|Preserved Bristol Theseus|
|First run||18 July 1945|
|Major applications||Handley Page Hermes|
The Theseus was the Bristol Aeroplane Company's first attempt at a gas-turbine engine design, a turboprop that delivered just over 2,000 hp (1,500 kW). A novel feature was the use of a heat exchanger to transfer waste heat from the exhaust to the compressor exit. The engine was soon superseded by the Proteus design with more power, and the only extended use of the engine was in two Handley Page Hermes 5 development aircraft.
Following 156 hours of ground runs and the receipt of a test certificate from the Ministry of Supply on 28 January 1947, two Theseus engines were fitted in the outer positions of a four-engined Avro Lincoln for air tests. After ground and taxying test the Lincoln first flew on 17 February 1947.
- Theseus Series TH.11
- Variant without heat exchanger
- Theseus Series TH.21
- Variant with heat exchanger
Specifications (Theseus Th.21)
Data from 
- Type: Mixed compressor turboprop with heat exchanger
- Length: 106 in (2,692.4 mm)
- Diameter: 49 in (1,244.6 mm)
- Dry weight: 2,310 lb (1,047.8 kg)
- Compressor: 8-stage axial + 1-stage centrifugal compressors feeding the combustion chambers through a heat exchanger
- Combustors: 8 x stainless steel can combustion chambers
- Turbine: 2-stage axial + 1-stage axial free turbine driving the propeller
- Fuel type: Kerosene (R.D.E. / F / KER)
- Oil system: pressure feed to bearings, dry sump, 40 S.U. secs (13 cSt) (Intavia 620) grade oil
- Maximum power output: 2,800 hp (2,087.96 kW) equivalent at 8,200 rpm at sea level (2,200 hp (1,640.54 kW) + 825 lbf (3.67 kN) residual thrust)
- Overall pressure ratio: 3:1
- Fuel consumption: 272 imp gal (1,236.5 l) /h
- Specific fuel consumption: 0.5 lb/equiv. hp/h ( kg/equiv. kW/h) [clarification needed]
- Thrust-to-weight ratio:
- Maximum flight rating: 1,500 hp (1,118.55 kW) equivalent at 8,200 rpm at 20,000 ft (6,096 m)
- Gunston 1989, p.34.
- "Theseus Air Testing - First Bristol Airscrew Turbines Fly in a Lincoln : Some Features Discussed". Flight: 270. 27 March 1947.
- Test bed only
- Wilkinson, Paul H. (1946). Aircraft Engines of the world 1946. London: Sir Isaac Pitman & Sons. pp. 284–285.
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