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. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbin ...

to be developed by

Rolls-Royce Limited Rolls-Royce Limited 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 Crane ( ...

. Introduced in 1915 to meet British military requirements during

World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

, 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 one of the largest aircraft in the world. There were two main variants, the Handley Page O/100 (H.P.11) and the Handley Page 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 The Vickers Vimy was a British heavy bomber aircraft developed and manufactured by Vickers Limited. Developed during the latter stages of the First World War to equip the Royal Flying Corps (RFC), the Vimy was designed by Rex Pierson, Vickers ...

bomber on the

transatlantic flight of Alcock and Brown John Alcock and Arthur Brown were British aviators who, in 1919, made the first non-stop transatlantic flight. They flew a modified First World War Vickers Vimy bomber from St. John's, Newfoundland, to Clifden, County Galway, Ireland. The Sec ...

in June 1919.

Background

At the outbreak of World War I in August 1914, the

Royal Aircraft Factory Royal may refer to: People * Royal (name), a list of people with either the surname or given name * A member of a royal family or royalty Places United States * Royal, Arkansas, an unincorporated community * Royal, Illinois, a village * Royal, ...

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 by air, which 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 J ...

from his home in

Kent Kent is a Ceremonial counties of England, ceremonial county in South East England. It is bordered by Essex across the Thames Estuary to the north, the Strait of Dover to the south-east, East Sussex to the south-west, Surrey to the west, and Gr ...

. Based initially on the 7.4 litre 40/50

Rolls-Royce Silver Ghost The Rolls-Royce Silver Ghost name refers both to a car model and one specific car from that series. Originally named the "Tax horsepower#Britain, 40/50 h.p." the chassis was first made at Royce's Manchester works, with production moving t ...

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 in which 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 combus ...

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

Mercedes D.II The Mercedes D.II was a six-cylinder, SOHC valvetrain liquid-cooled inline aircraft engine built by Daimler during the early stages of World War I. Producing about 110 to 120 hp, it was at the low-end of the power range of contemporary en ...

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. The engineering department of the

Royal Naval Air Service The Royal Naval Air Service (RNAS) was the air arm of the Royal Navy, under the direction of the Admiralty (United Kingdom), Admiralty's Air Department, and existed formally from 1 July 1914 to 1 April 1918, when it was merged with the British ...

(RNAS) played a key role in the success of the engine by directing the car designer

W.O. Bentley Walter Owen Bentley, (16 September 1888 – 13 August 1971) was an English engineer who founded Bentley in London. He was a motorcycle and car racer as a young man. After making a name for himself as a designer of aircraft and automobile engin ...

, who had enlisted in the

Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...

, to place his expertise in the design of aluminium pistons at the service of Rolls-Royce. This gave significant weight saving to the Eagle and contributed to its excellent performance. 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, Tra ...

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

Derby Derby ( ) is a City status in the United Kingdom, city and Unitary authorities of England, unitary authority area on the River Derwent, Derbyshire, River Derwent in Derbyshire, England. Derbyshire is named after Derby, which was its original co ...

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 The Handley Page Type O was a biplane bomber used by Britain during the First World War. When built, the Type O was one of the largest aircraft in the world. There were two main variants, the Handley Page O/100 (H.P.11) and the Handley Page O/4 ...

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 has referred to several British government organisations throughout history, all relating to the army. It was a department of the British Government responsible for the administration of the British Army between 1857 and 1964, at ...

, but the company resisted pressure to license other manufacturers to produce it. The fears of Rolls-Royce that the engine's much admired quality would be compromised by other manufacturers is often given as an explanation for this resistance, but the commercial terms sought by Rolls-Royce for licence production were so restrictive that other manufacturers - apart from Brazil Straker - refused to accept them. When the Ministry of Munitions took over coordination of aircraft production in 1917, Sir William Weir declined to intervene in the company's commercial strategy, even though success of the engine owed much to the technology transfer directed by the RNAS. He preferred to support untested engines using cast aluminium components like the

Siddeley Puma The Siddeley Puma is a British aero engine developed towards the end of World War I and produced by Siddeley-Deasy. The first Puma engines left the production lines of Siddeley-Deasy in Coventry in August 1917, production continued until Decem ...

and the

Sunbeam Arab The Sunbeam Arab was a British First World War-era aircraft engine, aero engine. Design and development By 1916 the demand for aero-engines was placing huge demands on manufacturing. To help ease the pressure, the War Office standardised on e ...

, believing them to be better suited to mass production, in comparison to the intricate machining required to build the Eagle and its smaller cousin the

Falcon Falcons () are birds of prey in the genus ''Falco'', which includes about 40 species. Some small species of falcons with long, narrow wings are called hobbies, and some that hover while hunting are called kestrels. Falcons are widely distrib ...

. 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 ma ...

