Safe Autonomous Flare and Landing during Autorotation through Wind Shear

This paper presents a method to compute the set of steady state autorotation conditions from which safe flare to landing through can be performed. Equations of motion of a helicopter in autorotation through wind shear are presented; these equations are used to compute an optimal trajectory to landing from candidate initial states (distance and height above the touchdown point, horizontal speed, descent rate, rotor speed) to a designated touchdown point. The effect of wind shear on these optimal trajectories and on the set of safe initial conditions is examined for two rotorcraft: the Bell OH-58A and a small electric-powered helicopter. The feasibility of using waypoint following control for autorotation landing is examined for the electric-powered helicopter.