Hovering Performance of a Rotor in an Inclined and Partial Ground Effect

To clarify the hovering performance of the rotor whose disk is partly outside the edge of a finite inclined ground plane, a hovering test was conducted with a model rotor and a ground effect plate. At a chain of the flight environment from out-of-ground effect to full ground effect cases, the thrust, torque, and blade flap angle of the rotor hovering above the inclined ground plane were measured. Such flight environment was simulated altering the horizontal distance from the rotor hub center to the ground edge, i.e., center-to-edge distance, at a constant rotor height and ground inclination angle. As a result, it is shown that the hovering performance of the rotor in the inclined and partial ground effect remarkably depends on the combinations of the center-to-edge distance, the ground inclination angle, and the rotor height, and that the hovering performance of the rotor in the partial ground effect on the mountain side of the inclined ground plane is very different from that on the valley side.