adaptation in terms of output accuracy for a given grid size.

High Order Finite Element Discretization of the Compressible Euler and Navier-Stokes Equations

2019-04-13T00:05:31Z

High Order Finite Element Discretization of the Compressible Euler and Navier-Stokes Equations Wong, J. S.; Darmofal, D. L.; Peraire, J. We present a high order accurate streamline-upwind/Petrov-Galerkin (SUPG) algorithm for the solution of the compressible Euler and Navier-Stokes equations. The flow equations are written in terms of entropy variables which result in symmetric flux Jacobian matrices and a dimensionally consistent Finite Element discretization. We show that solutions derived from quadratic element approximation are of superior quality next to their linear element counterparts. We demonstrate this through numerical solutions of both classical test cases as well as examples more practical in nature.

Computing Bounds for Linear Functionals of Exact Weak Solutions to Poisson’s Equation

2019-04-13T00:05:22Z

Computing Bounds for Linear Functionals of Exact Weak Solutions to Poisson’s Equation Sauer-Budge, A. M.; Bonet, J.; Huerta, A.; Peraire, J. We present a method for Poisson’s equation that computes guaranteed upper and lower bounds for the values of linear functional outputs of the exact weak solution of the infinite dimensional continuum problem using traditional finite element approximations. The guarantee holds uniformly for any level of refinement, not just in the asymptotic limit of refinement. Given a finite element solution and its output adjoint solution, the method can be used to provide a certificate of precision for the output with an asymptotic complexity which is linear in the number of elements in the finite element discretization.

Output-based Adaptive Meshing Using Triangular Cut Cells

2019-04-10T10:25:07Z

Output-based Adaptive Meshing Using Triangular Cut Cells Fidkowski, Krzysztof J.; Darmofal, David L. This report presents a mesh adaptation method for higher-order (p > 1) discontinuous Galerkin (DG) discretizations of the two-dimensional, compressible Navier-Stokes equations. The method uses a mesh of triangular elements that are not required to conform to the boundary. This triangular, cut-cell approach permits anisotropic adaptation without the difficulty of constructing meshes that conform to potentially complex geometries. A quadrature technique is presented for accurately integrating on general cut cells. In addition, an output-based error estimator and adaptive method are presented, with emphasis on appropriately accounting for high-order solution spaces in optimizing local mesh anisotropy. Accuracy on cut-cell meshes is demonstrated by comparing solutions to those on standard boundary-conforming meshes. Adaptation results show that, for all test cases considered, p = 2 and p = 3 discretizations meet desired error tolerances using fewer degrees of freedom than p = 1. Furthermore, an initial-mesh dependence study demonstrates that, for sufficiently low error tolerances, the final adapted mesh is relatively insensitive to the starting mesh.

Model-Constrained Optimization Methods for Reduction of Parameterized Large-Scale Systems

2019-04-13T00:05:22Z

Model-Constrained Optimization Methods for Reduction of Parameterized Large-Scale Systems Tan, Bui-Thanh Most model reduction techniques employ a projection framework that utilizes a reduced-space basis. The basis is usually formed as the span of a set of solutions of the large-scale system, which are computed for selected values (samples) of input parameters and forcing inputs. In existing model reduction techniques, choosing where and how many samples to generate has been, in general, an ad-hoc process. A key challenge is therefore how to systematically sample the input space, which is of high dimension for many applications of interest. This thesis proposes and analyzes a model-constrained greedy-based adaptive sampling approach in which the parametric input sampling problem is formulated as an optimization problem that targets an error estimation of reduced model output prediction. The method solves the optimization problem to find a locally-optimal point in parameter space where the error estimator is largest, updates the reduced basis with information at this optimal sample location, forms a new reduced model, and repeats the process. Therefore, we use a systematic, adaptive error metric based on the ability of the reduced-order model to capture the outputs of interest in order to choose the snapshot locations that are locally the worst case scenarios. The state-of-the-art subspace trust-region interior-reflective inexact Newton conjugate-gradient optimization solver is employed to solve the resulting greedy partial differential equation constrained optimization problem, giving a reduction methodology that is efficient for large-scale systems and scales well to high-dimensional input spaces. The model-constrained adaptive sampling approach is applied to a steady thermal fin optimal design problem and to probabilistic analysis of geometric mistuning in turbomachinery. The method leads to reduced models that accurately represent the full large-scale systems over a wide range of parameter values in parametric spaces up to dimension 21.

Simulations of a passively actuated oscillating airfoil using a Discontinuous Galerkin method

2019-04-13T00:05:21Z

Simulations of a passively actuated oscillating airfoil using a Discontinuous Galerkin method Israeli, Emily Renee Natural flappers, such as birds and bats, effectively maneuver in transitional, low Reynolds number flow, outperforming any current small engineered flapping vehicle. Thus, engineers are inspired to investigate the flapping dynamics present in nature to further understand the non-tradional flow aerodynamics in which they operate. Undeniably the success of biological flapping flight is the exploitation of fluid structure interaction response i.e. wing mechanics, deformation, and morphing. Even though all these features are encountered in nature, it is important to note that natural flappers have not just adapted to optimize their aerodynamic behavior, they also have evolved due to biological constraints. Therefore, in bio-inspired design one carefully uses the insight gained from understanding natural flappers. Here, a 2-D simulation of a pitching and heaving foil attempts to indicate flapping parameter specifics that generate an efficient, thrust producing flapper. The simulations are performed using a high-order Discontinuous Galerkin finite element solver for the compressible Navier Stokes equations. A brief investigation of a simple problem in which pitch and heave of a foil are prescribed highlights the necessity to use an inexpensive lower fidelity model to narrow down the large design space to a manageable region of interest. A torsional spring is placed at the foil's leading edge to passively modulate the pitch while the foil is harmonically heaved. This model gives the foil passive structural compliance that automatically determines the pitch. The two-way fluid structure interaction thus results from the simultaneous resolution of the fluid and moment equations. This thesis explores the pitch profile and force generation characteristics of the spring-driven, oscillating foil. The passive strategy is found to enhance the propulsive efficiency and thrust production of the flappers specifically in cases where separation is encountered. Furthermore, the passive spring system performs like an ideal actuator that enables the oscillating foil to extract energy from the fluid motion without additional power input. Thus, this is the optimal mechanism to drive the foil dynamics for efficient flight with kinematic flexibility.

Model Reduction for Dynamic Sensor Steering: A Bayesian Approach to Inverse Problems

2019-04-09T19:18:36Z

Model Reduction for Dynamic Sensor Steering: A Bayesian Approach to Inverse Problems Wogrin, Sonja In many settings, distributed sensors provide dynamic measurements over a specified time horizon that can be used to reconstruct information such as parameters, states or initial conditions. This estimation task can be posed formally as an inverse problem: given a model and a set of measurements, estimate the parameters of interest. We consider the specific problem of computing in real-time the prediction of a contamination event, based on measurements obtained by mobile sensors. The spread of the contamination is modeled by the convection diffusion equation. A Bayesian approach to the inverse problem yields an estimate of the probability density function of the initial contaminant concentration, which can then be propagated through the forward model to determine the predicted contaminant field at some future time and its associated uncertainty distribution. Sensor steering is effected by formulating and solving an optimization problem that seeks the sensor locations that minimize the uncertainty in this prediction. An important aspect of this Dynamic Sensor Steering Algorithm is the ability to execute in real-time. We achieve this through reduced-order modeling, which (for our two-dimensional examples) yields models that can be solved two orders of magnitude faster than the original system, but only incur average relative errors of magnitude O(10−3). The methodology is demonstrated on the contaminant transport problem, but is applicable to a broad class of problems where we wish to observe certain phenomena whose location or features are not known a priori.

