Towards Autonomous Autorotation Landing for Small Size Unmanned Helicopters

The consideration of safety issues in the operation of helicopters involves the capability to perform emergency descending maneuvers through the autorotation principle when the engine is no longer supplying power. When comparing manned and unmanned helicopters, the lower rotor inertia of UAV configurations makes this functionality even more challenging for the pilot since more accurate timing and speed control of the flare phase are required. This paper presents a complete set of guidelines to design a controller for the autonomous autorotation landing of an UAV. This analysis is based on experimental data that corresponds to autorotation landings of a small-size helicopter carried out by a skillful pilot.