The
Rolls-Royce Merlin is a British, liquid-cooled, 27-
litreThe litre or liter is a unit of volume. There are two official symbols: the Latin letter L in lower and upper case . The lower case L is also often written as a cursive ℓ, though this symbol has no official approval by any international bureau...
(1,650
cu inA cubic inch is a non-SI unit of volume, equal to the volume of a cube with sides of one inch.Cubic inches are still sometimes used as a unit of measurement in the United States and Canada, although SI is continuing to gradually displace non-SI usage.-Notation conventions:The following symbols...
)
capacityEngine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre to bottom dead centre . It is commonly specified in cubic centimeters , litres , or cubic inches...
,
V-12A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually at a 60° angle to each other, but in some cases at a wider or narrower angle, with all 12 pistons driving a common crankshaft....
pistonA reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...
aero engineAn aircraft engine is a propulsion system for an aircraft. Aircraft engines are almost always either lightweight piston engines or gas turbines. This article is an overview of the basic types of aircraft engines and the design concepts employed in engine development for aircraft.- Engine design...
, designed and built by
Rolls-Royce LimitedRolls-Royce Limited was a British car and, from 1914, aero-engine manufacturing company founded by Charles Stewart Rolls and Henry Royce on 15 March 1906 as the result of a partnership formed in 1904. In 1971, Rolls-Royce was crippled by the development of the advanced RB211 jet engine, resulting...
. Initially known as the
PV-12, Rolls-Royce named the engine the
MerlinThe Merlin is a smallish falcon that breeds in northern North America, Europe and Asia. In North America it was once and sometimes still is colloquially called "pigeon hawk" though it is not very closely related to true hawks....
following the company convention of naming its piston aero engines after
birds of preyBirds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as any bird that kills its prey with its talons. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh. In most cases,...
.
The PV-12 first ran in 1933, and a series of rapidly applied developments brought about by wartime needs improved the engine's performance markedly. The first operational aircraft to enter service using the Merlin were the
Fairey BattleThe Fairey Battle was a British single-engine light bomber built by the Fairey Aviation Company in the late 1930s for the Royal Air Force. The Battle was powered by the same Rolls-Royce Merlin piston engine that gave contemporary British fighters high performance; however, the Battle was weighed...
,
Hawker HurricaneThe Hawker Hurricane is a British single-seat fighter aircraft that was designed and predominantly built by Hawker Aircraft Ltd. Some production of the Hurricane was carried out in Canada by the Canada Car and Foundry Co Ltd....
and
Supermarine SpitfireThe Supermarine Spitfire is a British single-seat fighter aircraft used by the Royal Air Force and many other Allied countries through the Second World War. The Spitfire continued to be used into the 1950s both as a front line fighter and in secondary roles...
. More Merlins were made for the four-engined
Avro LancasterThe Avro Lancaster was a British four-engined Second World War heavy bomber made initially by Avro for the Royal Air Force . It first saw active service in 1942, and together with the Handley Page Halifax it was one of the main heavy bombers of the RAF, the RCAF and squadrons from other...
heavy bomber than any other aircraft; however, the engine is most closely associated with the Spitfire and powered its maiden flight in 1936.
An English Icon, the Merlin was one of the most successful aircraft engines of the World War II era, and many variants were built by Rolls-Royce in
DerbyDerby is a city in the East Midlands region of England. It lies upon the banks of the River Derwent and is located in the south of the ceremonial county of Derbyshire. In the 2001 census, the population of the city was 233,700, whilst that of the Derby Urban Area was 229,407...
,
CreweCrewe is a town within the unitary authority area of Cheshire East and the ceremonial county of Cheshire, England. According to the 2001 census the urban area had a population of 67,683...
and
GlasgowGlasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...
, as well as by
Ford of BritainFord Motor Company Limited was the manufacturing and sales arm of the Ford Motor Company for the United Kingdom and originally also Ireland. The firm both sold and manufactured cars, commercial vehicles, and farm tractors for sale in the United Kingdom and other countries...
in
Trafford ParkTrafford Park is an area of the Metropolitan Borough of Trafford, in Greater Manchester, England. Located opposite Salford Quays, on the southern side of the Manchester Ship Canal, it is west-southwest of Manchester city centre, and north of Stretford....
,
ManchesterManchester is a city and metropolitan borough of Greater Manchester, England. In 2007, the population of the city was estimated to be 458,100...
. The
Packard V-1650The Packard V-1650 was a liquid cooled 27 litre 60° V12 piston aircraft engine variant of the Rolls-Royce Merlin produced under licence by the Packard Motor Car Company.-Design and development:...
was a version of the Merlin built in the United States. Production ceased in 1950 after a total of almost 150,000 engines had been delivered, the later variants being used for
airlinerAn airliner is a large fixed-wing aircraft for transporting passengers and cargo. Such planes are owned by airlines....
s and
military transport aircraftMilitary transport aircraft are typically fixed and rotary wing cargo aircraft which are used to deliver troops, weapons and other military equipment by a variety of methods to any area of military operations around the surface of the planet, usually outside of the commercial flight routes in...
.
In military use the Merlin was superseded by its larger capacity stablemate, the
Rolls-Royce GriffonThe Rolls-Royce Griffon is a British 37-litre capacity, 60-degree V-12, liquid-cooled aero engine having a similar general configuration to its smaller capacity stablemate, the Merlin...
. Merlin engines remain in
Royal Air ForceThe Royal Air Force is the United Kingdom's air force, the oldest independent air force in the world. Formed on 1 April 1918, the RAF has taken a significant role in British military history ever since, playing a large part in World War II and in more recent conflicts.The RAF operates almost 1,109...
service today with the
Battle of Britain Memorial FlightThe Battle of Britain Memorial Flight is a Royal Air Force flight which provides an aerial display group comprising an Avro Lancaster, a Supermarine Spitfire and a Hawker Hurricane...
, and power many restored aircraft in private ownership worldwide.
Origin
In the early 1930s, Rolls-Royce started planning its future aero engine development programme and realised that there was a need for an engine larger than their 21-litre (1,296 cu in)
KestrelThe Kestrel or type F is a 700 horsepower class V-12 aircraft engine from Rolls-Royce, their first cast-block engine and the pattern for most of their future piston-engine designs...
that had been used with great success in a number of 1930s aircraft. Consequently, work was started on a new 1,100-
horsepowerHorsepower is the name of several non-SI units of power. It was originally defined to allow the output of steam engines to be measured and compared with the power output of draft horses. The horsepower was widely adopted to measure the output of piston engines, turbines, electric motors and other...
(820 kW)-class design known as the PV-12, with PV standing for
private venture as the company received no government funding for work on the project. The PV-12 was first run on 15 October 1933 and first flew in a
Hawker HartThe Hawker Hart was a British two-seater biplane light-bomber of the Royal Air Force , which had a prominent role during the RAF's inter-war period. The Hart was designed during the 1920s by Sydney Camm and built by Hawker Aircraft...
(
K3036In the United Kingdom to identify individual aircraft, all military aircraft are allocated and display a serial number. A unified serial number system, maintained by the Air Ministry, and its successor the Ministry of Defence, is used for aircraft operated by the Royal Air Force, Fleet Air Arm and...
) biplane on 21 February 1935. The engine originally used the evaporative cooling system then in vogue. This proved unreliable and when supplies of
ethylene glycolEthylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet tasting liquid....
from the U.S. became available, the engine was adapted to use a conventional liquid cooling system. The Hart was subsequently delivered to Rolls-Royce where, as a Merlin testbed, it completed over 100 hours of flying with the Merlin C and E engines.
In 1935, the
Air MinistryThe Air Ministry was formerly a department of the British Government with the responsibility of managing the affairs of the Royal Air Force, existing from 1918 to 1964...
issued a specification,
F10/35, for new
fighter aircraftA fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets by dropping bombs. Fighters are small, fast, and maneuverable...
with a minimum airspeed of 310
miles per hourThe mile per hour is a unit of speed, measured in Imperial units expressing the number of international miles covered per hour.It is currently the unit used for speed limits, and speeds, on roads in the United Kingdom and United States...
(500
km/hThe kilometre per hour is a unit of speed or velocity, expressing the number of kilometers traveled in one hour...
). Fortunately, two designs had been developed: the
Supermarine SpitfireThe Supermarine Spitfire is a British single-seat fighter aircraft used by the Royal Air Force and many other Allied countries through the Second World War. The Spitfire continued to be used into the 1950s both as a front line fighter and in secondary roles...
and the
Hawker HurricaneThe Hawker Hurricane is a British single-seat fighter aircraft that was designed and predominantly built by Hawker Aircraft Ltd. Some production of the Hurricane was carried out in Canada by the Canada Car and Foundry Co Ltd....
; the latter designed in response to another specification, F36/34. Both were designed around the PV-12 instead of the Kestrel, and were the only contemporary British fighters to have been so developed. Production contracts for both aircraft were placed in 1936, and development of the PV-12 was given top priority as well as government funding. Following the company convention of naming its piston aero engines after birds of prey, Rolls-Royce named the engine the
MerlinThe Merlin is a smallish falcon that breeds in northern North America, Europe and Asia. In North America it was once and sometimes still is colloquially called "pigeon hawk" though it is not very closely related to true hawks....
after a small, Northern Hemisphere falcon (
Falco columbarius).
