Blackburn Cirrus Minor
|Blackburn Cirrus Minor 2A|
|Type||Air-cooled 4-cylinder inline piston engine|
|National origin||United Kingdom|
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.
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.
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
- A preserved Blackburn Cirrus Minor II is on public display at the Royal Air Force Museum Cosford.
Specifications (Cirrus Minor I)
Data from Lumsden 
- 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
- Power output: 90 hp (67 kW) at 2,600 rpm
- Compression ratio: 5.8:1
- Power-to-weight ratio: 0.45 hp/lb (0.73 kW/kg)
- Related development
- Comparable engines
- Related lists
- RAF Museum Cosford - Blackburn Cirrus II www.rafmuseum.org.uk Retrieved:1 January 2014
- Lumsden 2003, p. 90.
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