Rolls-Royce Merlin

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Merlin
Type	Liquid-cooled V-12 piston engine
National origin	United Kingdom
Manufacturer	Rolls-Royce
First run	1935
Major applications	Supermarine Spitfire Avro Lancaster Curtiss P-40 De Havilland Mosquito Handley-Page Halifax Hawker Hurricane
Number built	149,659
Variants	Packard V-1650

The Rolls-Royce Merlin was a liquid cooled 27 litre (1649 in³) 60° V12 piston aircraft engine which became famous in World War II. An English Icon ^[1], several versions of the Merlin were built by Rolls-Royce (in Derby, Crewe and Glasgow)^[2] by Ford of Britain (in Trafford Park, Manchester)^[3] and in the United States as the Packard V-1650.^[4] They are widely considered to be among the most successful aircraft engines produced during World War II.

The name 'Merlin' comes from a type of small falcon (Falco columbarius), in line with the convention Rolls-Royce used in naming its other piston aero-engines after birds of prey, and has no connection to King Arthur's legendary magician.

Contents 1 History 1.1 Engine capacity and mass flow 1.2 Upgrades 1.3 Carburettor developments 1.4 Packard V-1650 2 Alternative uses 3 Variants 4 Applications 5 Specifications (Merlin II) 6 Specifications (Merlin 66) 7 See also 8 References 8.1 Notes 8.2 Bibliography 9 External links

[edit] History

In the early 1930s, Rolls-Royce started planning for the future of its aero engine development programmes, and eventually settled on two basic designs. The 700 horsepower (500 kW) Rolls-Royce Peregrine was an updated, supercharged development of their existing V-12, 22 L Rolls-Royce Kestrel, which had been used with great success in a number of 1930s designs. Two Peregrines bolted together on a common crankshaft into an X-24 layout would create the 1,700 hp (1,300 kW) 44 L Rolls-Royce Vulture, for use in larger aircraft such as bombers. There was also the possibility that the famous 36 L 'R' engine (itself a development of the Rolls-Royce Buzzard, a scaled-up Kestrel) from the Supermarine racing planes could be developed into a 1,500 hp (1,100 kW) class engine of its own.

This left a large gap between 700 and 1,500 hp (500 and 1,100 kW), and to fill it work was started on a new 1,100 hp (820 kW) class design known as the PV-12 – PV for "private venture" as the company received no government money for work on the project. The PV-12 first flew in a Hawker Hart (serialled K3036) biplane on 21 February 1935, using the evaporative cooling system then in vogue, but this proved unreliable and so, when supplies of ethylene glycol from the US became available, the engine was changed to the conventional liquid cooling system. The Hart was subsequently delivered to Rolls-Royce and as a Merlin "Testbed" completed over 100 hour of flying with the Merlin 'C' and 'E' engines.^[5]

Initially the new engine was plagued with problems, such as failure of the gear trains and constant failure of the coolant jackets, and several different construction methods were used before the basic design of the Merlin was set. The prototype engines were:

• PV-12: The original design retained the evaporative cooling system. Passed Type Testing in June 1934, generating 740 hp (552 kW) at 12,000 ft (3,657 m) equivalent.
• Merlin B: Changed to ethylene glycol coolant. "Ramp" cylinder heads (inlet valves were at a 45-degree angle to the cylinder). Passed Type Testing February 1935, generating 950 hp (708 kW) at 11,000 ft (3,353 m) equivalent.
• Merlin C: Crankcase and cylinder blocks became three separate castings with bolt-on cylinder heads.
• Merlin E: Similar to C; minor design changes. Passed 50 hour civil test generating a constant 955 hp (712 kW) and a maximum rating of 1,045 hp (779 kW).
• Merlin F: Similar to C and E. This became the first production engine; 172 were built as the Merlin I. The Merlin continued with the 'ramp head' where the inlet valves were at a 45-degree angle to the cylinder. This was not a success and only 172 were made. The Fairey Battle was the first production aircraft to be powered by the Merlin I.
• Merlin G: Replaced "ramp" cylinder heads with parallel pattern heads (valves parallel to the cylinder) scaled up from the Kestrel engine. It was first widely delivered as the 1,030 hp (770 kW) Merlin II in 1938, and production was quickly stepped up.

