Measurement of Ship Air Wake Impact on a Remotely Piloted Aerial Vehicle

A remotely piloted helicopter has been used to investigate the turbulent air wake behind a ship. As the helicopter, which has a 4.5 ft diameter rotor, maneuvers through regions in the ship's air wake where there are steep velocity gradients, an inertial measurement unit mounted on the helicopter records a noticeable change in the helicopter's flight path. At any time, the relative position of the helicopter can be determined by comparing the GPS derived position of the helicopter with that of a reference position on the ship. Combining these two measurement systems, the locations of sharp gradients in the air wake can be mapped relative to the ship (accurate within one rotor diameter of the helicopter) and compared with Computational Fluid Dynamics (CFD) simulations of similar wind-over-deck configurations. Data collected from underway flight operations show a macro-scale validation of CFD predictions of the ship's air wake at locations distant from the flight deck for winds 15° off the starboard bow.