Model Reduction for Large-Scale Systems with High Dimensional Parametric Input Space

2019-04-10T10:25:07Z

Model Reduction for Large-Scale Systems with High Dimensional Parametric Input Space Bui-Thanh, T.; Willcox, K.; Ghattas, O. A model-constrained adaptive sampling methodology is proposed for reduction of large-scale systems with high-dimensional parametric input spaces. Our model reduction method uses a reduced basis approach, which requires the computation of high-fidelity solutions at a number of sample points throughout the parametric input space. A key challenge that must be addressed in the optimization, control, and probabilistic settings is the need for the reduced models to capture variation over this parametric input space, which, for many applications, will be of high dimension. We pose the task of determining appropriate sample points as a PDE-constrained optimization problem, which is implemented using an efficient adaptive algorithm that scales well to systems with a large number of parameters. The methodology is demonstrated for examples with parametric input spaces of dimension 11 and 21, which describe thermal analysis and design of a heat conduction fin, and compared with statistically-based sampling methods. For this example, the model-constrained adaptive sampling leads to reduced models that, for a given basis size, have error several orders of magnitude smaller than that obtained using the other methods.

Reduced-order aerodynamic models for aeroelastic control of turbomachines

2019-04-13T00:05:21Z

Reduced-order aerodynamic models for aeroelastic control of turbomachines Willcox, Karen Elizabeth Aeroelasticity is a critical consideration in the design of gas turbine engines, both for stability and forced response. Current aeroelastic models cannot provide high-fidelity aerodynamics in a form suitable for design or control applications. In this thesis low-order, high-fidelity aerodynamic models are developed using systematic model order reduction from computational fluid dynamic (CFD) methods. Reduction techniques are presented which use the proper orthogonal decomposition, and also a new approach for turbomachinery which is based on computing Arnoldi vectors. This method matches the input-output characteristic of the CFD model and includes the proper orthogonal decomposition as a special case. Here, reduction is applied to the linearised two-dimensional Euler equations, although the methodology applies to any linearised CFD model. Both methods make efficient use of linearity to compute the reduced-order basis on a single blade passage. The reduced-order models themselves are developed in the time domain for the full blade row and cast in state-space form. This makes the model appropriate for control applications and also facilitates coupling to other engine components. Moreover, because the full blade row is considered, the models can be applied to problems which lack cyclic symmetry. Although most aeroelastic analyses assume each blade to be identical, in practice variations in blade shape and structural properties exist due to manufacturing limitations and engine wear. These blade to blade variations, known as mistuning, have been shown to have a significant effect on compressor aeroelastic properties. A reduced-order aerodynamic model is developed for a twenty-blade transonic rotor operating in unsteady plunging motion, and coupled to a simple typical section structural model. Stability and forced response of the rotor to an inlet flow disturbance are computed and compared to results obtained using a constant coefficient model similar to those currently used in practice. Mistuning of this rotor and its effect on aeroelastic response is also considered. The simple models are found to inaccurately predict important aeroelastic results, while the relevant dynamics can be accurately captured by the reduced-order models with less than two hundred aerodynamic states. Models are also developed for a low-speed compressor stage in a stator/rotor configuration. The stator is shown to have a significant destabilising effect on the aeroelastic system, and the results suggest that analysis of the rotor as an isolated blade row may provide inaccurate predictions.

Integral methods for three-dimensional boundary layers

2019-04-10T10:25:06Z

Integral methods for three-dimensional boundary layers Mughal, Bilal Hafeez Several distinct issues important in integral approximations of the three-dimensional boundary-layer equations are addressed. One of these is the requirement, justified on the basis of the nature of the full differential equations, for hyperbolicity of integral equation systems. It is generally not feasible to analytically determine the mathematical character of these systems, except in very simple cases, because of the empiricism necessary for closure. Furthermore, the use of general systems is inhibited because there is no guarantee that they are hyperbolic. A novel method accommodating the role of both equations and closure, so that systems are always hyperbolic with physically-consistent characteristic directions, is proposed. Another issue considered is the calculation of bidirectional crossflows for which a well-conditional system, for use in Newton solvers, is devised. The validity of this system is demonstrated by comparing results with a numerical solution of the full differential boundary-layer equations for the case of an infinite-swept wing. Finally, a fully-simultaneous scheme coupling inviscid flow, calculated using a simple Panel method, to general integral systems is devised with the facility to use empirical closure parameters as system parameters. The coupling scheme is demonstrated by computing the separated flow downstream of a smooth obstacle. For calculations, the equations are posed in conservation form in local Cartesian coordinates and discretized using the finite-element method. Unlike dissipation schemes used in previous methods, a Petrov-Galerkin streamline upwinding weight function, adapted heuristically for the coupled equation system, is used to control spurious oscillations.

A Posteriori Bounds for Linear Functional Outputs of Hyperbolic Partial Differential Equations

2019-04-13T00:05:21Z

A Posteriori Bounds for Linear Functional Outputs of Hyperbolic Partial Differential Equations Vailong, Hubert J. B. One of the major difficulties faced in the numerical resolution of the equations of physics is to decide on the right balance between computational cost and solutions accuracy, and to determine how solutions errors affect some given “outputs of interest.” This thesis presents a technique to generate upper and lower bounds for outputs of hyperbolic partial differential equations. The outputs of interest considered are linear functionals of the solutions of the equations. The method is based on the construction of an “augmented” Lagrangian, which includes a formulation of the output as a quadratic form to be minimized and the equilibrium equations as a constraint. The corresponding Lagrange multiplier, or adjoint , is determined by solving a problem involving the adjoint of the operator in the original equations. The bounds are then derived from the underlying unconstrained max-min problem. A predictor is also evaluated as the average value of the bounds. Because the resolution of the max-min problem implies the resolution of the original discrete equations, the adjoint on a fine grid is approximated by a hierarchical procedure that consists of the resolution of the problem on a coarser grid followed by an interpolation on the fine grid. The bounds derived from this approximation are then optimized by the choice of natural boundary conditions for the adjoint and by selecting the value of a stabilization parameter. The Hierarchical Bounds Method is illustrated on three cases. The first one is the convection-diffusion equation, where the bounds obtained are very sharp. The second one is a purely convective problem, discretized using a Taylor-Galerkin approach. The third case is based on the Euler equations for a nozzle flow, which can be reduced to a single nonlinear scalar continuous equation. The resulting discrete nonlinear system of equations is obtained by a Taylor-Galerkin method and is solved by the Newton-Raphson method. The problem is then linearized about the computed solution to obtain a linear system similar to the previous cases and produce the bounds. In a last chapter, the Domain Decomposition is introduced. The domain is decomposed into K subdomains and the problem is solved separately on each of them before continuity at the boundaries is imposed, allowing the computation of the bounds to be parallelized. Because the cost of sparse matrix inversion is of order O(N[third]), Domain Decomposition becomes very useful for two-dimensional problems,where the overall cost is divided by K[squared].

Corrections to "Geometric Properties of Gradient Projection Anti-windup Compensated Systems"

2019-04-10T16:02:46Z

Corrections to "Geometric Properties of Gradient Projection Anti-windup Compensated Systems" Teo, Justin; How, Jonathan P. In a conference paper titled "Geometric Properties of Gradient Projection Anti-windup Compensated Systems," two main results were presented. The first is the controller state-output consistency property of gradient projection anti-windup (GPAW) compensated controllers. The second is a geometric bounding condition relating the vector fields of the uncompensated and GPAW compensated closed-loop systems with respect to a star domain. While the controller state-output consistency property stands without modifications, the proof of the geometric bounding condition depends on two lemmas, the proofs of which were found to be faulty. In this report, we present a new proof of the geometric bounding condition using concepts from convex analysis, together with minor miscellaneous corrections.

Gradient Projection Anti-windup Scheme on Constrained Planar LTI Systems

2019-04-12T23:36:38Z

Gradient Projection Anti-windup Scheme on Constrained Planar LTI Systems Teo, Justin; How, Jonathan P. The gradient projection anti-windup (GPAW) scheme was recently proposed as an anti-windup method for nonlinear multi-input-multi-output systems/controllers, the solution of which was recognized as a largely open problem in a recent survey paper. This report analyzes the properties of the GPAW scheme applied to an input constrained first order linear time invariant (LTI) system driven by a first order LTI controller, where the objective is to regulate the system state about the origin. We show that the GPAW compensated system is in fact a projected dynamical system (PDS), and use results in the PDS literature to assert existence and uniqueness of its solutions. The main result is that the GPAW scheme can only maintain/enlarge the exact region of attraction of the uncompensated system. We illustrate the qualitative weaknesses of some results in establishing true advantages of anti-windup methods, and propose a new paradigm to address the anti-windup problem, where results relative to the uncompensated system are sought.