In 1935, the Air Ministry issued a specification, F10/35, for new fighter aircraft with a minimum airspeed of 310 mph (499 km/h). Fortunately, two designs had been developed; the Supermarine Spitfire and the Hawker Hurricane, the latter designed in response to another specification, F36/34.^[6] Both were designed around the PV-12 instead of the Kestrel, and were the only modern British fighters to have been so developed. Production contracts for both aircraft were placed in 1936. The PV-12 was given top priority and became the Merlin.

Early Merlins were rather unreliable, but Rolls-Royce soon introduced a superb reliability-improvement programme. This consisted of taking random engines from the end of the assembly line and running them continuously at full power until they failed. They were then dismantled to find out which part had failed, and that part was redesigned to be stronger. After two years of this, the Merlin had matured into one of the most reliable aero engines in the world, and could be run at full power for eight-hour bombing missions with no problems.

As it turned out the Peregrine saw use in only two aircraft, the Westland Whirlwind and the Gloster F9/37. Although the Peregrine appeared to be a satisfactory design, it was never allowed to mature: Rolls-Royce's priority was troubleshooting the Merlin. The Vulture was fitted to the Hawker Tornado and Avro Manchester, but proved unreliable owing to failures of the crankshaft to connecting-rod bearing caused by lubrication problems. With the Merlin itself soon pushing into the 1,500 hp (1,100 kW) range, the Peregrine and Vulture were both cancelled in 1943.

By the end of its production run, over 150,000 Merlin engines had been built.^{[7] [4]} By mid 1943 the Merlin was supplemented in service by the larger Rolls-Royce Griffon which incorporated several design improvements.

[edit] Engine capacity and mass flow

Although it is common practice to compare different piston engines and their performance potential by referring to the Engine displacement or Swept volume this does not give an accurate reading of an engine's capabilities. A. C Lovesey, a Rolls-Royce engineer who was a central figure in the development of the Merlin said in 1946:

Coming now to specific development items we can, for convenience, divide them into three general classes:

1. Improvement of the supercharger.
2. Improved fuels.
3. Development of mechanical features to take care of the improvements afforded by (1) and (2).

Dealing with (1) it can be said that the supercharger determines the capacity, or in other words the output, of the engine. The impression still prevails that the static capacity known as the swept volume is the basis of comparison of the possible power output for different types of engine, but this is not the case because the output of the engine depends solely on the mass of air it can be made to consume efficiently, and in this respect the supercharger plays the most important role. This applies equally to any engine but the engine has to be capable of dealing with the greater mass flows with respect to cooling, freedom from detonation and capable of withstanding high gas and inertia loads...During the course of research and development on superchargers it became apparent to us that any further increase in the altitude performance of the Merlin engine necessitated the employment of a two-stage supercharger.^[8][9]

[edit] Upgrades

Most of the upgrades to the Merlin were the result of ever-increasing octane ratings in the aviation fuel available from the US, and ever more efficient supercharger designs by Stanley Hooker in 1938.

At the start of the war the engine ran on the then standard 87 octane aviation spirit and could supply just over 1,000 hp (750 kW) from its 27 L displacement. However, as early as 1938 at the 16th Paris Air Show Rolls-Royce displayed two versions of the Merlin rated to use 100 octane fuel. The Merlin R.M 2M was capable of 1,265 hp (943 Kw) at 7,870 feet (2,392 m), 1,285 hp (958 Kw) at 9,180 feet (2,798 m) and 1,320 hp (984 Kw) on take-off, while the Merlin X with a two speed blower generated 1,150 hp (857 Kw) at 15,400 feet (4,694 m) and 1,160 hp (865 Kw) at 16,730 feet (5,099 m) with the supercharger in high gear.^[10]

