In 1951, the U.S. Army and Air Force announced a competition to develop a fixed-wing aircraft that could also take off and landing vertically as a helicopter. McDonnell responded a competition with the XV-1 mock-up. Designed by Friedrich von Doblhoff who had pioneered the WNF 342 rotor-craft in Austria during WWII. The XV-1 was powered by a single piston engine that drove the two air compressors to power the 3-blades main rotor with tip-jet for vertical lift, and power a two-bladed propeller at the fuselage rear for forward flight. McDonnell spent 22 months building the XV-1. The 1st prototype was test flown in 1954. The 2nd prototype became the first rotor-craft to reach a speed of 320km/h in 1956. Following the Air Force evaluation, its maximum speed capability was accomplished. With the other helicopters improving their cruise speed, the program was terminated in 1957.