McDonnell XV-1
The McDonnell XV-1 is an experimental Convertiplane developed by McDonnell Aircraft 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 (320 km/h; 170 kn), 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.