From late 1939 100 octane fuel became available from the U.S. and Merlin IIIs were found to be capable of running on it. Use of this fuel required that small modifications were made to the engine, which was now capable of generating 1,310 hp (877 kW)^[11][4]

The next major version was the XX which ran on 100 octane fuel. This allowed higher manifold pressures, which were achieved by increasing the boost from the centrifugal type supercharger. The Merlin XX also incorporated the first of the two-speed superchargers designed by Rolls-Royce. The result was 1,300 hp (970 kW) at higher altitudes than previous versions. Another improvement made to the XX and future Merlin variants was a redesign of the cooling system to use a 70/30% water/glycol mix rather than the 100% glycol of the earlier versions, allowing them to run some 70 degrees C cooler. This substantially improved engine life and reliability, removed the fire hazard of flammable pure ethylene glycol, and reduced the oil leaks which had been a flaw of the early Merlin I, II and III series.^[12]

The process of improvement continued, with later versions running on further-increased octane ratings, delivering ever higher power. Fundamental design changes were also made to all key components, again increasing the engine's life and reliability. By the end of the war the "little" engine was delivering over 1,600 hp (1,200 kW) in common versions, and as much as 2,070 hp (1,544 kW) in the Merlin 130/131 versions used on the de Havilland Hornet.

In late 1943, trials were run of a new fuel "100/150 grade". This rating was achieved by adding 2.5% mono methyl aniline (M.M.A.) to 100 octane fuel; tests determined that the mixture resulted in a buildup of tetraethyl lead deposited in the combustion chambers causing excessive fouling of the spark plugs.^[9]

The new fuel allowed the boost rating of the Merlin 66 to be raised to + 25 pounds. Starting in March 1944 the Merlin 66 powered Spitfire IXs of two squadrons were cleared to use the new fuel for operation trials, followed by other fighters flown by the ADGB, including Mustang IIIs. Continued problems with backfires were not sorted out until August. In November 1944 Spitfires of the 2 TAF began using 100/150 grade fuel, with full supplies becoming available the following February. Monty Berger, Senior Intelligence Officer of 126 (RCAF) Spitfire Wing, 2 TAF, noted in his daily operational summary on 20 April 1945 after the crashes of two Spitfires; "The incidents followed a number of engine problems that were attributed to the introduction of 150-grade fuel in early February. Pilots mistrusted it, and were no doubt relieved when the AF brass decided to revert to 130-grade. The vast majority of pilots, I'm sure, were beginning to wonder if the additional seven pounds of boost they got from 150-grade fuel were worth the price being paid."^[13]

Aircraft of the US 8th Air Force were running on 100/150 grade by the second week of June 1944; problems continued to be experienced with fouled spark-plugs and a new blend of fuel called P.E.P, using Ethylene dibromide to counter this, was introduced in early 1945. In March 1945 use of the PEP fuel was discontinued and 8th AF units reverted to the standard 100/150 grade.^[14] The 100/150 grade fuel could be recognised by its bright green colour and the "awful smell".^[15]

[edit] Carburettor developments

The Merlin's lack of direct fuel injection meant that both Spitfires and Hurricanes were, unlike the contemporary Bf-109E, unable to nose down into a deep dive. Luftwaffe fighters could therefore 'bunt' into a high-power dive to escape attack, leaving the pursuing aircraft spluttering behind as its fuel was forced by negative 'g' out of the carburettor. RAF fighter pilots soon learned to 'half-roll' their aircraft before diving to pursue their opponents. The use of carburettors was calculated to give a higher specific power output, due to the lower temperature, and hence greater density, of the fuel/air mixture, compared to injected systems. "Miss Shilling's orifice" (invented in March 1941 by Beatrice Shilling, an engineer at the Royal Aircraft Establishment, Farnborough), a holed diaphragm fitted across the float chambers, went some way towards curing the fuel starvation in a dive. Further improvements were introduced throughout the Merlins: 1943 saw the introduction of a Bendix-Stromberg pressure carburettor which injected fuel at 5 psi through a nozzle direct into the supercharger and was fitted to Merlins 66, 70, 76, 77 and 85. The final development was an SU injection carburettor which injected fuel into the supercharger using a fuel pump driven as a function of crankshaft speed and engine pressures, which was fitted to the 100 series Merlins.^[9][16] Production of the Griffon-engined Spitfire Mk. XII had begun the year before.

