Rolls-Royce Gem

Gem
Rolls-Royce Gem at The Helicopter Museum (Weston)
Type	Turboshaft
National origin	United Kingdom
Manufacturer	Rolls-Royce Limited
Major applications	Westland Lynx

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.

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).

Until recently all versions of the Lynx have been Gem powered. However, now that Rolls-Royce own Allison, they have been marketing the more modern LHTEC T800, developed jointly with Honeywell. The civil version, known as the CTS800, will power the AgustaWestland Super Lynx.

Data from Rolls-Royce

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