Beating Gravity - Bell Model 301 (XV-15)

Bell, having considerable experience in rotary-wing and tilt-rotor aircraft, was selected in 1973 as a prime contractor for a research program to prove the operational practicality of the tilt-rotor concept. The program was launched by the US Army's Air Mobility Research and Development Laboratory and NASA.

Drawing on their experience with the Bell Model 200, the Model 301 was developed. Further funding in the later 1970s allowed construction of two XV-15 prototypes. The first XV-15 prototype flew on 3rd May, 1977. After initial trials in VTOL mode it was used for wind-tunnel tests. The second prototype first flew in April 1979, and achieved the XV-15's first free-flight transition between vertical and horizontal flight that July.

The aircraft's layout was more or less conventional; a streamlined fuselage with tricycle undercarriage, high-mounted cantilever wing, and an upswept tail unit with endplate vertical surfaces. Advanced proprotors were located on swivelling nacelles at the wing tips. These nacelles housed individual turboshaft engines. Tranverse cross-shafting enabled either engine to drive both rotors in the event of single-engine failure.

The design provided for vertical takeoff and a 12-second transition to wing-borne forward flight as the proprotors tilted through 90 degrees. The XV-15 program was very successsful, and provided a sound background for development of the Osprey and other subsequent VTOL aircraft.

NASA XV-15 Images Images below are from the NASA Dryden Flight Research Center at Edwards, California Open XV-15 gallery on NASA website
NASA XV-15 Movies (requires Quicktime - download) NASA Dryden Flight Research Center website: XV-15 in flight

More 301 (XV-15) links:

http://avia.russian.ee/vertigo/bell_xv-15-r.html