Aviation Safety And Pilot Control

Understanding and Preventing Unfavorable Pilot-Vehicle Interactions

Committee on the Effects of Aircraft-Pilot Coupling on Flight Safety

Aeronautics and Space Engineering Board

Commission on Engineering and Technical Systems

National Research Council

NATIONAL ACADEMY PRESS
Washington, D.C.
1997



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--> Aviation Safety And Pilot Control Understanding and Preventing Unfavorable Pilot-Vehicle Interactions Committee on the Effects of Aircraft-Pilot Coupling on Flight Safety Aeronautics and Space Engineering Board Commission on Engineering and Technical Systems National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1997

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--> NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the panel responsible for the report were chosen for their special competencies and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. William A. Wulf is interim president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. William A. Wulf are chairman and interim vice chairman, respectively, of the National Research Council. This study was supported by the National Aeronautics and Space Administration under contract No. NASW-4938. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the organizations or agencies that provided support for the project. Library of Congress Catalog Card Number 97-65884 International Standard Book Number 0-309-05688-8 Additional copies are available for sale from: National Academy Press Box 285 2101 Constitution Ave., N.W. Washington, DC 20055 800-624-6242 202-334-3313 (in the Washington Metropolitan Area) http://www.nap.edu Copyright 1997 by the National Academy of Sciences. All rights reserved. Printed in the United States of America

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--> Committee on the Effects of Aircraft-Pilot Coupling on Flight Safety DUANE T. McRUER (chair), Systems Technology, Inc. CARL S. DROSTE, Lockheed Martin Tactical Aircraft Systems R. JOHN HANSMAN, JR., Massachusetts Institute of Technology RONALD A. HESS, University of California–Davis DAVID P. LeMASTER, Wright Laboratory STUART MATTHEWS, Flight Safety Foundation JOHN D. McDONNELL, McDonnell Douglas Aerospace JAMES McWHA, Boeing Commercial Airplane Group WILLIAM W. MELVIN, Air Line Pilots Association; Delta Air Lines (retired) RICHARD W. PEW, BBN Corporation Staff ALAN ANGLEMAN, Study Director JOANN CLAYTON-TOWNSEND, Director, Aeronautics and Space Engineering Board MARY MESZAROS, Senior Project Assistant Aeronautics and Space Engineering Board Liaison JOHN K. BUCKNER, Lockheed Martin Tactical Aircraft Systems (retired) Technical Liaisons RALPH A'HARRAH, National Aeronautics and Space Administration JIM ASHLEY, Federal Aviation Administration DAVID L. KEY, U.S. Army TOM LAWRENCE, U.S. Navy

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--> Aeronautics and Space Engineering Board JOHN D. WARNER (chair), The Boeing Company, Seattle, Washington STEVEN AFTERGOOD, Federation of American Scientists, Washington, D.C. GEORGE A. BEKEY, University of Southern California, Los Angeles GUION S. BLUFORD, JR., NYMA Incorporated, Brook Park, Ohio RAYMOND S. COLLADAY, Lockheed Martin, Denver, Colorado BARBARA C. CORN, BC Consulting Incorporated, Searcy, Arkansas STEVEN D. DORFMAN, Hughes Electronics Corp., Los Angeles, California DONALD C. FRASER, Boston University, Boston, Massachusetts DANIEL HASTINGS, Massachusetts Institute of Technology, Cambridge FREDERICK HAUCK, International Technology Underwriters, Bethesda, Maryland WILLIAM H. HEISER, United States Air Force Academy, Colorado Springs, Colorado WILLIAM HOOVER, U.S. Air Force (retired), Williamsburg, Virginia BENJAMIN HUBERMAN, Huberman Consulting Group, Washington, D.C. FRANK E. MARBLE, California Institute of Technology, Pasadena C. JULIAN MAY, Tech/Ops International Incorporated, Kennesaw, Georgia GRACE M. ROBERTSON, McDonnell Douglas, Long Beach, California GEORGE SPRINGER, Stanford University, Stanford, California Staff JOANN CLAYTON-TOWNSEND, Director

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--> Preface Unfavorable aircraft-pilot coupling (APC) events include a broad set of undesirable—and sometimes hazardous—phenomena that are associated with less-than-ideal interactions between pilots and aircraft. As civil and military aircraft technologies advance, pilot-aircraft interactions are becoming more complex. Recently, there have been accidents and incidents attributed to adverse APC in military aircraft. In addition, APC has been implicated in some civilian incidents. In response to this situation, and at the request of the National Aeronautics and Space Administration, the National Research Council established the Committee on the Effects of Aircraft-Pilot Coupling on Flight Safety. This committee evaluated the current state of knowledge about adverse APC and processes that may be used to eliminate it from military and commercial aircraft. The committee analyzed the information it collected and developed a set of findings and recommendations for consideration by the U.S. Air Force, Navy, and Army; National Aeronautics and Space Administration; and Federal Aviation Administration. In particular, the committee concluded that in the short term the risk posed by adverse APC could be reduced by increased awareness of APC possibilities and more disciplined application of existing tools and capabilities throughout the development, test, and certification process. However, new approaches are also needed to address the APC risk faced by many advanced aircraft designs. In order to develop new approaches, long-term efforts are needed in the area of APC assessment criteria, analysis tools, and simulation capabilities. (See Chapter 7 for a complete list of the committee's findings and recommendations.)

