The Rolls-Royce Gem is a

turboshaft A turboshaft engine is a form of gas turbine that is optimized to produce shaft horsepower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the ex ...

engine developed specifically for the

Westland Lynx The Westland Lynx is a British multi-purpose twin-engined military helicopter designed and built by Westland Helicopters at its factory in Yeovil. Originally intended as a utility craft for both civil and naval usage, military interest led to t ...

helicopter A helicopter is a type of rotorcraft in which Lift (force), lift and thrust are supplied by horizontally spinning Helicopter rotor, rotors. This allows the helicopter to VTOL, take off and land vertically, to hover (helicopter), hover, and ...

in the 1970s. The design started off at de Havilland Engine division (hence the name starting with "G") and passed to

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 ...

as the BS.360. Rolls-Royce bought out Bristol Siddeley in 1966 and after it dropped the Bristol Siddeley identity the engine became the RS.360.

Design and development

The Gem's three-shaft engine configuration is rather unusual for turboshaft/turboprop engines. Basic arrangement is a four-stage axial LP (Low Pressure) compressor, driven by a single stage LP turbine, supercharging a centrifugal HP (High Pressure) compressor, driven by a single stage HP turbine. Power from a two-stage free (power) turbine is delivered to the load via a third shaft. A reverse flow combustor is featured.Rolls-Royce Gem product page
/ref> The Gem 42 develops at Take-off, Sea Level Static, ISA, but the Maximum Contingency Rating (MCR) is . Until recently all versions of the Lynx have been Gem powered. However, now that Rolls-Royce owns

Allison Allison may refer to: People * Allison (given name) * Allison (surname) (includes a list of people with this name) * Eugene Allison Smith (1922-1980), American politician and farmer * Allison family, a family of RMS Titanic passengers Compan ...

, it has been marketing the more modern

LHTEC T800 The LHTEC T800 is a turboshaft engine for rotary wing applications. It is produced by the LHTEC (Light Helicopter Turbine Engine Company), a joint venture between Rolls-Royce and Honeywell. The commercial and export version is the CTS800. The ...

, developed jointly with

Honeywell Honeywell International Inc. is an American publicly traded, multinational conglomerate corporation headquartered in Charlotte, North Carolina. It primarily operates in four areas of business: aerospace, building automation, industrial automa ...

Applications

Agusta A129 Mangusta The Agusta A129 Mangusta () is an attack helicopter originally designed and produced by Italian company Agusta. It is the first attack helicopter to be designed and produced wholly in Europe. It has continued to be developed by AgustaWestland, t ...

Engines on display

*East Midlands Aeropark * Midland Air Museum *

The Helicopter Museum (Weston) The Helicopter Museum in Weston-super-Mare, North Somerset, England, is a museum featuring a collection of more than 80 helicopters and autogyros from around the world, both civilian and military. It is based at the southeastern corner of the fo ...

*111 (Sunderland) Squadron ATC *South Yorkshire Aircraft Museum

Specifications (Gem 42)

References

Notes

Bibliography

* Gunston, Bill. ''World Encyclopedia of Aero Engines''. Cambridge, England. Patrick Stephens Limited, 1989. *

External links

Rolls-Royce Gem product page
{{DHaeroengines 1970s turboshaft engines Gem Gem Mixed-compressor gas turbines