(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 maximum and minimum volume during the compression stage of the power cycle in a piston or Wankel engine. A fundamental specification for such engines, it can be measured in two different ways. Th ...

(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 (engine), cylinder a ...

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 syst ...

, 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 23 Class Airship *

Airco DH.4 The Airco DH.4 is a British two-seat biplane day bomber of the First World War. It was designed by Geoffrey de Havilland (hence "DH") for Airco, and was the first British two-seat light day-bomber capable of defending itself. It was desig ...

* Airco DH.9 *

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 yea ...

* Airco DH.16 * 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, t ...

* Curtiss H.12 Large America * Curtiss-Wanamaker Triplane * Dornier Do E *

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 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 * 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, Royal Navy, RN of the Seaplane Experimental Station in Felixstowe. Design and development Porte designed a better hull for the large ...

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

Handley Page V/1500 The Handley Page V/1500 was a British night-flying heavy bomber built by Handley Page towards the end of the First World War. It was a large four-engined biplane, which resembled a larger version of Handley Page's earlier O/100 and O/400 bombers ...

Handley Page Type W The Handley Page W.8, W.9 and W.10 were British two- and three-engine medium-range biplane airliners designed and built by Handley Page. The W.8 (also known as the H.P.18) was the company's first purpose-built civil airliner although it was a ...

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 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 a ...

Royal Aircraft Factory F.E.4 The Royal Aircraft Factory F.E.4 was a twin-engine biplane aircraft built by the Royal Aircraft Factory in 1916. Intended as a cannon armed ground-attack aircraft, it was unsuccessful, only two being built. Design and development Shortly after ...

* 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 exp ...

* Short N.1B Shirl *

Short Type 184 The Short Admiralty Type 184, often called the Short 225 after the power rating of the engine first fitted, was a British two-seat reconnaissance, bombing and torpedo carrying folding-wing seaplane designed by Horace Short of Short Brothers. It ...

* 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 Engla ...

* 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 *

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 commercial biplane flying boat designed by R.J. Mitchell. A single machine was built by Supermarine at their works at Woolston, Southampton. The world's first twin-engine amphibian aircraft, it was th ...

* Van Berkel W-B * 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 var ...

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, Brooklands Aerodrome, Surrey. It carried eight passengers and a pilot. Development The Vickers Vulcan was designed by Regin ...

* Vickers Vulture *

* Wight Converted Seaplane

Engines on display

Examples of the Rolls-Royce Eagle are on display at the: *

Polish Aviation Museum The Polish Aviation Museum () is a large museum of historic aircraft and aircraft engines in Kraków, Poland. It is located at the site of the no-longer functional Kraków-Rakowice-Czyżyny Airport. This airfield, established by Austr ...

Kraków , officially the Royal Capital City of Kraków, is the List of cities and towns in Poland, second-largest and one of the oldest cities in Poland. Situated on the Vistula River in Lesser Poland Voivodeship, the city has a population of 804,237 ...

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 (manufacturing), industry and Outline of industrial ...

London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...

Canada Aviation Museum The Canada Aviation and Space Museum () (formerly the Canada Aviation Museum (''Musée de l'aviation du Canada'') and National Aeronautical Collection (''Collection aéronautique nationale'')) is Canada's national aviation history museum. The m ...

South African National Museum of Military History The South African National Museum of Military History in Johannesburg was officially opened by Prime Minister Jan Smuts on 29 August 1947 to preserve the history of South Africa's involvement in the Second World War. In 1975, the museum was rena ...

Johannesburg Johannesburg ( , , ; Zulu language, Zulu and Xhosa language, Xhosa: eGoli ) (colloquially known as Jozi, Joburg, Jo'burg or "The City of Gold") is the most populous city in South Africa. With 5,538,596 people in the City of Johannesburg alon ...

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 named Port Elizabeth, and colloquially 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 Municipal ...

One of the two Eagles that powered Alcock and Brown's historic transatlantic flight is on display at the

Museum Of Making, Derby A museum is an institution dedicated to displaying or preserving culturally or scientifically significant objects. Many museums have exhibitions of these objects on public display, and some have private collections that are used by researchers ...

.Derby Industrial Museum - Eagle engine
Retrieved: 3 August 2009

Specifications (Eagle IX)

References

Notes

Bibliography

* Bentley, W.O. ''W.O. An Autobiography''. London: Hutchinson & Co., 1958 * Ewer, Peter. 'William Weir: architect of air power? The First World War chapter', ''The International Journal for the History of Engineering & Technology'', 2023 pp.1-19. . * Lloyd, Ian ''Rolls-Royce, the growth of a firm''. London: Macmillan, 1978 . * 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 the golden eagle, bald eagle, and other birds of prey in the family of the Accipitridae. Eagles belong to several groups of Genus, genera, some of which are closely related. True eagles comprise the genus ''Aquila ( ...

1910s aircraft piston engines Airship engines V12 aircraft engines