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

RAF 3
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

Variants

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.

Applications

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

Specifications (RAF 3a)

Data from Lumsden[2]

General characteristics

• 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)

Components

• Valvetrain: Overhead valve, both valves operated by a single pushrod
• Cooling system: Liquid-cooled
• Reduction gear: 0.5:1, left-hand tractor

Performance

• 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)

See also

Related development

• RAF 1
• RAF 4

Comparable engines

• Rolls-Royce Eagle
• Rolls-Royce Falcon

Related lists

• List of aircraft engines

References

Notes

Bibliography

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