On the Hybrid Tilt-Wing/Tilt-Propeller Active Flow Control Enabled Runway Independent Airplane

The extremely short takeoffs of the V-22 from the USS Iwo-Jima when its rotors were tilted forward by 19º relative to the traditional 88o used in hover, inspired a series of wind tunnel tests simulating the phenomenon that enabled the V-22 to takeoff within 30ft of run distance (only ½ of its body length. It transpired that the download force that normally consumes 12-13% of the rotor thrust was substantially reduced by the tilt forward of the rotor, while the Suck-Back (SB, lift force in wind tunnel coordinates) was increased. The introduction of Active Flow Control (AFC) reduced the download even more while increasing the SB. This suggested that a hybrid AFC augmented airplane configuration consisting of fixed wing attached to a fuselage and a tilt wing attached to the rotor or nacelle are most effective in hover. Namely, it can carry more weight per installed thrust. When some of these ideas were tested on a powered model in hover, its download was reduced by approximately 60% relative to an identical tilt rotor model in the absence of AFC.