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Royal Aircraft Factory RAF 3 / RAF 7


The RAF 3 was a British liquid-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 Armstrong Whitworth and Napier & Son. First run in September 1914, a total of 289 were built.

The RAF 7 was a high compression version of the same engine.


1914 - Prototype engine, 200 horsepower (150 kW).

RAF 3a
1914 - Main production variant, increased bore, 260 horsepower (194 kW). 29 built by Armstrong Whitworth, 260 built by Napier & Son.

300 horsepower (224 kW) high compression version with high-lift camshafts.


Airco DH.4
Royal Aircraft Factory R.E.7


RAF 3a
Type: 12-cylinder, upright, 60-degree Vee engine
Bore: 4.5 in (114.3 mm)
Stroke: 5.5 in (140 mm)
Displacement: 1,049.4 cu in (17.24 L)
Dry weight: 780 lb (354 kg)
Valvetrain: Overhead valve, both valves operated by a single pushrod
Cooling system: Liquid-cooled
Reduction gear: 0.5:1, left-hand tractor
Power output: 260 hp (194 kW) at 1,750 rpm (takeoff power)
Specific power: 0.25 hp/cu in (11.25 kW/L)
Compression ratio: 5.3:1
Power-to-weight ratio: 0.33 hp/lb (0.54 kW/kg)






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