Two more Rolls-Royce engines developed just prior to the war were added to the company's range. The 700-horsepower (500 kW)
Rolls-Royce PeregrineThe Peregrine was a 21-litre , 885-horsepower liquid-cooled V-12 aero engine designed and built by the British manufacturer Rolls-Royce in the late-1930s. It was essentially the ultimate development of their Rolls-Royce Kestrel, which had seen widespread use...
was an updated,
superchargedA supercharger is an air compressor used for forced induction of an internal combustion engine. The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally-aspirated engine, which allows more fuel to be provided and more work to be done per cycle,...
development of their V-12 Kestrel design, while the 1,700-horsepower (1,300 kW) 42-litre (2,560 cu in)
Rolls-Royce VultureThe Rolls-Royce Vulture was a British aero engine of the World War II era that was designed and built by Rolls-Royce Limited. The Vulture used the unusual "X-24" configuration, whereby a pair of V12 Rolls-Royce Peregrine engines were effectively joined by a common crankshaft...
was based on two joined Peregrines, using a common crankshaft and forming an X-24 cylinder layout. This was to be used in larger aircraft such as the
Avro ManchesterThe Avro 679 Manchester was a British twin-engine heavy bomber developed during the Second World War by the Avro aircraft company in the United Kingdom...
.
Although the Peregrine appeared to be a satisfactory design, it was never allowed to mature since Rolls-Royce's priority was refining the Merlin. As a result the Peregrine saw use in only two aircraft: the
Westland WhirlwindThe Westland Whirlwind was a British twin-engined heavy fighter developed by Westland Aircraft. It was the Royal Air Force's first single-seat, twin-engined, cannon-armed fighter, and a contemporary of the Supermarine Spitfire and Hawker Hurricane. It was one of the fastest aircraft when it flew in...
and the Gloster F9/37. The Vulture was fitted to the
Hawker TornadoThe Hawker Tornado was a British single-seat fighter aircraft evaluated during World War II by the Royal Air Force. The planned production of Tornados was cancelled after the engine it was designed to use proved unreliable in service...
and
Avro ManchesterThe Avro 679 Manchester was a British twin-engine heavy bomber developed during the Second World War by the Avro aircraft company in the United Kingdom...
, but proved unreliable in service. With the Merlin itself soon pushing into the 1,500-horsepower (1,100 kW) range, the Peregrine and Vulture were both cancelled in 1943, and by mid-1943 the Merlin was supplemented in service by the larger
Rolls-Royce GriffonThe Rolls-Royce Griffon is a British 37-litre capacity, 60-degree V-12, liquid-cooled aero engine having a similar general configuration to its smaller capacity stablemate, the Merlin...
. The Griffon incorporated several design improvements and ultimately superseded the Merlin.
Development
Initially the new engine was plagued with problems, such as failure of the accessory gear trains and coolant jackets, and several different construction methods were tried before the basic design of the Merlin was set. Early production Merlins were also unreliable: common problems were cylinder head cracking, coolant leaks, and excessive wear to the camshafts and
crankshaftThe crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
main bearingIn a piston engine, the main bearings are the bearings on which the crankshaft rotates, usually plain or journal bearings.All engines have a minimum of two main bearings, one at each end of the crankshaft, and they may have as many as one more than the number of crank pins...
s.
Early engines
The prototype and developmental engine types were the:
- The initial design using an evaporative cooling system. Two built, passed Type Testing in July 1934, generating 740 horsepower (552 kW) at 12,000 feet (3,657 m
The metre or meter is the basic unit of length in the International System of Units . Historically, the metre was defined by the French Academy of Sciences as the length between two marks on a platinum-iridium bar, which was designed to represent one ten-millionth of the distance from the Equator...
) equivalent. First flown 21 February 1935.
- Two built, ethylene glycol liquid cooling system introduced. "Ramp" cylinder head
In an internal combustion engine, the cylinder head sits above the cylinders and consists of a platform containing part of the combustion chamber and the location of the valves and spark plugs...
s (inlet valves were at a 45-degreeA degree , usually denoted by ° , is a measurement of plane angle, representing 1⁄360 of a full rotation; one degree is equivalent to π/180 radians...
angle to the cylinder). Passed Type Testing February 1935, generating 950 horsepower (708 kW) at 11,000 feet (3,353 m) equivalent.
- Crankcase
In an internal combustion engine, the crankcase is the housing for the crankshaft. The enclosure forms the largest cavity in the engine and is located below the cylinder block....
and cylinder blockThe cylinder block or engine block is a machined casting containing cylindrically bored holes for the pistons of a multi-cylinder reciprocating internal combustion engine, or for a similarly constructed device such as a pump...
s became three separate castings with bolt-on cylinder heads.
- Similar to C with minor design changes. Passed 50-hour civil test in December 1935 generating a constant 955 horsepower (712 kW) and a maximum rating of 1,045 horsepower (779 kW). Failed military 100-hour test in March 1936. Powered the Supermarine Spitfire prototype.
- Similar to C and E. This became the first production engine; and was designated as the Merlin I. The Merlin continued with the "ramp" head, but this was not a success and only 172 were made. The Fairey Battle
The Fairey Battle was a British single-engine light bomber built by the Fairey Aviation Company in the late 1930s for the Royal Air Force. The Battle was powered by the same Rolls-Royce Merlin piston engine that gave contemporary British fighters high performance; however, the Battle was weighed...
was the first production aircraft to be powered by the Merlin I and first flew on 10 March 1936.
- 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-horsepower (770 kW) Merlin II in 1938, and production was quickly stepped up.
Production engines
The Merlin II and III series were the first main production versions of the engine. The Merlin III was manufactured with a "universal" propeller shaft which allowed either
de HavillandThe de Havilland Aircraft Company was a British aviation manufacturer founded in 1920 when Airco, of which Geoffrey de Havilland had been chief designer, was sold to BSA by the owner George Holt Thomas. De Havilland then set up a company under his name in September of that year at Stag Lane...
or Rotol manufactured propellers to be used.
The next major version was the XX which ran on 100
octaneThe octane rating is a measure of the resistance of gasoline and other fuels to detonation in spark-ignition internal combustion engines. High-performance engines typically have higher compression ratios and are therefore more prone to detonation, so they require higher octane fuel...
fuel. This allowed higher
manifold pressuresManifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere....
, which were achieved by increasing the boost from the
centrifugal type superchargerThe centrifugal-type supercharger is an engine-driven compressor used to increase the power output of an internal-combustion engine by increasing the amount of available oxygen by compressing air that is entering the engine...
. The Merlin XX incorporated the two-speed superchargers designed by Rolls-Royce, resulting in increased horsepower at higher altitudes than previous versions. Another improvement, which allowed the XX and future Merlin variants to run some cooler, was the use of a 70/30% water/glycol coolant mix rather than the 100% glycol of the earlier versions. This substantially improved engine life and reliability, removed the fire hazard of the flammable
ethylene glycolEthylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet tasting liquid....
, and reduced the oil leaks that had been a problem with the early Merlin I, II and III series.
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 horsepower (1,200 kW) in common versions, and as much as 2,060 horsepower (1,536 kW) in the Merlin 130/131 versions specifically designed for the
de Havilland HornetThe British de Havilland DH.103 Hornet was a piston engine fighter that further exploited the wooden construction techniques pioneered by de Havilland's classic Mosquito. Entering service at the end of the Second World War, the Hornet equipped postwar RAF Fighter Command day fighter units in the UK...
. Ultimately, during tests conducted by Rolls-Royce at
DerbyDerby is a city in the East Midlands region of England. It lies upon the banks of the River Derwent and is located in the south of the ceremonial county of Derbyshire. In the 2001 census, the population of the city was 233,700, whilst that of the Derby Urban Area was 229,407...
, Merlin 130 series engines generated over 2,600 horsepower (1,939 kW).
Basic component overview (Merlin 61)
From Jane's:
Cylinders
- Twelve cylinders consisting of high-carbon steel liners set in two, two-piece cylinder blocks of cast "R.R.50" aluminium alloy
Aluminium alloys are mixtures of aluminium with other metals , often with copper, zinc, manganese, silicon, or magnesium. They are much lighter and more corrosion resistant than plain carbon steel, but not as corrosion resistant as pure aluminium...
having separate heads and skirts. Coolant in direct contact with external face of liners. Cylinder heads fitted with cast-iron inlet valve guides, phosphor bronzePhosphor bronze is an alloy of copper with 3.5 to 10% of tin and a significant phosphorus content of up to 1%. The phosphorus is added as deoxidizing agent during melting. These alloys are notable for their toughness, strength, low coefficient of friction, and fine grain...
exhaust valve guides, and renewable "Silchrome" steel-alloy valve seats. Two diametrically opposed spark plugA spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as, aerosol gasoline, Ethanol, and Liquefied petroleum gas by means of an electric spark...
s protrude into each combustion chamber-Internal combustion engine:The hot gases produced by the combustion occupy a far greater volume than the original fuel, thus creating an increase in pressure within the limited volume of the chamber. This pressure can be used to do work, for example, to move a piston on a crankshaft or a turbine...
.
Pistons
- Machined from "R.R.59" alloy forging
Forging is the term for shaping metal by using localized compressive forces. Cold forging is done at room temperature or near room temperature. Hot forging is done at a high temperature, which makes metal easier to shape and less likely to fracture. Warm forging is done at intermediate temperature...
s. Fully floating hollow gudgeon pins of hardened nickel-chrome steel. Three compression and one oil-control ringA piston ring is an open-ended ring that fits into a groove on the outer diameter of a piston in a reciprocating engine such as an internal combustion engine or steam engine.The three main functions of piston rings in reciprocating engines are:...
above the gudgeon pin, and one oil-control ring below.
