Rolls-Royce R engine was invaluable in the subsequent development of the Rolls-Royce Merlin engine and the Spitfire. A de-rated R engine, known as the Griffon, was tested in 1933, but it was not directly related to the production Rolls-Royce Griffon of 1939, of the same exact bore/stroke and resultant displacement figures as the "R" design. Three examples of the R engine are on public display in British museums as of 2014. Rolls-Royce realised that the Napier Lion engine used in the 1927 Supermarine S.5 Schneider Trophy winner had reached the peak of its development, and that for Britain's entrant in the next
Rolls-Royce Hawk of which 76 were built. Rolls-Royce Hawk The Rolls-Royce Hawk was a British aero engine designed by Rolls-Royce in 1915. Derived from one bank of six cylinders of the Rolls-Royce Eagle, it produced 75 horsepower at 1,370 rpm. Power was progressively increased to 91 hp by February 1916, and 105 hp by October 1918. After Rolls-Royce made the prototypes, the Hawk was manufactured under licence by Brazil Straker in Bristol between 1915 and 1918. During this period 204 engines were built, and the Hawk earned a reputation for high reliability. Many engines of this type were used to power the