ADC Cirrus

The ADC Cirrus and Cirrus-Hermes are British aero engines of the mid-1920s. Sometimes known as the Blackburn Cirrus,[1] examples remain airworthy today.

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
First run 1925
Major applications de Havilland DH.60 Moth
Avro Avian

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.[2]

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)[3] 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.[4]

The Cirrus III was also produced/converted by American Cirrus Engines Inc., Belleville NJ (later A.C.E. Corp, Marysville MI.).


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
American Cirrus III
American Cirrus III Hi-drive


List from Lumsden.[5][6]


Cirrus I

Cirrus II

Cirrus III

Cirrus IIIA


Cirrus-Hermes I

Cirrus-Hermes II

Cirrus-Hermes IIB

Cirrus-Hermes IV

Cirrus-Hermes IVA

Engines on display

Specifications (Cirrus I)

Data from Lumsden.[2]

General characteristics

  • 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


See also

Related development

Comparable engines

Related lists



  1. This name applies only to the revised range of Cirrus engines produced after 1934 by Blackburn, e.g. the Blackburn Cirrus Major.
  2. Lumsden 2003, p. 130.
  3. Gunston 1989, p. 40.
  4. Lumsden 2003, p.132.
  5. Lumsden 2003, pp. 130-132.
  6. Cirrus engines may not be the main powerplant for these aircraft types (test installations are included).
  7. Jackson p.190 1973
  8. Jackson p.495 1973
  9. Les Ailes 469, p.3 1930
  10. Wesselink 1982 p.80
  11. Wesselink 1982 p.81


  • Gunston, Bill. World Encyclopaedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
  • Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.
  • Jackson, A.J. (1973). British Civil Aircraft 1919-72. 2. London: Putnam Publishing. ISBN 0 85177 813 5.
  • Frachet, AndrĂ© (12 June 1930). "Le monoplan Koolhoven F.K.42". Les Ailes (469): 3.
  • Wesselink, Theo; Postma, Thijs (1982). De Nederlandse vliegtuigen. Haarlem: Romem. ISBN 90 228 3792 0.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.