An Intelligent Cooperative Control Architecture

2025-02-06T18:39:00Z

An Intelligent Cooperative Control Architecture How, Jonathan; Choi, Han-Lim; Undurti, Aditya; Redding, Joshua This paper presents an extension of existing cooperative control algorithms that have been developed for multi-UAV applications to utilize real-time observations and/or performance metric(s) in conjunction with learning methods to generate a more intelligent planner response. We approach this issue from a decentralized cooperative control perspective and embed elements of feedback control and active learning, resulting in an new intelligent Cooperative Control Architecture (iCCA). We describe this architecture, discuss some of the issues that must be addressed, and present illustrative examples of cooperative control problems where iCCA can be applied effectively.

Integrating Multiple Alarms & Driver Situation Awareness

2019-09-12T19:48:42Z

Integrating Multiple Alarms & Driver Situation Awareness Cummings, M. L.; Wang, Enlie; Ho, Angela W. L. This study addresses this gap in CAS and intelligent alarm research by examining whether or not a single master alarm warning versus multiple warnings for the different collision warning systems conveys adequate information to the drivers. Intelligent driver warning systems signaling impending frontal and rear collisions, as well as unintentional lane departures were used in this experiment, and all the warnings were presented to drivers through the auditory channel only. We investigated two critical research questions in this study: 1. Do multiple intelligent alarms as opposed to a single master alarm affect drivers’ recognition, performance, and action when they experience a likely imminent collision and unintentional lane departure? 2. Is driver performance and overall situation awareness under the two different alarm alerting schemes affected by reliabilities of the warning systems?

Mitigation of Human Supervisory Control Wait Times through Automation Strategies

2019-04-11T00:37:08Z

Mitigation of Human Supervisory Control Wait Times through Automation Strategies Mitchell, P. J.; Cummings, M. L.; Sheridan, T. B. The application of network centric operations principles to human supervisory control (HSC) domains means that humans are increasingly being asked to manage multiple simultaneous HSC processes. However, increases in the number of available information sources, volume of information and operational tempo, all which place higher cognitive demands on operators, could become constraints limiting the success of network centric processes. In time-pressured scenarios typical of networked command and control scenarios, efficiently allocating attention between a set of dynamic tasks is crucial for mission success. Inefficient attention allocation leads to system wait times, which could eventually lead to critical events such as missed times on targets and degraded overall mission success. One potential solution to mitigating wait times is the introduction of automated decision support in order to relieve operator workload. However, it is not obvious what automated decision support is appropriate, as higher levels of automation may result in a situation awareness decrement and other problems typically associated with excessive automation such as automation bias. To assess the impact of increasing levels of automation on human and system performance in a time-critical HSC multiple task management context, an experiment was run in which an operator simultaneously managed four highly autonomous unmanned aerial vehicles (UAVs) executing an air tasking order, with the overall goal of destroying a pre-determined set of targets within a limited time period. Four increasing levels automated decision support were investigated as well as high and low operational replanning tempos. The highest level of automation, management-byexception, had the best performance across several metrics but had a greater number of catastrophic events during which a UAV erroneously destroyed a friendly target. Contrary to expectations, the collaborative level of decision support, which provided predictions for possible periods of task overload as well as possible courses of action to relieve the high workload, produced the worst performance. This is attributable to an unintended consequence of the automation where the graphical visualization of the computer’s predictions caused users to try to globally optimize the schedules for all UAVs instead of locally optimizing schedules in the immediate future, resulting in them being overwhelmed. Total system wait time across both experimental factors was dominated by wait time caused by lack of situation awareness, which is difficult to eliminate, implying that there will be a clear upper limit on the number of vehicles that any one person can supervise because of the need to stay cognitively aware of unfolding events.

Conceptual Human-System Interface Design for a Lunar Access Vehicle

2019-04-11T00:37:06Z

Conceptual Human-System Interface Design for a Lunar Access Vehicle Smith, Cristin; Essama, Stephane; Duppen, Mark; Marquez, Jessica; Cummings, Mary; Wang, Enlie In support of the vision for humans to establish a large scale, economically viable, permanent human settlement on the Moon within the next 25 years (Space Frontier Foundation, 2005), the next generation lunar landing vehicle must be capable of achieving pinpoint, anytime, anywhere safe landing on the lunar surface with high precision (10- 100m). In addition, this vehicle should support both autonomous and manned lunar missions (NASA ASO-1160). Because of advances in technology over the past thirty-five years since the Apollo landings, the role of the human and automated systems in a new lunar lander system must be reevaluated and redesigned. This report details the design approach and resultant preliminary, conceptual design concepts for a Human-System Interface (H-SI) for a Lunar Access Vehicle (LAV).

Decision Support Design for Workload Mitigation in Human Supervisory Control of Multiple Unmanned Aerial Vehicles

2019-04-11T00:37:06Z

Decision Support Design for Workload Mitigation in Human Supervisory Control of Multiple Unmanned Aerial Vehicles Brzezinski, A. S.; Cummings, M. L. As UAVs become increasingly autonomous, the multiple personnel currently required to operate a single UAV may eventually be superseded by a single operator concurrently managing multiple UAVs. Instead of lower-level tasks performed by today’s UAV teams, the sole operator would focus on high-level supervisory control tasks such as monitoring mission timelines and reacting to emergent mission events. A key challenge in the design of such single-operator systems will be the need to minimize periods of excessive workload that could arise when critical tasks for several UAVs occur simultaneously. To a certain degree, it is possible to predict and mitigate such periods in advance. However, actions that mitigate a particular period of high workload in the short term may create long term episodes of high workload that were previously non-existent. Thus some kind of decision support is needed that facilitates an operator’s ability to evaluate different options for managing a mission schedule in real-time. This paper describes two decision support visualizations designed for supervisory control of four UAVs performing a time-critical targeting mission. A configural display common to both visualizations, named the StarVis, was designed to highlight potential periods of high workload corresponding to the current mission timeline, as well as “what if” projections of possible high workload periods based upon different operator options. The first visualization design allows an operator to compare different high workload mitigation options for individual UAVs. This is termed the local visualization. The second visualization is indicates the combined effects of multiple high workload mitigation decisions on the timeline. This is termed the global visualization. The main advantage of the local visualization is that options can be compared directly; however, the possible effects of these options on the mission timeline are only indicated for the individual UAV primarily affected by the decision. For the global visualization, different decisions can be combined to show possible effects on the system propagated across all UAVs, but the different alternatives of a single decision option alternative cannot be directly compared. An experiment was conducted testing these visualizations against a control with no visualization. Results showed that subject using the local visualization had better performance, higher situational awareness, and no significant increase in workload over the other two experimental conditions. This occurred despite the fact that the local and global StarVis displays were very similar. Not only did the Global StarVis produce degraded results as compared to the local StarVis, but those participants with no visualization performed as well as those with the global StarVis. This disparity in performance despite strong visual similarities in the StarVis designs is attributed to operators’ inability to process all the information presented in the global StarVis as well as the fact that participants with the local StarVis were able to rapidly develop effective cognitive problem strategies. This research effort highlights a very important design consideration, in that a single decision support design can produce very different performance results when applied at different levels of abstraction.

An Analysis of Information Complexity in Air Traffic Control Human Machine Interaction

2019-04-11T00:37:09Z

An Analysis of Information Complexity in Air Traffic Control Human Machine Interaction Tsonis, C. G. This thesis proposes, develops and validates a methodology to quantify the complexity of air traffic control (ATC) human-machine interaction (HMI). Within this context, complexity is defined as the minimum amount of information required to describe the human machine interaction process in some fixed description language and chosen level of detail. The methodology elicits human information processing via cognitive task analysis (CTA) and expresses the HMI process algorithmically as a cognitive interaction algorithm (CIA). The CIA is comprised of multiple functions which formally describe each of the interaction processes required to complete a nominal set of tasks using a certain machine interface. Complexities of competing interface and task configurations are estimated by weighted summations of the compressed information content of the associated CIA functions. This information compression removes descriptive redundancy and approximates the minimum description length (MDL) of the CIA. The methodology is applied to a representative en-route ATC task and interface, and the complexity measures are compared to performance results obtained experimentally by human-in-the-loop simulations. It is found that the proposed complexity analysis methodology and resulting complexity metrics are able to predict trends in operator performance and workload. This methodology would allow designers and evaluators of human supervisory control (HSC) interfaces the ability to conduct complexity analyses and use complexity measures to more objectively select between competing interface and task configurations. Such a method could complement subjective interface evaluations, and reduce the amount of costly experimental testing.

