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. 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 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 Claud ...

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 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 The Mercedes D.III, or F1466 as it was known internally, was a six-cylinder SOHC valvetrain liquid-cooled inline aircraft engine built by Daimler and used on a wide variety of German aircraft during World War I. The initial versions were introd ...

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 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 gain ...

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 (United Kingdom), Ministry of Defence (MoD ...

, 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 (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- ...

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, 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 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 The Airco DH.16 was a British four-seat commercial biplane of the 1910s designed by Geoffrey de Havilland, the chief designer at Airco. Design and development The DH.16 was a redesigned Airco DH.9A with a wider fuselage, accommodating an enclos ...

* ANEC III * BAT F.K.26 *

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, ...

* 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. De ...

* Fairey III * Fairey Campania * Felixstowe F.2 * Felixstowe F.3 * Felixstowe F.4 * Felixstowe F.5 * Fokker F.VII * Grahame-White G.W.E.7 *

Handasyde H.2 The Handasyde H.2 was a six seat airliner built in the UK in the early 1920s. Only one was completed. Design and development The Handasyde Aircraft Company was formed in 1921 by George Handasyde in collaboration with the ex-Martinsyde manage ...

* Handley Page Type O * 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 The Felixstowe Porte Baby (also known as the Porte F.B.2) was a British reconnaissance flying boat of the First World War, first flying in 1915. Design and development The Porte Baby was designed by John Cyril Porte RN at the naval air statio ...

* Porte Super Baby * Martinsyde F.1 *

Rohrbach Ro II The Rohrbach Ro II was an all-metal, 4-seat reconnaissance and bomber flying boat, designed and produced in Germany in 1923. Development Founded in 1923 by Dr.-Ing. Adolf Rohrbach, the Rohrbach Metall-Flugzeugbau GmbH designed and built man ...

Rohrbach Ro III The Rohrbach Ro III was a twin-engined, all-metal flying boat built in Germany in the mid-1920s. A development of the Ro II, it could be configured either as an airliner or a reconnaissance aircraft. It was developed into the similar but more pow ...

Royal Aircraft Factory F.E.2 Between 1911 and 1914, the Royal Aircraft Factory used the F.E.2 (Farman Experimental 2) designation for three quite different aircraft that shared only a common "Farman" pusher biplane layout. The third "F.E.2" type was operated as a day and n ...

* Royal Aircraft Factory F.E.4 *

Royal Aircraft Factory R.E.7 __NOTOC__ The Royal Aircraft Factory R.E.7 was a British two-seat light bomber and reconnaissance biplane designed by the Royal Aircraft Factory and built under contracts by the Coventry Ordnance Works, Austin, Napier and Siddeley-Deasy for the ...

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 exp ...

Short N.1B Shirl The Short N.1B Shirl was a British single-seat biplane, intended to carry heavy torpedoes from early aircraft carriers late in World War I. It met its specifications but planned production was ended with the Armistice of 1918. The design was d ...

* Short Type 184 * Sopwith Atlantic *

Sopwith Wallaby The Sopwith Wallaby was a British single-engined long-range biplane built during 1919 by Sopwith Aviation Company at Kingston upon Thames. Development The Wallaby was designed to compete in an Australian government £10,000 prize for an Englan ...

* 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, i ...

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-channel ...

* Supermarine Swan *

Van Berkel W-B The Van Berkel W-B was a single engine Dutch long range reconnaissance seaplane built in the early 1920s for work in the Dutch East Indies. Six were operated by the Dutch Naval Aviation Service (MLD) with disappointing results, though the last tw ...

* Vickers F.B.11 * Vickers Valparaiso *

Vickers Vernon The Vickers Vernon was a British biplane troop carrier used by the Royal Air Force. It entered service in 1921, and was the first dedicated troop transport of the RAF. The Vernon was a development of the Vickers Vimy Commercial, a passenger va ...

* Vickers Viking * Vickers Vulcan * Vickers Vulture * Vickers Vimy * Wight Converted Seaplane

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 River in Lesser Poland Voivodeship, the city dates back to the seventh century. Kraków was the official capital of Poland until 159 ...

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 The South African Air Force Museum houses exhibits and restores material related to the history of the South African Air Force. The museum is divided into three locations, AFB Swartkop outside Pretoria, AFB Ysterplaat in Cape Town and at the Por ...

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, S ...

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