[edit] Packard V-1650

The Merlin was considered to be so important to the war effort, negotiations soon started to establish an alternative production line outside the UK. Rolls-Royce had checked out a number of North American automobile manufacturers, in order to select one to build the Merlin in the USA or Canada, and Packard Motor Car Company's attention to high quality and engineering impressed the parent British company so much, Packard was selected to build the Merlin. Agreement was reached in September 1940, and the first Packard-built engine, designated V-1650-1, ran in August 1941.

[edit] Alternative uses

A non-supercharged version of the Merlin using more steel and iron components was produced for use in tanks. This engine, the Rolls-Royce Meteor, in turn led to the smaller Rolls-Royce Meteorite.

In 1938, Rolls Royce started work on modifying some Merlins which were later to be used in British MTBs, MGBs, and RAF Air-Sea Rescue Launches. For these the superchargers were modified single-stage units and the engine was re-engineered for use in a marine environment.^[17]

A Spanish-built version of the Messerschmitt Bf 109 G-2, the 1954 Hispano Aviacion Ha 1112-M1L Buchon, was built with the Rolls-Royce Merlin 500/45 engine of 1,600 hp (1,200 kW), with four-bladed propeller, in the Hispano Aviacion factory in Seville—a fitting powerplant for the last-produced version of the famous Messerschmitt fighter, as the Bf 109 V1 prototype aircraft had been powered by the Rolls-Royce Kestrel V-12 engine in 1935.

At the end of World War 2 new versions of the Merlin (the 600 and 700 series) were designed and produced for use in commercial airliners such as the Avro Tudor. These engines were basically military with some minor changes to suit the different operating environment.

In the United States many war surplus engines and airframes were sold relatively cheaply - two of the most popular items were P-51 Mustangs and Packard V-1650 Merlin engines, several of which were "souped up" and modified for air racing in the Bendix Trophy, the Cleveland Air Races^[18] and the Thompson Trophy.

The Merlin engine continues to be used in dozens of restored World War 2 vintage aircraft all over the world.

[edit] Variants

This is an incomplete list of representative Merlin variants. Engines of the same power output were typically assigned different model numbers based on supercharger or propeller gear ratios, differences in cooling system or carburettors, engine block construction, or arrangement of engine controls. All Merlin engines were "right hand tractor", i.e. propeller rotated to the right viewed from rear, unless otherwise noted.

