The Rolls-Royce RB.108 was a British

jet engine A jet engine is a type of reaction engine, discharging a fast-moving jet (fluid), jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition may include Rocket engine, rocket, Pump-jet, water jet, and ...

designed in the mid-1950s by

Rolls-Royce Rolls-Royce (always hyphenated) may refer to: * Rolls-Royce Limited, a British manufacturer of cars and later aero engines, founded in 1906, now defunct Automobiles * Rolls-Royce Motor Cars, the current car manufacturing company incorporated in ...

specifically for use as a

VTOL A vertical take-off and landing (VTOL) aircraft is one that can takeoff and landing, take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust- ...

lift engine. It was also used to provide horizontal thrust in the

Short SC.1 The Short SC.1 was the first British fixed-wing vertical take-off and landing (VTOL) jet aircraft. It was developed by Short Brothers. It was powered by an arrangement of five Rolls-Royce RB.108 turbojets, four of which were used for vertical ...

Design and development

The RB.108 was the first direct-lift turbojet produced by Rolls-Royce. It originated from a VTOL concept in which Alan A. Griffith proposed using a small number of specialised lift engines in a VTOL aircraft, separate from the engines which provided forward propulsion. Its power output (thrust) was not high enough for use as a practical engine in a production aircraft and was used only for research into VTOL. It was constructed from conventional materials. (The next lift engine, the RB.162, would have a compressor built mainly from glass-fibre composite and have a higher T/W ratio.) The RB.108 bearings and

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) and lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturate ...

system were designed to operate with an engine attitude envelope which covered engine and aircraft tilting while transitioning between hovering and forward flight. When a fifth engine was installed in the SC.1 to provide forward thrust it had to be mounted at about 45 degrees to remain within the envelope. The exhaust was directed horizontally with a curved jetpipe.

Operational history

The RB.108 was used in the

, which used four for lift with an additional one mounted at an angle at the rear for propulsion, and the

Dassault Balzac V The Dassault Balzac V was a French vertical takeoff and landing (VTOL) testbed of the early 1960s. It was built by Dassault Aviation from a prototype Dassault Mirage III, Mirage III aircraft to test the configuration for the Dassault Mirage IIIV ...

, which used eight vertically mounted RB.108s for lift. The

Vereinigte Flugtechnische Werke Vereinigte Flugtechnische Werke (VFW; English: "United Aviation Engineering Works") was a West German aerospace manufacturer. The company was formed by the 1964 merger of two German aerospace firms, Focke-Wulf and Weser Flugzeugbau GmbH (Weserfl ...

(VFW) SG 1262 used five RB.108s, three mounted in tandem on the centreline, with one RB.108 either side. The RB.108 was also the intended powerplant for several other VTOL aircraft designs, including one by Dornier. A similar lift jet was designed by

Bristol Siddeley Bristol Siddeley Engines Ltd (BSEL) was a British aero engine manufacturer. The company was formed in 1959 by a merger of Bristol Aero-Engines Limited and Armstrong Siddeley Motors Limited. In 1961 the company was expanded by the purchase of t ...

, the BS.59, with a thrust of 8,000 lb the engine was intended for the projected Focke-Wulf Fw 260.