The Rolls-Royce Eagle was the first

aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years ma ...

to be developed by

Rolls-Royce Limited Rolls-Royce was a British luxury car and later an aero-engine manufacturing business established in 1904 in Manchester by the partnership of Charles Rolls and Henry Royce. Building on Royce's good reputation established with his cranes, they ...

. Introduced in 1915 to meet British military requirements during

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...

, it was used to power the

Handley Page Type O The Handley Page Type O was a biplane bomber used by Britain during the First World War. When built, the Type O was the largest aircraft that had been built in the UK and one of the largest in the world. There were two main variants, the Handl ...

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.

Background

At the outbreak of World War I in August 1914, the Royal Aircraft Factory asked Rolls-Royce to develop a new air-cooled engine. Despite initial reluctance they agreed on condition that it be cooled by water rather than air, as this was the company's area of expertise.

Design and development

Development of the new 20 litre engine was led by

Henry Royce Sir Frederick Henry Royce, 1st Baronet, (27 March 1863 – 22 April 1933) was an English engineer famous for his designs of car and aeroplane engines with a reputation for reliability and longevity. With Charles Rolls (1877–1910) and Claude ...

from his home in

Kent Kent is a county in South East England and one of the home counties. It borders Greater London to the north-west, Surrey to the west and East Sussex to the south-west, and Essex to the north across the estuary of the River Thames; it faces ...

. 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 , although their bore remained at 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 An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion cha ...

design, closely following the original "side-slot" rocker arm design philosophy used on the contemporary German

Mercedes D.I The Mercedes D.I (also known as the Type E6F) was a six-cylinder, water-cooled, SOHC valvetrain inline engine developed in Germany for use in aircraft in 1913. Developing 75 kW (100 hp), it powered many German military aircraft during t ...

, Mercedes D.II and Mercedes D.III straight-six aviation powerplants. On 3 January 1915 the

Admiralty Admiralty most often refers to: *Admiralty, Hong Kong *Admiralty (United Kingdom), military department in command of the Royal Navy from 1707 to 1964 *The rank of admiral *Admiralty law Admiralty can also refer to: Buildings * Admiralty, Traf ...

ordered twenty-five of the new engines. The Eagle first ran on a test bed at Rolls-Royce's

Derby Derby ( ) is a city and unitary authority area in Derbyshire, England. It lies on the banks of the River Derwent in the south of Derbyshire, which is in the East Midlands Region. It was traditionally the county town of Derbyshire. Derby g ...

works in February 1915, producing at 1,600 rpm. This was quickly increased to 1,800, then in August 1915 to 2,000 rpm where it produced . After further testing, it was decided to approve the engine for production at 1,800 rpm and ; 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 to , followed by , and then , and finally 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 The War Office was a department of the British Government responsible for the administration of the British Army between 1857 and 1964, when its functions were transferred to the new Ministry of Defence (MoD). This article contains text from ...

, 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 Time between overhauls (abbreviated as TBO or TBOH) is the manufacturer's recommended number of running hours or calendar time before an aircraft engine or other component requires overhaul. On rotorcraft, many components have recommended or ...

(TBO) for later Eagles was around 100–180 hours.

Variants

''Note:'' ;Eagle I (''Rolls-Royce 250 hp Mk I'') :(1915), 225 hp, 104 engines produced in both left and right hand tractor versions. ;Eagle II (''Rolls-Royce 250 hp Mk II'') :(1916), 250 hp, 36 built at Derby. ;Eagle III (''Rolls-Royce 250 hp Mk III'') :(1917-1927), 250 hp, increased

compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stati ...

(4.9:1), strengthened

piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-t ...

s. 110 built at Derby. ;Eagle IV (''Rolls-Royce 250 hp Mk IV'') :(1916-17), 270/286 hp, 36 built at Derby. Rolls-Royce Eagle VIII-002

;Eagle V (''Rolls-Royce 275 hp Mk I'') :(1916-17), 275 hp, high-lift

camshaft A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems ...

, 100 built at Derby. ;Eagle VI (''Rolls-Royce 275 hp Mk II'') :(1917), 275 hp, first use of twin

spark plugs A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...

