Air Force Institute of Technology AFIT Scholar Theses and Dissertations Student Graduate Works 3-2008 Velocity Estimate Following Air Data System Failure Scott A. Mclaren Follow this and additional works at: https://scholar.afit.edu/etd Part of the Aerospace Engineering Commons Recommended Citation Mclaren, Scott A., "Velocity Estimate Following Air Data System Failure" (2008). Theses and Dissertations. 2687. https://scholar.afit.edu/etd/2687 This Thesis is brought to you for free and open access by the Student Graduate Works at AFIT Scholar. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of AFIT Scholar. For more information, please contact [email protected]. VELOCITY ESTIMATE FOLLOWING AIR DATA SYSTEM FAILURE THESIS Scott A. McLaren, Major, USAF AFIT/GAE/ENY/08-M21 DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY AIR FORCE INSTITUTE OF TECHNOLOGY Wright-Patterson Air Force Base, Ohio APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED The views expressed in this thesis are those of the author and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the U.S. Government. AFIT/GAE/ENY/08-M21 VELOCITY ESTIMATE FOLLOWING AIR DATA SYSTEM FAILURE THESIS Presented to the Faculty Department of Aeronautics and Astronautics Graduate School of Engineering and Management Air Force Institute of Technology Air University Air Education and Training Command In Partial Fulfillment of the Requirements for the Degree of Master of Science in Aeronautical Engineering Scott A. McLaren, BS Major, USAF March 2008 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED AFIT /GAE/ENY /08-M21 VELOCITY ESTIMATE FOLLOWING AIR DATA SYSTEM FAILURE Scott A. McLaren, BS Major, USAF Approved: /U/~ Paul A. Blue, Maj, USAF (Thesis Advisor) t/L- j~j ,/ ~ l 7 Fe-{ ()8' Bradley S. Liebst (Committee Member) Date 'I)~~c\ I JL.~ Z 7 i="e.-b 'Zoo 5 Donald L. Kunz (Committe~er) Date ~~'" :<.7,c;6 oil Timothy R. Joms, . aj, USAF (Committee Member) Date AFIT/GAE/ENY/08-M21 Abstract Modern high performance aircraft can provide amazing performance due in part to their advanced flight control systems that require gain scheduling to provide optimum performance over a huge flight envelope. In modern fighter aircraft, this gain scheduling is a function of airspeed, and almost all of the research involving aircraft gain scheduling assumes aircraft airspeed to be a known quantity. The purpose of this research was to investigate a method of determining an aircraft’s airspeed in the event of total air data system failure. The process began by combining known aircraft information following an air data system failure to determine an estimate of the inertial velocity. Then, an innovative airspeed estimation algorithm was developed using Kalman filtering with geometric concepts based on the velocity triangle that defines the relationship between airspeed, wind speed, and groundspeed. This algorithm used the inertial velocity and heading and provided a real-time estimate of the current wind and the aircraft’s true airspeed, which can be used in the flight control system for gain scheduling. The true airspeed estimate was also converted to calibrated airspeed for display in the cockpit to provide the pilot situational awareness. The culmination of this effort resulted in a successful flight test program as part of a Test Management Project at the United States Air Force Test Pilot School. The project consisted of two ground test and six flight test evaluation sorties. The average true airspeed error from the estimator algorithm during in-flight maneuvers was determined to be 12 knots, non-divergent, and minimally variable. The results of this research clearly showed the potential of the algorithm to determine an aircraft’s airspeed in the event of an air data system failure. Recommendations for future research and improvements to the operation of the velocity estimator algorithm are discussed. iv To my wife for making it possible to get this far! v Acknowledgments I would like to express my appreciation to my thesis advisor, Maj Paul Blue, for his guidance and support throughout the course of this thesis effort. The insight and sincere effort to make it to the end deserve my applause and sincere appreciation. I would also like to thank Michael Nielsen for his time and technical knowledge. The implementation of the inertial and wind estimators would not have been possible without his efforts. Finally, I thank Mr. Russ Easter. His technical expertise and dedication were tremendous when faced with the impossible task. Scott A. McLaren vi Table of Contents Page Abstract.............................................................................................................................. iv Acknowledgments.............................................................................................................. vi Table of Contents.............................................................................................................. vii List of Figures.................................................................................................................... xi List of Tables ................................................................................................................... xiii 1. Introduction......................................................................................................................1 1.1 Motivation ..............................................................................................................1 1.2 Problem Statement..................................................................................................3 1.3 Research Objectives ...............................................................................................3 1.4 Approach ................................................................................................................4 1.5 Preview of Results and Implications ......................................................................5 1.6 Thesis Overview.....................................................................................................7 2. Background......................................................................................................................8 2.1 Overview ................................................................................................................8 2.2 Aircraft Dynamic Motion.......................................................................................8 2.3 Aircraft Systems ...................................................................................................15 2.4 Dynamic Inversion ...............................................................................................27 2.5 Simultaneous Linear Equations............................................................................30 2.6 Summary...............................................................................................................34 3. Methodology.................................................................................................................35 3.1 Overview ..............................................................................................................35 3.2 Estimating True Airspeed from Wind Estimate ...................................................35 vii 3.3 Dynamic Inversion Algorithm..............................................................................44 3.4 Testing Airspeed Estimation Theory....................................................................45 3.5 True Airspeed Estimate in Simulation .................................................................46 3.6 Summary...............................................................................................................48 4. Simulation Results and Analysis ...................................................................................49 4.1 Overview ..............................................................................................................49 4.2 Wind Estimator Approach Results .......................................................................49 4.3 Dynamic Inversion Results...................................................................................51 4.4 Learjet Simulation Results ...................................................................................53 4.5 Summary...............................................................................................................58 5. Flight Test ......................................................................................................................60 5.1 Chapter Overview.................................................................................................60 5.2 Methodology.........................................................................................................60 5.3 Results and Analysis.............................................................................................75 5.4 Summary...............................................................................................................92 6. Discussion.....................................................................................................................94 6.1 Overview ..............................................................................................................94 6.2 Conclusions of Research ......................................................................................94