• Merlin II or III: 1,030 hp (775 kW) at 3,000 rpm at 5,500 ft (1,680 m). Merlin III fitted with "universal" propeller shaft able to be fitted with de Havilland or Rotol propellers.^[19] With 100 Octane fuel and increased (+12lb/sq.in) Boost: 1,310 hp (977 kW) at 3,000 rpm at 12,250 ft (3,730 m)^[20] (Merlin III); used in Spitfire Mk.I and Hurricane Mk.I fighters, the Boulton Paul Defiant, and Fairey Battle.^[21]
• Merlin X: 1,130 hp (840 kW) at 3,000 rpm at 5,250 ft (1,525 m); used in Halifax Mk.I, Wellington Mk.II, and Whitley Mk.V bombers.
• Merlin XII: fitted to Spitfire Mk. II.^[22]
• Merlin XX: 1,480 hp (1,105 kW) at 3,000 rpm at 6,000 ft (1,830 m); used in Hurricane Mk.II and Beaufighter Mk.II fighters, Halifax Mk.II and Lancaster Mk.I bombers.
• Merlin 32: 1,645 hp (1,230 kW) at 3,000 rpm at 2,500 ft (760 m); used in Barracuda Mk.II bomber.
• Merlin 45: 1,515 hp (1,130 kW) at 3,000 rpm at 11,000 ft (3,353 m); used in Spitfire Mk.V.
• Merlin 46: 1,415 hp (1,055 kW) at 3,000 rpm at 14,000 ft (4,270 m); high-altitude version used in Spitfire PR.Mk.IV and PR.Mk.VII
• Merlin 50.M: 1,585 hp (1,182 kW) at 3,000 rpm at 2,750 ft (838 m); Low altitude version with supercharger impeller "cropped" to 9.5 inches (240 mm) in diameter. Permitted boost was +18 lb/sq.in. instead of +16 lb/sq.in. as on a normal Merlin 50 engine. A "negative g" carburettor was fitted.^[23][21]
• Merlin 61: fitted with a new two-speed two-stage supercharger providing 1,565 hp (1,170 kW) at 3,000 rpm at 12,250 ft (3,740 m), and 1,390 hp (1,035 kW) at 3,000 rpm 23,500 ft (7,170 m); high-altitude version used in Spitfire Mk.IX, and PR.Mk.XI
• Merlin 76 & 77: 1,233 hp (920 kW); used in the Westland Welkin high-altitude fighter and some later Spitfire and Mosquito variants. Fitted with a two-speed, two-stage supercharger and a Bendix-Stromberg carburettor. The odd-numbered mark drove a blower for pressurising the cockpit.
• Merlin 130 & 131: 2,070 hp (1,543 kW); redesigned "slimline" versions made for the de Havilland Hornet. Engine modified to decrease frontal area to minimum and was first Merlin series to use down-draught induction systems. Coolant pump moved from the bottom of the engine to the starboard side. Two -speed, two-stage supercharger and S.U Injection carburettor. Maximum Boost was 25 lb (2,053mm Hg). The Merlin 131 had an additional idler gear in the reduction gear casing allowing "reverse" (left hand tractor) rotation. Merlin 130 was fitted in starboard nacelle, Merlin 131 in port on production Hornets.
• Merlin 133 & 134: 2,030 hp (1,514 kW); Derated variants of 130/131 used in Sea Hornet F. Mk. 20, N.F. Mk. 21 and P.R. Mk. 22. Maximum Boost was lowered to 18 lb (1,691 Hg).
• Merlin 266: the prefix 2 indicates built by Packard, otherwise as Merlin 66, optimised for low-altitude operation. Fitted to the Spitfire Mk. XVI.^[22]

