Rolls-Royce Clyde

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The Rolls-Royce RB.39 Clyde was Rolls-Royce's first purpose-designed turboprop engine and the first turboprop engine to pass its civil and military type-tests.<ref name="Gunston WEoAE"/><ref>Flight 1954, p. 582.</ref>

As with subsequent Rolls-Royce gas turbines, it was named after a river, the River Clyde.

Design and developmentEdit

The Clyde used a two-shaft design, with an axial compressor based on that of the Metrovick F.2<ref>Template:Cite book</ref><ref name="Sutton Publishing 2006, P.195">"World Encyclopedia of Aero Engines – 5th edition" by Bill Gunston, Sutton Publishing, 2006, P.195</ref> for the low-pressure section, and a single-sided centrifugal compressor scaled up from the Merlin 46 supercharger<ref>Template:Cite journal</ref> as the high-pressure stage, both mounted on the HP shaft and driven by a single stage HP turbine. A single stage power turbine drove the front mounted propeller reduction gearbox via the concentric LP shaft. A fairly novel feature of this compact gearbox was the power output to contra-rotating propellers.<ref>"Not much of an Engineer" by Sir Stanley Hooker, Airlife Publishing Ltd, 1984, P.227</ref>

The Clyde was a long engine with the axial LP compressor in front of what was, in effect, a scaled-down Derwent engine. Accessories were grouped around the axial compressor which conveniently narrowed towards the rear. Cooling for turbines and turbine bearings came from a small impeller on the main shaft as well as air taken from the axial and centrifugal compressors. Testing of the development engines exceeded expectations with the engine soon being rated at 4,030 eshp.<ref name="Sutton Publishing 2006, P.195"/><ref name="Kay"/> During testing potentially destructive vibrations were found originating in the straight-cut spur gears in the reduction gearbox.<ref name="Kay"/>

The engine was selected as the main engine of the Westland Wyvern TF Mk.2 strike aircraft.<ref name="Gunston WEoAE"/> However, despite the promising performance of the test engines Ernest Hives felt that pure-jets such as the Avon were the future and the Clyde programme was terminated, forcing Westland to use the less than satisfactory Armstrong Siddeley Python on the production Wyverns.<ref name="Gunston WEoAE"/> and so Rolls-Royce's first production turboprop would be the Dart.