Bell XV-3

The Bell XV-3, also called the Bell 200, was an American tiltrotor research aircraft that Bell Helicopter built for a joint United States Air Force and Army program exploring convertiplane technology. A single engine in the fuselage drove two-blade rotors on the wingtips through driveshafts, and the rotors tilted 90 degrees so that the aircraft could take off and land like a helicopter and cruise like an aeroplane. Two aircraft were ordered in October 1953 and the type first flew on 11 August 1955. The first prototype, with three-blade rotors, crashed from flutter two months after its first flight, but the second prototype made 110 transitions from helicopter to airplane mode between December 1958 and July 1962. A wind tunnel accident in May 1966 ended the program, and its data fed the Bell XV-15 and later the V-22 Osprey.