Rolls-Royce RB.39 Clyde
The RB.39 Clyde was Rolls-Royce's first purpose-designed turboprop engine, first run on 5 August 1945.
The Clyde used a two-spool design, with an axial compressor for the low-pressure section, and a single-sided centrifugal compressor as the high-pressure stage, running on concentric shafts. It had a nine-stage axial compressor and a single-stage centrifugal compressor, in addition to two turbines. The forward (high-pressure) turbine drove the centrifugal blower, and the rear (low-pressure) turbine the axial compressor and contra-rotating airscrews.
The Clyde was the first turboprop to pass its full civil and military type-tests. Its first tests were run at 2,500 s.h.p. and this was later increased to 3,020 s.h.p. Subsequent ratings were 3,500 e.h.p., 4,200 s.h.p. and 4,500 e.h.p.; these last proved that the reduction gear was capable of standing greatly increased overloads.
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 diffuser on the main shaft as well as tappings from the axial and centrifugal compressors. Testing of the development engines exceeded expectations with the engine soon being rated at 4,030 eshp. One problem un-earthed during testing was that damaging resonances emanated from the straight-cut spur gears in the reduction gearbox.
The 4,030 eshp versions were selected as the main engine of the Westland Wyvern TF Mk.2 strike aircraft.
Despite the promising performance of the test engines Ernest Hives felt that pure-jets were the future and the Clyde programme was terminated with only 9 built, forcing Westlands to use the less than satisfactory Armstrong Siddeley Python on the production Wyverns.