Design Considerations for Tilt-Rotor VTOL Aircraft to Minimize the Effects of the Recirculating Downwash Environment

Aerodynamic environmental disturbance effects resulting from near-hover flight conditions close to the ground have been measured on a 1/10-scale, full-span model. Propeller/rotor blade bending moments, flying qualities data, and flow visualization results are presented. Blade loads caused by ground proximity are shown to be predictable by a semiempirical approach. The implications of these data on the design of tilt-rotor aircraft are deduced.