ADC Cirrus

Cirrus
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

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]

Variants

A comparison of Cirrus Hermes I (left) and Cirrus III (right)

Cirrus I

(1925)

Cirrus II

(1926)

Cirrus III

(1929)

Cirrus IIIA

(1933)

Cirrus-Hermes I

(1929)

Cirrus-Hermes II

(1930)

Cirrus-Hermes IIB (inverted)

(1931)

Cirrus-Hermes IV

(1930)

Cirrus-Hermes IVA

(1929) Inverted engine

Applications

List from Lumsden.^[5][6]

Cirrus

Cirrus III fitted to a de Havilland DH.60 Moth

Cirrus I Avro Avian Avro Baby de Havilland DH.60 Moth Short Mussel Westland Widgeon

Cirrus II Avro Avian de Havilland DH.60 Moth de Havilland DH.71 Tiger Moth Piaggio P.9 Short Mussel Westland Widgeon

Cirrus III Avro Avian Blackburn Bluebird Cierva C.17 de Havilland DH.60 Moth de Havilland DH.71 Tiger Moth Dudley Watt D.W.2 Klemm L.26 Klemm L.27 Short Mussel Simmonds Spartan Spartan Arrow Westland Wessex Westland Widgeon

Cirrus IIIA Miles M.2 Hawk

Cirrus-Hermes

Cirrus-Hermes I Avro Avian Blackburn Bluebird de Havilland DH.60 Moth Desoutter I Hawker Tomtit Hendy 302 Parnall Elf Saro Cutty Sark Simmonds Spartan Southern Martlet Westland Wessex Westland Widgeon

Cirrus-Hermes II Avro Avian Blackburn Bluebird Desoutter I Spartan Arrow Spartan Three-Seater Westland Widgeon

Cirrus-Hermes IIB Arrow Active BFW M.23 Klemm L.27 Spartan Three-Seater

Cirrus-Hermes IV Avro Cadet Hendy 302 Miles M.2 Hawk Percival Gull Spartan Cruiser Spartan Three-Seater

Cirrus-Hermes IVA Avro Club Cadet Blackburn B-2 Blackburn Segrave

Engines on display

A Cirruss Hermes

• 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.^[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)

Components

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

Performance

• Power output: 60 hp ( kW)
• Compression ratio: 4.7:1

See also

Related development

• Blackburn Cirrus Minor
• Blackburn Cirrus Major
  

Comparable engines

• de Havilland Gipsy
  

Related lists

• List of aircraft engines
  

References

Notes

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).

Bibliography

• 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.

External links

• Period engine advertisement - Flight, June 1929