Date of Award


Document Type


Degree Name

Master of Science in Aeronautical Engineering


Department of Aeronautics and Astronautics

First Advisor

Richard G. Cobb, PhD


A multi-path automatic ground collision avoidance system (Auto-GCAS) for performance limited aircraft was further developed and improved to prevent controlled flight into terrain. This research includes flight test results from the United States Test Pilot School's Test Management Project (TMP) titled Have Multi-Path Escape Decisions Using Sophisticated Algorithms (MEDUSA). Currently, the bomber and mobility air- craft communities lack an Auto-GCAS. The F-16 Auto-GCAS was proven successful for fighter-type aircraft with seven aircraft and eight lives saved from 2014 to 2018. The newly developed and tested Rapidly Selectable Escape Trajectory (RSET) sys- tem included a 5-path implementation which continuously updated at a rate of up to 12.5 Hz. The research employed Level 1 Digital Terrain Elevation Data (DTED) to identify the offending terrain and an augmented 6 Degree-of-Freedom (DoF) Stitched aerodynamic model to create terrain avoidance paths based on the aircraft's current state and location. The system then triggered when all paths predicted collision with the DTED and automatically activated the path which had the longest time until impact. A terrain safety buffer (TSB) of 200 ft added to the DTED to allowed for the time needed to process and execute the maneuver. The RSET system was flight tested against DTED using the Calspan Learjet 25D Variable Stability System (VSS). Path prediction error (PPE) did not meet the specified criteria and was larger than expected for the 30-second path predictions; however, at the maximum refresh rate of 12.5 Hz, the RSET system ensured terrain clearance in all cases tested. The RSET system was able to achieve and maintain target load factor and flight path angle with momentary overshoots. The system showed no tendency for nuisance. The RSET hand-back was favorable and can be used as a baseline for future Auto-GCASs.

AFIT Designator


DTIC Accession Number