The Rolls-Royce Gem is a turboshaft engine developed specifically for the Westland Lynx helicopter in the 1970s. The design started off at de Havilland (hence the name starting with "G") and was passed to Bristol Siddeley as the BS.360. When Rolls-Royce bought out the latter in 1966, it became the RS.360.
|Rolls-Royce Gem at The Helicopter Museum (Weston)|
|National origin||United Kingdom|
|Major applications||Westland Lynx|
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.
The Gem 42 develops 1,000 shp (750 kW) at Take-off, Sea Level Static, ISA, but the Maximum Contingency Rating (MCR) is 1,120 shp (840 kW).
Engines on display
Specifications (Gem 42)
- Type: Triple-shaft two-spool turboshaft
- Length: 43.4 in (1090 mm)
- Diameter: 23.5 in (590 mm)
- Dry weight: 414 lb (187 kg)
- Compressor: 4-stage axial LP, single-stage centrifugal HP
- Turbine: 2-stage power turbine, single-stage LP, single-stage HP
- Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
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