, 300 built at Derby. ;Eagle VII (''Rolls-Royce 275 hp Mk III'') :(1917-18), 275 hp, 200 built at Derby. ;Eagle VIII :(1917-1922), 300 hp, extensive modifications, 3,302 built at Derby. ;Eagle IX :(1922-1928), 360 hp, developed as a civil use engine, 373 built at Derby.

Applications

Admiralty N.S.3 North Sea Airship Admiralty most often refers to: *Admiralty, Hong Kong *Admiralty (United Kingdom), military department in command of the Royal Navy from 1707 to 1964 *The rank of admiral *Admiralty law Admiralty can also refer to: Buildings * Admiralty, Traf ...

* Admiralty 23 Class Airship * Airco DH.4 *

Airco DH.9 The Airco DH.9 (from de Havilland 9) – also known after 1920 as the de Havilland DH.9 – was a British single-engined biplane bomber developed and deployed during the First World War. The DH.9 was a development of Airco's earlier successful ...

Airco DH.10 Amiens The Airco DH.10 Amiens was a twin-engined heavy bomber designed and produced by the British aircraft manufacturer Airco. It performed the first nighttime air mail service in the world on 14-15 May 1919. The DH.10 was developed in the final ye ...

* Airco DH.16 * ANEC III *

BAT F.K.26 The BAT F.K.26 was a British single-engined four-passenger biplane transport aircraft produced by British Aerial Transport Company Limited of London at the end of World War I. Design and development As the First World War drew to a close the a ...

Blackburn Blackburd The Blackburn Blackburd was a British prototype single-engine torpedo bomber developed by Blackburn Aircraft in 1918 as a replacement for the Sopwith Cuckoo. It was unsuccessful, only three being built. Design and development In January 1918, t ...

* Curtiss H.12 Large America * Curtiss-Wanamaker Triplane *

Dornier Do E The Dornier Do E was a small German flying boat of 1924, designed for reconnaissance missions. Development Conceptually, the Do E was very similar to the successful Dornier Wal, but smaller and single-engined. It was of all-metal construction, ...

Dornier Wal The Dornier Do J ''Wal'' (" whale") is a twin-engine German flying boat of the 1920s designed by ''Dornier Flugzeugwerke''. The Do J was designated the Do 16 by the Reich Air Ministry (''RLM'') under its aircraft designation system of 1933. ...

Fairey III The Fairey Aviation Company Fairey III was a family of British reconnaissance biplanes that enjoyed a very long production and service history in both landplane and seaplane variants. First flying on 14 September 1917, examples were still in u ...

Fairey Campania The Fairey Campania was a British ship-borne, patrol and reconnaissance aircraft of the First World War and Russian Civil War. It was a single-engine, two-seat biplane with twin main floats and backward-folding wings. The Campania was the first ...

Felixstowe F.2 The Felixstowe F.2 was a 1917 British flying boat class designed and developed by Lieutenant Commander John Cyril Porte RN at the naval air station, Felixstowe during the First World War adapting a larger version of his superior Felixstowe F ...

* Felixstowe F.3 * Felixstowe F.4 *

Felixstowe F.5 The Felixstowe F.5 was a British First World War flying boat designed by Lieutenant Commander John Cyril Porte RN of the Seaplane Experimental Station, Felixstowe. Design and development Porte designed a better hull for the larger Curtiss H-1 ...

* Fokker F.VII * Grahame-White G.W.E.7 * Handasyde H.2 *

* Handley Page V/1500 * Handley Page Type W *

Hawker Horsley The Hawker Horsley was a British single-engined biplane bomber of the 1920s. It was the last all-wooden aircraft built by Hawker Aircraft, and served as a medium day bomber and torpedo bomber with Britain's Royal Air Force between 1926 and 1935 ...

* Porte Baby * Porte Super Baby * Martinsyde F.1 * Rohrbach Ro II * Rohrbach Ro III * Royal Aircraft Factory F.E.2 * Royal Aircraft Factory F.E.4 * Royal Aircraft Factory R.E.7 *

Short Bomber The Short Bomber was a British two-seat long-range reconnaissance, bombing and torpedo-carrying aircraft designed by Short Brothers as a land-based development of the very successful Short Type 184 (of which more than 900 were built and many ex ...

