The Blackburn Cirrus Minor is a British four-cylinder, inverted, in-line air-cooled aero-engine that was designed and built by the Cirrus Engine Section of

Blackburn Aircraft Limited Blackburn () is an industrial town and the administrative centre of the Blackburn with Darwen borough in Lancashire, England. The town is north of the West Pennine Moors on the southern edge of the Ribble Valley, east of Preston and north- ...

in the late 1930s.

Design and development

The Cirrus Minor started life as a clean-sheet replacement for the original Cirrus and Hermes series of light aircraft engines. Design was led by Technical Director C. S. Napier, son of

Montague Napier Montague Stanley Napier (14 April 1870 – 22 January 1931) was an English automobile and aircraft engine manufacturer. His grandfather, David Napier (1785–1873), had moved to London from Scotland and by 1836 had established an engineering comp ...

, and was already under way when in 1934 Cirrus-Hermes Engineering was taken over by the

Blackburn Aeroplane & Motor Company Blackburn () is an industrial town and the administrative centre of the Blackburn with Darwen borough in Lancashire, England. The town is north of the West Pennine Moors on the southern edge of the Ribble Valley, east of Preston and north- ...

and moved to Brough in Yorkshire."A New Small Engine", ''Flight'', 28 February 1935, pp.218-9."The 'Cirrus Major'", ''Flight'', 13 June 1935. Supplement. Napier remained Technical Director and, while he completed the development and initial sales of the Cirrus Minor and its larger stablemate the

Cirrus Major The Blackburn Cirrus Major is a British, inline-four aircraft engine that was developed in the late 1930s. Design and development The Blackburn Cirrus Major started life as a continued evolution of the original Cirrus and Hermes series of air ...

, Blackburn kept Cirrus Hermes Engineering as a separate company (though without the hyphen in its name). Although completely new designs, they were of generally similar layout to the previous inverted engines, being air-cooled inverted four-cylinder inline designs. Like the others the Minor had a robust steel five-bearing crankshaft, but unlike them the long studs bolting the cylinder heads to the crank housing were replaced by short studs and flanges at each end of the cylinder barrels. Light alloy was used for the cylinder heads and con rods, while the valve gear was adopted with little change from the Hermes IV. The Claudel-Hobson down-draught carburetter featured independent altitude control, and the dual-redundant magnetos were of B.T.H. S.G.4/2 type. The Cirrus Minor was introduced in 1935. Two years later, Cirrus Hermes Engineering lost its identity as a separate company and was adopted as an operating division of its parent company, which by then had become

Blackburn Aircraft Blackburn () is an industrial town and the administrative centre of the Blackburn with Darwen borough in Lancashire, England. The town is north of the West Pennine Moors on the southern edge of the Ribble Valley, east of Preston and north- ...

. The Minor was known for excellent reliability, and had a major "win" when it was selected to power the

RAF The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and ...

Taylorcraft Auster The Taylorcraft Auster was a British military liaison and observation aircraft produced by the Taylorcraft Aeroplanes (England) Limited company during the Second World War. Design and development The Auster was a twice-removed development of ...

observation aircraft. The RAF's version had several modifications, known as the Series I. Although externally identical, the Series II engine was redesigned to operate on 77 octane fuel, as opposed to the original's 70, increasing power to 100 hp (75 kW).

Applications

Engines on display

*A preserved Blackburn Cirrus Minor II is on public display at the

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 ...

.RAF Museum Cosford - Blackburn Cirrus II
www.rafmuseum.org.uk Retrieved:1 January 2014

Specifications (Cirrus Minor I)

References

Notes

Bibliography

* * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. .

External links

{{Cirrus aeroengines Air-cooled aircraft piston engines Blackburn aircraft engines 1930s aircraft piston engines Inverted aircraft piston engines