NASA/TP{2017{219733 Vertical Motion Simulator Experiment on Stall Recovery Guidance Stefan Schuet National Aeronautics and Space Administration Thomas Lombaerts Stinger Ghaffarian Technologies, Inc. Vahram Stepanyan Universities Space Research Association John Kaneshige, Kimberlee Shish, Peter Robinson National Aeronautics and Space Administration Gordon Hardy Retired Research Test Pilot Science Applications International Corporation October 2017 NASA STI Program. in Profile Since its founding, NASA has been dedicated • CONFERENCE PUBLICATION. to the advancement of aeronautics and space Collected papers from scientific and science. The NASA scientific and technical technical conferences, symposia, seminars, information (STI) program plays a key part or other meetings sponsored or in helping NASA maintain this important co-sponsored by NASA. role. • SPECIAL PUBLICATION. Scientific, The NASA STI Program operates under the technical, or historical information from auspices of the Agency Chief Information NASA programs, projects, and missions, Officer. It collects, organizes, provides for often concerned with subjects having archiving, and disseminates NASA's STI. substantial public interest. The NASA STI Program provides access to the NASA Aeronautics and Space Database • TECHNICAL TRANSLATION. English- and its public interface, the NASA Technical language translations of foreign scientific Report Server, thus providing one of the and technical material pertinent to largest collection of aeronautical and space NASA's mission. science STI in the world. Results are Specialized services also include organizing published in both non-NASA channels and and publishing research results, distributing by NASA in the NASA STI Report Series, specialized research announcements and which includes the following report types: feeds, providing information desk and • TECHNICAL PUBLICATION. Reports of personal search support, and enabling data completed research or a major significant exchange services. phase of research that present the results For more information about the NASA STI of NASA programs and include extensive Program, see the following: data or theoretical analysis. Includes compilations of significant scientific and • Access the NASA STI program home page technical data and information deemed to at http://www.sti.nasa.gov be of continuing reference value. NASA counterpart of peer-reviewed formal • E-mail your question to professional papers, but having less [email protected] stringent limitations on manuscript length and extent of graphic presentations. • Phone the NASA STI Information Desk at 757-864-9658 • TECHNICAL MEMORANDUM. Scientific and technical findings that are • Write to: preliminary or of specialized interest, e.g., NASA STI Information Desk quick release reports, working papers, and Mail Stop 148 bibliographies that contain minimal NASA Langley Research Center annotation. Does not contain extensive Hampton, VA 23681-2199 analysis. • CONTRACTOR REPORT. Scientific and technical findings by NASA-sponsored contractors and grantees. NASA/TP{2017{219733 Vertical Motion Simulator Experiment on Stall Recovery Guidance Stefan Schuet National Aeronautics and Space Administration Thomas Lombaerts Stinger Ghaffarian Technologies, Inc. Vahram Stepanyan Universities Space Research Association John Kaneshige, Kimberlee Shish, Peter Robinson National Aeronautics and Space Administration Gordon Hardy Retired Research Test Pilot Science Applications International Corporation National Aeronautics and Space Administration Ames Research Center Intelligent Systems Division Moffett Field, California 94035 October 2017 The use of trademarks or names of manufacturers in this report is for accurate reporting and does not constitute an offical endorsement, either expressed or implied, of such products or manufacturers by the National Aeronautics and Space Administration. Available from: NASA STI Program / Mail Stop 148 NASA Langley Research Center Hampton, VA 23681-2199 Fax: 757-864-6500 Abstract A stall recovery guidance system was designed to help pilots improve their stall recovery performance when the current aircraft state may be unrecognized under various complicating operational factors. Candidate guidance algorithms were con- nected to the split-cue pitch and roll flight directors that are standard on large transport commercial aircraft. A new thrust guidance algorithm and cue was also developed to help pilots prevent the combination of excessive thrust and nose-up stabilizer trim. The overall system was designed to reinforce the current FAA rec- ommended stall recovery procedure. A general transport aircraft model, similar to a Boeing 757, with an extended aerodynamic database for improved stall dynam- ics simulation fidelity was integrated into the Vertical Motion Simulator at NASA Ames Research Center. A detailed study of the guidance system was then conducted across four stall scenarios with 30 commercial and 10 research test pilots, and the results are reported. 