The Armstrong Siddeley Cheetah was a seven-cylinder air-cooled, single-row radial aero-engine of 13.66 litres (833.77 cc). The Cheetah was a development of the Armstrong Siddeley Lynx engine using the increased bore cylinders from the Armstrong Siddeley Panther engine whilst retaining the stroke of the Lynx; it was initially known as the Lynx Major.

 

At first, only direct drive engines were produced, but later versions had propeller reduction gears of various ratios. All the early versions were normally aspirated, with later models being supercharged, both geared and directly driven by the crankshaft.

 

First introduced in 1935, it continued production through 1948, when over 37,200 were produced. It was an extremely reliable engine and as such, it was the first engine of its type to be certified for 1,200 hours of operational time between overhauls.