|ADC Cirrus II at the Science Museum, London|
|Type||Air-cooled 4-cylinder inline piston engine|
|National origin||United Kingdom|
|Manufacturer||Aircraft Disposal Company, Cirrus Aero-Engines Limited|
|Major applications||de Havilland DH.60 Moth
The ADC Cirrus and Cirrus-Hermes are British aero engines of the mid-1920s. Sometimes known as the Blackburn Cirrus, examples remain airworthy today.
Design and development
ADC Cirrus engines were originally built by ADC Aircraft until Cirrus Aero Engines Limited was formed in 1927. The company became Cirrus-Hermes in 1931 when it was bought by the Cirrus-Hermes Engineering Company and later became the Cirrus Engine Section of Blackburn & General Aircraft Limited in 1934, and operated as a separate division until production ended in the post-World War II era.
Cirrus's first product was the 90 hp (67 kW) Cirrus I, which passed its 50-hour type rating in 1925. It was the first air-cooled inline engine, a design by Frank Halford that proved extremely popular for light aircraft. The basic layout (using one cylinder bank of an ADC Airdisco V-8 engine) was quickly copied by a number of other manufacturers. 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).
The next model line, Cirrus-Hermes I, II, and IV were produced ranging in power from 105 hp to 140 hp depending on type. The later Cirrus engines were designed to run inverted.
- Cirrus I
- Cirrus II
- Cirrus III
- Cirrus IIIA
- Cirrus-Hermes I
- Cirrus-Hermes II
- Cirrus-Hermes IIB (inverted)
- Cirrus-Hermes IV
- Cirrus-Hermes IVA
- (1929) Inverted engine
Engines on display
- A preserved ADC Cirrus II is on display at the Science Museum (London).
- A Cirrus Hermes is on display at the EAA AirVenture Museum in Oshkosh, Wisconsin.
Specifications (Cirrus I)
Data from Lumsden.
- Type: Inline, air-cooled, upright 4-cylinder piston engine
- Bore: 4.13 in (105 mm)
- Stroke: 5.12 in (130 mm)
- Displacement: 274.36 cu in (4.5 L)
- Length: 45.8 in (116.3 cm)
- Width: 18.26 in (46.4 cm)
- Height: 34.3 in (87.1 cm)
- Dry weight: lb ( kg)
- Valvetrain: 1 inlet and 1 exhaust valve per cylinder
- Fuel system: 1 Claudel carburettor
- Fuel type: 70 octane
- Cooling system: air
- Power output: 60 hp ( kW)
- Compression ratio: 4.7:1
- Related development
- Comparable engines
- Related lists
- This name applies only to the revised range of Cirrus engines produced after 1934 by Blackburn, e.g. the Blackburn Cirrus Major.
- Lumsden 2003, p. 130.
- Gunston 1989, p. 40.
- Lumsden 2003, p.132.
- Lumsden 2003, pp. 130-132.
- Cirrus engines may not be the main powerplant for these aircraft types (test installations are included).
- Wesselink 1982 p.80
- Wesselink 1982 p.81
- Wesselink, Theo; Postma, Thijs (1982). De Nederlandse vliegtuigen. Haarlem: Romem. ISBN 90 228 3792 0.
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