Connecting rods
- H-section machined nickel-steel forgings, each pair consisting of a plain and a forked rod
In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft.- History :The earliest evidence for a connecting rod appears on a late 3rd century AD Roman relief of a saw mill from Hierapolis, Asia Minor, as well as two 6th century Roman saw mills...
. The forked rod carries a nickel-steel bearing block which accommodates steel-backed lead-bronze-alloy bearing shells. The "small-end" of each rod houses a floating phosphor bronze bushA bushing is a type of bearing. It is a cylindrical lining designed to reduce friction and wear inside a hole, or constrict and restrain motion of mechanical parts.- Threaded Insert :...
.
Crankshaft
- One-piece, machined from a nitrogen-hardened nickel-chrome molybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The free element, which is a silvery metal, has the sixth-highest melting point of any element. It readily forms hard, stable carbides, and for this reason it is often used in high-strength steel alloys...
steel forging. Statically and dynamically balancedEngine balance is the design, construction and tuning of an engine to run smoothly. Engine balance reduces vibration and other stresses, and may improve the performance, efficiency, cost of ownership and reliability of the engine, as well as reducing the stress on other machinery and people near...
. Seven main bearings and six throws.
Crankcase
- Two aluminium-alloy castings joined together on the horizontal centreline. The upper portion bears the wheelcase, supercharger and accessories; and carries the cylinder blocks, crankshaft main bearings (split mild-steel shells lined with lead–bronze alloy), and part of the housing for the airscrew reduction gear
A Propeller Speed Reduction Unit is a gearbox or a belt and pulley device used to reduce the output revolutions per minute when compared to the higher input rpm of the powerplant...
. The lower half forms an oil sump and carries the oil pumps and filters.
Wheelcase
- Aluminium casting fitted to rear of crankcase. Houses drives to the camshafts, magnetos
A magneto is an electrical generator that uses permanent magnets to produce pulses of high voltage alternating current. At one time the magneto was used in the ignition system of most gasoline-powered internal combustion engines to provide power to the spark plugs...
, coolant and oil pumps, superchargerA supercharger is an air compressor used for forced induction of an internal combustion engine. The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally-aspirated engine, which allows more fuel to be provided and more work to be done per cycle,...
, hand and electric starters, and the electric generatorIn electricity generation, an electrical generator is a device that converts mechanical energy to electrical energy. The reverse conversion of electrical energy into mechanical energy is done by a motor; motors and generators have many similarities...
.
Valve gear
- Two inlet and two exhaust poppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...
s of "K.E.965" steel per cylinder. Both the inlet and exhaust valves have hardened "stelliteStellite alloy is a range of cobalt-chromium alloys designed for wear resistance. It may also contain tungsten or molybdenum and a small but important amount of carbon...
d" ends; while the exhaust valves also have sodiumSodium is a metallic element with a symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals within "group 1"...
-cooled stems, and heads protected with a "BrightRay" (nickel-chromium) coating. Each valve is kept closed by a pair of concentric coil-springsA Coil spring, also known as a helical spring, is a mechanical device, which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces...
. A single, seven-bearing camshaft, located on the top of each cylinder head operates 24 individual steel rockersGenerally referred to within the internal combustion engine of automotive, marine, motorcycle and reciprocating aviation engines, the rocker arm is a reciprocating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it...
; 12 pivoting from a rocker shaft on the inner, intake side of the block to actuate the exhaust valves, the others pivoting from a shaft on the exhaust side of the block to actuate the inlet valves.
Technical improvements
Most of the Merlin's technical improvements resulted from more efficient
superchargerThe centrifugal-type supercharger is an engine-driven compressor used to increase the power output of an internal-combustion engine by increasing the amount of available oxygen by compressing air that is entering the engine...
s, designed by
Stanley HookerSir Stanley George Hooker was a jet engine engineer, first at Rolls-Royce where he worked on the earliest designs such as the Welland and Derwent, and later at Bristol Aero Engines where he helped bring the troubled Proteus and Olympus to market, and then designed the famous Pegasus.Stanley George...
, and the introduction of aviation spirits with increased
octane ratingThe octane rating is a measure of the resistance of gasoline and other fuels to detonation in spark-ignition internal combustion engines. High-performance engines typically have higher compression ratios and are therefore more prone to detonation, so they require higher octane fuel...
s. Numerous detail changes were made internally and externally to the engine to withstand increased power ratings and to incorporate advances in engineering practices.
Ejector exhausts
The Merlin consumed an enormous volume of air at full power (equivalent to the volume of a
single-decker busA single-decker bus or single-decker is a bus that has a single level. Normally the use of the term single-decker refers to a standard 2 axled rigid bus, in direct contrast to the use of the term double-decker bus, which is essentially a single decked bus with an extra deck and staircase...
per minute), and with the exhaust gases exiting at 1,300 miles per hour (2,100 km/h) it was realised that useful
thrustThrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a proportional but opposite force on that system.-Examples:...
could be gained simply by angling the gases backwards instead of venting sideways. During tests, 70
pounds-forceThe pound-force or simply pound is a unit of force.- Definitions :The pound-force is approximately equal to the gravitational force exerted on a mass of one avoirdupois pound on the surface of Earth...
(32
kgfThe unit kilogram-force or kilopond is defined as the magnitude of the force exerted on one kilogram of mass by a gravitational field . So one kilogram-force is by definition equal to newtons...
) thrust at 300 miles per hour (480 km/h), or roughly 70 horsepower (52 kW) was obtained which increased the level maximum speed of the Spitfire by 10 miles per hour (16 km/h) to 360 miles per hour (580 km/h). The first versions of the ejector exhausts featured round outlets, while subsequent versions of the system used "fishtail" style outlets which marginally increased thrust and reduced exhaust glare for night flying.
In September 1937 the Spitfire prototype,
K5054In the United Kingdom to identify individual aircraft, all military aircraft are allocated and display a serial number. A unified serial number system, maintained by the Air Ministry, and its successor the Ministry of Defence, is used for aircraft operated by the Royal Air Force, Fleet Air Arm and...
, was fitted with ejector type exhausts. Later marks of the Spitfire used a variation of this exhaust system fitted with forward-facing intake ducts to distribute hot air out to the wing-mounted guns to prevent freezing and stoppages at high
altitudeAltitude is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object...
s, replacing an earlier system that used heated air from the engine coolant radiator. The latter system had become ineffective due to improvements to the Merlin itself which allowed higher operating altitudes where air
temperatures are lowerThe lapse rate is defined as the rate of decrease with height for an atmospheric variable. The variable involved is temperature unless specified otherwise. The terminology arises from the word lapse in the sense of a decrease or decline; thus, the lapse rate is the rate of decrease with height and...
. Ejector exhausts were also fitted to other Merlin-powered aircraft.
Supercharger
Central to the success of the Merlin was the supercharger.
A.C. LoveseyAlfred Cyril Lovesey CBE, AFRAeS, was an English engineer who was a key figure in the development of the Rolls-Royce Merlin aero engine.-Early life:...
, an engineer who was a key figure in the design of the Merlin, delivered a lecture on the development of the Merlin in 1946; in this extract he explained the importance of the supercharger:
"Coming now to specific development items we can ... divide them into three general classes:
- Improvement of the supercharger.
- Improved fuels.
- 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 ... 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 ... 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."
As the Merlin evolved so too did the supercharger; the latter fitting into three broad categories:
- Single-stage, single-speed gearbox: Merlin I to III, XII, 30, 40, and 50 series (1937–1942).
- Single-stage, two-speed gearbox: experimental Merlin X (1938), Merlin XX (1940–1945).
- Two-stage, two-speed gearbox with intercooler: mainly Merlin 60, 70, and 80 series (1942–1946).
The Merlin supercharger was originally designed to allow the engine to generate maximum power at an
altitudeAltitude is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object...
of about 16,000 feet (5,000 m). In 1938 Stanley Hooker, an
OxfordThe University of Oxford , located in the UK city of Oxford, is the oldest surviving university in the English-speaking world and is regarded as one of the world's leading academic institutions. Although the exact date of foundation remains unclear, there is evidence of teaching there as far back...
graduate in applied mathematics, explained "...I soon became very familiar with the construction of the Merlin supercharger and carburettor.... Since the supercharger was at the rear of the engine it had come in for pretty severe design treatment, and the air intake duct to the impeller looked very squashed...." Tests conducted by Hooker showed the original intake design was inefficient, limiting the performance of the supercharger. Hooker subsequently designed a new air intake duct with improved flow characteristics which increased maximum power at a higher altitude of over 19,000 feet (5800 m); and also improved the design of both the impeller, and the diffuser which controlled the airflow to it. These modifications led to the development of the single-stage Merlin XX and 45 series.
A significant advance in supercharger design was the incorporation in 1938 of a two-speed drive, designed by the French company Farman, to the impeller of the Merlin X. The later Merlin XX incorporated the two-speed drive as well as several improvements that enabled an increase in the production rate of Merlins. The low-ratio gear, which operated from take-off to an altitude of 10,000 feet (3,050 m), drove the impeller at 21,597 rpm and developed 1,240 horsepower (925 kW) at that height; while the high gear's (25,148 rpm) power rating was 1,175 horsepower (876 kW) at 18,000 feet (5,490 m). These figures were achieved at 2,850 rpm engine speed using +9
pounds per square inchThe pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...
