Packard Merlin
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The Packard V-1650 Merlin is a version of the
Rolls-Royce Merlin The Rolls-Royce Merlin is a British Coolant#Liquids, liquid-cooled V12 engine, V-12 Reciprocating engine, piston aero engine of 27-litre (1,650 cu in) Engine displacement, capacity. Rolls-Royce Limited, Rolls-Royce designed the engine an ...
aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbin ...
, produced under
license A license (American English) or licence (Commonwealth English) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit). A license is granted by a party (licensor) to another part ...
in the United States by the
Packard Motor Car Company Packard (formerly the Packard Motor Car Company) was an American luxury automobile company located in Detroit, Michigan. The first Packard automobiles were produced in 1899, and the last Packards were built in South Bend, Indiana, in 1958. One ...
.Gunston 1995, p. 144. The engine was licensed to expand production of the Rolls-Royce Merlin for British use. The engine also filled a gap in the U.S. at a time when similarly powered American-made engines were not available. The first V-1650s, with a one-stage
supercharger In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement (engine), displacement. It is a form of forced induction that is mechanically ...
, equivalent to the Merlin XX, were used in the P-40F Kittyhawk fighter and in Canadian-built
Hawker Hurricanes The Hawker Hurricane is a British single-seat fighter aircraft of the 1930s–40s which was designed and predominantly built by Hawker Aircraft Ltd. for service with the Royal Air Force (RAF). It was overshadowed in the public consciousness by ...
. Later versions based on the Merlin 60 series included a more advanced two-stage supercharger for improved performance at high altitudes. It found its most notable application in the
North American P-51 Mustang The North American Aviation P-51 Mustang is an American long-range, single-seat fighter and fighter-bomber used during World War II and the Korean War, among other conflicts. The Mustang was designed in 1940 by a team headed by James H. Kin ...
fighter, improving the aircraft's performance so it could escort Allied heavy bombers from Britain to Germany and back.