1 Advisory Committee A committee of experts independently advised the design of the recovery guidance technology, and the experiment detailed in this report. Members of this committee provided impactful feedback on the experiment plan, and recommendations after flying fixed-base simulations at various points in time throughout the experiment development process. Any good idea in this report likely sprang from their feedback, and credit should be extended to them. We are sincerely grateful for their diligence and support. Gordon Hardy Retired Research Test Pilot, NASA Ames Research Center Science Applications International Corporation Mark Humphreys, Heather Ogburn Pilots, FAA Aircraft Evaluation Group, Long Beach, CA Scott Howe, David Fedors Research Test Pilots, NASA Armstrong Flight Research Center Jeffery Schroeder Engineer, FAA Chief Scientific and Technical Advisor for Flight Simulation Systems 2 Executive Summary Despite stall warning systems in most all commercial aircraft, full stalls do still sometimes occur. In several such cases, the pilots applied control in a direction op- posite to that required to recover the aircraft after it had stalled. After performing a detailed analysis of representative Loss-of-Control accident cases, including some that involved stall, an international Commercial Aviation Safety Team of govern- ment and industry experts recommended numerous safety enhancements to address the primary issues identified. Among these was a recommendation to conduct re- search into algorithms and display strategies to provide guidance for recovery from approach-to-stall and stall. The study detailed in this report examines one such stall recovery guidance system that has been designed to help pilots improve their stall recovery performance when the current aircraft state may be unrecognized in the presence of complicating operational factors. The focus of the study was on two candidate pitch guidance algorithms, in addition to a new thrust guidance system. The thrust guidance system was developed to help pilots avoid the loss of nose-down elevator authority caused by the application of too much thrust and nose-up stabilizer trim on aircraft with low mounted engines. A basic roll guidance strategy was also implemented to complete the pitch-roll-thrust guidance system. The outputs of the pitch and roll guidance computation were connected to split-cue pitch and roll flight directors that are standard on most large transport commercial aircraft. The overall system was designed to reinforce the current FAA recommended stall recovery procedure, and to potentially provide a benefit to that procedure when justified by the guidance computation. The objectives of the study were to investigate the degree to which the candidate stall recovery guidance algorithms and displays could improve pilot stall recovery performance criteria in four scenarios: a high altitude stall recovery, a low altitude stall recovery with and without a misaligned stabilizer, and an approach stall re- covery. The scenarios were designed specifically for baselining the potential safety benefits of the recovery strategy, computation, and display employed by the guid- ance system. In total, 30 commercial and 10 research test pilots flew three runs of each sce- nario, each with and without guidance, in the Vertical Motion Simulator at NASA Ames Research Center. A general transport aircraft model, similar to a Boeing 757, was implemented for the study. This model contained an important extended aerodynamic database with improved stall dynamics simulation fidelity. The main findings of the study were: (1) that aggressive pitch down guidance was effective at preventing secondary aerodynamic stall during the recovery, especially at high altitude, (2) pitch and thrust guidance helped prevent excessive altitude loss in the low altitude scenario, (3) pitch-up guidance had a minor effect on reducing flap overspeed conditions while recovering with full thrust in the approach scenario, and (4) the addition of thrust guidance was effective at preventing over thrust in combi- nation with excessive nose-up trim, but to the detriment of maintaining margin to secondary aerodynamic stall. 3 Contents 1 Introduction 9 1.1 Literature Survey . 11 1.2 Basic Flight Dynamics of Stall and Stall Recovery . 12 1.3 A Brief History of Stall Simulator Training . 16 1.4 The FAA's Revised Recovery Guidance . 18 1.5 Motivating Accidents and Incidents . 18 1.6 The Benefit of Stall Recovery Guidance . 26 1.7 Guidance System Design Criteria . 27 2 Recovery Guidance