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Bristol Siddeley Theseus




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. First run on 18 July 1945, the engine was soon superseded by the Proteus design with more power, and the only extended use of the engine was in two Handley Page Hermes 5 development aircraft.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.

Avro Theseus Lincoln
Handley Page Hermes 5


Theseus Series TH.11
Variant without heat exchanger

Theseus Series TH.21
Variant with heat exchanger


Theseus Th.21
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 cs) (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) /hr
Specific fuel consumption: 0.5 lb/equiv. hp/hr ( kg/equiv. kW/hr)
Maximum flight rating: 1,500 hp (1,118.55 kW) equivalent at 8,200 rpm at 20,000 ft (6,096 m)



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