The Armstrong Siddeley Cheetah is a seven-cylinder British air-cooled aircraft

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ca ...

of 834 cu in (13.65 L) capacity introduced in 1935 and produced until 1948. Early variants of the Cheetah were initially known as the Lynx Major.Lumsden 2003, p.74. The Cheetah was used to power many British

trainer aircraft A trainer is a class of aircraft designed specifically to facilitate flight training of pilots and aircrews. The use of a dedicated trainer aircraft with additional safety features—such as tandem flight controls, forgiving flight characteristi ...

during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

including the

Avro Anson The Avro Anson is a British twin-engined, multi-role aircraft built by the aircraft manufacturer Avro. Large numbers of the type served in a variety of roles for the Royal Air Force (RAF), Fleet Air Arm (FAA), Royal Canadian Air Force (RCAF) a ...

and

Airspeed Oxford The Airspeed AS.10 Oxford is a twin-engine monoplane aircraft developed and manufactured by Airspeed. It saw widespread use for training British Commonwealth aircrews in navigation, radio-operating, bombing and gunnery roles throughout the Seco ...

Design and development

The Cheetah was developed from the earlier Lynx using the increased

bore Bore or Bores often refer to: *Boredom * Drill Relating to holes * Boring (manufacturing), a machining process that enlarges a hole ** Bore (engine), the diameter of a cylinder in a piston engine or a steam locomotive ** Bore (wind instruments), ...

cylinders from the

Armstrong Siddeley Panther The Armstrong Siddeley Panther was a 27-litre 14-cylinder twin-row air-cooled radial aero engine developed by Armstrong Siddeley. It was originally named the Jaguar Major.Lumsden 2003, p.72. Applications * Armstrong Whitworth Atlas Mk II * A ...

but the engine retained the

stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...

of the Lynx. Initially only direct-drive variants were produced with later engines being made available with propeller reduction gear of various

ratios In mathematics, a ratio shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...

Supercharger In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement. The current categorisation is that a supercharger is a form of forced induct ...

s were also available for later variants, both geared and directly driven by the

crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting ...

. The basic design of the Cheetah remained unchanged from its introduction in 1935 to the last examples built in 1948. It was the first engine of its type to be certified for 1,200 hours of operational

time between overhaul Time between overhauls (abbreviated as TBO or TBOH) is the manufacturer's recommended number of running hours or calendar time before an aircraft engine or other component requires overhaul. On rotorcraft, many components have recommended or man ...

s (TBO), with over 37,200 examples built.

Variants

''List from:'' Lumsden''Note:'' ;Lynx V (Lynx Major) :1930, 230 hp (171 kW). ;Cheetah V :1935, 270 hp (201 kW) at 2,100 rpm. ;Cheetah VA :1935, 285 hp (212 kW) at 2,425 rpm. ;Cheetah VI :1935, 307 hp (229 kW) at 2,425 rpm. ;Cheetah VIA :1936, as Mk VI but with Mk IX cylinders. Armstrong Siddeley Cheetah Mk

;Cheetah IX :1937, 345 hp (257 kW) at 2,425 rpm. ;Cheetah X :1938, 375 hp (280 kW) at 2,300 rpm. ;Cheetah XI :345 hp (257 kW) at 2,425 rpm, geared version of Cheetah X. ;Cheetah XII :Similar to Mk X, adapted for target drone aircraft. ;Cheetah XV :420 hp (313 kW) at 2,425 rpm. ;Cheetah XVII :1948, 385 hp (287 kW) at 2,425 rpm. ;Cheetah XVIII :385 hp (287 kW) at 2,425 rpm, carburettor modified for aerobatics. ;Cheetah XIX :355 hp (265 kW) at 2,425 rpm ;Cheetah 25 :345 hp (257 kW) at 2,425 rpm, Cheetah XV uprated to 475 hp (355 kW) at 2,700 rpm, modified constant-speed unit. ;Cheetah 26 :385 hp (287 kW). ;Cheetah 27 :1948, 385 hp (287 kW).

