Engineering topics

Williams, D. H.

Publications and source records attributed to Williams, D. H..

11 records

NASA NTRS1986

Advanced ATC - An aircraft perspective

The principal operational improvements desired by commercial aircraft operators in the United States are efficient aircraft operations and delay reductions at the major terminals. This paper describes efforts underway within the Advanced Transport Operating Systems Program at the Langley Research Center to provide a technology basis for reducing delay while improving aircraft efficiency. The principal thrust is the development of time-based traffic control concepts which could be used within the framework of the upgraded National Airspace System and which would allow conventionally equipped aircraft to operate in a manner compatible with advanced aircraft.

Credeur, L.↗

NASA NTRS1986

Design factors and considerations for a time-based flight management system

Recent NASA Langley Research Center research to develop a technology data base from which an advanced Flight Management System (FMS) design might evolve is reviewed. In particular, the generation of fixed range cruise/descent reference trajectories which meet predefined end conditions of altitude, speed, and time is addressed. Results on the design and theoretical basis of the trajectory generation algorithm are presented, followed by a brief discussion of a series of studies that are being conducted to determine the accuracy requirements of the aircraft and weather models resident in the trajectory generation algorithm. Finally, studies to investigate the interface requirements between the pilot and an advanced FMS are considered.

Vicroy, D. D.↗

NASA NTRS1986

Impact of mismodeled idle engine performance on calculation and tracking of optimal 4-D descent trajectories

Advanced flight management systems are being developed which are capable of calculating optimal 3-D and 4-D flight trajectories for arbitrary fuel and time costs. These systems require mathematical models of airplane performance in order to compute the optimal profiles. Mismodeled idle engine characteristics can result in descent trajectories requiring excessive throttle and/or speedbrake activity in order to achieve the desired end conditions. This paper evaluates the cost and fuel penalties, trajectory variations, and flight control requirements associated with typical idle engine modeling errors for a twin-jet transport airplane. Variations in idle power setting, thrust, fuel flow, and surge bleed operation were evaluated for a cruise/descent flight segment. The results of this analysis provide insight into the penalties associated with uncertainties in idle engine performance and suggest methods of modeling which minimize these penalties.

Williams, D. H.↗

NASA NTRS1983

Time-based self-spacing techniques using cockpit display of traffic information during approach to landing in a terminal area vectoring environment

A simulation study was undertaken to evaluate two time-based self-spacing techniques for in-trail following during terminal area approach. An electronic traffic display was provided in the weather radarscope location. The displayed self-spacing cues allowed the simulated aircraft to follow and to maintain spacing on another aircraft which was being vectored by air traffic control (ATC) for landing in a high-density terminal area. Separation performance data indicate the information provided on the traffic display was adequate for the test subjects to accurately follow the approach path of another aircraft without the assistance of ATC. The time-based technique with a constant-delay spacing criterion produced the most satisfactory spacing performance. Pilot comments indicate the workload associated with the self-separation task was very high and that additional spacing command information and/or aircraft autopilot functions would be desirable for operational implementational of the self-spacing task.

Williams, D. H.↗

NASA NTRS1983

Simulation study of traffic-sensor noise effects on utilization of traffic situation display for self-spacing task

The effect of traffic sensor noise on the ability of a pilot to perform an intrail spacing task was determined. The tests were conducted in a fixed base cockpit simulator configured as a current generation transport aircraft, with an electronic traffic display provided in the weather radarscope location. The true positions of the traffic were perturbed in both relative range and azimuth by random errors to simulate traffic sensor noise associated with an onboard sensor. The evaluation task involved simulated instrument approaches into a terminal area while maintaining self separation on a lead aircraft. Separation performance data and pilot subjective ratings and comments were obtained. The results of the separation data indicate that displayed traffic position errors, having standard deviation values up to 0.3-n.mi. range and 8 deg azimuth, had negligible effect on the spacing performance achieved by the pilots. Speed profiles of the lead aircraft, display of the lead aircraft groundspeed, and individual pilot techniques were found to significantly affect the mean spacing performance.

