The Rolls-Royce Eagle was the company's first aircraft engine. Rolls-Royce Limited developed the liquid-cooled V12 during the opening years of the First World War, and the engine first ran in February 1915.
The project began after British military authorities asked Rolls-Royce to develop an aero engine. Although the original request called for an air-cooled design, Rolls-Royce insisted on water cooling, drawing on its experience with powerful motor-car engines. The resulting Eagle produced roughly 225 horsepower in its earliest form and was progressively improved through several variants.
The engine first flew in a Handley Page O/100 bomber in December 1915. It went on to power aircraft including the Handley Page Type O, Airco D.H.4 and Vickers Vimy. Two Eagle engines famously powered John Alcock and Arthur Whitten Brown's nonstop transatlantic flight in 1919.
The Eagle should not be confused with later Rolls-Royce engines such as the Falcon and Merlin. The Falcon was developed from the Eagle, while the Merlin became one of the company's best-known later piston engines.