Design and development

At the outbreak of World War Two, the British aviation industry expanded greatly. There was great need for the
Rolls-Royce Merlin The Rolls-Royce Merlin is a British Coolant#Liquids, liquid-cooled V12 engine, V-12 Reciprocating engine, piston aero engine of 27-litre (1,650 cu in) Engine displacement, capacity. Rolls-Royce Limited, Rolls-Royce designed the engine an ...
engine with shadow factories being established in Crewe, Manchester, and Glasgow. This was not enough to meet increasing demand with the British government looking to expand production using U.S. manufacturers. An agreement was reached between Rolls-Royce and the
Packard Motor Car Company Packard (formerly the Packard Motor Car Company) was an American luxury automobile company located in Detroit, Michigan. The first Packard automobiles were produced in 1899, and the last Packards were built in South Bend, Indiana, in 1958. One ...
in September 1940 to manufacture the Merlin under license, with a $130,000,000 order being placed. The first Packard-built engine, designated V-1650-1, ran in August 1941."Business: Ford's Rolls-Royces."
''Time Magazine'', 8 July 1940. Retrieved: 26 August 2009.
The first American model was a version of the Mark XX, designated the V-1650-1 by the American military and the Packard Merlin 28 by the British. This engine used a single-stage, two-speed supercharger, the gear changing mechanism of which originally came from a French Farman patent license. The Merlin 28 was used for the
Avro Lancaster The Avro Lancaster, commonly known as the Lancaster Bomber, is a British World War II, Second World War heavy bomber. It was designed and manufactured by Avro as a contemporary of the Handley Page Halifax, both bombers having been developed to ...
bomber. The USAAF V-1650-1 version of this engine was used in the Curtiss P-40Fs. The initial Packard modifications to this engine changed the main
crankshaft A crankshaft is a mechanical component used in a reciprocating engine, piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating Shaft (mechanical engineering), shaft containing one or more crankpins, ...
bearings from a copper-lead alloy to a silver-lead combination and featured
indium Indium is a chemical element; it has Symbol (chemistry), symbol In and atomic number 49. It is a silvery-white post-transition metal and one of the softest elements. Chemically, indium is similar to gallium and thallium, and its properties are la ...
plating. This had been developed by General Motors' Pontiac Division to prevent corrosion, which was possible with lubricating oils that were used at that time. The bearing coating also improved the break-in (running-in) and load-carrying abilities of the surface. In answer to a request from the British
Air Ministry The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force and civil aviation that existed from 1918 to 1964. It was under the political authority of the ...
for a high-altitude Merlin for the pressurised Wellington VI high-altitude bomber, a Rolls-Royce team under the direction of
Stanley Hooker Sir Stanley George Hooker, CBE, FRS, DPhil, BSc, FRAeS, MIMechE, FAAAS (30 September 1907 – 24 May 1984), was an English mathematician and jet engine engineer. He was employed first at Rolls-Royce where he worked on the earliest design ...
developed a Merlin with two-stage supercharging, which became the Merlin 60-series. The first 60-series engine ran in March 1941, and was first flown in July the same year. When only 63 examples of the otherwise-cancelled Wellington VI were produced, these engines were instead introduced on the Spitfire IX as the Merlin 61. This model was later produced by Packard as the V-1650-3 and became known as the "high altitude" Merlin destined for the P-51, the first two-stage Merlin-Mustang conversion flying with a Merlin 65 as the
Mustang X The North American Mustang Mk.X, also known as the "Rolls-Royce Mustang" or Mustang X, was an experimental variant of the North American P-51 Mustang, North American Mustang I, (factory designation Model NA-73) where the Allison engine was rep ...
in October 1942, the production V-1650-3 engined P-51B (Mustang III) entering service in 1943. The two-speed, two-stage supercharger section of the two-stage Merlins and V-1650-3 featured two separate impellers on the same shaft that were normally driven through a gear train at a ratio of 6.391:1. A hydraulic gear change arrangement of oil-operated clutches could be engaged by an electric solenoid to increase this ratio to 8.095:1 in high speed blower position. The high speed gear ratio of the impellers was not as high as the ratio used in the
Allison Allison may refer to: People * Allison (given name) * Allison (surname) (includes a list of people with this name) * Eugene Allison Smith (1922-1980), American politician and farmer * Allison family, a family of RMS Titanic passengers Compan ...
, but impeller speed is not the only factor that determines engine performance, which is also a function of the size and pitch of the impeller blades. The gear-driven supercharger is a parasitic accessory; therefore, impeller gearing and blade profiles are carefully designed for maximum power at altitude without compromise of available power at the critical take off stage of flight. The double staging of the compressed fuel/air mixture provided the boost pressure through a diffuser to the intake manifolds that increased the
critical altitude In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement. It is a form of forced induction that is mechanically powered (usually by a b ...
of the power plant. The ability of the supercharger to maintain a sea level pressure in the induction system to the cylinders allowed the Packard Merlin to develop more than above . The two-stage impeller created extreme heating of the fuel/air mixture during the compression process, and, to prevent detonation of the compressed charge, it was necessary to cool the mixture prior to entry into the cylinders. The cooling was accomplished in an
intercooler An intercooler is a heat exchanger used to cool a gas after compression. Often found in turbocharged engines, intercoolers are also used in air compressors, air conditioners, refrigeration and gas turbines. Internal combustion engines Mo ...
passage cast into the wheel case housing between the first and second-stage impellers and an additional cooling fin and tube core placed between the outlet of the blower and the induction manifold to the cylinders.
Ethylene glycol Ethylene glycol ( IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes: as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odo ...
coolant was circulated by a pump through these to carry off the excess heat generated by the impellers. Without the intercooler the temperature increase in the charge could be as high as 205 °C (401 °F). The glycol mixture used for cooling was independent of the main engine cooling system and used a centrifugal pump driven by the engine to circulate the coolant through an aircraft radiator system at a maximum rate of 36 U.S. gallons (136 litres, 30 Imperial gallons) per minute, depending on engine rpm. This combined system reduced the charge temperature to suitable levels. Throttle valves in the updraft carburettor throat were controlled by an automatic boost control through the throttle linkage to maintain the selected manifold pressure with changes in altitude. The valves were only partially open during ground and low-level operation to prevent overboosting of the engine. As air density decreases with increased altitude, the throttle valves were progressively opened in response to the reducing atmospheric pressure. This system provided full power within engine boost limitations up to the critical altitude of .