Variant[24]	Take-off Power[24]	Application[24]	Notes[24]
Merlin I	890hp at 2850 rpm	Battle I [25]	First production Merlin; 172 built. Merlin I through III used 100% glycol coolant.[12]
Merlin II	880hp at 3000 rpm	Spitfire I, Defiant I, Hurricane I, Sea Hurricane I, Battle I
Merlin III	880hp at 3000 rpm	Spitfire I, Defiant I, Hurricane I, Sea Hurricane I, Battle I	1310 hp at 9,000 ft, +12 lb/sq.in, with 100 octane fuel (5 minute limit) [20]
Merlin VIII	1080hp at 3000rpm	Fulmar I	1275hp 100 octane
Merlin X	1075hp at 3000rpm	Halifax I, Wellington II, Whitley V and VII
Merlin XII	1175hp at 3000rpm	Spitfire II	Coffman cartridge starter. First version of Merlin to use 30/70% glycol/water coolant.[12]
Merlin XX	1280hp at 3000rpm	Beaufighter II, Defiant II, Halifax II and V, Hurricane II and IV, Lancaster I and III, Spitfire III [26]
Merlin 21	1280hp at 3000rpm	Mosquito I, II, III, IV and VI
Merlin 22	1280hp at 3000rpm	Lancaster I and III, York I
Merlin 23	1390hp at 3000rpm	Mosquito I, II, IV, VI, XII and XIII
Merlin 24	1620hp at 3000rpm	Lancaster I and VII, York I, Handley Page Halifax II [27]
Merlin 25	1620hp at 3000rpm	Mosquito VI and XIX
Merlin 27	1620hp at 3000rpm	Hurricane IV
Merlin 28	1300hp at 3000rpm	Lancaster I and III, Kittyhawk II (P-40F)	Built by Packard as the V-1650-1
Merlin 29	1300hp at 3000rpm	Hurricane (Canadian-built), Kittyhawk II (P-40F).	Built by Packard as the V-1650-1, splined airscrew shaft
Merlin 30	1300hp at 3000rpm	Barracuda I, Fulmar II
Merlin 31	1300hp at 3000rpm	Mosquito XX (Canadian), Mosquito 40 (Australia), Kitthawk II (P-40F and L)	Built by Packard as the V-1650-1
Merlin 32	1600hp at 3000rpm	Barracuda II, Seafire II, Hurricane V, Spitfire PR Mk. XIII[28]
Merlin 33	1390hp at 3000rpm	Mosquito XX (Canadian), Mosquito 40 (Australia)	Packard-built Merlin 23
Merlin 38	1390hp at 3000rpm	Lancaster I and II	Packard built Merlin 24
Merlin 45	1185hp at 3000rpm	Spitfire V, PR Mk. IG (later redesignated PR.VII), PR Mk IV, Seafire IB, IIC[19]
Merlin 45M	1230hp at 3000rpm	Spitfire LF.V
Merlin 46	1100hp at 3000rpm	Spitfire V, PR.IV and VII, Seafire IB, IIC[19]
Merlin 47	1415hp at 3000rpm	Spitfire HF.VI high-altitude intercepter	Fitted with a cabin pressure blower.
Merlin 50	1185hp at 3000rpm	Spitfire V
Spitfire 50M	1230hp at 3000rpm	Spitfire LF Mk.V
Merlin 55	1185hp at 3000rpm	Spitfire V, Seafire III
Merlin 55M	1230hp at 3000rpm	Spitfire LF.V, Seafire III
Merlin 60	1165hp at 3000rpm	Wellington VI
Merlin 61	1290hp at 3000rpm	Spitfire F Mk. IX, PR Mk. XI	Two-stage supercharger fitted
Merlin 62	1165hp at 3000rpm	Wellington VI
Merlin 63	1290hp at 3000rpm	Spitfire VIII[29], IX, PR.XI	Replaced Merlin 61.
Merlin 63A[30]	1710hp at 3000rpm[30]	Spitfire PR.XI[30]
Merlin 64	1290hp at 3000rpm	Spitfire F Mk. VII[29]	Cabin pressure blower[30]
Merlin 66	1315hp at 3000rpm	Spitfire LF.VIII[29], LF Mk.IX	Bendix-Stromberg anti-g carburettor.[29]
Merlin 67	1315hp at 3000rpm
Merlin 68	1400hp at 3000rpm	Mustang III (P-51B and C)	Packard-built as V-1650-3
Merlin 69	1490hp at 3000rpm	Mustang III and IV (P-51C,D,F and K)	Packard-built as V-1650-7
Merlin 70	1250hp at 3000rpm	Spitfire HF.VIII[29], HF.IX, PR.XI	Bendix-Stromberg anti-g carburettor.[29]
Merlin 71	1250hp at 3000rpm	Spitfire HF.VII[29]	Cabin pressure blower[30], Bendix-Stromberg anti-g carburettor.[29]
Merlin 72	1290hp at 3000rpm	Mosquito PR.IX, B.IX, XVI, 30, Welkin I
Merlin 73	1290hp at 3000rpm	Mosquito XVI, Welkin I
Merlin 76	1250hp at 3000rpm	Mosquito XVI, 30, Welkin I	Same as Merlin 72 with a cabin pressure blower
Merlin 77	1250hp at 3000rpm	Mosquito XVI, Welkin I, Spitfire PR.X[30]	Same as Merlin 73 with a cabin pressure blower[30]
Merlin 85	1635hp at 3000rpm	Lancaster VI, Lincoln I
Merlin 224	1620hp at 3000rpm	Lancaster I and III	Packard-built Merlin 24
Merlin 225	1620hp at 3000rpm	Mosquito 25 and 26	Packard-built Merlin 25
Merlin 266	1315hp at 3000rpm	Spitfire LF. Mk. XVI	Packard-built Merlin 66