A Framework for an HSI Downselection Tool

2019-04-10T08:43:41Z

A Framework for an HSI Downselection Tool Cunio, Phillip M.; Cummings, M. L. This technical report describes the concept and development of SITHE, the Systems Integration Tool for HSI Evaluation. SITHE is a framework for selecting tools to be used in evaluating complex technical systems in terms of Human-Systems Integration, or HSI. HSI, or Human-Systems Integration, is the process of integrating people, technology, and an organization at a systems level, with full consideration given to the human requirements of the user (Booher, 2003). HSI focuses on the human aspects of system definition, development, and deployment, and integrates considerations related to personnel, training, human factors, habitability, and other human-related concerns into the overall systems acquisition process (US Department of Defense, 2004). HSI is a field of interest to researchers in academia and industry because, although systems continue to grow more complex, they have not achieved the level of autonomy that would permit them to operate successfully without humans either in or on the loop. Humans are still an essential component of most complex systems, especially when the context of operation for the complex system is subject to uncertainty, as in military applications. However, HSI as a broad field can encompass a large number of types of interaction between humans and systems, including but not necessarily limited to supervisory control, mechanics and ergonomics of control operation, and visualization and decision support. The universe of tools for HSI (including hardware, software, processes, and techniques used to evaluate HSI aspects of complex systems) is already large and growing quickly. Many HSI tools are developed for research purposes only, or in an ad-hoc fashion for specific projects, and as such there is no such thing as a standard catalogue of HSI tools. In addition, the need to consider downstream competencies such as flexibility, robustness, and usability, is increasing as HSI systems become more complex. Thus the HSI cost-benefit trade space is ever increasing, making it difficult for decision makers to determine if and to what degree a system actually meets some pre-specified HSI criteria.

Modified Cooper Harper Scales for Assessing Unmanned Vehicle Displays

2019-04-11T00:37:09Z

Modified Cooper Harper Scales for Assessing Unmanned Vehicle Displays Graham, Hudson; Cummings, M. L.; Donmez, Birsen; Brzezinski, A. S. In unmanned vehicle (UV) operations, displays are often the only information link between operators and vehicles. It is essential these displays present information clearly and efficiently so that operators can interact with the UVs to achieve mission objectives. While there are a variety of metrics to evaluate displays, there is no current standardized methodology for operators to subjectively assess a display’s support and identify specific deficiencies. Such a methodology could improve current displays and ensure that displays under development support operator processes. This report presents a quasi- subjective display evaluation tool called the Modified Cooper-Harper for Unmanned Vehicle Displays (MCH-UVD) diagnosis tool. This tool, adapted from the Cooper-Harper aircraft handling scale, allows operators to assess a display, translating their judgments on potential display shortcomings into a number corresponding to a particular deficiency in operator support. The General MCH-UVD can be used to diagnose deficiencies for any UV display, while the Specific MCH-UVD is UV and mission specific in its evaluation of displays. This report presents the General MCH-UVD and provides guidance on how to adapt it to create a Specific MCH-UVD through the use of UV mission taxonomies and a questioning method. A UGV search mission case study provides a how-to guide example for generating a Specific MCH-UVD. The report also presents an experiment conducted to validate the MCH-UVD and assess if a mission-specific version is necessary, or if the general form of the MCH-UVD is sufficient for different UV display evaluation. The report concludes with discussion on how to administer the scale, when a Specific scale is necessary, MCH-UVD diagnosis tool limitations, and future work.

A Predictive Model for Human-Unmanned Vehicle Systems : Final Report

2019-04-10T11:56:07Z

A Predictive Model for Human-Unmanned Vehicle Systems : Final Report Crandall, J. W.; Cummings, M. L. Advances in automation are making it possible for a single operator to control multiple unmanned vehicles (UVs). This capability is desirable in order to reduce the operational costs of human-UV systems (HUVS), extend human capabilities, and improve system effectiveness. However, the high complexity of these systems introduces many significant challenges to system designers. To help understand and overcome these challenges, high-fidelity computational models of the HUVS must be developed. These models should have two capabilities. First, they must be able to describe the behavior of the various entities in the team, including both the human operator and the UVs in the team. Second, these models must have the ability to predict how changes in the HUVS and its mission will alter the performance characteristics of the system. In this report, we describe our work toward developing such a model. Via user studies, we show that our model has the ability to describe the behavior of a HUVS consisting of a single human operator and multiple independent UVs with homogeneous capabilities. We also evaluate the model’s ability to predict how changes in the team size, the human-UV interface, the UV’s autonomy levels, and operator strategies affect the system’s performance.

Selecting Metrics to Evaluate Human Supervisory Control Applications

2019-04-12T10:03:54Z

Selecting Metrics to Evaluate Human Supervisory Control Applications Cummings, M. L.; Pina, P. E.; Donmez, B. The goal of this research is to develop a methodology to select supervisory control metrics. This methodology is based on cost-benefit analyses and generic metric classes. In the context of this research, a metric class is defined as the set of metrics that quantify a certain aspect or component of a system. Generic metric classes are developed because metrics are mission-specific, but metric classes are generalizable across different missions. Cost-benefit analyses are utilized because each metric set has advantages, limitations, and costs, thus the added value of different sets for a given context can be calculated to select the set that maximizes value and minimizes costs. This report summarizes the findings of the first part of this research effort that has focused on developing a supervisory control metric taxonomy that defines generic metric classes and categorizes existing metrics. Future research will focus on applying cost benefit analysis methodologies to metric selection. Five main metric classes have been identified that apply to supervisory control teams composed of humans and autonomous platforms: mission effectiveness, autonomous platform behavior efficiency, human behavior efficiency, human behavior precursors, and collaborative metrics. Mission effectiveness measures how well the mission goals are achieved. Autonomous platform and human behavior efficiency measure the actions and decisions made by the humans and the automation that compose the team. Human behavior precursors measure human initial state, including certain attitudes and cognitive constructs that can be the cause of and drive a given behavior. Collaborative metrics address three different aspects of collaboration: collaboration between the human and the autonomous platform he is controlling, collaboration among humans that compose the team, and autonomous collaboration among platforms. These five metric classes have been populated with metrics and measuring techniques from the existing literature. Which specific metrics should be used to evaluate a system will depend on many factors, but as a rule-of-thumb, we propose that at a minimum, one metric from each class should be used to provide a multi-dimensional assessment of the human-automation team. To determine what the impact on our research has been by not following such a principled approach, we evaluated recent large-scale supervisory control experiments conducted in the MIT Humans and Automation Laboratory. The results show that prior to adapting this metric classification approach, we were fairly consistent in measuring mission effectiveness and human behavior through such metrics as reaction times and decision accuracies. However, despite our supervisory control focus, we were remiss in gathering attention allocation metrics and collaboration metrics, and we often gathered too many correlated metrics that were redundant and wasteful. This meta-analysis of our experimental shortcomings reflect those in the general research population in that we tended to gravitate to popular metrics that are relatively easy to gather, without a clear understanding of exactly what aspect of the systems we were measuring and how the various metrics informed an overall research question.

