The first Rolls-Royce aero engine to be mass-produced.
Work on aero engines at the Rolls-Royce factory began in 1914, following an order by the British Admiralty for a 200 hp aero engine. The first type to enter series production in 1915 was the Eagle I. It was a 12-cylinder water-cooled engine producing 240 hp, fed by 2 Claudel carburettors, with a reduction gear allowing 1024 rpm at the propeller.
Continuous improvements to this design allowed successive versions (II, III, IV, V, VI, VII, VIII) to enter production, offering greater power and reliability. The last military version was the Eagle VIII, producing 360 hp at 1800 rpm, equipped with 4 carburettors, each feeding 3 cylinders.
After the war, work began on a high-power engine intended for civil aviation. The result was the Eagle IX, equipped with 2 Claudel-Hobson carburettors and four magnetos. The design emphasised operational safety. To reduce the risk of fire, the two carburettors were placed on either side of the oil sump, away from hot engine components. Stable operation was ensured by as many as 4 magnetos. Production at the Derby factory lasted from 1922 to 1928. A total of 373 engines were produced. It was used in aircraft including the Handley-Page 0/400 and Dornier Do J II Wal.
| Configuration | 12-cylinder V-type |
| Cooling | water |
| Compression ratio | 5.22 |
| Propeller reduction | 0.6 |
| Displacement | 20.3 l |
| Weight | 438 kg |
| Maximum power | 390 hp at 2000 rpm |
| Rated power | 360 hp at 1800 rpm |
