Armstrong Siddeley Python

The Armstrong Siddeley Python was an early British turboprop engine designed and built by the Armstrong Siddeley company in the mid-1940s. Its main use was in the Westland Wyvern carrier-based heavy fighter. The prototypes had used the Rolls-Royce Eagle piston engine, but Pythons were used in production aircraft. In this application, the Python was rated at 4,110 equivalent shaft horsepower (eshp).

An Armstrong Siddeley Python during NACA wind tunnel testing in 1949
Type Gas turbine turboprop
National origin United Kingdom
Manufacturer Armstrong Siddeley
First run April 1945
Major applications Westland Wyvern
Developed from Armstrong Siddeley ASX

Design and development

The design started as an experimental pure-turbojet known as the ASX, which commenced testing in 1943. By this point other engine designs were already entering pre-production, and it seemed there was little need for the ASX in its existing form. The design was then modified by the addition of a reduction gearbox to drive a propeller. The turboprop thus formed was named ASP.[1]

Flight testing

Early flight-testing of the Python was carried out using the Lancaster B.1 (FE) TW911 and the Lincoln B.2 RE339/G: in each aircraft Pythons replaced the two outboard Rolls-Royce Merlins.

Lincoln B.2 RF403 had two Pythons similarly installed and was used for high-altitude bombing trials at Woomera, South Australia. These trials were principally of the ballistic casings for the Blue Danube atomic weapon: the Lincoln was the only available aircraft that could accommodate the large weapon casing, measuring 62 inches diameter x 24 feet (7.3 m) in length. The Pythons were fitted to increase the height from which tests could be carried out. Maximum release height and speed for the first eleven tests was 275 mph and 34,783 ft (10,602 m) with a bombing error of 61 ft.[2]


Specifications (ASP.3)

Data from Flight.[3]

General characteristics

  • Type: Turboprop
  • Length: 123.2 in (313 cm)
  • Diameter: 54 in (137 cm)
  • Dry weight: 3,450 lb (1,565 kg)


  • Compressor: Axial flow; 14 stages
  • Combustors: 11 combustion chambers
  • Turbine: Axial flow; two stages


See also

Related development

Related lists



  1. Gunston 1998, p.19.
  2. The National Archives, London, file ES 1/44 E4C Appendix 3 page 1.
  3. Flight Global Archive - 1954 Retrieved: 3 November 2008


  • Gunston, Bill (1998). World encyclopaedia of aero engines : all major aircraft power plants, from the Wright brothers to the present day (4th ed.). Sparkford, Nr Yeovil, Somerset, [England]: P. Stephens. ISBN 978-1852605971.
  • Gunston, Bill (1989). World Encyclopaedia of Aero Engines (2nd ed.). Cambridge, England: Patrick Stephens Limited. ISBN 978-1-85260-163-8.
  • Bridgman, Leonard, ed. (1947). Jane's all the World's Aircraft 1947. London: Sampson Low, Marston & Co. pp. 4d–5d.
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