Assessing the Impact of Haptic Peripheral Displays for UAV Operators

2019-04-11T00:37:05Z

Assessing the Impact of Haptic Peripheral Displays for UAV Operators Cummings, M. L.; Donmez, B.; Graham, H. D. Objectives: A pilot study was conducted to investigate the effectiveness of continuous haptic peripheral displays in supporting multiple UAV supervisory control. Background: Previous research shows that continuous auditory peripheral displays can enhance operator performance in monitoring events that are continuous in nature, such as monitoring how well UAVs stay on their pre-planned courses. This research also shows that auditory alerts can be masked by other auditory information. Command and control operations are generally performed in noisy environments with multiple auditory alerts presented to the operators. In order to avoid this masking problem, another potentially useful sensory channel for providing redundant information to UAV operators is the haptic channel. Method: A pilot experiment was conducted with 13 participants, using a simulated multiple UAV supervisory control task. All participants completed two haptic feedback conditions (continuous and threshold), where they received alerts based on UAV course deviations and late arrivals to targets. Results: Threshold haptic feedback was found to be more effective for late target arrivals, whereas continuous haptic feedback resulted in faster reactions to course deviations. Conclusions: Continuous haptic feedback appears to be more appropriate for monitoring events that are continuous in nature (i.e., how well a UAV keeps its course). In contrast, threshold haptic feedback appears to better support response to discrete events (i.e., late target arrivals). Future research: Because this is a pilot study, more research is needed to validate these preliminary findings. A direct comparison between auditory and haptic feedback is also needed to provide better insights into the potential benefits of multi-modal peripheral displays in command and control of multiple UAVs.

Assessing the Impact of Auditory Peripheral Displays for UAV Operators

2019-04-11T00:37:05Z

Assessing the Impact of Auditory Peripheral Displays for UAV Operators Graham, H. D.; Cummings, M. L. A future implementation of unmanned aerial vehicle (UAV) operations is having a single operator control multiple UAVs. The research presented here explores possible avenues of enhancing audio cues of UAV interfaces for this futuristic control of multiple UAVs by a single operator. This project specifically evaluates the value of continuous and discrete audio cues as indicators of course deviations or late arrivals to targets for UAV missions. It also looks at the value of the audio cues in single and multiple UAV scenarios. To this end, an experiment was carried out on the Multiple Autonomous Unmanned Vehicle Experimental (MAUVE) test bed developed in the Humans and Automation Laboratory at the Massachusetts Institute of Technology with 44 military participants. Specifically, two continuous audio alerts were mapped to two human supervisory tasks within MAUVE. One of the continuous audio alerts, an oscillating course deviation alert was mapped to UAV course deviations which occurred over a continual scale. The other continuous audio alert tested was a modulated late arrival alert which alerted the operator when a UAV was going to be late to a target. In this case the continuous audio was mapped to a discrete event in that the UAV was either on time or late to a target. The audio was continuous in that it was continually on and alerting the participant to the current state of the UAV. It either was playing a tone indicating the UAV was on time to a target or playing a tone indicating the UAV was late to a target. These continuous alerts were tested against more traditional single beep alerts which acted as discrete alerts. The beeps were discrete in that when they were used for monitoring course deviations a single beep was played when the UAV got to specific threshold off of the course or for late arrivals a single beep was played when the UAV became late. The results show that the use of the continuous audio alerts enhances a single operator’s performance in monitoring single and multiple semi-autonomous vehicles. However, the results also emphasize the necessity to properly integrate the continuous audio with the other auditory alarms and visual representations in a display, as it is possible for discrete audio alerts to be lost in aural saliency of continuous audio, leaving operators reliant on the visual aspects of the display.

Information Requirements for MCM and ISR Missions : PUMA Phase II

2019-04-11T00:37:07Z

Information Requirements for MCM and ISR Missions : PUMA Phase II Cummings, M. L.; Massie, A. E.; Nehme, C. E. This document contains display requirements for Littoral Combat Ship (LCS) control station displays to be used by unmanned vehicle units in support of heterogeneous unmanned vehicle missions (such as Special Operations Force (SOF) insertion). The method used for generating the requirements was that of a Hybrid Cognitive Task Analysis (CTA)1 which entails describing a scenario overview of a representative mission, generating event flow diagrams, and depicting decision ladders for the key decisions identified in the event flow diagrams. These steps are then used together to generate an informational requirements summary which includes the situational awareness requirements that are derived from the event flow and display requirements of the decision ladders. This method was developed in Phase I of the PUMA (Plan Understanding for Mixed-initiative control of Autonomous systems) project2. In PUMA I, the mission scenario primarily consisted of Intelligence, Surveillance and Reconnaissance (ISR) tasks. For PUMA II, the scenario has been expanded to include Mine Counter Measures (MCM), Harbor Bottom Image-Mapping (HBI), and Anti- Terrorism / Force Protection (AT/FP) mission types. There is a specific emphasis on the MCM and ISR missions to highlight the informational requirement differences between the two task types. This document incorporates the expanded vehicle and mission type heterogeneities that are present in PUMA II in order to develop a cohesive set of informational requirements necessary for such a complex mission.

An Analysis of Heterogeneity in Futuristic Unmanned Vehicle Systems

2019-04-12T10:03:54Z

An Analysis of Heterogeneity in Futuristic Unmanned Vehicle Systems Nehme, C. E.; Cummings, M. L. Recent studies have shown that with appropriate operator decision support and with enough automation aboard unmanned vehicles, inverting the multiple operators to single-vehicle control paradigm is possible. These studies, however, have generally focused on homogeneous teams of vehicles, and have not completely addressed either the manifestation of heterogeneity in vehicle teams, or the effects of heterogeneity on operator capacity. An important implication of heterogeneity in unmanned vehicle teams is an increase in the diversity of possible team configurations available for each operator, as well as an increase in the diversity of possible attention allocation schemes that can be utilized by operators. To this end, this paper introduces a resource allocation framework that defines the strategies and processes that lead to alternate team configurations. The framework also highlights the sub-components of operator attention allocation schemes that can impact overall performance when supervising heterogeneous unmanned vehicle teams. A subsequent discrete event simulation model of a single operator supervising multiple heterogeneous vehicles and tasks explores operator performance under different heterogeneous team compositions and varying attention allocation strategies. Results from the discrete event simulation model show that the change in performance when switching from a homogeneous team to a heterogeneous one is highly dependent on the change in operator utilization. Heterogeneous teams that result in lower operator utilization can lead to improved performance under certain operator strategies.

Design Methodology for Unmanned Aerial Vehicle (UAV) Team Coordination

2019-04-12T10:03:52Z

Design Methodology for Unmanned Aerial Vehicle (UAV) Team Coordination Cummings, M. L.; da Silva, F. B.; Scott, S. D. Unmanned Aerial Vehicle (UAV) systems, despite having no onboard human pilots, currently require extensive human involvement to accomplish successful mission operations. Further, successful operations also require extensive colalboration between mission stakeholders, including operators, mission commanders, and information consumers (e.g. ground troops relying on intelligence reports in their area). Existing UAV system interfaces provide little to no support for collaboration between remote operators or for operators to collaborate with information consumers. As reliance on UAVs continues to increase in military and civilian operations, this lack of support for collaboration will likely become a substantial limitation of existing UAV systems. In order to introduce effective collaboration support to UAV system interfaces, it is essential to understand, and be able to derive system design requirements that address, the necessary group interactions that occur in UAV task enviroments. However, few collaborative requirements analysis methods exist, and to our knowledge, no method exists that captures design requirements for collaborative decision making in complex, time-critical environments. This report describes the development of a new design requirements analysis method for deriving information and functional requirements that address the collaboration needs of UAV (and other complex task) operators, and the needs of stakeholders interacting with these operators. More specifically, theis method extends a recently developed requirements analysis method, called the Hybrid Cognitive Task Analysis (CTA) method, which enables the generation of information and functional requirements for futuristic UAV system interfaces. The original Hybrid CTA method focused on deriving single user system interface requirements. This work extends this method by introducing analytic steps to identify task and decision-making dependencies between different UAV operations collaborators. This collaborative extension to the Hybrid CTA utilizes the notion of boundary objects, an analytic construct commonly used in the study of group work. Boundary objects are physical or information artifacts that cross the task boundaries between members of distinct groups. Identifying boundary objects in complex task operations help the analyst to identify task and decision-making dependencies between local and remote collaborators. Understanding these dependencies helps to identify information sharing requirements that the UAV system should support. This report describes the analytic steps of the collaborative extension, and provides background information on the original Hybrid CTA method and the boundary object construct. The report also describes a project in which the new design requirements method was used to revise a proposed set of UAV operator displays.

