Aircraft autolander safety analysis through optimal control-based reach set computation

A method for the numerical computation of reachable sets for hybrid systems is presented and applied to the design and safety analysis of autoland systems. It is shown to be applicable to specific phases of landing: descent, flare, and touchdown. The method is based on optimal control and level set methods; it simultaneously computes a maximal controlled invariant set and a set-valued control law guaranteed to keep the aircraft within a safe set of states under autopilot mode switching. The method is applied to the sequenced flap and slat deflections of a simplified model of a DC9-30. The paper concludes with a demonstration of the method on higher dimensional aircraft models.