The Rolls-Royce Gem is a

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

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 t ...

helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attribu ...

in the 1970s. The design started off at

de Havilland The de Havilland Aircraft Company Limited () was a British aviation manufacturer established in late 1920 by Geoffrey de Havilland at Stag Lane Aerodrome Edgware on the outskirts of north London. Operations were later moved to Hatfield in H ...

(hence the name starting with "G") and was 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. When Rolls-Royce bought out the latter in 1966, it 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 is delivered to the load via a third shaft, connected to a two-stage free (power) turbine. 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 own

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 Companies * Allison Engine Company, American aircraft engine ...

, they have 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 technologies, performance ma ...

Applications

Agusta A129 Mangusta The Agusta A129 Mangusta ( en, Mongoose) 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 Agus ...

Engines on display

*East Midlands Aeropark * Midland Air Museum * The Helicopter Museum (Weston)
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
a 1972 ''Flight'' article {{DHaeroengines 1970s turboshaft engines

Gem A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, an ...

Mixed-compressor gas turbines