Armstrong Siddeley Leopard

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Type Radial engine
National origin United Kingdom
Manufacturer Armstrong Siddeley
First run 1927

The Armstrong Siddeley Leopard was a British 14-cylinder twin-row air-cooled radial aero engine developed in 1927 by Armstrong Siddeley. It was the most powerful radial engine in the world when introduced.[1]


Leopard I
700 hp, medium supercharged. Direct drive propeller.
Leopard II
700 hp, geared epicyclic drive.
Leopard III
800 hp, two-valve cylinder head, direct drive.
Leopard IIIA
800 hp, geared epicyclic drive.


Specifications (Leopard I)[edit]

Data from [3]

General characteristics

  • Type: 14-cylinder twin-row air-cooled radial engine
  • Bore: 6.0 in (152.4 mm)
  • Stroke: 7.5 in (190.5 mm)
  • Displacement: 2,970 cu in (48.6 L)
  • Length: 60.85 in (1546 mm)
  • Diameter: 58 in (1473 mm)
  • Dry weight: 1,466 lb (665 kg)


  • Valvetrain: Overhead valve, four valves per cylinder
  • Fuel type: Petrol
  • Cooling system: Air-cooled


See also[edit]

Comparable engines
Related lists



  1. ^ Smith 1981, p.112.
  2. ^ Single engine version only
  3. ^ Lumsden 2003, p.69.


  • Smith, Herschel. Aircraft Piston Engines. New York, New York: McGraw-Hill, 1981. ISBN 0-07-058472-9.
  • Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.