The most famous piston engine by Rolls-Royce, the powerplant of the Hurricane, Spitfire, Lancaster and Mustang.
A V-type engine with a two-speed, single-stage supercharger and reduction gear. In accordance with Rolls-Royce practice, the engine was named after a bird of prey (the Merlin is a small falcon). Various variants of the Merlin engine powered the Hawker Hurricane, Supermarine Spitfire, Fairey Battle, Fairey Barracuda, De Havilland Mosquito, Avro Lancaster, Handley Page Halifax and many other aircraft.
A total of 168,040 Merlin engines of all versions were produced, of which 28,021 were the Mk XX version. Variants produced under licence at the Packard factory in the USA were used in the Curtiss P-40 Kittyhawk, North American P-51 Mustang and Supermarine Spitfire Mk XVI fighter aircraft. The Merlin Mk XX version was used in the Avro Lancaster Mk I, III, VII, Boulton Paul Defiant Mk II and Bristol Beaufighter Mk II.
| Configuration | 12-cylinder V-type |
| Cooling | liquid (ethylene glycol) |
| Compression ratio | 6.0 |
| Propeller reduction | 0.69 |
| Displacement | 27 l |
| Weight | 660 kg |
| Maximum power | 1390 hp at 3000 rpm at sea level |
| Rated power | 1300 hp at 3000 rpm at 2900 m altitude |
