Blackburn Cirrus Minor

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 in the late 1930s.

Cirrus Minor
Blackburn Cirrus Minor 2A
Type Air-cooled 4-cylinder inline piston engine
National origin United Kingdom
Manufacturer Blackburn Aircraft
First run 1937

Design and development

The Cirrus Minor started life as a development of the original Cirrus series of engines which progressed through a number of variants Cirrus I, II, & III. Each with slightly different displacement and power. Later Cirrus was bought by Hermes Engine Company and they produced the Cirrus Hermes I, II, III and IV. Again each differing slightly in displacement and power.

In 1934 Cirrus was bought again by the Blackburn Aircraft company and later that year the Cirrus Minor was produced and in 1935 the Blackburn Cirrus Major was produced.

The Minor was known for excellent reliability, and had a major "win" when it was selected to power the RAF's Taylorcraft Auster 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).


Engines on display

Specifications (Cirrus Minor I)

Data from Lumsden [2]

General characteristics

  • Type: Inline air-cooled inverted 4-cylinder
  • Bore: 3.94 in (100 mm)
  • Stroke: 5.00 in (127 mm)
  • Displacement: 243 cu in (4 L)
  • Length: 39.9 in (1,013 mm)
  • Width: 17.9 in (455 mm)
  • Height: 25.6 in (650 mm)
  • Dry weight: 200 lb (91 kg)


  • Valvetrain: 1 inlet and 1 exhaust valve per cylinder
  • Fuel system: 1 Claudel carburettor
  • Fuel type: 70 octane
  • Cooling system: Air-cooled


See also

Related development

Comparable engines

Related lists



  1. RAF Museum Cosford - Blackburn Cirrus II Retrieved:1 January 2014
  2. Lumsden 2003, p. 90.


  • Gunston, Bill (1986). World Encyclopedia of Aero Engines. Wellingborough: Patrick Stephens. p. 40.
  • Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.
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