11/15/2014. Remarks by Johan Visschedijk: "In 1962, the Federal Ministry of Defense awarded Dornier a design contract for the Do 31 V/STOL transport aircraft. Under this experimental program, the production program covered a small and a large hovering rig for studying design principles, an airframe for structural testing, and a systems test stand for hydraulic and electric systems.
The two test aircraft Do 31 E-1 (without lift engines) and Do 31 E-3 were successlully tested between 1967 and 1971. The Do 31 E-1 was equipped with two Rolls-Royce Pegasus 5-2 lift/thrust engines rated at 15,432 lb (7,000 kg) of thrust each which provided power for cruising flight as well as lift during takeoff and landing via vectored nozzles. To support the cruise engines in hover flight, a total of eight Rolls-Royce RB-162-4D, rated at 4,409 lb (2,000 kg) of thrust each, were installed in nacelles at the wing ends. By tilting the cruise engine nozzles, the Do 31 was accelerated to the speed of approximately 155 mph (250 kmh) required for aerodynamic horizontal flight, and the eight lift-producing engines were stopped again after twenty seconds.
The Do 31, which established several FAI world records during its ferry flight to the 1969 Paris Air Show, was the first and so-far only vertical takeoff jet transport built in the world. Both aircraft are preserved in Germany, the Do 31 E-1 is on display at the Dornier Museum in Friedrichshafen, the Do 31 E-3 at the Deutsche Museum at Munich."