RAF 4

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

 * RAF 4
 * 1914 - Prototype engine, 140 horsepower (104 kW).


 * RAF 4a
 * 1917 - Main production variant, 150 horsepower (112 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.

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).