Experimental helicopters

attack helicopter prototype by Boeing and Sikorsky

type of aircraft

proposed high-speed scout and attack compound helicopter

experimental high-speed compound helicopter

experimental high-speed compound helicopter with coaxial rotors

aircraft manufacturer

1950s British compound gyroplane

US experimental hybrid helicopter/fixed-wing aircraft

experimental co-axial compound helicopter

1962 light helicopter

1958 quadrotor helicopter prototype model by Curtiss-Wright

1952 experimental helicopter model by American Helicopter Company