Williams, D. H.↗

NASA NTRS1983

Self-separation in terminal areas using CDTI

The Langley Research Center is participating in a joint NASA/FAA program designed to explore the potential benefits and liabilities of Cockpit Display of Traffic Information (CDTI) for a broad range of applications. As a part of this effort, part-task piloted simulations have been conducted to determine the effect of various display parameters and separation criteria on terminal area in-trail following using CDTI. Current experiments are evaluating cockpit procedures and crew workload aspects of self-separation tasks in a simulated full-system terminal area environment. This paper will summarize the results of the part-task terminal area experiments and discuss the current full-system simulation experiments involving active self-separation tasks.

Williams, D. H.↗

NASA NTRS1983

Voice interactive electronic warning system (Views)

The ability of military helicopters to penetrate the Forward Line of Troops (FLOT) has increased in connection with the utilization of low-level 'Nap-of-the-Earth' (NOE) flying procedures. However, the workload of the pilot engaged in the implementation of the required maneuvers is very high. Possibilities for reducing this workload are being investigated. The present study is concerned with the introduction of an integrated warning system in the cockpit. An integrated warning system simulation study is discussed, taking into account aspects of methodology, and results. Three voice types were evaluated, including male digitized, female digitized, and digitized.

Voorhees, J. W.↗

NASA NTRS1980

Response time effects of alerting tone and semantic context for synthesized voice cockpit warnings

Some handbooks and human factors design guides have recommended that a voice warning should be preceded by a tone to attract attention to the warning. As far as can be determined from a search of the literature, no experimental evidence supporting this exists. A fixed-base simulator flown by airline pilots was used to test the hypothesis that the total 'system-time' to respond to a synthesized voice cockpit warning would be longer when the message was preceded by a tone because the voice itself was expected to perform both the alerting and the information transfer functions. The simulation included realistic ATC radio voice communications, synthesized engine noise, cockpit conversation, and realistic flight routes. The effect of a tone before a voice warning was to lengthen response time; that is, responses were slower with an alerting tone. Lengthening the voice warning with another work, however, did not increase response time.

Simpson, C. A.↗

NASA NTRS1980

Some human factors issues in the development and evaluation of cockpit alerting and warning systems

A set of general guidelines for evaluating a newly developed cockpit alerting and warning system in terms of human factors issues are provided. Although the discussion centers around a general methodology, it is made specifically to the issues involved in alerting systems. An overall statement of the current operational problem is presented. Human factors problems with reference to existing alerting and warning systems are described. The methodology for proceeding through system development to system test is discussed. The differences between traditional human factors laboratory evaluations and those required for evaluation of complex man-machine systems under development are emphasized. Performance evaluation in the alerting and warning subsystem using a hypothetical sample system is explained.

Randle, R. J., Jr.↗

NASA NTRS1976

The keystroking ability of commercial pilots

A sample of airline and commercial pilots was tested on a standard computer keyboard (QWERTY). They were found to have a useful level of proficiency in operation of this keyboard. Implications for the design of alphabetic keyboards for airborne use are discussed.

Williams, D. H.↗

NASA NTRS1976

A systematic approach to advanced cockpit warning systems for air transport operations: Line pilot preferences

Line pilots (fifty captains, first officers, and flight engineers) from 8 different airlines were administered a structured questionnaire relating to future warning system design and solutions to current warning system problems. This was followed by a semantic differential to obtain a factor analysis of 18 different cockpit warning signals on scales such as informative/distracting, annoying/soothing. Half the pilots received a demonstration of the experimental text and voice synthesizer warning systems before answering the questionnaire and the semantic differential. A control group answered the questionnaire and the semantic differential first, thus providing a check for the stability of pilot preferences with and without actual exposure to experimental systems. Generally, the preference data obtained revealed much consistency and strong agreement among line pilots concerning advance cockpit warning system design.

Williams, D. H.↗