The WWII race to the best engines. The story of how the Rolls Royce Merlin engine equipped the extraordinary P-51 Mustang and the evolution of the Focke-Wulf Fw 190's engine, all the way to the story of the first functioning centrifugal turbojet in April 1937, Frank Whittle's creation.
The Rolls-Royce Merlin is a British liquid-cooled V-12 piston aero engine of 27-litres (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.
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. A series of rapidly-applied developments, brought about by wartime needs, 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 Post-war, the Merlin was largely superseded by the Rolls-Royce Griffon for military use, with most Merlin variants being designed and built for airliners and military transport aircraft.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.
During his spare time on the squadron and at CFS Frank Whittle gave much thought to the application of the internal combustion turbine as a means to drive the aeroplane propeller. As others had before him, he soon discovered that the levels of component efficiency in any suitable gas turbine engine would be dauntingly difficult to achieve. And then, as he would say in later life, “the penny dropped” and he perceived the possibility of using the high velocity/high mass flow exhaust to obtain propulsion by reaction. In doing so, he was dismissing the altitude limitations of the internal combustion engine and the speed limitations of the propeller. A practical form of turbojet was borne. An entirely new horizon for aeronautics was about to materialize.
Whittle worked on the business of the design of an engine with a potential thrust sufficient to propel a small airplane at very high speeds and at very high altitudes. He settled on an arrangement that incorporated a two-stage centrifugal compressor and a two-stage (Curtis) turbine.
He showed his idea to the station commandant, Group Captain Baldwin, who, perceiving strategic importance and a need for secrecy, sent him to be interviewed by the engine division at the Air Ministry. They in turn, arranged for him to meet Dr A A Griffith at the Royal Aircraft Establishment (RAE). Griffith had started seriously considering gas turbines for propeller-driven aircraft as early as 1926. In a meeting of considerable consequence, Griffith rejected Whittle’s proposals and convinced the Ministry that the idea did not warrant any further attention. Unfortunately, Griffith had his own agenda. He would have known full well that he would be instructed to work on the turbojet should he admit any serious practicality. Despite this setback, Whittle went ahead and applied for a patent – granted in January 1930. However, as the President of the Air Council declared that there was no need for secrecy, it was published in 1931. Copies were purchased by, amongst others, the German Trade Commission in London. It was then circulated by technical journals to the German Air Ministry (RLM), aero-engine and airframe manufacturers, and, most significantly, to the research establishments. Unfortunately, the patent lapsed in January 1934 because Whittle could not afford the extension fee and the Air Ministry declined to help. In the meantime, the Germans added the turbojet to the list of alternative forms of aero-propulsion under scrutiny in their country: Rocket, pulse-jet, turbo-prop, ducted fan jet, and ramjet.
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