The ADC Cirrus is a series of British aero engines manufactured using surplus Renault parts by the

Aircraft Disposal Company The Aircraft Disposal Company (ADC) or Airdisco, was a British firm established in March 1920 to take advantage of the large number of World War I-surplus military aircraft on the market.Gunston 2005, p.7. The company changed name in 1925 to ADC ...

(ADC) in the 1920s. The engines were air-cooled, four-cylinder inline types. They were widely used for private and light aircraft.

Design and development

The Cirrus engine originated in Geoffrey de Havilland's 1924 search for a powerplant suitable for the light two-seat sports biplane which would become the

de Havilland Moth The de Havilland Moths were a series of light aircraft, sports planes, and military trainers designed by Geoffrey de Havilland. In the late 1920s and 1930s, they were the most common civilian aircraft flying in Britain, and during that time ever ...

. No engine existed at the time with a suitable level of power combined with a low weight. The

, also known as Airdisco and ADC, were producing the low-cost

Airdisco The Aircraft Disposal Company (ADC) or Airdisco, was a British firm established in March 1920 to take advantage of the large number of World War I-surplus military aircraft on the market.Gunston 2005, p.7. The company changed name in 1925 to ADC ...

V8 which had been developed by

Frank Halford Major Frank Bernard Halford CBE FRAeS (7 March 1894 – 16 April 1955) was an English aircraft engine designer. He is best known for the series of de Havilland Gipsy engines, widely used by light aircraft in the 1920s and 30s. Career Educat ...

from their large stocks of war surplus Renault V8 aero engines. De Havilland realised that half of this engine would make an air-cooled four-cylinder inline engine of just the right size at low cost. He persuaded Halford to undertake its design and development. The cylinders, pistons, con-rods and gearing were taken from the Renault, with the valve gear based on the Airdisco, and a new five-bearing crankshaft and cast crankcase were designed. It became the first Cirrus engine, and the first air-cooled four-cylinder inline aero engine to go into quantity production. The original Cirrus engines were all designed by Halford and built by ADC. The Cirrus I passed its 50-hour type rating in 1925. De Havilland launched his product as the

Cirrus Moth Cirrus may refer to: Science *Cirrus (biology), any of various thin, thread-like structures on the body of an animal * Cirrus (botany), a tendril *Infrared cirrus, in astronomy, filamentary structures seen in infrared light *Cirrus cloud, a typ ...

and it proved a winning combination. The engine was soon adopted for other aircraft. Later versions named the Cirrus II, and Cirrus III were produced, each with slightly greater displacement and power (Cirrus II - 85 hp, Cirrus III - 90 hp).Gunston 1989 ADC ceased manufacture when it ran out of surplus Renault engines around 1928.

Subsequent manufacture

When ADC ran out of parts, manufacture of the Cirrus III was taken up by Cirrus Aero Engines, also based at Croydon. The Cirrus III was also adapted and improved by American Cirrus Engines, who manufactured it under license.

Variants

;Cirrus I :(1925) ;Cirrus II :(1926) ;Cirrus III :(1929)

Applications

''List from Lumsden'' except where noted. The list includes trial installations where a different engine was principally adopted.

Cirrus

Cirrus I

Avro Avian The Avro Avian was a series of British light aircraft designed and built by Avro in the 1920s and 1930s. While the various versions of the Avian were sound aircraft, they were comprehensively outsold by the de Havilland Moth and its descendants ...

Avro Baby The Avro 534 Baby (originally named the "Popular") was a British single-seat light sporting biplane built shortly after the First World War. Development The Avro Baby was a single-bay biplane of conventional configuration with a wire-braced wo ...

* de Havilland DH.60 Moth * Short Mussel * Westland Widgeon

Cirrus II

* de Havilland DH.60 Moth *

de Havilland DH.71 Tiger Moth The de Havilland DH.71 Tiger Moth was a British single-seat monoplane, designed to research high-speed flight and to test replacement engines for the Cirrus. Only two were built. Design and development It was a low-wing monoplane based on th ...

Piaggio P.9 __NOTOC__ The Piaggio P.9 was an Italian single-engined strut-braced In aeronautics, bracing comprises additional structural members which stiffen the functional airframe to give it rigidity and strength under load. Bracing may be applied both ...

* Short Mussel * Westland Widgeon * Bloudek XV Lojze

Cirrus III

Blackburn Bluebird The Blackburn L.1 Bluebird was a British single-engine biplane light trainer/tourer with side-by-side seating, built in small numbers by Blackburn Aircraft in the 1920s. Design and development The Bluebird L.1 was initially designed as a co ...

* Cierva C.17 * de Havilland DH.60 Moth *

Dudley Watt D.W.2 __NOTOC__ The Dudley Watt D.W.2 was a 1930s British two-seat light biplane designed by K.N. Pearson for Dudley Watt. The D.W.2 was built at Brooklands and was a wood and fabric biplane with a tailskid landing gear. It had two open cockpits and ...

* Emsco B-4 Cirrus * Koolhoven FK.41Jackson p.190 1973 *

Klemm L.26 The Klemm Leichtflugzeugbau GmbH ("Klemm Light Aircraft Company") was a German aircraft manufacturer noteworthy for sports and touring planes of the 1930s. The company was founded in Böblingen in 1926 by Dr. Hanns Klemm, who had previously work ...

* Klemm L.27 * Short Mussel * Simmonds Spartan * Spartan Arrow * Westland Wessex * Westland Widgeon

Engines on display

*A preserved ADC Cirrus II is on display at the Science Museum (London).

Specifications (Cirrus I)

References

Notes

Bibliography

* The Aviation Ancestry Database of British Aviation Advertisements 1909–1990
Cirrus advertisements
(retrieved 23 April 2020). * Gunston, Bill. ''World Encyclopaedia of Aero Engines''. Cambridge, England. Patrick Stephens Limited, 1989. * * * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. . * Taylor, Douglas R. ''Boxkite to Jet: The Remarkable Career of Frank B. Halford''. Rolls-Royce Heritage Trust. 1999. . * {{Cirrus aeroengines 1920s aircraft piston engines Cirrus