Encounters with Aircraft Vortex Wakes: The Impact on Helicopter Handling Qualities

A study concerning the risks associated with locating a helicopter final approach and takeoff area alongside an active runway at a busy international airport is documented. Specifically, by the use of desktop simulation, the problem is addressed of an in-flight helicopter encountering the shed wing tip vortex from a large transport aircraft. Measurements are reviewed of vortices taken using coherent laser radar equipment located under the final approach path to London Heathrow Airport to establish a model of the vortex velocity profile. The simulations have shown the helicopter can experience transient pitch attitude changes of up to 40 deg and accumulated descent rates of 1500 ft/min (457 m/min) during the encounter, assuming that no pilot intervention is made. Established handling qualities metrics have been adapted and suggest that these responses may produce handling difficulties. The simulations were also broadened to consider a range of helicopter designs and the effects of shed vortices from a number of large transport aircraft