Rolls-Royce Gem

The Rolls-Royce Gem is a three-shaft turboshaft engine developed for the Westland Lynx helicopter in the 1970s. Its design began in the de Havilland engine division, which explains the G in the name, and passed to Bristol Siddeley as the BS.360. After Rolls-Royce bought Bristol Siddeley in 1966 and dropped that identity, the engine became the RS.360. A four-stage axial low pressure compressor, driven by a single-stage low pressure turbine, supercharges a centrifugal high pressure compressor with its own single-stage turbine, and a two-stage free power turbine delivers power to the load through a third shaft, behind a reverse-flow combustor. The Gem 42 develops 1,000 shaft horsepower at take-off, with a maximum contingency rating of 1,120. Besides the Lynx it powers the Agusta A129 Mangusta, and examples are displayed in several British museums.