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.
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.
Blackburn Iris
Junkers Ju 52
Hawker Dantorp
Hawker Horsley
Data from
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
Power output: 700 hp (522 kW) at 1,650 rpm at sea level
Compression ratio: 5.00:1
Fuel consumption: 45 gal/hr (169 l/hr) at cruise speed
Power-to-weight ratio: 0.47 hp/lb
