Bell XV-15

The Bell XV-15 was an American tiltrotor VTOL research aircraft, the second successful experimental tiltrotor and the first to demonstrate the concept's high-speed performance relative to conventional helicopters. The program began in 1971 at NASA Ames Research Center, and after a review of two proposals NASA selected Bell's Bell 301 design and issued a research contract on 31 July 1973. Two XV-15 aircraft were built, the first, N702NA, flying on 3 May 1977, and they were tested at Bell, at NASA Ames and at NASA Dryden. One crashed on 20 August 1992 while flown by a guest test pilot, and the other, after retirement from test operations, was donated to the Smithsonian National Air and Space Museum. The experience gained led to the Bell Boeing V-22 Osprey.