(1.66
atmThe standard atmosphere is an international reference pressure defined as 101,325 Pa and formerly used as unit of pressure . For practical purposes it has been replaced by the bar which is 100,000 Pa...
) boost.
In 1940 Rolls-Royce considered adapting the Merlin to use an exhaust-driven
turbochargerA turbocharger, or turbo, is a gas compressor that is used for forced-induction of an internal combustion engine. A form of supercharger, the purpose of a turbocharger is to increase the density of air entering the engine to create more power...
to increase the power of the Merlin. Although a lower fuel consumption was an advantage, the turbocharger was rejected in favour of a two-stage supercharger. The basic design, first tested in September 1941, used a modified Vulture supercharger for the first stage while a Merlin 46 supercharger was used for the second. A liquid-cooled
intercoolerAn intercooler , or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric cooling...
on top of the supercharger casing was used to prevent the compressed air/fuel mixture from becoming too hot. Fitted with the two-stage two-speed supercharger, the Merlin 60 series gained 300 horsepower (224 kW) at 30,000 feet (9,144 m) over the Merlin 45 series, at which altitude a Spitfire IX was nearly 70 miles per hour (113 km/h) faster than a Spitfire V.
The two-stage Merlin family was extended in 1943 with the Merlin 66 which had its supercharger geared for increased power ratings at low altitudes, and the Merlin 70 series that were designed to deliver increased power at high altitudes.
The development in 1942 of the single-stage supercharger with a smaller "cropped" impeller resulted in the Merlin 45M and 55M, both of which developed greater power at low altitudes. In squadron service the LF.V variant of the Spitfire fitted with these engines became known as the "clipped, clapped and cropped Spitty" to indicate the shortened
wingspanThe wingspan of an airplane or a bird, is the distance from the left wingtip to the right wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent,...
, the less-than-perfect condition of the used
airframeThe term airframe refers to the mechanical structure of an aircraft, and as generally used does not include the propulsion system. Airframe design is a challenging field of engineering, combining aerodynamics, materials technology and manufacturing methods to achieve favorable balances of...
s and the cropped supercharger impeller.
Carburettor developments
The use of
carburettorsA carburetor or carburettor is a device that blends air and fuel for an internal combustion engine. It was invented by Karl Benz before 1885 and patented in 1886...
was calculated to give a higher
specific powerIn engineering, the term specific power can refer to power either per unit of mass, volume or area, although power per unit of volume is more formally known as power density, and power per unit area as surface power density...
output, due to the lower temperature, hence greater density, of the fuel/air mixture compared to injected systems. However, the Merlin's lack of direct
fuel injectionFuel injection is a system for mixing fuel with air in an internal combustion engine. It has become the primary fuel delivery system used in gasoline automotive engines, having almost completely replaced carburetors in the late 1980s....
meant that both
SpitfiresThe Supermarine Spitfire is a British single-seat fighter aircraft used by the Royal Air Force and many other Allied countries through the Second World War. The Spitfire continued to be used into the 1950s both as a front line fighter and in secondary roles...
and
HurricanesThe Hawker Hurricane is a British single-seat fighter aircraft that was designed and predominantly built by Hawker Aircraft Ltd. Some production of the Hurricane was carried out in Canada by the Canada Car and Foundry Co Ltd....
were unable to
pitchFlight dynamics is the science of air and space vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control...
nose down into a steep dive. The contemporary
Bf 109EThe Messerschmitt Bf 109 was a German World War II fighter aircraft designed by Willy Messerschmitt in the early 1930s. It was one of the first true modern fighters of the era, including such features as an all-metal monocoque construction, a closed canopy, and retractable landing gear...
, which had direct fuel injection, could "bunt" into a high-power dive to escape attack, leaving the pursuing aircraft behind because its fuel had been forced out of the carburettor's float chamber by the effects of negative
g-forceThe g-force experienced by an object is its acceleration relative to free-fall. The term g-force is considered a misnomer, as g-force is not a force but an acceleration....
(g). RAF fighter pilots soon learned to "half-roll" their aircraft before diving to pursue their opponents. "
Miss Shilling's orificeThe Miss Shilling orifice was a very simple technical device made to counter engine cut-out in early Spitfire and Hurricane fighter aeroplanes during the Battle of Britain. It was named after its inventor, Beatrice "Tilly" Shilling.-Engine cut out problems:...
", a holed diaphragm fitted across the float chambers, went some way towards curing the fuel starvation in a dive; however, at less than maximum power a "fuel rich" mixture still resulted. Another improvement was made by moving the fuel outlet from the bottom of the
S.U. carburettorSU carburettors were a brand of carburettor usually of the sidedraught type but downdraught variants were used on some pre-war cars. They were widely used in British and Swedish automobiles for much of the twentieth century...
to exactly halfway up the side, which allowed the fuel to flow equally well under negative or positive g.
Further improvements were introduced throughout the Merlin range: 1943 saw the introduction of a
Bendix-StrombergThe Bendix Corporation was an American manufacturing and engineering company which during various times in its 60 year existence made brake systems, aeronautical hydraulics, avionics, radios, televisions and computers, and which licensed its name for use on home washing machines.-History:Bendix was...
pressure carburettorA pressure carburetor is a type of fuel metering system for piston aircraft engines manufactured by the Bendix Corporation starting in the 1940s. It is recognized as an early type of fuel injection and was developed to prevent fuel starvation during inverted flight.-Concept:Most aircraft of the...
that injected fuel at 5
pounds per square inchThe pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...
(0.34
barThe bar is a unit of pressure equal to 100 kilopascals, and rougly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the decibar , centibar , and millibar...
) through a nozzle directly into the supercharger, and was fitted to Merlin 66, 70, 76, 77 and 85 variants. The final development, which was fitted to the 100-series Merlins, was an S.U. injection carburettor that injected fuel into the supercharger using a fuel pump driven as a function of crankshaft speed and engine pressures.
Improved fuels
At the start of the war the engine ran on the then standard 87 octane
aviation spiritAvgas is a high-octane aviation fuel used to power many aircraft and racing cars. Avgas is a portmanteau for aviation gasoline, as distinguished from mogas , which is the everyday gasoline used in cars. Some light aircraft also use automobile fuel instead of avgas.Avgas is used in aircraft that...
and could supply just over 1,000 horsepower (750 kW) from its 27-litre displacement: the maximum boost pressure at which the engine could be run using 87 octane fuel was +6 pounds per square inch (1.45
atmThe standard atmosphere is an international reference pressure defined as 101,325 Pa and formerly used as unit of pressure . For practical purposes it has been replaced by the bar which is 100,000 Pa...
). 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 horsepower (943 kW) at 7,870 feet (2,400 m), 1,285 horsepower (958 kW) at 9,180 feet (2,800 m) and 1,320 horsepower (984 kW) on take-off; while a Merlin X with a two-speed supercharger in high gear generated 1,150 horsepower (857 kW) at 15,400 feet (4,700 m) and 1,160 horsepower (865 kW) at 16,730 feet (5,100 m).
From late-1939, 100 octane fuel became available from the U.S., West Indies, Persia and domestically. Merlin IIs and IIIs were adapted to run on the new fuel, using an increased boost pressure of +12 pounds per square inch (1.85 atm). Small modifications were made to the engines which were now capable of generating 1,310 horsepower (877 kW) at while running at 3,000 revolutions per minute. This increased boost was available for a maximum of five minutes, and if the pilot resorted to emergency boost he had to report this on landing and have it noted in the engine log book. Using +12 pounds per square inch (1.85 atm) of boost was considered a "definite overload condition on the engine" and the engineering officer was subsequently required to examine the engine and reset the throttle gate.
In late-1943 trials were run of a new "100/150" grade fuel, recognised by its bright-green colour and "awful smell". Initial tests were conducted using 6.5
cubic centimetreA cubic centimetre or cubic centimeter is a commonly used unit of volume extending the derived SI-unit cubic metre and corresponds to the volume of a cube measuring 1×1×1 cm...
s of tetraethyl lead (T.E.L.) for every one gallon of 100 octane fuel; but this mixture resulted in a build-up of lead in the combustion chambers, causing excessive fouling of the
spark plugA spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as, aerosol gasoline, Ethanol, and Liquefied petroleum gas by means of an electric spark...
s. Better results were achieved by adding 2.5%
mono methyl anilineAniline, phenylamine or aminobenzene is an organic compound with the formula C
6H
7N. It is the simplest and one of the most important aromatic amines, being used as a precursor to more complex chemicals. Its main application is in the manufacture of polyurethane...
(M.M.A.) to 100 octane fuel. The new fuel allowed the boost rating of the Merlin 66 to be raised to +25 pounds per square inch (2.79 atm).
Starting in March 1944, the Merlin 66-powered Spitfire IXs of two squadrons were cleared to use the new fuel for operation trials, and it was put to good use in the summer of 1944 when it enabled Spitfire L.F. Mk. IXs to intercept
V-1 flying bombThe Fieseler Fi 103, better known as V-1 , colloquially know in Britain as the 'Doodlebug', was an early cruise missile used during World War II. The V-1 was developed at Peenemünde by the German Luftwaffe during the Second World War. Between 13 June 1944 and 29 March 1945, it was fired at...
s coming in at low altitudes, as well as by other fighters flown by the
ADGBThe Air Defence of Great Britain refers to two different components of the RAF depending on the time period in question.-1925 to 1936:...
