Analysis of the loads acting on the rotor of a helicopter model close to an obstacle in moderate windy conditions

The present paper describes an experimental investigation of the loads acting on a rotor when it interacts with a simplified cuboid obstacle, representing a low-rise building, in moderate windy conditions. Measurements of forces and moments acting on the rotor were carried out by means of a six-component balance in order to assess the rotor performance for several helicopter positions with respect to the obstacle. Wind tunnel tests have been carried out at an advance ratio of μ=0.05 and compared with the corresponding wind-off tests. The investigation showed that ground effect on the obstacle is generally mitigated in windy conditions and that severe detrimental effects are encountered when the helicopter enters the obstacle wake, especially when the helicopter interacts with its lateral vortex structures.