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Stall Recovery Guidance Experiment To Run in The Ames Vertical Motion Simulator
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Stall Recovery Guidance Experiment To Run in The Ames Vertical Motion Simulator

Though rare, stall-related accidents and incidents still occur in commercial aircraft. To address this concern, the Stall Recovery Guidance experiment is investigating the degree to which candidate guidance algorithms and displays can aid pilots during manual stall recovery. The research leading up to this study focused on the development of three different guidance algorithms based on: energy management, pseudo-control hedging, and model-predictive control (i.e., optimal control). The energy management approach exploits the knowledge of the flight mechanics in a total energy control setup by means of dynamic inversion. The pseudo-control hedging-based algorithm calculates a pitch angle guidance signal by inverting the aircraft pitch rate dynamics when the angle of attack exceeds the stall limit. For the model-predictive control approach, an optimal recovery is computed using a fast convex optimization algorithm, which is capable of running reliably from inside the Ames Vertical Motion Simulator (VMS) frame calculation loop on a 1.25 GHz DEC-Alpha, Real-Time Operating System.

The study also includes the first VMS integration of the Generic Transport Aircraft model, which includes the stall dynamics representative for commercial aircraft, derived from validated subscale wind tunnel data in collaboration with NASA Langley Research Center. To test the guidance algorithms, approximately 40 professional research, commercial, and Federal Aviation Administration (FAA) pilots will fly simulated stall scenarios in the VMS facility through the end of May, 2017.

BACKGROUND: Aerodynamic stall is a dangerous condition that occurs when an aircraft’s speed becomes too slow and the desired smooth airflow across its wings separates, generating insufficient lift force to support the weight of the aircraft. While multiple systems on commercial aircraft exist for preventing stall, stall-related accidents and incidents still occur. Two relatively recent accidents that made headlines in the news were the 2009 Air France Flight 447 accident, and the Colgan Air Flight 3407 accident. Based on a review of loss-of-control accidents, a Commercial Aviation Safety Team (CAST), comprised of both industry and government experts, determined that further addressing the problem required additional research into, among other things, improving flight simulator fidelity, new pilot training requirements, and pilot display algorithms and guidance.

The Technologies for Airplane State Awareness (TASA) sub-project, which is part of the Airspace Technologies Demonstration (ATD) project under the Airspace Operations and Safety Program (AOSP), investigates stall recovery guidance. In particular, the Stall Recovery Guidance Experiment is focused on the algorithm and pilot display guidance aspect of the CAST recommended research. The central idea is that by combining sensor measurements and flight dynamics, an algorithm can compute the specific trajectory that an aircraft should fly to either prevent or recover from a stalled aircraft condition. The results of the computation are displayed for the pilot by means of flight directors presented on the Primary Flight Display. This work supports the FY17 TASA congressional milestone, which includes the evaluation of algorithms and display strategies to aid in the prevention of, and recovery from, approach-to-stall or stall conditions.

NASA PROGRAM FUNDING: Technologies for Airplane State Awareness (TASA), Airspace Technologies Demonstration (ATD) project, Airspace Operations and Safety Program (AOSP), NASA Aeronautics Research Mission Directorate (ARMD)

TEAM MEMBERS: John Kaneshige, Thomas Lombaerts, Peter Robinson, Stefan Schuet, and Vahram Stepanyan; AFS: Gordon Hardy and Nick Riccobono

POINT OF CONTACT: Stefan Schuet, stefan.r.schuet@nasa.gov

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