page_title: Rolls-Royce Eagle
section_title: Design and development
hierarchical_section_title: Rolls-Royce Eagle / Design and development
caption_attribution_description: English: Rolls-Royce Eagle engines at Derby in 1919 Español: Motores Rolls-Royce Eagle fabricados en Derby en 1919
context_page_description: The Rolls-Royce Eagle was the first aircraft engine to be developed by Rolls-Royce Limited. Introduced in 1915 to meet British military requirements during World War I, it was used to power the Handley Page Type O bombers and a number of other military aircraft.
  The Eagle was the first engine to make a non-stop trans-Atlantic crossing by aeroplane when two Eagles powered the converted Vickers Vimy bomber on the Transatlantic flight of Alcock and Brown in June 1919.
context_section_description: Development of the new 20 litre engine was led by Henry Royce from his home in Kent.  Based initially on the 7.4 litre 40/50 Rolls-Royce Silver Ghost engine, and drawing also on the design of a 7.2 litre Daimler DF80 aero engine used in a 1913 Grand Prix Mercedes that had been acquired, the power was increased by doubling the number of cylinders to twelve and increasing their stroke to 6.5 inches (170 mm), although their bore remained at 4.5 inches (110 mm) of the 40/50.  The engine was also run faster, and an epicyclic reduction gear was designed to keep the propeller speed below 1,100 rpm.  To reduce inertia and improve performance the valvetrain design was changed from sidevalves to a SOHC design, closely following the original "side-slot" rocker arm design philosophy used on the contemporary German Mercedes D.I, Mercedes D.II and Mercedes D.III straight-six aviation powerplants.
  On 3 January 1915 the Admiralty ordered twenty-five of the new engines.  The Eagle first ran on a test bed at Rolls-Royce's Derby works in February 1915, producing 225 hp (168 kW) at 1,600 rpm.  This was quickly increased to 1,800, then in August 1915 to 2,000 rpm where it produced 300 hp (220 kW). After further testing, it was decided to approve the engine for production at 1,800 rpm and 225 hp (168 kW); 1,900 rpm was allowed for short periods. The engine first flew on a Handley Page O/100 bomber in December 1915, the first flight of a Rolls-Royce aero engine.
  The Eagle was developed further during 1916 and 1917, with power being progressively increased from 225 hp (168 kW) to 266 hp (198 kW), followed by 284 hp (212 kW), and then 322 hp (240 kW), and finally 360 hp (270 kW) by February 1918 by which time eight Eagle variants had been produced.  Throughout World War I Rolls-Royce struggled to build Eagles in the quantities required by the War Office, but the company resisted pressure to license other manufacturers to produce it, fearing that the engine's much admired quality would risk being compromised.
  After the War, a Mark IX version of the Eagle was developed for civilian use. Production continued until 1928, and in total 4,681 Eagle engines were built.
  Time between overhaul (TBO) for later Eagles was around 100-180 hours.
caption: Rolls-Royce Eagle engines at Derby in 1919
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