An Experimental Platform for Investigating Decision and Collaboration Technologies in Time-Sensitive Mission Control Operations

2019-04-11T00:37:07Z

An Experimental Platform for Investigating Decision and Collaboration Technologies in Time-Sensitive Mission Control Operations Scott, S. D.; Cummings, M. L. This report describes the conceptual design and detailed architecture of an experimental platform developed to support investigations of novel decision and collaboration technologies for complex, time-critical mission control operations, such as military command and control and emergency response. In particular, the experimental platform is designed to enable exploration of novel interface and interaction mechanisms to support both human-human collaboration and human-machine collaboration for mission control operations involving teams of human operators engaged in supervisory control of intelligent systems, such as unmanned aerial vehicles (UAVs). Further, the experimental platform is designed to enable both co-located and distributed collaboration among operations team members, as well as between team members and relevant mission stakeholders. To enable initial investigations of new information visualization, data fusion, and data sharing methods, the experimental platform provides a synthetic task environment for a representative collaborative time-critical mission control task scenario. This task scenario involves a UAV operations team engaged in intelligence, surveillance, and reconnaissance (ISR) activities. In the experimental task scenario, the UAV team consists of one mission commander and three operators controlling multiple, homogeneous, semi-autonomous UAVs. In order to complete its assigned missions, the UAV team must coordinate with a ground convoy, an external strike team, and a local joint surveillance and target attack radar system (JSTARS). This report details this task scenario, including the possible simulation events that can occur and the logic governing the simulation dynamics. In order to perform human-in-the-loop experimentation within the synthetic task environment, the experimental platform also consists of a physical laboratory designed to emulate a miniature command center. The Command Center Laboratory comprises a number of large-screen displays, multi-screen operator stations, and mobile, tablet-style devices. This report details the physical configuration and hardware components of this Command Center Laboratory. Details are also provided of the software architecture used to implement the synthetic task environment and experimental interface technologies to facilitate user experiments in this laboratory. The report also summarizes the process of conducting an experiment in the experimental platform, including details of scenario design, hardware and software instrumentation, and participant training. Finally, the report suggests several improvements that could be made to the experimental platform based on insights gained from initial user experiments that have been conducted in this environment.

Assisting Interruption Recovery in Mission Control Operations

2019-04-10T20:29:01Z

Assisting Interruption Recovery in Mission Control Operations Wan, J.; Scott, S. D.; Cummings, M. L. Frequent interruptions are commonplace in modern work environments. The negative impacts of interruptions are well documented and include increased task completion and error rates in individual task activities, as well as interference with team coordination in team-based activities. The ramifications of an interruption in mission control operations, such as military command and control and emergency response, can be particularly costly due to the time and life-critical nature of these operations. The negative impacts of interruptions have motivated recent developments in software tools, called interruption recovery tools, which help mitigate the effects of interruptions in a variety of task environments. However, mission control operations introduce particular challenges for the design of these tools due to the dynamic and highly collaborative nature of these environments. To address this issue, this report investigates methods of reducing the negative consequences of interruptions in complex, mission control operations. In particular, this report focuses on supporting interruption recovery for team supervisors in these environments, as the research has shown that supervisors are particularly susceptible to frequent interruptions. Based on the results of a requirements analysis, which involved a cognitive task analysis of a representative mission control task scenario, a new interruption recovery tool, named the Interruption Recovery Assistance (IRA) tool, was developed. In particular, the IRA tool was designed to support a military mission commander overseeing a team of unmanned aerial vehicle (UAV) operators performing ground force protection operations. The IRA tool provides the mission commander a visual summary of mission changes, in the form of an event bookmark timeline. It also provides interactive capabilities to enable the commander to view additional information on the primary task displays when further detail about a particular mission event is needed. The report also presents the findings from a user study that was conducted to evaluate the effectiveness of the IRA tool on interruption recovery during collaborative UAV mission operations. The study produced mixed results regarding the effectiveness of the IRA tool. The statistical analysis indicated a negative impact on recovery time, while indicating a positive impact on decision accuracy, especially in complex task situations. The study also indicated that the effect of the IRA tool varied across differ user populations. In particular, the IRA tool tended to provide greater benefits to participants without military experience, compared to military participants involved in the study. The qualitative findings from the study provided key insights into the impact and utility of the IRA tool. These insights were used to identify several future research and design directions related to interruption recovery in mission control operations.

Designing Decision and Collaboration Support Technology for Operators in Multi-UAV Operations Teams

2019-04-12T10:03:53Z

Designing Decision and Collaboration Support Technology for Operators in Multi-UAV Operations Teams Scott, S. D.; Cummings, M. L.; Almirao, F. M.; da Silva, F. B. Effective team collaboration and timely decision-making significantly influence the outcome of time-sensitive military operations. The increasing complexity introduced by the recent move towards network centric operations (NCO) in U.S. military operations provides additional challenges for efficient decision-making. Future operations will include co-located and distributed teams composed of operators from difference services, often at different global locations. Military operations which require extremely quick decisions, such as operations dealing with time-sensitive targets (TST) like improvised explosive devices (IEDs), are particularly challenging in NCO teaming environments. Operators in TST environments not only have to manage overwhelming amounts of target-related information, but also have the overhead of communicating and coordinating with co-located and distributed team members. Given the increasing trend for modern hostile forces to employ unconventional weapons such as IEDs and suicide bombs, the success of TST operations are becoming critical to current and future military operations. Providing TST teams with effective tools for communicating and coordinating their efforts is key to enabling their success.

Shadow TUAV Single Operator Consolidation : Display Assessment

2019-04-10T20:42:37Z

Shadow TUAV Single Operator Consolidation : Display Assessment Visser, Mark; Cummings, M. L.; Marquez, Jessica J. Currently, Shadow UAV operations require two people: the Air Vehicle Operator (AVO) and the Mission Payload Operator (MPO). A previous workload study demonstrated that it is possible to combine these two positions such that one person can assume both roles (Appendix A). However, to achieve this consolidation, improved displays in terms of usability and increased automated functionality will be necessary to keep the workload of the single operator to acceptable levels. To demonstrate the types of changes that will need to occur for successful AVO and MPO consolidation, this report focuses on display and automation improvements in the following three areas: systems management, vehicle situation awareness, and payload operations. For each of these areas, a previous display has either been designed or improved upon, always applying human factors design principles. Each of these display redesigns exemplifies how operator workload can be decreased, as well as improve overall mission capability.

A UAV Mission Hierarchy

2019-04-12T10:03:54Z

A UAV Mission Hierarchy Crandall, J. W.; Nehme, C. E.; Cummings, M. L. In the following sections, each of the primary missions are decomposed into mission planning, management, and replanning segments in order to identify what the primary functions a human operator will need to perform. The goal is to understand what tasks/functions are common across different UAV missions and platforms in order to map the generalizability of any particular research project.

Integrating Automobile Multiple Intelligent Warning Systems : Performance and Policy Implications

2019-04-09T16:18:02Z

Integrating Automobile Multiple Intelligent Warning Systems : Performance and Policy Implications Ho, Angela Wei Ling Intelligent driver warning systems can be found in many high-end vehicles on the road today, which will likely rapidly increase as they become standard equipment. However, introducing multiple warning systems into vehicles could potentially add to the complexity of the driving task, and there are many critical human factors issues that should be considered, such as how the interaction between alarm alerting schemes, system reliabilities, and distractions combine to affect driving performance and situation awareness. In addition, there are also questions with respect to whether there should be any minimum safety standards set to ensure both functional and usage safety of these systems, and what these standards should be. An experiment was conducted to study how a single master alert versus multiple individual alerts of different reliabilities affected drivers’ responses to different imminent collision situations while distracted. A master alert may have advantages since it reduces the total number of alerts, which could be advantageous especially with the proliferation of intelligent warning systems. However, a master alert may also confuse drivers, since it does not warn of a specific hazard, unlike a specific alert for each warning systems. Auditory alerts were used to warn of imminent frontal and rear collisions, as well as unintentional left and right lane departures. Low and high warning reliabilities were also tested. The different warning systems and reliability factors produced significantly different reaction times and response accuracies. The warning systems with low reliability caused accuracy rates to fall more than 40% across the four warning systems. In addition, low reliability systems also induced negative emotions in participants. Thus, reliability is one of the most crucial determinants of driving performance and the safety outcome, and it is imperative that warning systems are reliable. For the master versus distinct alarms factor, drivers responded statistically no different to the various collision warnings for both reaction times and accuracy of responses. However, in a subjective postexperiment assessment, participants preferred distinct alarms for different driver warning systems, even though their objective performance showed no difference to the different alerting schemes. This study showed that it was essential to design robust and reliable intelligent warning systems. However, there are no existing safety standards today to ensure that these systems are safe before they are introduced into vehicles, even though such systems are already available in high-end cars. Even though there are tradeoffs in having standards, such as increased time-to-market and possible loss of innovation, I recommend that safety standards be set nonetheless, since standards will ensure the safety performance of warning systems, to an extent. In terms of functional safety, safety standards should be performance-based, and should specify a minimum level of reliability. In terms of usage safety, the standards should also be performance-based, where driving performance can be indicated by measures such as reaction time, lane position, heading distance and accuracy of responses. In addition, multiple threat scenarios should also be tested. In terms of design guidelines, the various human factors guidelines from different countries should be harmonized internationally to ensure that manufacturers have access to a consistent set of guidelines. Finally, it is also important that these standards, especially for usage safety, specify tests with not just the average driver, but also with peripheral driving populations including novice and elderly drivers.