, but continued problems with
backfiresA Back-fire or backfire is an explosion produced by a running internal combustion engine that occurs in the intake or exhaust system rather than inside the combustion chamber...
were not remedied until August.
In early February 1945, Spitfires of the 2 TAF also began using 100/150 grade fuel. Monty Berger, Senior Intelligence Officer of 126 (RCAF) Spitfire Wing, 2 TAF, noted that there were still problems being experienced with the new fuel, leading to several fatal accidents. Pilots were relieved when the return to 130 grade was authorised by April 1945.
Production
Production of the Rolls-Royce Merlin was driven by the forethought and determination of Ernest Hives, who at times was enraged by the apparent complacency and lack of urgency encountered in his frequent correspondence with
Air MinistryThe Air Ministry was formerly a department of the British Government with the responsibility of managing the affairs of the Royal Air Force, existing from 1918 to 1964...
and local authority officials. Hives was an advocate of shadow factories, and sensing the imminent outbreak of war pressed ahead with plans to produce the Merlin in sufficient numbers for the rapidly expanding Royal Air Force. Despite the importance of uninterrupted production several factories were affected by
industrial actionIndustrial action or job action refers collectively to any measure taken by trade unions or other organised labour meant to reduce productivity in a workplace. Quite often it is used and interpreted, mistakenly, as a euphemism for strike, but the scope is much wider...
.
Derby
The existing Rolls-Royce facilities at
Osmaston, DerbyOsmaston is a suburb of the city of Derby, England. It is situated about 4 km south of the city centre. It was the location of Osmaston Hall the residence of the Wilmots Baronets of Osmaston. It is the location of the main offices of the aeronautical engineering company, Rolls-Royce plc.-Notable...
were not suitable for large-scale engine production although the
floor spaceArea is a quantity expressing the two-dimensional size of a defined part of a surface, typically a region bounded by a closed curve. The term surface area refers to the total area of the exposed surface of a 3-dimensional solid, such as the sum of the areas of the exposed sides of a polyhedron...
had been increased by some 25% between 1935 and 1939; nevertheless, Hives planned to build the first two- or three hundred engines there until engineering teething troubles had been resolved. Having a workforce that consisted mainly of design engineers and highly skilled men, the Derby factory carried out the majority of development work on the Merlin, with flight testing carried out at nearby
RAF HucknallFormerly RAF Hucknall, Hucknall Airfield is located north northwest of Nottingham, Nottinghamshire, England.Hucknall Aerodrome has a CAA Ordinary Licence that allows flights for the public transport of passengers or for flying instruction as authorised by the licensee...
. The original factory closed in March 2008, but
Rolls-Royce plcRolls-Royce plc is a British aircraft engine maker, and the second-largest in the world, behind GE Aviation. The company has related businesses in the defence aerospace, marine and energy markets....
still maintains a large presence in Derby.
Crewe
To meet the increasing demand for Merlin engines, Rolls-Royce started building work on a new factory at
CreweCrewe is a town within the unitary authority area of Cheshire East and the ceremonial county of Cheshire, England. According to the 2001 census the urban area had a population of 67,683...
in May 1938, with engines leaving the factory in 1939. The Crewe factory had convenient road and rail links to their existing facilities at Derby. Production at Crewe was originally planned to use unskilled labour and
sub-contractorsA subcontractor is an individual or in many cases a business that signs a contract to perform part or all of the obligations of another's contract....
with which Hives felt there would be no particular difficulty, but the number of required sub-contracted parts such as crankshafts, camshafts and cylinder liners eventually fell short and the factory was expanded to manufacture these parts "in house".
Initially the local authority promised to build 1,000 new houses to accommodate the workforce by the end of 1938, but by February 1939 it had only awarded a contract for 100. Hives was incensed by this complacency and threatened to move the whole operation, but timely intervention by the Air Ministry improved the situation. In 1940 a
strikeStrike action, often simply called a strike, is a work stoppage caused by the mass refusal of employees to perform work. A strike usually takes place in response to employee grievances. Strikes became important during the industrial revolution, when mass labour became important in factories and mines...
took place when women replaced men on
capstan lathesThe turret lathe is a form of metalworking lathe that is used for repetitive production of duplicate parts, which by the nature of their cutting process are usually interchangeable...
, the workers'
unionA trade union is an organization of workers who have banded together to achieve common goals in key areas, such as working conditions. The trade union, through its leadership, bargains with the employer on behalf of union members and negotiates labor contracts with employers...
insisting that this was a skilled labour job; however, the men returned to work after 10 days. Post-war the factory was used for the production of
BentleyBentley Motors Limited is a British manufacturer of automobiles founded on 18 January 1919 by Walter Owen Bentley . Mr. Bentley had been previously known for his range of rotary aero-engines in World War I, the most famous being the Bentley BR1 as used in later versions of the Sopwith Camel...
motor cars, and in 1998 Volkswagen AG bought both the marque and the factory.
Glasgow
Hives further recommended that a factory be built near
GlasgowGlasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...
to take advantage of the abundant local work force and the supply of steel and forgings from Scottish manufacturers. This
governmentHer Majesty's Government is the government of the United Kingdom. Under the Constitution of the United Kingdom, executive authority notionally lies with the monarch but is exercised in practice by her ministers...
-funded and -operated factory was built at
HillingtonHillington is a residential suburb and an industrial estate on the southwestern edge of the Scottish city of Glasgow.The industrial estate and the residential area are divided by the Glasgow to Paisley railway line...
starting in June 1939 with workers moving into the premises in October, one month after the outbreak of war, the factory becoming fully occupied by September 1940. A housing crisis also occurred at Glasgow where Hives again asked the Air Ministry to step in.
Having 16,000 employees, the factory was one of the largest industrial operations in Scotland, with engines beginning to leave the line in November 1940. By the start of the
Battle of BritainThe Battle of Britain is the name given to the air campaign waged by the German Air Force against the United Kingdom during the summer and autumn of 1940. The objective of the campaign was to gain air superiority over the Royal Air Force , especially Fighter Command...
2,000 Merlins had been produced at Hillington, the final total being 23,675. Worker
absenteeismAbsenteeism is a habitual pattern of absence from a duty or obligation.-Workplace:Frequent absence from the workplace may be indicative of poor morale or of sick building syndrome. However, many employers have implemented absence policies which make no distinction between absences for genuine...
became a problem after some months due to the physical and mental effects of wartime conditions such as the frequent occupation of
air-raid shelterAir-raid shelters, also known as bomb shelters, are structures for the protection of the civil population as well as military personnel against enemy attacks from the air...
s. It was agreed to cut the punishing working hours slightly to 82 hours a week, with one half-Sunday per month awarded as holiday. Record production is reported to have been 100 engines in one day.
Immediately after the war the site repaired and overhauled Merlin and Griffon engines, and continued to manufacture spare parts. Finally, following the production of the
Rolls-Royce AvonThe Rolls-Royce Avon was the first axial flow jet engine designed and produced by Rolls-Royce. Introduced in 1950, it went on to become one of their most successful post-World War II engine designs...
turbojetTurbojets are the oldest kind of general purpose jet engines. Two engineers, Frank Whittle in the United Kingdom and Hans von Ohain in Germany, developed the concept independently into practical engines during the late 1930s, although credit for the first turbojet is given to Whittle who submitted...
and others, the factory was closed in 2005.
Manchester
The
Ford Motor CompanyFord Motor Company Limited was the manufacturing and sales arm of the Ford Motor Company for the United Kingdom and originally also Ireland. The firm both sold and manufactured cars, commercial vehicles, and farm tractors for sale in the United Kingdom and other countries...
was asked to produce Merlins at
Trafford ParkTrafford Park is an area of the Metropolitan Borough of Trafford, in Greater Manchester, England. Located opposite Salford Quays, on the southern side of the Manchester Ship Canal, it is west-southwest of Manchester city centre, and north of Stretford....
,
ManchesterManchester is a city and metropolitan borough of Greater Manchester, England. In 2007, the population of the city was estimated to be 458,100...
, and building work on a new factory was started in May 1940 on a site. Built with two distinct sections to minimise potential bomb damage, it was completed in May 1941 and bombed in the same month. At first, the factory had difficulty in attracting suitable labour, and large numbers of women, youths and untrained men had to be taken on. Despite this, the first Merlin engine came off the production line one month later and it was building the engine at a rate of 200 per week by 1943, at which point the joint factories were producing 18,000 Merlins per year. In his autobiography
Not much of an Engineer, Sir Stanley Hooker states: "... once the great Ford factory at Manchester started production, Merlins came out like shelling peas ...".
Some 17,316 people worked at the Manchester plant, including 7,260 women and two resident doctors and nurses. Merlin production started to run down in August 1945, and finally ceased on 23 March 1946.
Packard V-1650
As the Merlin was considered to be so important to the war effort, negotiations were soon started to establish an alternative production line outside the UK. Rolls-Royce staff visited a number of North American automobile manufacturers in order to select one to build the Merlin in the U.S. or Canada.
Henry FordHenry Ford was the American founder of the Ford Motor Company and father of modern assembly lines used in mass production. His introduction of the Model T automobile revolutionized transportation and American industry. He was a prolific inventor and was awarded 161 U.S. patents...
rescinded an initial offer to build the engine in the U.S. in July 1940, and the Packard Motor Car Company was subsequently selected to take on the
$The United States dollar is the unit of currency of the United States. The U.S. dollar is normally abbreviated as the dollar sign, $, or as USD or US$ to distinguish it from other dollar-denominated currencies and from others that use the $ symbol. It is divided into 100 cents .The U.S...
