The RAF 4 is a British air-cooled, V12 engine developed for aircraft use during World War I. Based on the eight–cylinder RAF 1 it was designed by the Royal Aircraft Factory but produced by the two British companies of Daimler and Siddeley-Deasy. The RAF 5 was a pusher version of the same engine.

Turbocharger

A turbocharged experimental version of the RAF 4, the RAF 4d, was developed using a Rateau exhaust-driven turbocharger. The engine was test-flown in a R.E.8, but the turbocharging experiments were abandoned after the turbine failed on 4 May 1918.

Variants

1. RAF 4

2. 1914 - Prototype engine, 140 horsepower (104 kW).

3. RAF 4a

4. 1917 - Main production variant, 150 horsepower (112 kW). 3,608 built.

5. RAF 4d

6. 1916 - 180 horsepower (134 kW), experimental supercharger installation. 16 built.

7. RAF 4e

8. 1917 - 240 horsepower (180 kW), strengthened cylinders and enlarged valves.

9. RAF 5

10. 1915 - 150 horsepower (112 kW), pusher version with fan-cooling.

11. RAF 5b

12. 170 horsepower (127 kW), increased bore version of RAF 5.

Applications

RAF 4

• Armstrong Whitworth F.K.8

• Bristol F.2 Fighter

• Royal Aircraft Factory B.E.12

• Royal Aircraft Factory R.E.7

• Royal Aircraft Factory R.E.8

• Siddeley-Deasy R.T.1

• Vickers F.B.14

RAF 5

• Royal Aircraft Factory F.E.2

• Royal Aircraft Factory F.E.4

Engines on display

A preserved RAF 4a engine is on public display at the Science Museum (London).

Specifications (RAF 4a)

See also

References

Notes

Bibliography

• Gunston, Bill. World Encyclopaedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989.

• Hare, Paul R. The Royal Aircraft Factory. London: Putnam, 1990.

• Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. .