RAF 3

RAF 3
RAF 3a on display at the Polish Aviation Museum
Type	Piston inline aero engine
National origin	United Kingdom
Manufacturer	Royal Aircraft Factory
First run	September 1914
Major applications	Royal Aircraft Factory R.E.7
Number built	289
Developed from	RAF 1
Developed into	RAF 4

The RAF 3 is 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. The RAF 7 was a high compression version of the same engine.^[1]

RAF 3

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.

RAF 7

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

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

Data from Lumsden^[2]

• 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)

Related development

• RAF 1
• RAF 4

Comparable engines

• Rolls-Royce Eagle
• Rolls-Royce Falcon

Related lists

• List of aircraft engines

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