The Bristol Mercury is a British nine-cylinder, air-cooled, single-row, piston

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ...

. Designed by

Roy Fedden Sir Alfred Hubert Roy Fedden MBE, FRAeS (6 June 1885 – 21 November 1973) was an engineer who designed most of Bristol Engine Company's successful piston aircraft engine designs. Early life Fedden was born in the Bristol area to fairly wealt ...

of the

Bristol Aeroplane Company The Bristol Aeroplane Company, originally the British and Colonial Aeroplane Company, was both one of the first and one of the most important British aviation companies, designing and manufacturing both airframes and aircraft engines. Notable a ...

it was used to power both civil and military aircraft of the 1930s and 1940s. Developed from the earlier

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...

engine, later variants could produce 800

horsepower Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are t ...

(600 kW) from its capacity of 1,500

cubic inch The cubic inch (symbol in3) is a unit of volume in the Imperial units and United States customary units systems. It is the volume of a cube with each of its three dimensions (length, width, and height) being one inch long which is equivalent ...

es (25 L) by use of a geared

supercharger In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement. The current categorisation is that a supercharger is a form of forced indu ...

. Almost 21,000 engines were produced, with a number also being built under license elsewhere in Europe. Several examples remain airworthy, with other preserved examples on public display in

aviation museum An aviation museum, air museum, or air and space museum is a museum exhibiting the history and artifacts of aviation. In addition to actual, replica or accurate reproduction aircraft, exhibits can include photographs, maps, models, dioramas ...

Design and development

The Mercury was developed by the

in 1925 as their

Bristol Jupiter The Bristol Jupiter was a British nine-cylinder single-row piston radial engine built by the Bristol Aeroplane Company. Originally designed late in World War I and known as the Cosmos Jupiter, a lengthy series of upgrades and developments turn ...

was reaching the end of its lifespan. Although the Mercury initially failed to attract much interest, the

Air Ministry The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force, that existed from 1918 to 1964. It was under the political authority of the Secretary of Stat ...

eventually funded three prototypes and it became another winner for the designer

. With the widespread introduction of

s to the aviation industry in order to improve altitude performance, Fedden felt it was reasonable to use a small amount of boost at all times in order to improve performance of an otherwise smaller engine. Instead of designing an entirely new block, the existing Jupiter parts were re-used with the stroke reduced by one inch (25 mm). The smaller capacity engine was then boosted back to Jupiter power levels, while running at higher rpm and thus requiring a reduction gear for the

propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

. The same techniques were applied to the original Jupiter-sized engine to produce the

Pegasus Pegasus ( grc-gre, Πήγασος, Pḗgasos; la, Pegasus, Pegasos) is one of the best known creatures in Greek mythology. He is a winged divine stallion usually depicted as pure white in color. He was sired by Poseidon, in his role as hor ...

. The Mercury's smaller size was aimed at fighter use and it powered the

Gloster Gauntlet The Gloster Gauntlet was a single-seat biplane fighter designed and produced by the British aeroplane manufacturer Gloster Aircraft in the 1930s. It was the last fighter to be operated by the Royal Air Force (RAF) to have an open cockpit, and ...

and its successor, the

Gloster Gladiator The Gloster Gladiator is a British biplane fighter. It was used by the Royal Air Force (RAF) and the Fleet Air Arm (FAA) (as the Sea Gladiator variant) and was exported to a number of other air forces during the late 1930s. Developed private ...

. It was intended that the larger Pegasus would be for

bomber A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped from an air ...

s, but as the power ratings of both engines rose, the Mercury was used in almost all roles. Perhaps its most famous use was in a twin-engine

light bomber A light bomber is a relatively small and fast type of military bomber aircraft that was primarily employed before the 1950s. Such aircraft would typically not carry more than one ton of ordnance. The earliest light bombers were intended to dro ...

, the

Bristol Blenheim The Bristol Blenheim is a British light bomber aircraft designed and built by the Bristol Aeroplane Company (Bristol) which was used extensively in the first two years of the Second World War, with examples still being used as trainers until ...

