Autonomous landing of a fixed-wing aircraft with partial horizontal stabiliser loss

This paper presents the design and simulation of an autonomous landing system for an unmanned fixed-wing aircraft that can accommodate partial horizontal stabiliser loss. A dynamic model for the damaged aircraft is based on an asymmetric, six degrees-of-freedom, equations of motion model. The effect of partial horizontal stabiliser loss on the aerodynamics, mass, centre of mass location, and moments of inertia are calculated as a function of the percentage of horizontal stabiliser loss using vortex lattice techniques and CAD software respectively. The aircraft equilibrium states are determined as a function of the percentage of horizontal stabiliser loss by solving the nonlinear equations with a Newton-Raphson algorithm. For the damage cases where a valid equilibrium exists, the nonlinear flight dynamics model is linearised about the equilibrium and the stability of the natural modes of motion is analysed. It is found that partial horizontal stabiliser loss mostly affects the short period mode of the aircraft. A fault-tolerant longitudinal flight control system is designed with an inner-loop controller that is robust to partial horizontal stabiliser loss. Autonomous landing is accomplished using a state machine that guides the aircraft through the landing phases. The landing strategy that is employed is a single glide slope crabbed landing. The flight control laws and landing system are verified using a high-fidelity simulation environment. Landing accuracies of within a 1.5 m radius circle are accomplished.