Armstrong Siddeley ASX

The Armstrong Siddeley ASX
Type Experimental turbojet
National origin United Kingdom
Manufacturer Armstrong Siddeley
First run April 1943
Major applications Avro Lancaster (test bed only)
Developed into Armstrong Siddeley Python

The ASX was an early axial flow jet engine built by Armstrong Siddeley that first ran in April 1943.[1] Very little information on the engine is available, and it appears it was never put into production. A turboprop version as the ASP was somewhat more successful, and as the Armstrong Siddeley Python saw use in the Westland Wyvern.

Design and development

The ASX was unique in layout. The inlet to the 14-stage compressor was placed near the middle of the engine, the air flowing forward as it was compressed. From there it fed into 11 flame cans arranged around the outside of the compressor, flowing back past the inlet, and finally through the turbine.[2]

This layout allowed the compressor and combustion areas to be "folded" together to make the engine shorter, although the overall reduction in the case of the ASX appears to be fairly limited. Additionally this makes it more difficult to service the compressor, although in modern designs it is the "hot section" that generally requires most servicing.[2]

The ASX was flight tested fitted to the bomb bay of a modified Avro Lancaster, ND784, the first flight taking place on 28 September 1945.

At full power the engine ran at 8,000 rpm and developed 2,600 lbf (12 kN) of thrust at sea level. For cruise the engine ran at 7,500 rpm and developed 2,050 lbf (9.1 kN). It weighed 1,900 lb (865 kg). The ASP conversion used a second turbine stage to drive the propeller through a gearbox, producing 3,600 shp, as well as 1,100 lbf (4.9 kN) of leftover jet thrust.

Beyond this, little has been published about this engine. Armstrong Siddeley appears to have given up on the design just after the war, and took over the Metrovick F.9 Sapphire design instead.


Specifications (ASX)

Data from [3]

General characteristics



See also

Related development

Related lists



  1. Gunston 1989, p.18.
  2. 1 2 Smith 1946, p.89.
  3. Wilkinson, Paul H. (1946). Aircraft Engines of the world 1946. London: Sir Isaac Pitman & Sons. pp. 282–283.


  • Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
  • Jane's Fighting Aircraft of World War II. London. Studio Editions Ltd, 1998. ISBN 0-517-67964-7
  • Smith, Geoffrey G.Gas Turbines and Jet Propulsion for Aircraft, London S.E.1, Flight Publishing Co.Ltd., 1946.
  • Kay, Anthony L. (2007). Turbojet History and Development 1930-1960. 1 (1st ed.). Ramsbury: The Crowood Press. ISBN 978-1-86126-912-6. 
  • Wilkinson, Paul H. (1946). Aircraft Engines of the world 1946. London: Sir Isaac Pitman & Sons. pp. 282–283. 
  • Bridgman, Leonard, ed. (1947). Jane's all the World's Aircraft 1947. London: Sampson Low, Marston & Co. pp. 3d–4d. 

External links

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