Date of Award

3-2008

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Paul A. Blue, PhD

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.

AFIT Designator

AFIT-GAE-ENY-08-M21

DTIC Accession Number

ADA483268

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