[edit] Applications

[edit] Specifications (Merlin II)

Data from ^[21] and ^[31]

General characteristics

• Type: 12-cylinder supercharged liquid-cooled 60° "Vee" piston aircraft engine
• Bore: 5.4 in (137.2 mm)
• Stroke: 6 in (152.4 mm)
• Displacement: 1,648.96 in³ (27.04 L)
• Length: 69 in (175.3 cm)
• Width: 29.8in (75.7 cm)
• Height: 41.2 in (104.6 cm)
• Dry weight: 1,375 lb (623.7 kg)

Components

• Valvetrain: Overhead camshaft-actuated, two intake and two exhaust valves per cylinder, sodium-filled exhaust valve stems
• Supercharger: Centrifugal, 8.588:1 reduction.
• Fuel system: Twin-choke updraft SU carburetor with automatic mixture control
• Fuel type: 87 octane rating gasoline
• Oil system: Dry sump with one pressure pump and two scavenge pumps.
• Cooling system: 100% ethylene glycol, pressurised.
• Reduction gear: Spur, 0.477:1

Performance

• Power output:
  Note: Maximum boost pressures = 87 Octane +6.25lb; 100 Octane fuel +9 lb boost.
  • 880 (656 kW) at 3,000 rpm at take-off.
  • 1,030 hp (768 kW) at 3,000 rpm at 16,000 ft (4,877 m) (+6.25 lb)^[32]
  • 1,160 hp (865 kW) at 3,000 rpm at 12,250 ft (3,734 m) (+9 lb) (bmep = 185.7psi)
• Specific power: 0.70 hp/in³ (42.9 kW/L)
• Compression ratio: 6:1
• Specific fuel consumption: 0.63 lb/(hp•h) (382 g/(kW•h))
• Power-to-weight ratio: 0.844 hp/lb (1.86 kW/kg)

[edit] Specifications (Merlin 66)

Data from ^[21]

General characteristics

• Type: 12-cylinder supercharged liquid-cooled 60° "Vee" piston aircraft engine
• Bore: 5.4 in (137.2 mm)
• Stroke: 6 in (152.4 mm)
• Displacement: 1,648.96 in³ (27.04 L)
• Length: 88.7 in (225.3 cm)
• Width: 30.8 in (78.1 cm)
• Height: 40 in (101.6 cm)
• Dry weight: 1,645 lb (746.5 kg)^[33]

Components

• Valvetrain: Overhead camshaft-actuated, two intake and two exhaust valves per cylinder, sodium-cooled exhaust valve stems
• Supercharger: Two-speed two-stage, boost pressure automatically linked to the throttle, water-air aftercooler installed between the second stage and the engine.
• Fuel system: Twin-choke updraft carburettor with automatic mixture control
• Fuel type: 100 Octane from mid 1944 100/150 Grade Aviation fuel
• Oil system: Dry sump with one pressure pump and two scavenge pumps.
• Cooling system: 70% water and 30% ethylene glycol coolant mixture, pressurised.

