Considerations of the differences of small helicopters and the trajectories about the automatic autorotation landing

Abstract

Differences in induced velocity models are made clear from experimental results of autorotation landing control by using two small helicopters with similar size and gross mass. In addition, a new desired trajectory of translational speed which is designed to reduce the descent speed and load factor at touchdown is demonstrated by flight experiments. By comparing simulation results with experiment results, the difference of the induced velocity can be approximately twice in spite of using airframes of the same size. Therefore, the design of the trajectory of the desired vertical velocity is changed and the suppression of the descent speed at touchdown is achieved; the flare starting altitude is reduced, and the formulation of the trajectory function is made to decelerate immediately after the flare started rather than to decelerate immediately just before touchdown. Furthermore, it becomes clear that the higher horizontal speed can further suppress the descent speed at touchdown.