Applications

Survivors

As of October 2008 at least four Cheetah engines remained airworthy. Two Cheetah 17s power the Anson T21 operated by the

Classic Air Force Classic Air Force was a charitably-based aircraft preservation organisation sited in Coventry, West Midlands (county), West Midlands. Specialising in classic aircraft from the period between the end of the World War II, Second World War and the ...

and another pair of Cheetah 17s are fitted to Avro Nineteen, ''G-AHKX'' registered to

BAE Systems BAE Systems plc (BAE) is a British multinational arms, security, and aerospace company based in London, England. It is the largest defence contractor in Europe, and ranked the seventh-largest in the world based on applicable 2021 revenues. ...

but normally based at the

Shuttleworth Collection The Shuttleworth Collection is a working aeronautical and automotive collection located at the Old Warden Aerodrome, Old Warden in Bedfordshire, England. It is the oldest in the world and one of the most prestigious, due to the variety of old a ...

Engines on display

Preserved Armstrong Siddeley Cheetah engines are on public display at the following museums: * Arkansas Air & Military Museum *

Aviation Heritage Museum (Western Australia) The Aviation Heritage Museum is a museum created and maintained by the RAAF Association of Western Australia. It houses many military and civilian aircraft, aircraft replicas and aircraft engines, of types that have served in the Royal Australia ...

Brooklands Museum Brooklands Museum is a motoring and aviation museum occupying part of the former Brooklands motor-racing track in Weybridge, Surrey, England. Formally opened in 1991, the museum is operated by the independent Brooklands Museum Trust Ltd, a pri ...

Fleet Air Arm Museum The Fleet Air Arm Museum is devoted to the history of British naval aviation. It has an extensive collection of military and civilian aircraft, aero engines, models of aircraft and Royal Navy ships (especially aircraft carriers), and paintin ...

Historical Aircraft Restoration Society The Historical Aircraft Restoration Society, often referred to by its acronym, HARS, is an Australian based aircraft restoration group. The group has two museums, at Shellharbour Airport in New South Wales, Australia, and Parkes, New South Wales ...

Albion Park, New South Wales, Australia *

Malta Aviation Museum Malta Aviation Museum is an aircraft museum situated on the site of the former Royal Air Force airfield in the village of Ta'Qali, on the island of Malta. The museum, based in three hangars, covers the history of aviation on the island with exhi ...

Port Elizabeth Gqeberha (), formerly Port Elizabeth and colloquially often referred to as P.E., is a major seaport and the most populous city in the Eastern Cape province of South Africa. It is the seat of the Nelson Mandela Bay Metropolitan Municipality, Sou ...

branch of the

South African Air Force Museum The South African Air Force Museum houses exhibits and restores material related to the history of the South African Air Force. The museum is divided into three locations, AFB Swartkop outside Pretoria, AFB Ysterplaat in Cape Town and at the Por ...

Royal Air Force Museum Cosford The Royal Air Force Museum Cosford, located in Cosford in Shropshire, is a free (currently, 2022) museum dedicated to the history of aviation and the Royal Air Force in particular. The museum is part of the Royal Air Force Museum, a non-departme ...

South Australian Aviation Museum The South Australian Aviation Museum, located in Port Adelaide, South Australia, is an aviation museum which displays aircraft, aircraft engines, and rockets of relevance to South Australia, and the history of aviation and the aerospace industr ...

, Adelaide. Two Mk9 Operational Displays

Specifications (Cheetah IX)

References

Notes

Bibliography

* Gunston, Bill. ''World Encyclopedia of Aero Engines''. Cambridge, England. Patrick Stephens Limited, 1989. * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. .

External links

''Flight'' magazine, 19 May 1939 - Introduction of the Cheetah X - Flightglobal.com
{{ASaeroengines 1930s aircraft piston engines Aircraft air-cooled radial piston engines

Cheetah The cheetah (''Acinonyx jubatus'') is a large cat native to Africa and central Iran. It is the fastest land animal, estimated to be capable of running at with the fastest reliably recorded speeds being , and as such has evolved specialized ...