Audio Decision Support for Supervisory Control of Unmanned Vehicles : Literature Review

2019-04-11T00:37:06Z

Audio Decision Support for Supervisory Control of Unmanned Vehicles : Literature Review Nehme, C. E.; Cummings, M. L. Purpose of this literature review: To survey scholarly articles, books and other sources (dissertations, conference proceedings) relevant to the use of the audio supervisory control of unmanned vehicles.

Multiple Alarms and Driving Situational Awareness

2019-04-12T10:03:52Z

Multiple Alarms and Driving Situational Awareness Ho, Angela W. L.; Cummings, Mary L. There is increasing interest in actively mitigating safety in vehicles beyond that of improving crash worthiness. According to the National Highway Transportation Safety Administration (NHTSA), there are more than 40,000 deaths on highways each year. This number may be decreasing with increasing active public concern and awareness for the use of safety restraints, but the numbers are still in excess of 40,000 deaths annually. Focusing on crash-worthiness as a measure of safety in vehicles will eventually reach a point of diminishing return, thus there is a need for automotive manufacturers to shift their safety focus to crash avoidance safety systems (Runge, 2002). In the public domain, significant progress and advancements have been made under the Intelligent Vehicles Initiative (IVI) set up by U.S. Department of Transportation to prevent motor vehicle crashes by assisting drivers in avoiding hazardous mistakes (U.S DOT, 1998). One IVI focus area is facilitating the rapid deployment of Collision Avoidance Systems (CAS) in vehicles. Collision Avoidance Systems are a subset of Advanced Vehicle Control Safety Systems (AVCSS) which come under the umbrella of Intelligent Transportation Systems (ITS). These Collision Avoidance Systems warn drivers of imminent collisions and can potentially help to save lives. Primary directions of research in CAS are determining implementation strategies and technologies in vehicles and roadway infrastructure, as well as optimizing the driving performance of different populations of drivers when using CAS. In CAS implementation, vehicles will communicate with other vehicles as well as with the roadway infrastructure via sensors and telecommunication networks. The data obtained can then be used in Collision Avoidance Systems. Vehicle-to-vehicle CAS include warnings that trigger when a vehicle is about to collide with another vehicle. Examples include Frontal Warning, Rear Warning and Blind Spot Detection Warnings. Vehicle-to-infrastructure CAS include warnings that trigger when a vehicle is about to have a collision with the roadway infrastructure. Examples include Intersection Warnings, Lane Departure Warnings, Curve Speed Warnings and Road-condition Warnings. Driving in a dynamic environment has become increasingly complex, such that drivers must visually track objects, monitor a constantly changing system, manage system information, to include the explosion of telematics, and make decisions in this dynamic and potentially high mental workload environment. Introducing Collision Avoidance Systems into vehicles could add to the complexity of this dynamic environment as different drivers will respond differently to Collision Avoidance Systems and there are many critical human factors issues that require investigation.

Cognitive Task Analysis for the LCS Operator

2019-04-12T10:03:52Z

Cognitive Task Analysis for the LCS Operator Scott, S. D.; Cummings, M. L. The following Tables and Figures detail the cognitive task analysis (CTA) performed to determine the information requirements needed to support a single operator located aboard the futuristic Littoral Combat Ship (LCS). This operator is responsible for controlling four underwater unmanned vehicles in conjunction with a UAV operating on a shared network. • Table 1 is a scenario task overview that breaks the overall mission into 3 phases (planning, execution, and recovery) and then details the subtasks for each of the 3 mission phases. • Figure 1 is an event flow diagram that demonstrates what events must occur in a temporal order for each of the 3 phases. There are three basic event types in Figure 1: 1) a loop (L) that represents a process that occurs in a looping fashion until some predetermined event occurs, 2) a decision (D) that represents some decision that is required from the LCS operator, and 3) a process (P) which requires some human-computer interaction to support the required tasks. In each event block, an alphanumeric code is included which labels that particular event type (L#, D#, P#). This label is important because later information requirements will be mapped to one of these events. • Table 2, which details the situation awareness (SA) requirements for the LCS Operator for each of the 3 mission phases and associated subtasks. Each of these SA requirements is mapped directly to one or more events in Figure 1. Because the decisions in Figure 1 represent critical events that require detailed understanding of what information and knowledge is needed to support the operator’s decision-making process, decision ladders were constructed for the diamonds and loops in Figure 1 that correspond to an involved decision process to resolve the question being posed at that stage in the event flow (Figures 2-4). Decision ladders are modeling tools that capture the states of knowledge and information-processing activities necessary to reach a decision. Decision ladders can help identify the information that either the automation and/or the human will need to perform or monitor a task. Decision Ladders, illustrate the need not only for the same information identified by the cognitive task analysis, but the need for several other pieces of information such as the need for visual or aural alerts in contingency situations. In Figures 2-4, three versions are included that detail (a) the basic decision ladder, (b) the decision ladder with corresponding display requirements, and (c) the decision ladder with possible levels of automation. • Figure 2 represents the automated target recognition (ATR) decision ladder (D3 from Event Flow): (a) decision ladder, (b) decision ladder with corresponding display requirements, and (c) decision ladder with possible levels of automation. • Figure 3 shows the decision ladder information and knowledge requirements for the sentry handoff (L3 from Event Flow). • Figure 4, the UUV Recovery Decision Ladder (D7 from Event Flow), illustrates what information is nominally needed. Since this phase was not a major focus, the decision ladder is not as detailed as it could be. This should be a point of focus in Phase II. Lastly Figure 5 demonstrates the coordination loop that must occur in the case where a handoff failure occurs (for a number of reasons to include equipment failure, communication delays, etc.) Again, because the multi-player coordination issues are not a primary focus in Phase I but are a significant consideration for any follow-on phases. In support of Plan Understanding for Mixed-initiative control of Autonomous systems (PUMA)

Using Support Vector Machines and Bayesian Filtering for Classifying Agent Intentions at Road Intersections

2019-04-11T00:37:05Z

Using Support Vector Machines and Bayesian Filtering for Classifying Agent Intentions at Road Intersections Aoude, Georges S.; How, Jonathan P. Classifying other agents’ intentions is a very complex task but it can be very essential in assisting (autonomous or human) agents in navigating safely in dynamic and possibly hostile environments. This paper introduces a classification approach based on support vector machines and Bayesian filtering (SVM-BF). It then applies it to a road intersection problem to assist a vehicle in detecting the intention of an approaching suspicious vehicle. The SVM-BF approach achieved very promising results.

