Dornier Do 31

https://en.wikipedia.org/wiki/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 (NBMR-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 owing to high
costs, technical problems and a change of requirement.

In the early 1960s, the German Air Force 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 German 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 realized, the
German Air Force 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 5,000 lbf (22 kN) 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.


Role
VTOL transport

Manufacturer
Dornier Flugzeugwerke

First flight
10 February 1967

Status
Project cancelled April 1970

Primary user
German Air Force

Number built
3

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 takeoff 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 and fast computations necessary for vertical takeoff,
the Do 31 was equipped with a Dornier DO-960 hybrid computer.

A development of the Do 31, called Do 131 with twelve or fourteen liftjets, was
explored, but no prototype was built.

Specifications (Do 31E)

General characteristics
Crew: two
Capacity: 36 troops or 24 casualty stretchers
Length: 20.53 m (67 ft 4 in)
Wingspan: 18 m (59 ft 3 in)
Height: 8.53 m (28 ft)
Wing area: 57 m² (613.56 ft²)
Useful load: 3,500 kg (7,715 lb)
Loaded weight: 22,453 kg (49,500 lb)
Max. takeoff weight: 27,422 kg (60,500 lb)
Powerplant: 2 × Rolls-Royce Pegasus BE.53/2 turbofan, 68.95 kN (15,500 lbf) each
8 × Rolls-Royce RB162-4D Vertically mounted turbojet lift engines, 19.57 kN
(4,400 lbf) each


Performance
Maximum speed: 730 km/h (452 mph)
Cruise speed: 650 km/h (404 mph)
Range: 1,800 km (1,120 mi) with maximum payload
Service ceiling: 10,700 m (35,100 ft)
Rate of climb: 19.2 m/s (3,780 ft/min) -using Pegasus engines only



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