Flight Test Investigation of Rotorcraft Wake Vortices in Forward Flight

摘要

This report presents the results of helicopter flight tests and wake vortexmeasurements which were designed to provide data necessary for the assessment of hazards to following aircraft. The tests described in this report were conducted using small probe airplanes and a Laser Doppler Velocimeter for wake vortex measurements during forward-flight helicopter operations. Four helicopters, having weights ranging from 7,600 to 70,000 pounds, were used in the tests as the wake vortex generating aircraft. Wake vortex strength and decay characteristics as determined from the flight test results are discussed. In the absence of encounter measurements for the case of hover flight, it is recommended that small airplanes, at the same altitude and downwind of a hovering helicopter, maintain at least 500 feet of separation.