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--> The study committee met four times between September 1995 and June 1996. (See Appendix A for a list of committee members and their professional background.) To ensure that the committee's work included a broad range of perspectives, the second and third meetings included workshop presentations involving 38 outside individuals with experience in aircraft research, design, development, manufacture, test, and operations. The committee's outreach also extended internationally to France, Germany, Russia, Sweden, and the United Kingdom. The committee wishes to thank all of its meeting participants, who are listed in Appendix B, for their contributions to the work of the committee. The committee also expresses special thanks for the assistance provided by each of its liaisons (see page iii). DUANE T. McRUER COMMITTEE CHAIR

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--> Contents     EXECUTIVE SUMMARY   1 1   AIRCRAFT-PILOT COUPLING PROBLEMS: DEFINITIONS, DESCRIPTIONS, AND HISTORY   14     Introduction   14     Pilot-Vehicle Closed-Loop System   17     Necessary Conditions for Oscillatory Aircraft-Pilot Coupling Events   19     Historical Antecedents   22     Study Overview   26 2   VARIETIES OF AIRCRAFT-PILOT COUPLING EXPERIENCE   30     Introduction   30     Categories of Oscillatory Aircraft-Pilot Coupling Events   33     Nonlinear, Cliff-Like, Pilot-Involved Oscillations   37     Non-Oscillatory Aircraft-Pilot Coupling   47     Triggers   50     Case Studies of Recent Aircraft-Pilot Coupling Events in Fly-By-Wire Systems   55 3   AIRCRAFT-PILOT COUPLING AS A CURRENT PROBLEM IN AVIATION   81     Trends from a Review of Accidents and Incidents   82     Flight Data Recorders   84     Flight Operational Quality Assurance   85     Military Aircraft   86     Accident Investigations   87

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--> 4   PRECLUDING ADVERSE AIRCRAFT-PILOT COUPLING EVENTS   88     Introduction   88     Lessons Learned   88     Recommended Processes for Identifying and Precluding Adverse Aircraft-Pilot Coupling Events   90     Technical Fixes   102     Summary of Future Considerations   103 5   SIMULATION AND ANALYSIS OF THE PILOT-VEHICLE SYSTEM   106     Ground and In-Flight Simulation   107     Simulation Types   108     Overview of Human Pilot Characteristics   118     Pilot Models and Pilot-Vehicle Analyses   120 6   CRITERIA FOR ASSESSING AIRCRAFT-PILOT COUPLING POTENTIAL   126     Prerequisites for Criteria   128     Prominent Assessment Criteria for Category I   129     Military Status and Trends   153     Criteria for Assessing Other Conditions   155     Conclusions   158 7   FINDINGS AND RECOMMENDATIONS   161     Chapter 1:Aircraft-Pilot Coupling Problems: Definitions, Descriptions, and History   161     Chapter 2:Varieties of Aircraft-Pilot Coupling Experience   162     Chapter 3:Aircraft-Pilot Coupling as a Current Problem in Aviation   163     Chapter 4:Precluding Adverse Aircraft-Pilot Coupling Events   164     Chapter 5:Simulation and Analysis of the Pilot-Vehicle System   165     Chapter 6:Criteria for Assessing Aircraft-Pilot Coupling Potential   167     APPENDICES         A   BIOGRAPHICAL SKETCHES OF COMMITTEE MEMBERS   171     B   PARTICIPANTS IN COMMITTEE MEETINGS   176

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-->     C  DETAILS OF AIRCRAFT-PILOT COUPLING EXAMPLES   181     D  RESEARCH   192     ACRONYMS   197     GLOSSARY   199     REFERENCES   203

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--> Tables and Figures TABLES 1-1a   Single Axis PIOs Associated with Extended Rigid Body Effective Aircraft Dynamics   23 1-1b   Single-Axis PIOs Associated with Extended Rigid Body Plus Mechanical Elaborations   23 1-1c   Single-Axis, Higher-Frequency PIOs   24 1-1d   Combined Three-Dimensional, Multi-Axis PIOs   24 1-2   Noteworthy APC Events Involving FBW Aircraft   26 2-1   Cross Section of Frequencies   35 4-1   Flying Qualities Requirements and Metrics   93 4-2   Suggested Tasks and Inputs for APC Evaluation   100 6-1   Idealized Rate-Command Controlled Element Characteristics   139 6-2   Prediction of PIO Susceptibility with Smith-Geddes Attitude-Dominant Type III Criterion for Operational and Test Aircraft   143 FIGURES 1-1   Flight recording of T-38 PIO   18 1-2   The pilot controlled-element system   20 1-3   Conditions associated with oscillatory APCs   21 1-4   Interacting constituents of oscillatory APCs   22 2-1   Taxonomy of APC phenomena   32

