Dornier Do 31

The Dornier Do 31 was a West German experimental VTOL jet transport built by Dornier. The Do 31 was designed to meet a NATO specification (BMR-4) for a tactical support aircraft for the EWR VJ 101 VTOL strike aircraft designed under the NATO contract of BMR-3. The project was cancelled in 1970 due to high costs, technical problems and a change of requirement.

Design and development
In the early 1960s, the Luftwaffe became increasingly concerned that its airfields were vulnerable to air attack from Eastern Bloc forces and actively researched the possibility of dispersed operations which included flying from Autobahnen but required aircraft with STOVL capabilities. Part of these trials involved the modification of Luftwaffe F-104 Starfighters to be rocket launched from stationary ramps in what became known as the ZELL program. The Starfighters were to be recovered to short strips using aircraft carrier-type arresting gear. The Do 31 was intended to use the same strips as forward operating bases.

When the high cost, technical and logistical difficulties were realised the Luftwaffe ceased trials involving VTOL aircraft such as the Do 31, VJ101 and the later VFW VAK 191B which resulted in the cancellation of these projects and further use of these aircraft was limited to research purposes only.

Initial designs incorporated a Bristol Pegasus vectored-thrust turbofan in each of the two inboard nacelles and four Rolls-Royce RB162 lift engines in each of the outer nacelles. It was planned to dispense with the outer nacelles and their engines when larger RB153 turbofans (of approximately 5000 lbf thrust) became available. By mounting the engines in pods, the fuselage could provide a capacious hold with a rear loading ramp.

In all, three test prototypes were built, these being E1, E2 and E3 - the "E" indicating Experimentell (Experimental). E1 was powered only by the Pegasus engines, and was designed to test 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 first prototype (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 Do 31 established several Fédération Aéronautique Internationale (FAI) world records during its ferry flight to the 1969 Paris Air Show. It was the first, and so far only, vertical take-off jet transport ever built. The project was cancelled in April 1970, although it made its final public flight on 4 May 1970 during the ILA in Hanover. One of the factors that led to the cancellation was the large drag and weight of the lift engine pods which reduced the useful payload and range compared to conventional transport aircraft.

To cope with the complex computations necessary for vertical take-off, the Do 31 was equipped with a Dornier DO-960 hybrid computer.

Survivors


Both flying prototypes have been preserved in Germany, the fate and current location of the non-flying test bed (E2) is not known.
 * Dornier Do 31 E1, D-9530, is preserved and displayed at the de in Friedrichshafen.
 * Dornier Do 31 E3, D-9531, was initially put into storage at Oberpfaffenhofen, then for several years on display in the open in front of the entrance of the Deutsche Museum and  after restoration is now on display at the Deutsches Museum Flugwerft Schleissheim at Oberschleissheim near Munich

Operators

 * Luftwaffe
 * Luftwaffe