RAF 3
RAF 3a on display at thePolish Aviation Museum
Type	Pistoninlineaero 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

TheRAF 3 is a British liquid-cooled,V-12 engine developed foraircraft use duringWorld War I. Based on the eight–cylinderRAF 1 it was designed by theRoyal Aircraft Factory but produced by the two British companies ofArmstrong Whitworth andNapier & Son. TheRAF 7 was ahigh compression version of the same engine.^[1]

RAF 3

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

RAF 3a

1914 - Main production variant, increasedbore, 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-liftcamshafts.

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

Data fromLumsden^[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

Wikimedia Commons has media related toRAF 3.

• 1910s aircraft piston engines
• V12 aircraft engines

• Articles with short description
• Short description matches Wikidata
• Commons category link from Wikidata