An experimental investigation of helicopter slipstream in the presence of elevated heliport

Abstract

An unsteadiness of pressure in a helicopter rotor slipstream may bring a significant problem during operation from the elevated heliports, as the oscillating slipstream acts on the heliport plate and causes vibration of building’s structure. However, still it is an unappreciated issue, discussed mainly in the literature focused on the brownout. In this case researchers usually neglect the loads acting on the ground. On the other hand, investigations of interaction between rotor slipstream and helicopter’s surroundings, e.g. [7], [4], are often limited to a time-averaged case. Meanwhile, results of the investigation presented in the paper show that amplitude of the pressure oscillation cannot be omitted, as it can achieve its value of roughly 50% of the rotor disc load. This value, however, is dependent on thrust coefficient and height above the ground. Presented results have been obtained in an experimental way, using the helicopter with the rotor diameter of 0.7 m and validated by comparison with the full-scale rotor (with its diameter of 8 m).