130,000,000 Merlin order. Agreement was reached in September 1940, and the first Packard-built engine, designated
V-1650-1, ran in August 1941.
By the end of its production run in 1950, almost 150,000 Merlin engines had been built; over 112,000 in Britain and more than 37,000 under license in the U.S.
Variants
This is a summary 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 but the Merlin 131 and 134 engines were "right-hand tractor",
i.e. the propeller rotated to the right when viewed from the rear.
Data from Bridgman (Jane's) unless otherwise noted:
- 1,030 hp (775 kW) at 3,000 rpm at 5,500 ft (1,680 m) using + 6 lb boost (1.45 atm); Merlin III fitted with "universal" propeller shaft able to mount either de Havilland
de havilland Propellers was established in 1935, as a division of the de Havilland Aircraft company when that company acquired a license from the Hamilton Standard company of America for the manufacture of variable pitch propellers...
or RotolDowty Rotol is a British manufacturing company based in Cheltenham manufacturing propellers.-History:The Company was formed as Rotol Airscrews in 1937 by Rolls-Royce and Bristol Engines to take over both company's propeller development, the market being too small to really need more than one...
propellers,
- 1,310 hp (977 kW) at 3,000 rpm at with 100 octane fuel and +12 lb (1.85 atm) boost (Merlin III); both used in Spitfire Mk.I
The British Supermarine Spitfire was the only fighter aircraft of the Second World War to fight in front line service, from the beginnings of the conflict, in September 1939, through to the end in August 1945. Post-war the Spitfire's service career continued into the 1950s...
and Hurricane Mk.IThe Hawker Hurricane is a British single-seat fighter aircraft that was designed and predominantly built by Hawker Aircraft Ltd. Some production of the Hurricane was carried out in Canada by the Canada Car and Foundry Co Ltd....
fighters, the Boulton Paul DefiantThe Boulton Paul Defiant was a British fighter aircraft and bomber interceptor used early in the Second World War. The Defiant was designed and built by Boulton Paul Aircraft as a "turret fighter" and served with the Royal Air Force . Contemporary with the Royal Navy's Blackburn Roc, the concept...
, and Fairey BattleThe Fairey Battle was a British single-engine light bomber built by the Fairey Aviation Company in the late 1930s for the Royal Air Force. The Battle was powered by the same Rolls-Royce Merlin piston engine that gave contemporary British fighters high performance; however, the Battle was weighed...
.
- 1,130 hp (840 kW) at 3,000 rpm at 5,250 ft (1,525 m); used in Halifax Mk.I, Wellington Mk.II
The Vickers Wellington was a British twin-engine, long range medium bomber designed in the mid-1930s at Brooklands in Weybridge, Surrey, by Vickers-Armstrongs' Chief Designer, R. K. Pierson. It was widely used as a night bomber in the early years of the Second World War, before being displaced as a...
, and Whitley Mk.V bombers.
- 1,150 hp (860 kW); fitted with Coffman engine starter
The Coffman engine starter was a starting system used on many piston engines in aircraft and armored vehicles of the 1930s and 1940s. The Coffman system was one of the most common brands; another was the Breeze cartridge system, which was produced under Coffman patents...
; first version to use 70/30% water/glycol coolant rather than 100% glycol. Fitted to Spitfire Mk. II.
- 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
The Bristol Type 156 Beaufighter, often referred to as simply the Beau, was a British long-range heavy fighter modification of the Bristol Aeroplane Company's earlier Beaufort torpedo bomber design...
fighters, Halifax Mk.II and Lancaster Mk.IThe Avro Lancaster was a British four-engined Second World War heavy bomber made initially by Avro for the Royal Air Force . It first saw active service in 1942, and together with the Handley Page Halifax it was one of the main heavy bombers of the RAF, the RCAF and squadrons from other...
bombers.
- 1,645 hp (1,230 kW) at 3,000 rpm at 2,500 ft (760 m); used mainly in Fleet Air Arm
The Fleet Air Arm is the branch of the Royal Navy responsible for the operation of aircraft. The Fleet Air Arm operates the AgustaWestland Merlin, Westland Sea King and Westland Lynx helicopters, as well as the Harrier GR7/GR9...
aircraft; used in Barracuda Mk.IIThe Fairey Barracuda was a British carrier-borne torpedo- and dive bomber used during the Second World War, the first of its type to be fabricated entirely from metal. It was introduced to the Fleet Air Arm as a replacement for the Fairey Swordfish and Fairey Albacore biplanes...
torpedo bomber and Seafire IIcThe Supermarine Seafire was a naval version of the Supermarine Spitfire specially adapted for operation from aircraft carriers. The name Seafire was arrived at by collapsing the longer name Sea Spitfire.-Origins of the Seafire:...
. Also Spitfire P.R Mk XIII.
- 1,515 hp (1,130 kW) at 3,000 rpm at 11,000 ft (3,353 m); used in Spitfire Mk.V, PR.Mk.IV and PR.Mk.VII, Seafire Ib and IIc.
- 1,415 hp (1,055 kW) at 3,000 rpm at 14,000 ft (4,270 m); high-altitude version used in Spitfire H.F Mk VI
The British Supermarine Spitfire was the only fighter aircraft of the Second World War to fight in front line service, from the beginnings of the conflict, in September 1939, through to the end in August 1945. Post-war the Spitfire's service career continued into the 1950s...
. Adapted with a Marshall compressor (often called a "blower") to pressurise the cockpit.
- 1,585 hp (1,182 kW) at 3,000 rpm at 3,800 ft (1,160 m); low-altitude version with supercharger impeller "cropped" to in diameter. Permitted boost was +18 lb (2.3 atm) instead of +16 lb (2.15 atm) on a normal Merlin 50 engine. A "negative-g" carburettor was fitted.
- 1,565 hp (1,170 kW) at 3,000 rpm at 12,250 ft (3,740 m)
- 1,390 hp (1,035 kW) at 3,000 rpm at 23,500 ft (7,170 m); fitted with a new two-speed two-stage supercharger providing increased power at medium to high altitudes; used in Spitfire F. Mk IX, and P.R.Mk XI.
- 1,720 hp (1,283 kW) at 5,750 ft (1,752 m) using +18 lb boost (2.3 atm); low-altitude version of Merlin 61. Fitted with a Bendix-Stromberg anti-g carburettor; used in Spitfire L.F Mk VIII and L.F Mk IX.
- 1,233 hp (920 kW); used in the Westland Welkin
The Westland Welkin was a British twin-engine heavy fighter from the Westland Aircraft Company, designed to fight at extremely high altitudes in the stratosphere; the word welkin meaning "the vault of heaven"...
high-altitude fighter and some later Spitfire and MosquitoThe de Havilland Mosquito was a British combat aircraft that excelled in versatility during the Second World War. Originally conceived as an unarmed fast bomber, the Mosquito adapted to many other roles in during the air war in both the Pacific theatre of Operations and the European theatre,...
variants. Fitted with a two-speed, two-stage supercharger and a Bendix-Stromberg carburettor. The odd-numbered mark drove a blower for pressurisingCabin pressurization is the active pumping of compressed air into an aircraft cabin when flying at altitude to maintain a safe and comfortable environment for crew and passengers in the low outside atmospheric pressure....
the cockpit.
- 2,060 hp (1,536 kW); redesigned "slimline" versions for the de Havilland Hornet
The British de Havilland DH.103 Hornet was a piston engine fighter that further exploited the wooden construction techniques pioneered by de Havilland's classic Mosquito. Entering service at the end of the Second World War, the Hornet equipped postwar RAF Fighter Command day fighter units in the UK...
. Engine modified to decrease frontal area to a minimum and was the first Merlin series to use down-draught induction systems. Coolant pump moved from the bottom of the engine to the starboardStarboard is the nautical term that refers to the right side of a vessel as perceived by a person on board a vessel and facing the bow . The equivalent for the left-hand side is port. The starboard side of a vessel is indicated with a
green navigation light at...
side. Two-speed, two-stage supercharger and S.U. injection carburettor. Maximum boost was 25 lb (2.79 atm). The Merlin 131 had an additional idler gear in the reduction gear casing allowing "reverse" (left-hand tractor) rotation. The Merlin 130 was fitted in the starboard nacelleThe nacelle is a cover housing that holds engines, fuel, or equipment on an aircraft or wind turbine. In some cases—most notably the World War II-era P-38 Lightning airplane—an aircraft's cockpit may also be housed in a nacelle...
, Merlin 131 in the portPort is the nautical term that refers to the left side of a ship, as perceived by a person on board the ship and facing towards the bow . The port side of a vessel is indicated with a red navigation light at night.The term is also used on aircraft, spacecraft, and analogous...
nacelle on production Hornets.
- 2,030 hp (1,514 kW); derated variants of 130/131 used in Sea Hornet
The British de Havilland DH.103 Hornet was a piston engine fighter that further exploited the wooden construction techniques pioneered by de Havilland's classic Mosquito. Entering service at the end of the Second World War, the Hornet equipped postwar RAF Fighter Command day fighter units in the UK...
F. Mk. 20, N.F. Mk. 21 and P.R. Mk. 22. Maximum boost was lowered to +18 lb (2.3 atm).
- The prefix "2" indicates engines built by Packard
Packard was an American luxury automobile marque built by the Packard Motor Car Company of Detroit, Michigan, and later by the Studebaker-Packard Corporation of South Bend, Indiana...
