The Dornier Do 31 was a West German experimental VTOL aircraft built in the late 1960s. To this day it is the only VTOL jet transport aircraft ever built. The aircraft was designed to meet a NATO requirement for a tactical support aircraft to work in conjunction with the EWR VJ 101 VTOL strike aircraft.
The origins of the Dornier Do 31 project began in the early 1960s when German air force top brass started to realise that their airfields were vulnerable to attack from Eastern Bloc forces and the Soviet Union. In an effort to counteract this weakness the Luftwaffe started looking at VTOL and STOVL options. The Dornier Do 31 was one of the results.
Dornier built three prototypes of the Do 31, the E1, the E2 and the E3. The “E” stood for Experimantal. The three examples of the aircraft were all different. E1 lacked VTOL capability and was powered only by the Pegasus engines used for horizontal flight. E2 was a static test airframe, and did not fly. E3 had both Pegasus and RB162 lift engines installed, and was designed to test the vertical flight mode.
The Do 31 E1 first flew on 10 February 1967 with just the two Pegasus engines. The third prototype (E3) flew in July 1967 with all ten engines fitted. The first hovering flight took place on 22 November 1967. Full forward and backward transitions were made in December 1967.
The Dornier Do 31 was flown by a crew of two, however it could carry up to 36 fully armed troops, or up to 24 stretchers.
The Dornier Do 31 established several Fédération Aéronautique Internationale (FAI) world records during its flight to the 1969 Paris Air Show.
However despite its ingenuity and abilities, the Dornier Do 31 proved to be extremely costly. The project was cancelled in April 1970.
Both flying prototypes have been preserved (E1 and E3). Dornier Do 31 E1, D-9530, is housed at the Dornier-Museum in Friedrichshafen. Dornier Do 31 E3, D-9531, is on display at the Deutsches Museum Flugwerft Schleissheim at Oberschleissheim near Munich.