Lockheed XV-4 Hummingbird

The Lockheed XV-4 Hummingbird, first designated VZ-10, was a United States Army project to show that vertical takeoff and landing could serve a surveillance aircraft carrying target-acquisition and sensor equipment. Lockheed designed and built it in the 1960s as one of many attempts at a V/STOL jet. Lift on takeoff came from exhausting engine flow downward through several nozzles, augmented by a secondary flow of cold air, but performance fell far short of estimates with a thrust-to-weight ratio of only 1.04. The first prototype flew conventionally on 7 July 1962, hovered free on 24 May 1963 and made the first transition to forward flight on 8 November 1963, then crashed on 10 June 1966, killing the pilot. The second airframe was rebuilt as the XV-4B with lift jets and also crashed, on 14 March 1969, with the pilot ejecting safely. No early American V/STOL design of this kind reached production.