FULL-SCALE ROTORCRAFT DOWNWASH SURVEYS IN A SHIPBOARD ENVIRONMENT

The paper describes recent V-22 Integrated Test Team/NAVAIR full-scale downwash survey activity conducted as part of the V-22 Uncommanded Roll On-Deck test program. The objectives of the surveys were to quantify the aerodynamic disturbances driving the V-22’s on-deck uncommanded roll response experienced during recovery operations of upwind rotorcraft. Over 300 wake survey events were conducted aboard LHA and LHD class ships between October 2002 and November 2003, using an array of ultrasonic anemometers designed to measure the variation in wake induced velocities across the span of the V-22’s rotors. Data were recorded as various rotorcraft flew constant height and mission representative approaches, upwind hovers, departures, and air taxis past the array. Aircraft surveyed include the UH-1N, CH-46, and the CH-53E platforms. In addition to the anemometer data, the trajectory of the approaching aircraft was recorded using an IR tracking/laser ranging system. Ship motion and wind-over-deck data were also acquired, completing a comprehensive dataset.