The Vertol 76 was the world’s first successful tilt wing aircraft; it received the Army designation VZ-2 in early 1956. The 26.5 ft fuselage was built of metal tube construction, and had a helicopter-like two seat cockpit. A single 860 bhp Lycoming YT53-L-1 was mounted on the fuselage, and drove the two 9.5 ft three-bladed propellers by a cross-shaft through the 25 ft span wings. In hover, pitch and yaw were controlled by two ducted propellers in the tail; in transition, aerodynamic controls were phased in until the tail propellers were no longer needed in horizontal flight. Ground testing began in April 1957. The first vertical flight was made on 13 August 1957, first horizontal flight on 7 January 1958, and first complete transition on 15 July 1958. It continued to fly until 1965, making over 450 flights, including 34 full conversions.
Further reading: NASA report, Summary of Flight-Test Results of the VZ-2 Tilt-Wing Aircraft, 1962.