Rolls-Royce Merlin

Merlin
The Rolls-Royce Merlin
Type	Liquid-cooled V-12 four-stroke piston aero engine
National origin	United Kingdom
Manufacturer	Rolls-Royce Limited
First run	15 October 1933
Major applications	Avro Lancaster de Havilland Mosquito Handley Page Halifax Hawker Hurricane Supermarine Spitfire
Number built	149,659
Variants	Packard V-1650 Merlin
Developed into	Rolls-Royce Meteor

The Rolls-Royce Merlin is a British liquid-cooled V-12 piston aero engine of 27-litre (1,650 cu in) capacity. Rolls-Royce designed the engine and first ran it in 1933 as a private venture. Initially known as the PV-12, it was later called Merlin following the company convention of naming its four-stroke piston aero engines after birds of prey. The engine benefitted from the racing experiences of precursor engines in the 1930s.

After several modifications, the first production variants of the PV-12 were completed in 1936. The first operational aircraft to enter service using the Merlin were the Fairey Battle, Hawker Hurricane and Supermarine Spitfire. The Merlin remains most closely associated with the Spitfire and Hurricane, although the majority of the production run was for the four-engined Avro Lancaster heavy bomber.

The Merlin continued to benefit from a series of rapidly-applied developments, derived from experiences in use since 1936. These markedly improved the engine's performance and durability. Starting at 1,000 horsepower (750 kW) for the first production models, most late war versions produced just under 1,800 horsepower (1,300 kW), and the very latest version as used in the de Havilland Hornet over 2,000 horsepower (1,500 kW).

One of the most successful aircraft engines of the World War II era, some 50 versions of the Merlin were built by Rolls-Royce in Derby, Crewe and Glasgow, as well as by Ford of Britain at their Trafford Park factory, near Manchester. A de-rated version was also the basis of the Rolls-Royce/Rover Meteor tank engine. Post-war, the Merlin was largely superseded by the Rolls-Royce Griffon for military use, with most Merlin variants being designed and built for airliners and military transport aircraft.

The Packard V-1650 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. Merlin engines remain in Royal Air Force service today with the Battle of Britain Memorial Flight, and power many restored aircraft in private ownership worldwide.