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RAF 4
Preserved RAF 4a engine at the Science Museum (London)

The RAF 4 was a British air-cooled, V-12 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.[1]

Turbocharger[]

In April 1918 a turbocharged experimental version of the RAF 4d was developed using a Rateau turbocharger, the engine being flown in the R.E.8 B738.[2]

Variants[]

RAF 4
1914 - Prototype engine, 140 horsepower (104 kW).
RAF 4a
1917 - Main production variant, 160 horsepower (119 kW). 3,608 built.
RAF 4d
1916 - 180 horsepower (134 kW), experimental supercharger installation. 16 built.
RAF 4e
1917 - 240 horsepower (180 kW), strengthened cylinders and enlarged valves.
RAF 5
1915 - 150 horsepower (112 kW), pusher version with fan-cooling.
RAF 5b
170 horsepower (127 kW), increased bore version of RAF 5.

Applications[]

RAF 4[]

Royal Aircraft Factory RE8 1

The Royal Aircraft Factory R.E.8

RAF 5[]

Engines on display[]

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

Specifications (RAF 4a)[]

Data from Lumsden[3]

General characteristics

  • Type: 12-cylinder, upright, 60-degree Vee engine
  • Bore: 3.94 in (100 mm)
  • Stroke: 5.51 in (140 mm)
  • Displacement: 806.15 cu in (13.2 L)
  • Dry weight: 680 lb (308 kg)

Components

  • Valvetrain: EOI (side-valve inlet, exhaust overhead)
  • Fuel system: Twin Claudel-Hobson Mk.1A carburettors
  • Cooling system: Air-cooled
  • Reduction gear: 0.5:1, Left-hand tractor

Performance

  • Power output: 163 hp (122 kW) at 1,800 rpm (takeoff power)
  • Specific power: 0.2 hp/cu in (9.2 kW/L)
  • Compression ratio: 4.3:1
  • Power-to-weight ratio: 0.24 hp/lb (0.4 kW/kg)

See also[]

References[]

Notes[]

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.
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