Overhead view of Bell XV-3 Convertiplane. First tilt rotor tested in the 40 x 80 wind tunnel. Transition aerodynamics studied; shown in hover mode.

Foreword, front view of McDonnell Model XV-1 Convertiplane in the Ames 40x80 Foot Wind Tunnel. The McDonnell XV-1 was an experimental compound gyroplane developed for a joint research program between the United States Air Force and the United States Army to explore technologies to develop an aircraft that could take off and land like a helicopter but fly at faster airspeeds, similar to a conventional airplane. The XV-1 would reach a speed of 200 mph (322 km/h), faster than any previous rotorcraft, but the program was terminated due to the tip-jet noise and complexity of the technology which gave only a modest gain in performance.

BELL XV-3 (AF54-148) Convertiplane (experimental tilt rotor) IN FLIGHT Note: Used in publication in Flight Research at Ames; 57 Years of Development and Validation of Aeronautical Technology NASA SP-1998-3300 fig. 121

XV-3 HOVERING ON RAMP. Flight Test of Bell XV-3 Convertiplane. Bell VTOL tilt-rotor aircraft hovering in front of building N-211 at Moffett Field. The XV-3 design combined a helicopter rotor and a wing. A 450 horsepower Pratt & Whitney piston engine drove the two rotors. The XV-3, first flown in 1955 , was the first tilt-rotor to achieve 100% tilting of rotors. The vehicle was underpowered, however, and could not hover out of ground effect. Note the large ventral fin, which was added to imrpove directional stability in cruse (Oct 1962)

XV-3 HOVERING ON RAMP. Flight Test of Bell XV-3 Convertiplane. Bell VTOL tilt-rotor aircraft hovering along side Hangar One at Moffett Field. The XV-3 design combined a helicopter rotor and a wing. A 450 horsepower Pratt & Whitney piston engine drove the two rotors. The XV-3, first flown in 1955 , was the first tilt-rotor to achieve 100% tilting of rotors. The vehicle was underpowered, however, and could not hover out of ground effect. Note the large ventral fin, which was added to imrpove directional stability in cruse (Oct 1962)