Beating Gravity - Bell Model 200 / XV-3

Bell, pioneers of rotorcraft construction, realised as early as 1943 that a helicopter could not match the overall performance of a fixed wing aircraft. They therefore turned their interest to the convertiplane concept, in which an aircraft could take off like a helicopter, then tilt its wings and rotors for conventional fixed-wing horizontal flight.

The Model 200 program began in 1950, following a joint US Army and USAF to investigate the convertiplane concept for possible military use. Bell, McDonnell and Sikorsky submitted the most impressive designs for, respectively, their Model 200, Model 82 and S-57. The Sikorsky design, believed to have been designated XH-36, and later XV-2, never got beyond design stage. Two prototypes were ordered of each of the Bell and McDonnell types, designated XV-3 and XV-1 respectively.

The four-seat XV-3 carried a Pratt & Whitney R-985 radial engine behind the glazed cockpit area. It had fixed twin-skid landing gear and a conventional tail unit. The mid/shoulder mounted cantilever wings carried at their tips two three-bladed prop-rotors, driven from the fuselage engine by means of transmission shafts and gearboxes.
The prop-rotors acted like conventional helicopter rotors for takeoff, and then tilted forward to power the aircraft in horizontal flight, with the fixed wing providing the lift.

The first vertical take-off of the XV-3 was on 23rd August, 1955. It achieved a number of partial transitions before being damaged in an accident on 25th October, 1956. The second prototype was fitted with semi-rigid two-bladed prop-rotors in 1957, and made its first full transition on 18th December, 1958. It was found capable of a speed range from 15 mph (24 km/h) backwards, to over 180 mph (290 km/h) forwards, at altitudes up to 12,000 ft (3660 m).

The XV-3 was grounded after a prop-rotor/pylon instability problem in 1962. After some work, it was used from 1965 in NASA's Ames Research Centre wind tunnel, in California. It was further damaged and was finally discarded.

More XV-3 links:

http://avia.russian.ee/vertigo/bell_xv-3-r.html