Measurement of boost pressure

The British measured boost pressure as lbf/in2 (psi). The normal atmospheric pressure at sea level is 14.7 psi, so a reading of +6 means that the air/fuel mix is being compressed by a supercharger blower to 20.7 psi before entering the engine; +25 means that the air/fuel mix is now being compressed to 39.7 psi. The Americans measured their boost ratings using
inches of mercury Inch of mercury (inHg, ″Hg, or in) is a non- SI unit of measurement for pressure. It is used for barometric pressure in weather reports, refrigeration and aviation in the United States. It is the pressure exerted by a column of mercury in ...
(inHg). One pound-force per square inch equals or , and a standard atmosphere is 101.325 kPa =29.92 inHg =14.70 lbf/in2. In early Merlin engines the maximum manifold (boost) pressure was +12 on 100 octane fuel. This was increased in later models.


Postwar use

In the United States many war surplus engines and airframes were sold relatively cheaply – two of the most popular items were
North American P-51 Mustang The North American Aviation P-51 Mustang is an American long-range, single-seat fighter and fighter-bomber used during World War II and the Korean War, among other conflicts. The Mustang was designed in 1940 by a team headed by James H. Kin ...
s and Packard V-1650 Merlin engines, several of which were "souped up" and modified for air racing in the
Bendix Trophy The Bendix Trophy is a 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 f ...
, the Cleveland
Air Races An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere ...
, and the
Thompson Trophy The Thompson Trophy race was one of the National Air Races of the heyday of early airplane racing in the 1930s. Established in 1929, the last race was held in 1961. The race was long with pylons marking the turns, and emphasized low altitude fly ...
. Many of these engines remain heavily used to this day in
Drag Racing Drag racing is a type of motor racing in which automobiles or motorcycles compete, usually two at a time, to be first to cross a set finish line. The race follows a short, straight course from a standing start over a measured distance, mos ...
,
Hydroplane racing Hydroplane racing (also known as hydro racing) is a sport involving racing hydroplanes on lakes, rivers, and bays. It is a popular spectator sport in several countries. Racing circuits International professional outboard hydroplane racing The ...
, and
Land Speed Racing Land speed racing is a form of motorsport. Land speed racing is best known for the efforts to break the absolute land speed record, but it is not limited to specialist vehicles. A record is defined as the speed over a course of fixed length, av ...
at places like the
Bonneville Salt Flats The Bonneville Salt Flats are a densely packed salt pan in Tooele County in northwestern Utah, United States. A remnant of the Pleistocene Lake Bonneville, it is the largest of many salt flats west of the Great Salt Lake. It is public land ma ...
. The Mynarski Lancaster flown by the Canadian Warplane Heritage Museum in Hamilton, Ontario, Canada, one of only two Lancasters flying in the world, uses four Packard Merlin engines. Work continues on increasing the power output of the Merlin for the Unlimited Class racers at the
Reno Air Races The Reno Air Races, or Roswell Air Races, officially known as the National Championship Air Races, are a multi-day event tailored to the aviation community that took place each September at the Reno Stead Airport a few miles north of Reno, ...
. Innovations, such as the use of
Allison V-1710 The Allison V-1710 aircraft engine designed and produced by the Allison Engine Company was the most common United States, US-developed V12 engine, V-12 Internal combustion engine cooling, liquid-cooled engine in service during World War II. Ve ...
connecting rods and the replacement of the intercooler with ADI (Anti-Detonation Injection) (50% Distilled Water and 50%
Methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...
), nearly identical in chemical composition to the Luftwaffe's wartime
MW 50 MW 50 (Methanol-''Wasser'' 50) was a 50-50 mixture of methanol and water (German: ''Wasser'') that was often sprayed into the supercharger of World War II aircraft engines primarily for its anti-detonation effect, allowing the use of increased bo ...
system, and similar to the water injection system used on Pratt & Whitney engines during World War II, have allowed great increases in power output. Many of the fastest Unlimited racers increase Merlin manifold pressures as high as 145 inHg (56.6 psi, 4.8 atm) to obtain up to 2,835 kW (3,800 horsepower), achieving Mustang speeds up to 490 mph."Masters of the V-12."
''airspacemag.com.'' Retrieved: 25 September 2011.