, otherwise as Merlin 66, optimised for low-altitude operation. Fitted to the Spitfire Mk. XVI.
Applications
In chronological order, the first operational aircraft powered by the Merlin to enter service were the Fairey Battle, Hawker Hurricane and Supermarine Spitfire. Although the engine is most closely associated with the Spitfire, the four-engined Avro Lancaster was the most numerous application, followed by the twin-engined de Havilland Mosquito.
Aircraft list
List from Lumsden 2003
- Armstrong Whitworth Whitley
The Armstrong Whitworth A.W.38 Whitley was one of three British twin-engine, front line medium bomber types in service with the Royal Air Force at the outbreak of the Second World War. It took part in the first RAF bombing raid on German territory, and remained an integral part of the early British...
- Avro Athena
The Avro 701 Athena was a British advanced trainer aircraft built by Avro in the late 1940s. It was designed to replace the North American Harvard in the Royal Air Force, but was only brought in small numbers, the competing Boulton Paul Balliol being preferred.-Design and development:The Athena was...
- Avro Lancaster
The Avro Lancaster was a British four-engined Second World War heavy bomber made initially by Avro for the Royal Air Force . It first saw active service in 1942, and together with the Handley Page Halifax it was one of the main heavy bombers of the RAF, the RCAF and squadrons from other...
- Avro Lancastrian
The Avro 691 Lancastrian was a British passenger and mail transport aircraft of the 1940s and 1950s developed from the Avro Lancaster heavy bomber...
- Avro Lincoln
The Avro Type 694 Lincoln was a British four-engined heavy bomber, first flown on 9 June, 1944. It was the last piston-engined bomber in the Royal Air Force; 604 were built....
- Avro Manchester
The Avro 679 Manchester was a British twin-engine heavy bomber developed during the Second World War by the Avro aircraft company in the United Kingdom...
- Avro Tudor
Avro's Type 688 Tudor was a British piston-engined airliner based on their four-engine Lincoln bomber, itself a descendant of the famous Lancaster heavy bomber, and was Britain's first pressurised airliner...
- Avro York
The Avro York was a British transport aircraft that was derived from the Second World War Lancaster heavy bomber, and used in both military and airliner roles between 1943 and 1964.-Design and development:...
- Boulton Paul Balliol
The Boulton Paul Balliol and the related Sea Balliol were monoplane military advanced trainer aircraft built for the United Kingdom's Royal Air Force and the Royal Navy Fleet Air Arm by Boulton Paul Aircraft...
- Boulton Paul Defiant
The Boulton Paul Defiant was a British fighter aircraft and bomber interceptor used early in the Second World War. The Defiant was designed and built by Boulton Paul Aircraft as a "turret fighter" and served with the Royal Air Force . Contemporary with the Royal Navy's Blackburn Roc, the concept...
- Bristol Beaufighter
The Bristol Type 156 Beaufighter, often referred to as simply the Beau, was a British long-range heavy fighter modification of the Bristol Aeroplane Company's earlier Beaufort torpedo bomber design...
- CAC CA-18 Mark 23 Mustang
The North American Aviation P-51 Mustang was a long-range single-seat World War II fighter aircraft. Designed, built and airborne in just 117 days, the Mustang first flew in RAF service as a fighter-bomber and reconnaissance aircraft before conversion to a bomber escort, employed in raids over...
- Canadair North Star
The Canadair North Star was a 1940s Canadian development of the Douglas C-54 / DC-4 aircraft. Instead of radial piston engines found on the Douglas design, Canadair employed Rolls-Royce Merlin engines in order to achieve a 35 mph faster cruising speed. The prototype flew on 15 July 1946 and...
- CASA 2.111
The CASA 2.111 was a medium bomber derived from the Heinkel He 111 and produced in Spain under license by Construcciones Aeronáuticas S.A.. The 2.111 models differed significantly from Heinkel's original design, featuring heavier armament and eventually Rolls Royce Merlin engines.-Designa and...
- Cierva Air Horse
The Cierva W.11 Air Horse was a British helicopter which was the largest helicopter in the world when it first flew in 1948.-Development:The W.11 "Air Horse" heavy lift helicopter was developed by the G& J Weir, Ltd., Aircraft Department, reconstituted in 1943 as the Cierva Autogiro Company, Ltd...
- de Havilland Mosquito
The de Havilland Mosquito was a British combat aircraft that excelled in versatility during the Second World War. Originally conceived as an unarmed fast bomber, the Mosquito adapted to many other roles in during the air war in both the Pacific theatre of Operations and the European theatre,...
- de Havilland Hornet
The British de Havilland DH.103 Hornet was a piston engine fighter that further exploited the wooden construction techniques pioneered by de Havilland's classic Mosquito. Entering service at the end of the Second World War, the Hornet equipped postwar RAF Fighter Command day fighter units in the UK...
- Fairey Barracuda
The Fairey Barracuda was a British carrier-borne torpedo- and dive bomber used during the Second World War, the first of its type to be fabricated entirely from metal. It was introduced to the Fleet Air Arm as a replacement for the Fairey Swordfish and Fairey Albacore biplanes...
- Fairey Battle
The Fairey Battle was a British single-engine light bomber built by the Fairey Aviation Company in the late 1930s for the Royal Air Force. The Battle was powered by the same Rolls-Royce Merlin piston engine that gave contemporary British fighters high performance; however, the Battle was weighed...
- Fairey Fulmar
The Fairey Fulmar was a British carrier-borne fighter aircraft that served with the Fleet Air Arm during the Second World War. A total of 600 were built by Fairey Aviation at their Stockport factory between January 1940 and December 1942...
- Fairey P.4/34
The Fairey P.4/34 was a competitor for an order for a light bomber to serve with the Royal Air Force. Although not produced in that form, it formed the basis for the Fulmar long-range carrier-based fighter for the Fleet Air Arm.-Development:...
- Fiat G.59
- Handley Page Halifax
The Handley Page Halifax was one of the British front-line, four-engine heavy bombers of the Royal Air Force during the Second World War. A contemporary of the famous Avro Lancaster, the Halifax remained in service until the end of the war, performing a variety of duties in addition to bombing...
- Handley Page Halton
- Hawker Hart
The Hawker Hart was a British two-seater biplane light-bomber of the Royal Air Force , which had a prominent role during the RAF's inter-war period. The Hart was designed during the 1920s by Sydney Camm and built by Hawker Aircraft...
- Hawker Henley
The Hawker Henley was a British two-seat target tug derived from the Hawker Hurricane that was operated by the RAF during the Second World War.-Design and development:...
- Hawker Horsley
The Hawker Horsley was a British single engined biplane bomber of the 1920s. It was the last all wooden aircraft built by Hawker Aircraft, and served as a medium day bomber and torpedo bomber with Britain's Royal Air Force between 1926 and 1935, also serving with the Navies of Greece and...
- Hawker Hotspur
The Hawker Hotspur was a Hawker Henley redesigned to take a Boulton-Paul semi-powered four gun turret. It was designed in response to Air Ministry Specification F.9/35, which required a powered turret as the main armament to replace the Hawker Demon....
- Hawker Hurricane and Sea Hurricane
The Hawker Hurricane is a British single-seat fighter aircraft that was designed and predominantly built by Hawker Aircraft Ltd. Some production of the Hurricane was carried out in Canada by the Canada Car and Foundry Co Ltd....
- Hispano Aviación HA-1112
- North American Mustang Mk X
- Miles M.20
The Miles M.20 was a Second World War fighter developed by Miles Aircraft in 1940. Designed and built as a simple and cheap alternative to the Royal Air Force's Spitfires and Hurricanes, its design was overtaken by events.-Design and development:...
- Renard R.38
The Renard R-36 was a Belgian all-metal fighter aircraft designed to replace the Fairey Firefly II within the Belgian Air Force. Designed to improve on the Renard Epervier, which was never adopted by the Belgian government, the prototype R-36 first flew on 5 November 1937...
- Short Sturgeon
The Short Sturgeon was a British aircraft originally designed in the Second World War as a high-performance torpedo bomber. Through shifting priorities postwar, the Sturgeon was redesigned first into a target tug and then later as an anti-submarine aircraft...
- Supermarine Seafire
The Supermarine Seafire was a naval version of the Supermarine Spitfire specially adapted for operation from aircraft carriers. The name Seafire was arrived at by collapsing the longer name Sea Spitfire.-Origins of the Seafire:...
- Supermarine Spitfire
The Supermarine Spitfire is a British single-seat fighter aircraft used by the Royal Air Force and many other Allied countries through the Second World War. The Spitfire continued to be used into the 1950s both as a front line fighter and in secondary roles...
- Vickers F.7/41
The Vickers Type 432 was a British fighter aircraft developed by the Vickers group during the Second World War. It was intended to enable the Royal Air Force to engage the enemy’s high-altitude bomber aircraft...
- Vickers Wellington
The Vickers Wellington was a British twin-engine, long range medium bomber designed in the mid-1930s at Brooklands in Weybridge, Surrey, by Vickers-Armstrongs' Chief Designer, R. K. Pierson. It was widely used as a night bomber in the early years of the Second World War, before being displaced as a...
- Vickers Windsor
The Vickers Windsor was a Second World War British four-engine heavy bomber, designed by Barnes Wallis and R.K. Pierson at Vickers-Armstrongs.-Design and development:...