Performance

• Power output:
  Note: 100 Octane fuel, +12 lb boost.
  • 1,315 hp (981 kW) at 3,000 rpm at take-off.
  • 1,705 hp (1,271 kW) at 3,000 rpm at 5,750 ft (1,753 m) (MS gear)
  • 1,580 hp (1,178 kW) at 3,000 rpm at 16,000 ft (4,877 m) (FS gear)^[34]
  100/150 Grade fuel, +25 lb boost
  • 2,000 hp (1,481 kW) at 5,250 ft (1,600 m) (MS gear) (bmep = 320.2psi)
  • 1,860 hp (1,387 kW) at 11,000 ft (3,353 m) (FS gear)
• Specific power: 0.95 hp/in³ (43.3 kW/L)
• Compression ratio: 6:1
• Power-to-weight ratio: 0.80 hp/lb (1.76 kW/kg) take-off; 1.21 hp/lb (2.69 kW/kg) 100/150 grade fuel/MS gear.

[edit] See also

• Rolls-Royce Merlin alternative uses
  

Related development

• Packard V-1650
• Rolls-Royce Meteor
• Rolls-Royce Meteorite
• Rolls-Royce Griffon
  

Comparable engines

• Allison V-1710
• Daimler-Benz DB 601
• Junkers Jumo 213
• Klimov VK-107
• Mikulin AM-35
• Napier Sabre
  

Related lists

• List of aircraft engines
  

[edit] References

[edit] Notes

[edit] Bibliography

[edit] External links

Wikimedia Commons has media related to: Rolls-Royce Merlin

• Merlin engines in Manchester
• Rolls Royce V-1650 Design and development
• Merlin 60 series comparison drawings
• Rolls Royce Merlin 61
• John Dodd RR-Merlin engined car

v • d • e Rolls-Royce aero-engines Rolls-Royce Ltd. Piston engines (1914-1971) Four-stroke piston engines: Buzzard · Condor · Eagle (V-12) · Eagle (H-24) · Exe · Falcon · Goshawk · Griffon · Hawk · Kestrel · Merlin · Pennine · Peregrine · "R" · Vulture Two-stroke piston engines: Crecy Rolls-Royce Ltd. Gas turbine engines (1943-1971) Turbojets: Avon · Derwent · Nene · Olympus · Soar · Tay · Thames · Viper · Welland Turbofans: Conway · Medway · Pegasus · Spey · Tay Turboprops: Clyde · Dart · Trent · Tyne Turboshafts: Gem · Gnome · Nimbus RB (Rolls-Royce Barnoldswick) designation: RB23 · RB37 · RB39 · RB41 · RB44 · RB50 · RB53 · RB80 · RB82 · RB106 · RB108 · RB109 · RB140 · RB141 · RB142 · RB146 · RB162 · RB163 · RB168 · RB172 · RB183 · RB193 · RB199 · RB211 · RB282 · RB401 Rolls-Royce plc Gas turbine engines (1987-Present) Fans: LiftSystem Turbofans: Trent Rolls-Royce Corporation (formerly the Allison Engine Company) (1995-Present) Turbofans: AE 3007 · RB282 Turboprop/Turboshafts: AE 2100 · 250 · RR300 · RR500 · T56 · T406 Joint development BMW Rolls-Royce: BR700 (Turbofan) EuroJet Turbo GmbH: Eurojet EJ200 (Turbofan) Europrop International: EuroProp TP400 (Turboprop) General Electric/Rolls Royce: F136 (Turbofan) International Aero Engines: V2500 (Turbofan) LHTEC: LHTEC T800 (Turboshaft) MTU Turbomeca Rolls-Royce: MTR390 (Turboshaft) Rolls-Royce/Snecma: Olympus 593 (Turbojet) · M45H (Turbofan) Rolls-Royce Turbomeca Limited: Adour (Turbofan) · RTM322 (Turboshaft) Turbo-Union: RB199 (Turbofan) Designers Alan Arnold Griffith · Ernest Hives · Stanley Hooker · Cyril Lovesey · Harry Ricardo · Henry Royce

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