ADC Cirrus

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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

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.

Design and development[edit]

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.).


A comparison of Cirrus Hermes I (left) and Cirrus III (right)
Cirrus-Hermes I engine in Roe IV replica, Shuttleworth collection
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[edit]

Cirrus II[edit]

Cirrus III[edit]

Cirrus IIIA[edit]


Cirrus-Hermes I[edit]

Cirrus-Hermes II[edit]

Cirrus-Hermes IIB[edit]

Cirrus-Hermes IV[edit]

Cirrus-Hermes IVA[edit]

Engines on display[edit]

A Cirrus Hermes

Specifications (Cirrus I)[edit]

Cirrus III fitted to a de Havilland DH.60 Moth

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[edit]

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. ^ a b 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, André (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. 

External links[edit]