- Westland Welkin
The Westland Welkin was a British twin-engine heavy fighter from the Westland Aircraft Company, designed to fight at extremely high altitudes in the stratosphere; the word welkin meaning "the vault of heaven"...
Postwar
At the end of World War II, new versions of the Merlin (the 600- and 700-series) were designed and produced for use in commercial airliners such as the
Avro TudorAvro's Type 688 Tudor was a British piston-engined airliner based on their four-engine Lincoln bomber, itself a descendant of the famous Lancaster heavy bomber, and was Britain's first pressurised airliner...
,
military transport aircraftMilitary transport aircraft are typically fixed and rotary wing cargo aircraft which are used to deliver troops, weapons and other military equipment by a variety of methods to any area of military operations around the surface of the planet, usually outside of the commercial flight routes in...
such as the
Avro YorkThe Avro York was a British transport aircraft that was derived from the Second World War Lancaster heavy bomber, and used in both military and airliner roles between 1943 and 1964.-Design and development:...
, and the
Canadair North StarThe Canadair North Star was a 1940s Canadian development of the Douglas C-54 / DC-4 aircraft. Instead of radial piston engines found on the Douglas design, Canadair employed Rolls-Royce Merlin engines in order to achieve a 35 mph faster cruising speed. The prototype flew on 15 July 1946 and...
which performed in both roles. These engines were basically military specification with some minor changes to suit the different operating environment.
A Spanish-built version of the
Messerschmitt Bf 109The Messerschmitt Bf 109 was a German World War II fighter aircraft designed by Willy Messerschmitt in the early 1930s. It was one of the first true modern fighters of the era, including such features as an all-metal monocoque construction, a closed canopy, and retractable landing gear...
G-2, the 1954 Hispano Aviación HA-1112-M1L
Buchon, was built in
Hispano'sHispano Aviacion was a Spanish aircraft factory which began production in 1939, after a section of the Hispano-Suiza factory was isolated into a "Nationalist" area during the Spanish Civil War....
factory in
SevilleSeville is the artistic, cultural, and financial capital of southern Spain. It is the capital of Andalusia and of the province of Seville. It is situated on the plain of the River Guadalquivir, with an average elevation of above sea level. The inhabitants of the city are known as Sevillanos or...
with the Rolls-Royce Merlin 500/45 engine of – 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.
The
CASA 2.111The CASA 2.111 was a medium bomber derived from the Heinkel He 111 and produced in Spain under license by Construcciones Aeronáuticas S.A.. The 2.111 models differed significantly from Heinkel's original design, featuring heavier armament and eventually Rolls Royce Merlin engines.-Designa and...
was another Spanish-built version of a German aircraft, the
Heinkel He 111The Heinkel He 111 was a German aircraft designed by Siegfried and Walter Günter in the early 1930s in violation of the Treaty of Versailles. Often described as a "Wolf in sheep's clothing", it masqueraded as a transport aircraft, but its purpose was to provide the Luftwaffe with a fast medium...
, that was adapted to use the Merlin after the supply of
Junkers Jumo 211The Jumo 211 was an inverted V-12 aircraft engine, Junkers Motoren's primary aircraft engine of World War II. It was the direct competitor to the famous Daimler-Benz DB 601 and closely paralleled its development...
F-2 engines ran out at the end of the war. A similar situation existed with the Fiat G.59 when available stocks of the Italian licence-built version of the
Daimler-Benz DB 605The Daimler-Benz DB 605 is a German aircraft engine, built during World War II. Developed from the DB 601, the DB 605 was used from 1942 to 1945 in the Messerschmitt Bf 109 fighter, the Bf 110 and Me 210C heavy fighters...
engine ran short.
In the United States many
war surplusMilitary surplus are goods, usually matériel, that are sold or otherwise disposed of when no longer needed by the military. Entrepreneurs often buy these goods and resell them at surplus stores. Military surplus rarely includes weapons or munitions, though they are occasionally found in such stores...
engines and airframes were sold relatively cheaply – two of the most popular items were
P-51 MustangThe North American Aviation P-51 Mustang was a long-range single-seat World War II fighter aircraft. Designed, built and airborne in just 117 days, the Mustang first flew in RAF service as a fighter-bomber and reconnaissance aircraft before conversion to a bomber escort, employed in raids over...
s and Packard V-1650 Merlin engines, several of which were "souped up" and modified for air racing in the
Bendix TrophyThe Bendix Trophy is an U.S. aeronautical racing trophy. The transcontinental, point-to-point race, sponsored by industrialist Vincent Bendix founder of Bendix Corporation, began in 1931 as part of the National Air Races. Initial prize money for the winners was $15,000...
, the Cleveland
Air RacesThe National Air Races were a series of pylon and cross-country races that took place from 1920 to 1949. The science of aviation, and the speed and reliability of aircraft and engines grew rapidly during this period; the National Air Races were both a proving ground and showcase for...
and the
Thompson TrophyThe Thompson Trophy race was one of the National Air Races of the heyday of early airplane racing in the 1930's. Established in 1929, the last race was held in 1961. The race was 10 miles long with 50-foot-high pylons marking the turns, and emphasized low altitude flying and maneuverability at high...
.
Alternative applications
A non-supercharged version of the Merlin using a larger proportion of steel and iron components was produced for use in
tankA tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility and tactical offensive and defensive capabilities...
s. This engine, the
Rolls-Royce MeteorThe Rolls-Royce Meteor was a British tank engine of the Second World War.It was developed from the Rolls-Royce Merlin aero-engine by W. A. Robotham and his chassis design and development division at Belper...
, in turn led to the smaller
Rolls-Royce MeteoriteThe Rolls-Royce Meteorite, also known as the Rover Meteorite was a V8 petrol or diesel engine of capacity, and was derived from the Rolls-Royce Meteor. In essence it was two-thirds of a V12 Meteor, and it shared the Meteor's 60° vee angle...
.
In 1938, Rolls-Royce started work on modifying some Merlins which were later to be used in British
MTBsMotor Torpedo Boat was the name given to fast torpedo boats by the Royal Navy, the Royal Canadian Navy and the United States Navy.During World War II the US Navy boats were usually called by their hull classification symbol of "PT" and are covered under PT boat though the class type was still...
,
MGBsMotor Gun Boat was a Royal Navy term for a small military vessel of the Second World War. They were physically similar to the Motor Torpedo Boats but equipped with a mix of guns instead of torpedoes. Their small size and high speed made them difficult targets for E-boats or torpedo bombers, but...
, 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.
Survivors
One of the most successful of the
World War IIWorld War II, or the Second World War , was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis...
era aircraft engines, the Merlin continues to be used in many restored World War II vintage aircraft all over the world. The
Royal Air ForceThe Royal Air Force is the United Kingdom's air force, the oldest independent air force in the world. Formed on 1 April 1918, the RAF has taken a significant role in British military history ever since, playing a large part in World War II and in more recent conflicts.The RAF operates almost 1,109...
Battle of Britain Memorial FlightThe Battle of Britain Memorial Flight is a Royal Air Force flight which provides an aerial display group comprising an Avro Lancaster, a Supermarine Spitfire and a Hawker Hurricane...
is a notable current operator of the Merlin. In England the
Shuttleworth CollectionThe Shuttleworth Collection is an aeronautical and automotive museum located at the Old Warden airfield in Bedfordshire, England. It is one of the most prestigious in the world due to the variety of old and well preserved aircraft.- History :...
owns and operates a Merlin-powered Hawker Sea Hurricane IB and a Supermarine Spitfire VC – the Hurricane can be seen flying at home displays throughout the summer months, while the Spitfire is currently undergoing a major restoration project.
Engines on display
Many aerospace museums possess examples of the Merlin that are on public display, including the:
- Imperial War Museum Duxford
Imperial War Museum Duxford is a branch of the Imperial War Museum near the village of Duxford in Cambridgeshire, United Kingdom, which houses the museum's large exhibits. These include nearly 200 aircraft, military vehicles, artillery and minor naval vessels in seven main exhibitions buildings...
- Royal Air Force Museum Cosford
The Royal Air Force Museum Cosford is a museum dedicated to the history of aviation, and the British Royal Air Force in particular. The museum is a non-departmental public body sponsored by the Department for Culture, Media and Sport and a registered charity...
- Royal Air Force Museum London
- Science Museum (London)
The Science Museum on Exhibition Road, South Kensington, London is part of the National Museum of Science and Industry. The museum is a major London tourist attraction.-Origin:...
- Shuttleworth Collection
The Shuttleworth Collection is an aeronautical and automotive museum located at the Old Warden airfield in Bedfordshire, England. It is one of the most prestigious in the world due to the variety of old and well preserved aircraft.- History :...
Specifications (Merlin 61)
See also
Further reading
- Gunston, Bill. Development of Piston Aero Engines. Cambridge: Patrick Stephens, 2006. ISBN 0-7509-4478-1
- Henshaw, Alex
Alexander Adolphus Dumfries Henshaw MBE was a British air racer in the 1930s and a test pilot for Vickers Armstrong in the Second World War.-Early life:...
. Sigh for a Merlin: Testing the Spitfire. London: Crecy, 1999 (2nd revised edition). ISBN 0-9475-5483-1.
- Jackson, Robert. The Encyclopedia of Military Aircraft Bath, UK: Parragon Books, 2006. ISBN 1-40542-465-6.
- Price, Alfred. Spitfire Mark I/II Aces 1939–41. London: Osprey Aerospace, 1996. ISBN 1-85532-627-2.
External links