Other types of engine produced at the time included the Spanish Hispano-Suiza, a design well ahead of its time with eight steel cylinders arranged in a V and screwed into an aluminum block. In the later years of the war this engine yielded, in successive versions, 150, 220 and 300 hp.
The Rolls-Royce Eagle, a V12 engine with a broadly similar layout adapted from an original Mercedes design, produced 360 hp in its Mark 8 version. This was the engine of the Vickers Vimy that carried Britons Alcock and Brown across the Atlantic in 1919.
Both the Rolls and Hispano engines had conventional water cooling. This often gave trouble, since vibration and the shock of landing caused the plumbing to break. It was to overcome this problem that a third type of engine was introduced; the air cooled radial engine, in which static cylinders were arranged in a circle and cooled by the backwash of the propeller.
This was not a completely new idea, since the water cooled Manly-Balzer engine of 1902, fitted to the unsuccessful Langley Aerodrome, had also been a radial. The air cooled Anzani engine that powered Bleriot’s cross-Channel flight of 1909 was also a kind of half-radial, with three cylinders set in a fan shape. The first of the new generation of radials was the 14-cylinder Jaguar engine made by the RAF factory at Farnborough in England in 1918.
Proper cooling is one of the most critical points of aero engine design. Aero engines have always produced far more power for their size than automobile engines of the same date, and have consequently run at much higher temperatures.
These problems led to great rivalry between the designers of air and water cooled engines.