Aviation Safety and Pilot Control: Understanding and Preventing Unfavorable Pilot-vehicle Interactions - Softcover

National Research Council (U. S.); Division On Engineering And Physical Sciences

Softcover

ISBN 10: 0309056888 ISBN 13: 9780309056885

Verlag: National Academies Press, 1997

Inhaltsangabe

Adverse aircraft-pilot coupling (APC) events include a broad set of undesirable and sometimes hazardous phenomena that originate in anomalous interactions between pilots and aircraft. As civil and military aircraft technologies advance, interactions between pilots and aircraft are becoming more complex. Recent accidents and other incidents have been attributed to adverse APC in military aircraft. In addition, APC has been implicated in some civilian incidents. This book evaluates the current state of knowledge about adverse APC and processes that may be used to eliminate it from military and commercial aircraft. It was written for technical, government, and administrative decisionmakers and their technical and administrative support staffs; key technical managers in the aircraft manufacturing and operational industries; stability and control engineers; aircraft flight control system designers; research specialists in flight control, flying qualities, human factors; and technically knowledgeable lay readers.

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Committee on the Effects of Aircraft-Pilot Coupling on Flight Safety, National Research Council

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AVIATION SAFETY AND PILOT CONTROL

Understanding and Preventing Unfavorable Pilot-Vehicle Interactions

NATIONAL ACADEMIES PRESS

Copyright © 1997 National Academy of Sciences
All right reserved.
ISBN: 978-0-309-05688-5

Chapter One

Executive Summary

Unfavorable aircraft-pilot coupling (APC) events are rare, unexpected, and unintended excursions in aircraft attitude and flight path caused by anomalous interactions between the aircraft and the pilot. The temporal pattern of these pilot-vehicle system (PVS) excursions can be oscillatory or divergent (non-oscillatory). The pilot's interactions with the aircraft can form either a closed-loop or open-loop system, depending on whether or not the pilot's responses are tightly coupled to the aircraft response. When the dynamics of the aircraft (including the flight control system [FCS]) and the dynamics of the pilot combine to produce an unstable PVS, the result is called an APC event.

Although it is often difficult to pinpoint the cause of specific APC events, a majority of severe APC events result from deficiencies in the design of the aircraft (especially with regard to the FCS) that result in adverse coupling of the pilot with the aircraft. In certain circumstances, this adverse coupling produces unintended oscillations or divergences when the pilot attempts to precisely maneuver the aircraft. If the PVS instability takes the form of an oscillation, the APC event is called a "pilot-involved oscillation" (PIO). PIOs differ from aircraft oscillations caused by deliberate, pilot-imposed periodic control motions, such as "stick-pumping," that are open-loop in character. An open-loop, forced oscillation does not constitute a PIO. If the unstable motions of the closed-loop PVS are divergent rather than oscillatory in nature, they are referred to as either APC events or as non-oscillatory APC events.

APC events can result if the pilot is operating with a behavioral mode that is inappropriate for the task at hand, and such events are properly ascribed to pilot error. However, the committee believes that most severe APC events attributed to pilot error are the result of adverse APC that misleads the pilot into taking actions that contribute to the severity of the event. It is often possible, after the fact, to carefully analyze an event and identify a sequence of actions that the pilot could have taken to overcome the aircraft design deficiencies. However, it is typically not feasible for the pilot to identify and execute the required actions in real time.

PIO phenomena comprise a complete spectrum. At one end of the spectrum is a momentary, easily corrected, low-amplitude bobble, a type of oscillation often encountered by pilots getting used to new configurations-basically a learning experience. This type of oscillation can happen on any aircraft and has been experienced by most pilots at one time or another. At the other end of the spectrum is a fully-developed, large amplitude PIO, a chilling and terrifying event that jeopardizes the safety of the aircraft, crew, and passengers. Fortunately, severe PIOs are rare.

Other severe APC events have been noted in which the excursions in aircraft motion diverge over time rather than oscillate. The few events of this nature that have been positively identified have had serious consequences. Large amplitude, dangerous PIOs and non-oscillatory APC events are the particular concerns of this report.

Recently, there have been several highly visible APC-related accidents involving military aircraft, as well as a number of incidents involving civil aircraft. At the same time, there has been widespread introduction of new fly-by-wire (FBW) FCSs into commercial transports. Almost all new FBW-equipped aircraft have exhibited APC events at some time during development, and these untoward coincidences have captured the attention of policymakers, test pilots, technical managers, and engineers. Although FBW systems are not inherently more or less susceptible to severe APC events, the flurry of incidents in aircraft development programs suggests that some side effects have not been fully explored or anticipated. Thus, as a matter of prudence the National Aeronautics and Space Administration asked the Aeronautics and Space Engineering Board of the National Research Council to conduct a study to assess APC-related aspects of recent incidents and accidents, aircraft development processes, the introduction of FBW and fly-by-light technology into FCSs, and national and international efforts devoted to APC research. This report is the result of that study, and it recommends steps that could be taken to improve aviation safety by reducing the kinds of APC problems seen recently and countering new types of APC problems that may arise.

The following high-level conclusions of the study committee are worth highlighting. (Subsequent sections include the committee's key findings and recommendations, and all findings and recommendations are listed in Chapter 7.)

There are many varieties of oscillatory and non-oscillatory APC events. Although none of these is welcome, only a rare subset is dangerous. Among the dangerous ones are events that exhibit "cliff-like" characteristics, which means that a PVS may fly superbly up to the sudden onset of a dramatic and potentially catastrophic APC event. What these severe APCs are, when they are likely to occur, and how to find (and fix) them are key issues. Most of the severe PIOs for which flight recordings exist have exhibited oscillations characterized by rate limited responses in control surface actuators or effectors. (Control surface actuators and effectors are rate or position limited when commanded movement exceeds limits imposed by design intent or physical structure on the rate of movement or extreme position of the control surface.) In most cases the pilots indicated that the onset of the PIO was sudden, unexpected, and cliff-like.

Piloted simulations have proved to be useful for investigating APC tendencies. However, neither piloted simulations nor available design and testing criteria can guarantee that a new aircraft will not be involved in an APC event.

Severe APC events are invariably new "discoveries" that often occur in transient and highly unusual circumstances. To avoid their discovery by operational pilots under unfavorable circumstances, test pilots must be allowed some freedom to search for APC tendencies in simulations and flight tests.

Data on recent APC events indicate that they are not uncommon in development testing where data recording and pilot reports are sufficient for causes to be determined and solutions developed. There are only a few reports of severe APC events in operational aircraft, but because there are no mandatory reporting requirements and recordings are often inadequate, the danger cannot be assessed adequately.

The committee was disturbed by the lack of awareness of severe APC events among pilots, engineers, regulatory authorities, and accident investigators.

THE AIRCRAFT-PILOT COUPLING EXPERIENCE

APC events usually occur when the pilot is engaged in a highly demanding, closed-loop control task. For example, many of the reported APC events have taken place during air-to-air refueling operations or approaches and landings, especially if the pilot is concerned about low fuel, adverse weather, emergencies, or other circumstances. Under these conditions, the...

Details zur Ausgabe

• Verlag: National Academies Press
• Erscheinungsdatum: 1997
• Sprache: Englisch
• ISBN 10: 0309056888
• ISBN 13: 9780309056885
• Einband: Taschenbuch
• Anzahl der Seiten: 208
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Nicht verfügbar