Armstrong Siddeley Jaguar

The Armstrong Siddeley Jaguar was an aircraft engine developed by Armstrong Siddeley. The Jaguar was a petrol-fuelled air-cooled 14-cylinder two-row radial engine design. The Jaguar III was first used in 1923, followed in 1925 by the Jaguar IV and in 1927 by the Jaguar VI. In 1925 the Jaguar became the first production aero engine incorporating a geared supercharger.[1]

Armstrong Siddeley Jaguar IV
Type Radial engine
National origin United Kingdom
Manufacturer Armstrong Siddeley
First run 21 June 1922

Design and development

The Jaguar was developed from the Royal Aircraft Factory RAF.8 design proposal of 1917, and was engineered to use a gear-driven supercharger. First run on 21 June 1922 initial performance was not as expected; as a result the stroke was increased to 5.5 in (139.7 mm) on all variants after the Jaguar I. Throughout its career the Jaguar suffered from vibration due to a lack of a crankshaft centre bearing.[2]

The most powerful version of the engine, the Jaguar VIC, produced a maximum of 490 hp (365 kW) on takeoff at 1,950 rpm and weighed 910 lb (413 kg).[3] The later Lynx was designed using one row of Jaguar cylinders.[4]


Jaguar I
1922, 300 hp.
Jaguar II
1923, 385 hp, increased stroke, capacity 1,512 cu in (24.8 L).
Jaguar III
1923, 385 hp.
Jaguar IIIA
1923, 380 hp.
Jaguar IV
1925, 385 hp, twin carburettors
Jaguar IVA
420 hp, Geared propeller drive.
Jaguar IVC
1928, 400 hp, revised connecting rod design, enclosed valve gear.
Jaguar IV(S)
1925, 365 hp, fully supercharged.[nb 1]
Jaguar V
Jaguar VI
Jaguar VI(S)
1928, supercharged version of Jaguar VI.
Jaguar VIC
1927, 470 hp, geared propeller drive version of Jaguar VI.
Jaguar VID
Jaguar VIIA
1929, 400 hp, fully supercharged.
Jaguar VIII
1928, 405 hp, fully supercharged, geared propeller drive


Engines on display

A preserved Armstrong Siddeley Jaguar is on public display at the Science Museum (London).

Specifications (Jaguar I)

Data from Lumsden[6]

General characteristics

  • Type: 14-cylinder 2-row radial engine
  • Bore: 5 in (127 mm)
  • Stroke: 5 in (127 mm)
  • Displacement: 1,375 cu in (22.5 L)
  • Length: 41 in (1,041 mm)
  • Diameter: 43 in (1,092 mm)
  • Dry weight: 710 lb (322 kg)


  • Supercharger: Gear driven
  • Fuel system: Carburettor
  • Cooling system: Air-cooled


See also

Related development

Comparable engines

Related lists



  1. "World Encyclopedia of Aero Engines – 5th edition" by Bill Gunston, Sutton Publishing, 2006. p.13
  2. Lumsden 2003, p. 63.
  3. Lumsden 2003, Part 4 - Engine Performance Figures.
  4. Gunston 1989, p. 18.
  5. "Development of the Aircraft Supercharger". Flightglobal Archive.
  6. Lumsden 2003, pp. 63–66.


  1. MS and FS refer to the supercharger blower speeds: Moderate/Fully Supercharged. Moderate Supercharging referred to low- to medium-altitudes operation, Full Supercharging to medium- to high-altitude operation[5]


  • Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.
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