Allison / Rolls-Royce XJ99

The Allison / Rolls-Royce XJ99 (Rolls-Royce factory designation RB.189) is a lightweight jet engine from the 1960s and 1970s, which was primarily intended to be used as a lift engine in VTOL aircraft and as a drive in STOL aircraft. The engine was a joint development begun in October 1965 by the Detroit Diesel Allison Division of General Motors Corporation and the Derby Engine Division of Rolls-Royce .

history

The development of the XJ99 took place under an agreement between the governments of the USA and Great Britain. Program monitoring was carried out by the US Air Force Aero Propulsion Laboratory and the UK Department of Defense.

The intended goal when designing the XJ99 was to increase the thrust-to-weight ratio compared to the lifting engines of the 1960s. Rolls-Royce was able to draw on its experience with the lift engines RB.108 (thrust / weight: 8: 1) and RB.162 (thrust / weight: 16: 1). In addition, the ratio of thrust to construction volume, which is particularly important for military deployed VTOL aircraft, has been significantly increased compared to its predecessors. In addition to its use as a lift engine, the XJ99 could also be used as a booster, which was only temporarily in operation, to support take-off in conventional aircraft.

Originally, the XJ99 was supposed to serve as a lift engine for the AVS VTOL fighter aircraft planned by the USA and Germany, but it did not get beyond the drawing board stage. However, development continued after that, and the first test bench runs of the XJ99-RA-1 were carried out in 1969. In 1971 the achievement of the intended thrust could be demonstrated. Interest in the engine increased again in 1972, but the project was ultimately abandoned.

Planned uses

• Grumman Model 754 VTOL drone
• Fairchild Republic FR-150 VTOL jet fighter aircraft
• EWR / Fairchild AVS swing-wing -VTOL fighter aircraft

Technical specifications

Parameter	Dates (after Jane's 1972, p. 673)
Type	Twin-shaft turbojet
compressor	Two-stage low-pressure axial compressor, four-stage high-pressure axial compressor
Combustion chamber	Annular combustion chamber
turbine	Single-stage low-pressure axial turbine, single-stage high-pressure axial turbine
Max. Diameter	69.5 cm
length	114.1 cm
Weight (with oil and fuel system)	204 kg
Thrust / weight ratio	20: 1
Nominal thrust	40.1 kN (9000 lb)

literature

• John WR Taylor (Ed.): Jane's All The World's Aircraft - 1972-73 , Sampson Low, Marston & Company Ltd., London, 1972, p. 673

Individual evidence

1. ↑ ^{a b} XJ99 engine in search of an airframe (Flight from June 1, 1972)
2. ↑ Bundeswehr / whiz kid - died violently (Spiegel 4/1969)
3. ↑ http://www.designation-systems.net/usmilav/engines.html
4. ^ Rose, Bill, 2013. Vertical Take-off Fighter Aircraft . Hersham, UK: Ian Allan Publishing.