Human Supervisory Control Issues in Network Centric Warfare

2019-04-12T10:03:52Z

Human Supervisory Control Issues in Network Centric Warfare Cummings, M. L.; Mitchell, P. J.; Sheridan, T. B. Network centric warfare (NCW) is a concept of operations that seeks to increase combat power by linking battlespace entities to effectively leverage information superiority. A network centric force must be supported by sophisticated automated systems, so human-computer interactions are an important aspect of overall performance. These interactions are examples of human supervisory control (HSC), in which a human operator intermittently interacts with a computer, receiving feedback from and providing commands to a controlled process or task environment, which is connected to that computer. The Department of Defense (DoD) has recognized that a lack of understanding of HSC issues relevant to NCW is a significant barrier limiting NCW’s potential benefits. This report identifies eight central HSC issues that could significantly impact operator performance in NCW: Appropriate levels of automation, information overload, adaptive automation, distributed decision-making through team coordination, complexity measures, decision biases, attention allocation, and supervisory monitoring of operators. The adoption of NCW principles is often misunderstood as requiring increased levels of automation, which makes this a particularly acute problem as NCW is implemented. For the average operator, implementation of NCW will exponentially add to the number of available information sources as well as the volume of information flow. Without measures to mediate this volume, information overload will occur much more often than in the past, as it will be far easier for operators to obtain or be given more information than they can adequately handle. One way to alleviate this problem is through adaptive automation, which has been shown in certain cases to lower workload. There will also be a corresponding increase in information complexity, quantified by complexity measures, which can cause a loss of situation awareness or an unmanageable increase in mental workload. It is therefore essential that the interfaces with which NCW operators interact help to reduce and manage this increased level of data complexity. A more fundamental issue associated with the increase in the number of available information sources, volume of information, and operational tempo under NCW are operator attention allocation strategies. NCW hinges on successful information sharing, so knowledge of the relationship between perceived and actual high priority tasks and associated time management strategies, as well as the impact of task disruptions is critical. As a result of NCW information sharing, command and control (C2) structures will change significantly. Traditional methods where commands are passed down from higher levels in a command hierarchy will, at least, be partially replaced by distributed decisionmaking and low-level team coordination. Therefore, understanding how to make effective, timepressured decisions within these organizational structures takes on greater importance in NCW. These redefined C2 structures will drive an increase in information-sharing tempo and rapid decision-making. Under these time pressures, the use of heuristics and other naturalistic decisionmaking methods may be subject to undesirable decision biases, both for individuals and groups. Lastly, how automated technology can be leveraged in order to observe and diagnose HSC issues during supervisory monitoring of operators is another significant area of concern since NCW will contain embedded HSC systems.

Potential Flow Calculations of Axisymmetric Ducted Wind Turbines

2019-04-10T16:50:12Z

Potential Flow Calculations of Axisymmetric Ducted Wind Turbines Widnall, Sheila An incompressible potential-flow vortex method has been constructed to analyze the flow field of a ducted wind turbine following that outlined by Lewis (1991). Attention is paid to balancing the momentum change in the flow to the total longitudinal forces acting on the duct-turbine combination: the pressure force on the actuator disk plus the pressure forces acting on the duct, which typically includes a negative component of drag due to high leading-edge suction. These forces are shown to balance the momentum changes in the flow, resulting in a model for power output from a ducted wind turbine over a wide range of pressure changes across the actuator disk. The results are compared to the Betz actuator disk model and it is shown that the maximum power output from a ducted turbine occurs at a lower value of pressure drop/momentum extraction than that for a bare turbine.

On Approximate Dynamic Inversion

2019-04-12T09:57:40Z

On Approximate Dynamic Inversion Teo, Justin; How, Jonathan P. Approximate Dynamic Inversion has been established as a method to control minimum-phase, nonaffine-in-control systems [1]. In this report, we re-state the main results of [1], clarify some minor notational errors, and prove the same results in an expanded form. In the large, the main results of [1] still stand. The development follows [1] closely, and no novelty is claimed herein. The purpose of this report is mainly to supplement our existing results in [2]–[4] that rely heavily on the results of [1].

Reaching Consensus with Imprecise Probabilities over a Network

2019-04-12T09:51:10Z

Reaching Consensus with Imprecise Probabilities over a Network Bertuccelli, Luca F.; How, Jonathan P. This paper discusses the problem of a distributed network of agents attempting to agree on an imprecise probability over a network. Unique from other related work however, the agents must reach agreement while accounting for relative uncertainties in their respective probabilities. First, we assume that the agents only seek to agree to a centralized estimate of the probabilities, without accounting for observed transitions. We provide two methods by which such an agreement can occur which uses ideas from Dirichlet distributions. The first methods interprets the consensus problem as an aggregation of Dirichlet distributions of the neighboring agents. The second method uses ideas from Kalman Consensus to approximate this consensus using the mean and the variance of the Dirichlet distributions. A key results of this paper is that we show that when the agents are simultaneously actively observing state transitions and attempting to reach consensus on the probabilities, the agreement protocol can be insensitive to any new information, and agreement is not possible. Ideas from exponential fading are adopted to improve convergence and reach a consistent agreement.

Equivalence between Approximate Dynamic Inversion and Proportion-Integral Control

2019-04-11T01:18:54Z

Equivalence between Approximate Dynamic Inversion and Proportion-Integral Control Teo, Justin; How, Jonathan P. Approximate Dynamic Inversion (ADI) has been established as a method to control minimum-phase, nonaffine-in-control systems. Previous results have shown that for single-input nonaffine-in-control systems, every ADI controller admits a linear Proportional-Integral (PI) realization that is largely independent of the nonlinear function that defines the system. In this report, we first present an extension of the ADI method for single-input nonaffine-in-control systems that renders the closed-loop error dynamics independent of the reference model dynamics. The equivalent PI controller will be derived and both of these results are then extended to multi-input nonaffine-in-control systems.

Spatial orientation and navigation in microgravity

2019-04-12T07:40:32Z

Spatial orientation and navigation in microgravity Oman, Charles M. This chapter summarizes the spatial disorientation problems and navigation difficulties described by astronauts and cosmonauts, and relates them to research findings on orientation and navigation in humans and animals. Spacecraft crew are uniquely free to float in any relative orientation with respect to the cabin, and experience no vestibular and haptic cues that directly indicate the direction of “down”. They frequently traverse areas with inconsistently aligned visual vertical cues. As a result, most experience “Visual Reorientation Illusions” (VRIs) where the spacecraft floors, walls and ceiling surfaces exchange subjective identities. The illusion apparently results from a sudden reorientation of the observer’s allocentric reference frame. Normally this frame realigns to local interior surfaces, but in some cases it can jump to the Earth beyond, as with “Inversion Illusions” and EVA height vertigo. These perceptual illusions make it difficult for crew to maintain a veridical perception of orientation and place within the spacecraft, make them more reliant upon landmark and route strategies for 3D navigation, and can trigger space motion sickness. This chapter distinguishes VRIs and Inversion Illusions, based on firsthand descriptions from Vostok, Apollo, Skylab, Mir, Shuttle and International Space Station crew. Theories on human “gravireceptor” and “idiotropic” biases, visual “frame” and “polarity” cues, top-down processing effects on object orientation perception, mental rotation and “direction vertigo” are discussed and related to animal experiments on limbic head direction and place cell responses. It is argued that the exchange in perceived surface identity characteristic of human VRIs is caused by a reorientation of the unseen allocentric navigation plane used by CNS mechanisms coding place and direction, as evidenced in the animal models. Human VRI susceptibility continues even on long flights, perhaps because our orientation and navigation mechanisms evolved to principally support 2D navigation. Manuscript for Spatial Processing in Navigation, Imagery and Perception, F. Mast and L. Janeke, eds.

Hover, Transition, and Level Flight Control Design for a Single-Propeller Indoor Airplane

2019-04-12T08:06:29Z

Hover, Transition, and Level Flight Control Design for a Single-Propeller Indoor Airplane Frank, Adrian; McGrew, James; Valenti, Mario; Levine, Daniel; How, Jonathan P. This paper presents vehicle models and test flight results for an autonomous fixed-wing airplane that is designed to take-off, hover, transition to and from level-flight modes, and perch on a vertical landing platform in a highly space constrained environment. By enabling a fixed-wing UAV to achieve these feats, the speed and range of a fixed-wing aircraft in level flight are complimented by hover capabilities that were typically limited to rotorcraft. Flight and perch landing results are presented. This capability significantly eases support and maintenance of the vehicle. All of the flights presented in this paper are performed using the MIT Real-time Autonomous Vehicle indoor test ENvironment (RAVEN).