The Bristol Orion aero engine was a two-shaft turboprop intended for use in later marks of the Bristol Britannia and Canadair CL-44. Although the engine was built and underwent a development program, the BE.25 Orion project was cancelled in 1958 by the British Ministry of Supply. At that time, interest in turboprop powered aircraft was beginning to wane, because of the successful introduction of the Boeing 707 and Douglas DC-8 jetliners into airline service.
A single stage HP turbine drove a five stage all-axial HP compressor, whilst a three stage LP turbine drove both the seven stage LP compressor and the propeller, via a reduction gearbox. Thus the Orion used a shared load LP turbine (like the Rolls-Royce Tyne), whereas its predecessor, the Bristol Proteus, had a free-power turbine. The combustor used separate flame cans.
One novel feature of the Orion was a derate from a thermodynamic rating of 9,000 shp at sea level, to enable a constant 5,150 ehp power level to be maintained all the way up to 15,000 ft altitude.
The Orion project was cancelled in January 1958, at a reported total cost of £ 4.75 million.
Type: Twin-spool turboprop
Length: 112.3 in (2,852 mm)
Diameter: 41 in (1,041 mm)
Dry weight: 3,150 lb (1,429 kg)
Compressor: 7 stage low pressure, 5 stage high pressure
Combustors: Annular combustor with 10 flame tubes
Turbine: Single stage high pressure, 3 stage low pressure
Fuel type: Kerosene
Maximum power output: 5,150 eshp (3,840 kW) (maximum takeoff)
Overall pressure ratio: 10:1
Specific fuel consumption: 0.64 lb/eshp/hr
Thrust-to-weight ratio: 1.63 eshp/lb (2.68 kW/kg)