A variable structure control system for the propulsion controlled automatic landing of a contemporary large transport aircraft

Propulsion Controlled Aircraft (PCA) techniques address the problem of controlling an aircraft through only the propulsion system after the primary flight control system has failed. There have been several major commercial accidents in which over 1200 people have lost their lives due to these type of accidents. In addition during the Vietnam War it is estimated that 18% of the aircraft lost...around 1800 aircraft...were lost due to flight control system failures. PCA techniques have been shown to have the potential to prevent some of these commercial aircraft accidents and have also been shown to have the potential to significantly improve military aircraft survivability to flight control system damage or failures. This paper will present a brief history of accidents that might have been avoided through PCA techniques and will apply the modern nonlinear Variable Structure Control System (VSCS) method to the aircraft PCA problem for a contemporary large transport aircraft. The VSCS controller will be compared with a classical linear controller for the task of glide slope tracking. The robustness of the VSCS controller to sensor noise and model uncertainty will be evaluated. It will be shown that the VSCS controller performs as well as the classical controller with improved robustness to model uncertainty.