Dornier Flugzeugwerke
Dornier Do-31 VTOL
First flight 10 February 1967 Status Project cancelled in April 1970 
Number build 3

Programme launch and design

During February 1962, the formal launch of the Do 31 programme occurred with the issuing of a development contract from the West German government. By the start of 1964, Dornier had started building a pair of prototype aircraft; their manufacture was largely performed at the company's Oberpfaffenhofen plant.A total of three test prototypes were constructed, these being E1, E2 and E3 - the "E" indicating Experimentell (Experimental). E1 was powered only by the Pegasus engines, having been designed to test horizontal flight. E2 was a static test airframe, and did not ever fly. E3 was furnished with both Pegasus and RB162 lift engines installed, being intended to evaluate the design's vertical flight mode.

The design of the Do 31 was heavily reliant upon its engine configuration. Dornier had opted to incorporate the British-built Bristol Pegasus vectored-thrust turbofan engine, an existing powerplant that was most famously used to power the Harrier jump jet. On the Do 31, a pair of Pegasus engines were housed in each of the two inboard nacelles; during the vertical phase of flight, additional lift was provided by an arrangement of four vertically mounted Rolls-Royce RB162 lift engines located in each of the outer nacelles.