* Short N.1B Shirl * Short Type 184 * Sopwith Atlantic * Sopwith Wallaby * Sopwith Tractor Triplane *

Supermarine Commercial Amphibian The Supermarine Commercial Amphibian (originally named the Supermarine Amphibian, later designated N147 by the British Air Ministry) was a passenger-carrying flying boat. The first aircraft to be designed by Supermarine's Reginald Mitchell, ...

Supermarine Scarab The Supermarine Sea Eagle was a British, passenger–carrying, amphibious flying boat. It was designed and built by the Supermarine Aviation Works for its subsidiary, the British Marine Air Navigation Co Ltd, to be used on their cross-channel ...

Supermarine Sea Eagle The Supermarine Sea Eagle was a British, passenger–carrying, amphibious flying boat. It was designed and built by the Supermarine Aviation Works for its subsidiary, the British Marine Air Navigation Co Ltd, to be used on their cross-channe ...

Supermarine Swan The Supermarine Swan was a 1920s British experimental amphibian aircraft built by Supermarine at Woolston, Southampton. The single aircraft that was built was used for a passenger service between England and France. Design and development The ...

* Van Berkel W-B * Vickers F.B.11 * Vickers Valparaiso * Vickers Vernon *

Vickers Viking The Vickers Viking was a British single-engine amphibious aircraft designed for military use shortly after World War I. Later versions of the aircraft were known as the Vickers Vulture and Vickers Vanellus. Design and development Resear ...

Vickers Vulcan The Vickers Vulcan was a British single-engine biplane airliner of the 1920s built by Vickers Limited at Brooklands Aerodrome, Surrey. It carried eight passengers and a pilot. Development The Vickers Vulcan was designed by Rex Pierson of Vi ...

* Vickers Vulture * Vickers Vimy *

Wight Converted Seaplane The Wight Converted Seaplane was a British twin-float patrol seaplane produced by John Samuel White & Company Limited (Wight Aircraft). Design and development Developed from the unsuccessful Wight Bomber for use as an anti-submarine patrol ai ...

Engines on display

Examples of the Rolls-Royce Eagle are on display at the: * Polish Aviation Museum,

Kraków Kraków (), or Cracow, is the second-largest and one of the oldest cities in Poland. Situated on the Vistula, Vistula River in Lesser Poland Voivodeship, the city dates back to the seventh century. Kraków was the official capital of Poland un ...

Science Museum A science museum is a museum devoted primarily to science. Older science museums tended to concentrate on static displays of objects related to natural history, paleontology, geology, industry and industrial machinery, etc. Modern trends in ...

London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...

* Canada Aviation Museum * South African National Museum of Military History,

Johannesburg Johannesburg ( , , ; Zulu language, Zulu and xh, eGoli ), colloquially known as Jozi, Joburg, or "The City of Gold", is the largest city in South Africa, classified as a Megacity#List of megacities, megacity, and is List of urban areas by p ...

* South African Air Force Museum,

Port Elizabeth Gqeberha (), formerly Port Elizabeth and colloquially often referred to as P.E., is a major seaport and the most populous city in the Eastern Cape province of South Africa. It is the seat of the Nelson Mandela Bay Metropolitan Municipality, So ...

One of the two Eagles that powered Alcock and Brown's historic transatlantic flight is on display at the Derby Industrial Museum.Derby Industrial Museum - Eagle engine
Retrieved: 3 August 2009

Specifications (Eagle IX)

References

Notes

Bibliography

* Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. . * Pugh, Peter. ''The Magic of a Name - The Rolls-Royce Story: The First 40 Years''. Duxford, Cambridge: Icon Books, 2001. . * Rubbra, A.A.''Rolls-Royce Piston Aero Engines - A Designer Remembers''. Rolls-Royce Heritage Trust. Historical Series no 16. * Taulbut, Derek S. ''Eagle - Henry Royce’s First Aero Engine'', Rolls-Royce Heritage Trust, 2011. .

External links

{{Rolls-Royce aeroengines

Eagle Eagle is the common name for many large birds of prey of the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. Most of the 68 species of eagle are from Eurasia and Africa. Outside this area, j ...

1910s aircraft piston engines Airship engines