Control of Commercial Aircraft with Vertical Tail Loss

Abstract

This study develops a method of aircraft controller design to accommodate the possible complete loss of a vertical tail on a commercial airliner. A representative aircraft configured with and without a vertical tail at landing and cruise conditions tests possible control schemes for flying qualities and saturation. A stability augmentation system using a linear quadratic regulator with implicit ideal-model following does stabilize flight without the tail as it normally can. Without mechanical modifications, differential elevator or differential thrust may be used to generate rolling or yawing moments; landing conditions without vertical tail are controllable with differential thrust and model-following. Cruise conditions are too unstable for model-following but may be empirically stabilized. Furthermore, this study further develops a robust proportional-integral roll-angle command augmentation system. Design methods to successfully control an aircraft that loses its vertical tail through differential thrust are presented.