Rolls-Royce Pegasus

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Rolls-Royce Pegasus

This engine should not be confused with the older Bristol Pegasus

The Rolls Royce Pegasus is a turbofan engine originally designed by Bristol and now manufactured by Rolls-Royce plc.

The unique Pegasus engine powers all versions of the Harrier multi-role military aircraft. The engine employs a simple thrust vectoring system that uses four swivelling nozzles, giving the Harrier thrust both for lift and forward propulsion, allowing for STOVL flight. This eliminates the need for conventional runways and is a major advantage at sea, where Harriers can operate from a wide variety of ships.

The Pegasus vectored-thrust turbofan is a two-shaft design featuring three LP and eight HP compressor stages driven by two LP and two HP turbine stages respectively. Just as the airframe was licence built by McDonnell Douglas Rolls-Royce allowed Pratt & Whitney to build the Pegasus under licence.



Bristol Engine Company began work on the BE.53 Pegasus in 1958. The engine was designed in tandem with the Hawker P.1127 which first flew in 1960. Production and development of the Pegasus was continued by Rolls-Royce when it acquired Bristol in 1966.


RAF Harrier GR7
RAF Harrier GR7

Pegasus 11

The Pegasus 11 powered the first generation Harriers, the RAF's Hawker Siddeley Harrier, the USMC AV-8A and the Royal Navy's Sea Harrier. The Pegasus 11 produced 21,000 lbf (93.4 kN) and entered service in 1974.

Pegasus 11-21/Mk.105/Mk.106

The 11-21 was developed for the second generation Harriers, the USMC AV-8B and the RAF Harrier IIs. The original model provided an extra 450 lbf (2 kN). The RAF Harriers entered service with the 11-21 Mk.105 which generates 21,500 lbf (96 kN). The Mk.106 development was produced for the Sea Harrier FA2 upgrade and generates 21,750 lbf (97 kN).

Pegasus 11-61/Mk.107

The 11-61 is the latest and most powerful version of the Pegasus, providing 23,800 lbf (106 kN). This equates to up to 15 percent more thrust at high ambient temperatures, allowing upgraded Harriers to return to an aircraft carrier with any unused weapons which previously had to be dumped. This and the reduced maintenance required enhance the combat effectiveness of the Harrier while cutting the cost of engine ownership.

This latest Pegasus has also enabled a highly effective radar equipped version of the AV-8 Harrier II to be introduced. This version, the Harrier II+, combines the proven advantages of day and night STOVL operations with an advanced radar system and beyond-visual-range missiles. The RAF is in the process of upgrading its GR7 fleet to GR9 standard. Part of this process is the upgrade of the Mk.105 engines to Mk.107 standard. These aircraft will be known as GR7As and GR9As.

Future STOVL powerplants

Rolls-Royce's experience in STOVL flight through the Pegasus has allowed it to play a leading role in the propulsion of the next generation STOVL aircraft, the F-35. Whether powered by the Pratt & Whitney F135 or the GE/RR F136, significant workshare rests with the UK based company. Whatever powerplant is selected for STOVL variants they will both employ the Rolls-Royce LiftSystem ® which incorporates:

  • Rolls Royce LiftFan ®
  • Engine to fan driveshaft
  • 3 Bearing swivel module (thrust vectoring)
  • Roll posts

The engine delivers 18,000 lbf (80 kN), the LiftFan 20,000 lbf (89 kN) cold thrust and the roll posts 1,950 lbf (9 kN) each for a sum of 39,950 lbf (178 kN) for the entire system. This compares with the a maximum thrust of 23,800 lbf (106 kN) for the Harrier's Rolls-Royce Pegasus engine.

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