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--> 2-2   Most common FCS locations of command gain shaping, rate limiters, and position limiters   40 2-3a   Surface actuator rate limiting effects for various input amplitudes in a closed-loop surface actuator system   41 2-3b   Surface actuator rate limiting effects for various input amplitudes showing linear system response times   43 2-3c   Surface actuator rate limiting effects for various input amplitudes showing near saturation response times   44 2-3d   Surface actuator rate limiting effects for various input amplitudes showing highly saturated response times   45 2-4   Example of command gain shaping for a nonlinear element   48 2-5   JAS 39 accident time history   50 2-6   JAS 39 accident cross plot of stick deflection in roll and pitch during a roll PIO and unintended pitch up maneuver   51 2-7   YF-22 accident time history   58 2-8   YF-22 pitch rate command stick gradients   59 2-9   Time history for 777 landing derotation, baseline control law   61 2-10   Normal mode elevator control law   62 2-11   Time history for 777 attitude tracking on runway, baseline control law   63 2-12   Time history for 777 attitude tracking on runway, secondary mode   64 2-13   Time history for 777 attitude tracking on runway, revised control law   66 2-14   Time history for 777 attitude tracking on runway, revised control law plus command filter   67 2-15   Bandwidth criteria applied to landing derotation, effect of 777 control law changes on pitch attitude/column position frequency response   68 2-16   Elevator/column gain and phase, effect of 777 control law changes on landing derotation   69 2-17   C-17 test aircraft lateral oscillations during approach to landing with hydraulic system #2 inoperative   72 2-18   C-17 test aircraft lateral oscillations during approach to landing with hydraulic system #2 inoperative, continued   73 2-19   A 320 incident time history   75 2-20   Response time analysis for the advanced digital optical control system demonstrator   77 2-21   Sample time history for a rotorcraft vertical landing task   77 2-22   Schematic drawing of a helicopter tracking a vehicle-mounted hover board   78 2-23   Helicopter lateral-position tracking task, velocity profile for the lateral vehicle displacement   78 2-24   Time history of the helicopter lateral-position tracking task with no added time delay   79

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--> 2-25   Time history of the helicopter lateral-position tracking task with 100 msec of added time delay   79 2-26   Small-amplitude handling qualities criterion (target acquisition and tracking) from ADS-33D   80 4-1   Design process for avoiding adverse APC events   92 5-1   A comparison of NASA and U.S. Air Force simulators for principal piloting tasks, circa 1975   113 5-2   A PIO (APC) rating scale   114 5-3   A comparison of PIO ratings showing normal and offset landing tasks by the NASA Flight Simulator for Advanced Aircraft (FSAA) and the U.S. Air Force Total in-Flight Simulator (TIFS)   114 5-4   A comparison of PIO ratings for formation-flying by the NASA Flight Simulator for Advanced Aircraft (FSAA) and the U.S. Air Force Total In-Flight Simulator (TIFS)   115 5-5   A comparison of PIO ratings for demanding landing tasks by the NASA Vertical Motion Simulator (VMS) and the U.S. Air Force Total In-Flight Simulator (TIFS)   115 5-6   A feedback system involving the human pilot   119 5-7   A block diagram representation of the human pilot transfer function   122 5-8   A block diagram of an open-loop PVS   122 5-9   A block diagram of a closed-loop PVS   124 6-1   Definitions of aircraft pitch attitude bandwidth and phase delay   131 6-2   Aircraft-Bandwidth/Phase Delay/Dropback requirements for PIO resistance in terminal flight phases   134 6-3   Aircraft-Bandwidth/Phase Delay parameters as indicators of PIO susceptibility for sample operational and test aircraft   135 6-4   Bode and gain phase diagram presentations for Kc e-sτ/s   138 6-5   Gain/Phase Template, ω180/Average Phase Rate Boundaries   141 6-6   Correlation between Smith-Geddes criterion frequency and Have PIO flight data   146 6-7   Moscow Aviation Institute PIO boundaries   149 6-8   Neal-Smith trends with variation of effective delay for Kc e-sτ /s   150 6-9   Pitch rate overshoot and pitch attitude dropback   151 6-10   Tentative forbidden zones for Category II PIOs   158 C-1a   Bode and Nichols diagrams for a synchronous PVS of an aircraft with low susceptibility to oscillatory APC events   182 C-1b   Bode and Nichols diagrams for a synchronous PVS of an aircraft with high susceptibility to oscillatory APC events   183 C-2   Input amplitude-dependent stability boundaries as a function of command-path gain shaping ratio for a linear system gain margin δG M = 1.5   188 C-3   Time domain and transfer characteristics for fully developed rate limiting   190