McDonnell XV-1

The McDonnell XV-1 was an experimental convertiplane built by McDonnell Aircraft for a joint research programme of the United States Air Force and the United States Army. The aim was an aircraft that could take off and land like a helicopter yet cruise at speeds closer to a conventional airplane. It used a three-bladed main rotor driven by pressure jets at the blade tips, fed with compressed air from a single Continental R-975 radial piston engine, and for forward flight the engine was disconnected from the compressors and turned a rear pusher propeller while short stub wings carried most of the lift. The first prototype began tethered hovering tests in February 1954, and in October 1955 the second aircraft became the first rotorcraft to exceed 200 miles per hour. The programme was cancelled in 1957 because the configuration was complex, noisy and gave only a modest gain over conventional helicopters. Both prototypes survive in museum collections.