Variants

* V-1650-1: ; Based on Merlin 28, used in
P-40 Kittyhawk The Curtiss P-40 Warhawk is an American single-engined, single-seat, all-metal fighter-bomber that first flew in 1938. The P-40 design was a modification of the previous Curtiss P-36 Hawk which reduced development time and enabled a rapid entry ...
and Curtiss XP-60 fighters * V-1650-3: ; Based on Merlin 63. * V-1650-5: ; Experimental. * V-1650-7: ; Similar to Merlin 66, primary powerplant of the P-51D Mustang. * V-1650-9: ; Based on Merlin 100-series, 2,218 hp WEP with Water methanol injection. * V-1650-9A: ; as 9 with non-water injection for the P-51M * V-1650-11: ; Modified fuel system. * V-1650-21: ; Opposite rotation for
P-82 Twin Mustang The North American F-82 Twin Mustang is an American long-range escort fighter aircraft, fighter. Based on the North American P-51 Mustang, the F-82 was designed as an escort for the Boeing B-29 Superfortress in World War II, but the war ended ...
* V-1650-23: * V-1650-25:


Applications

*
Avro Lancaster The Avro Lancaster, commonly known as the Lancaster Bomber, is a British World War II, Second World War heavy bomber. It was designed and manufactured by Avro as a contemporary of the Handley Page Halifax, both bombers having been developed to ...
B.III/B.X * Bell XP-63 Kingcobra * Curtiss P-40F/L/Kittyhawk Mk.II *
Curtiss P-60 The Curtiss P-60 was a 1940s American single-engine single-seat, low-wing monoplane fighter aircraft developed by the Curtiss-Wright company as a successor to its Curtiss P-40, P-40. It went through a lengthy series of prototype versions, eventua ...
*
de Havilland Mosquito The de Havilland DH.98 Mosquito is a British twin-engined, multirole combat aircraft, introduced during the World War II, Second World War. Unusual in that its airframe was constructed mostly of wood, it was nicknamed the "Wooden Wonder", or " ...
B.VII/B.25 *
Hawker Hurricane The Hawker Hurricane is a British single-seat fighter aircraft of the 1930s–40s which was designed and predominantly built by Hawker Aircraft Ltd. for service with the Royal Air Force (RAF). It was overshadowed in the public consciousness by ...
Mk.X, XI, XII *
North American P-51 Mustang The North American Aviation P-51 Mustang is an American long-range, single-seat fighter and fighter-bomber used during World War II and the Korean War, among other conflicts. The Mustang was designed in 1940 by a team headed by James H. Kin ...
*
North American F-82 Twin Mustang The North American F-82 Twin Mustang is an American long-range escort fighter aircraft, fighter. Based on the North American P-51 Mustang, the F-82 was designed as an escort for the Boeing B-29 Superfortress in World War II, but the war ended ...
*
Supermarine Spitfire The Supermarine Spitfire is a British single-seat fighter aircraft that was used by the Royal Air Force and other Allies of World War II, Allied countries before, during, and after World War II. It was the only British fighter produced conti ...
Mk.XVI


Specifications (V-1650)


See also


References


Notes


Bibliography

* Bridgman, L. (ed.) ''Jane's fighting aircraft of World War II.'' London: Crescent, 1998. . * Fozard, John W (editor).''Sydney Camm and the Hurricane: Perspectives on the Master Fighter Designer and his Finest Achievement''. Shrewsbury, Shropshire, UK: Airlife, 1991. . * Gunston, Bill. ''World Encyclopaedia of Aero Engines (3rd edition)''. Sparkford, Somerset, UK: Patrick Stephens Limited, 1995. . * Harvey-Bailey, Alec. ''The Merlin in Perspective: The Combat Years.'' Derby, England: Rolls-Royce Heritage Trust, 1983. . * Harvey-Bailey, Alec and Piggott, Dave. ''The Merlin 100 Series - The Ultimate Military Development.'' Derby, England: Rolls-Royce Heritage Trust, 1993. . * Hooker, Stanley ''Not Much of an Engineer.'' London: Airlife, 1984. * Lovesey, AC ''Development of the Rolls-Royce Merlin from 1939 to 1945.'' Aircraft Engineering, July 1946, pp. 218–226. * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. . * Rubbra, AA. ''Rolls-Royce Piston Aero Engines: A Designer Remembers.'' Derby, England: Rolls-Royce Heritage Trust, 1990. .


External links


The Mustang – the longest-ranged single-engined fighter in the world
a 1944 ''Flight'' advertisement
Packard V-1650 Merlin 12-Cylinder V Reports Collection 1941–1945 at the Smithsonian Air and Space Archives
{{US military piston aeroengines 1940s aircraft piston engines V-1650 V12 aircraft engines