. In 1938 Roy Fedden pressed the Air Ministry to import supplies of 100 octane aviation spirit (gasoline) from the USA. This new fuel would allow aero engines to run at higher

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 ...

s and

boost pressure than the existing 87-octane fuel, thus increasing the power. The Mercury XV was one of the first British aero engines to be type-tested and cleared to use the 100-octane fuel in 1939. This engine was capable of running with a boost pressure of +9 lbs/sq.in (0.62 bar) and was first used in the Blenheim Mk IV. The Mercury was also the first British aero engine to be approved for use with variable-pitch propellers. The Bristol company and its

shadow factories British shadow factories were the outcome of the Shadow Scheme, a plan devised in 1935 and developed by the British Government in the buildup to World War II to try to meet the urgent need for more aircraft using technology transfer from the mo ...

produced 20,700 examples of the engine. Outside the United Kingdom, Mercury was licence-built in Poland and used in their PZL P.11 fighters. It was also built by

NOHAB NOHAB (Nydqvist & Holm AB) was a manufacturing company based in the city of Trollhättan, Sweden. History The company was founded by Antenor Nydqvist, Johan Magnus Lidström and Carl Olof Holm in 1847 as ''Trollhättans Mekaniska Verkstad'' as ...

in Sweden and used in the Swedish Gloster Gladiator fighters and in the

Saab 17 The Saab 17 is a Swedish single-engine monoplane reconnaissance dive-bomber aircraft of the 1940s originally developed by ASJA prior to its merger into Saab. It was the first all-metal stressed skin aircraft developed in Sweden. Design and de ...

dive-bomber. In Italy, it was built by

Alfa Romeo Alfa Romeo Automobiles S.p.A. () is an Italian luxury car manufacturer and a subsidiary of Stellantis. The company was founded on 24 June 1910, in Milan, Italy. "Alfa" is an acronym of its founding name, "Anonima Lombarda Fabbrica Automobili." "A ...

as the Mercurius. In

Czechoslovakia , rue, Чеськословеньско, , yi, טשעכאסלאוואקיי, , common_name = Czechoslovakia , life_span = 1918–19391945–1992 , p1 = Austria-Hungary , image_p1 ...

it was built by

Walter Engines Walter Aircraft Engines is an aircraft engine manufacturer and former automotive manufacturer. Its notable products include the M601 turboprop. The company is based in Prague, Czech Republic. It has been a subsidiary of GE Aviation since July ...

. In Finland, it was built by

Tampella Oy Tampella Ab was a Finnish heavy industry manufacturer, a maker of paper machines, locomotives, military weaponry, as well as wood-based products such as packaging. The company was based mainly in the Naistenlahti district of the city o ...

and mainly used on

bombers.

Variants

''Note:'' ;Mercury I :(1926) , direct drive. Schneider Trophy racing engine ;Mercury II :(1928) ,

5.3:1 ;Mercury IIA :(1928) ;Mercury III :(1929) , compression ratio 4.8:1, 0.5:1 reduction gear Bristol (NOHAB) Mercury

;Mercury IIIA :Minor modification of Mercury III ;Mercury IV :(1929) , 0.656:1 reduction gear ;Mercury IVA :(1931) ;Mercury IVS.2 :(1932) ;Mercury (Short stroke) :Unsuccessful experimental short stroke (5.0 in) version, ;Mercury V : (became the Pegasus IS.2) ;Mercury VIS :(1933) Bristol Mercury

;Mercury VISP :(1931) , 'P' for

Persia Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...

. ;Mercury VIS.2 :(1933) ;Mercury VIA :(1928) (became the Pegasus IU.2) ;Mercury VIIA : (became the Pegasus IM.2) ;Mercury VIII :(1935) , compression ratio 6.25:1, lightened engine. ;Mercury VIIIA :Mercury VIII fitted with gun synchronisation gear for the Gloster Gladiator MkII ;Mercury VIIIA :535 hp, second use of VIIIA designation, (became the Pegasus IU.2P) ;Mercury IX :(1935) , lightened engine. ;Mercury X :(1937) ;Mercury XI :(1937) ;Mercury XII (1937) ;Mercury XV :(1938) , developed from Mercury VIII. Converted to run on 100 Octane fuel (previously 87 Octane). ;Mercury XVI : ;Mercury XX :(1940) ;Mercury 25 :(1941) , Mercury XV with crankshaft modifications. ;Mercury 26 :, Mercury 25 with modified carburettor. ;Mercury 30 :(1941) , Mercury XX with crankshaft modifications. ;Mercury 31 :(1945) , Mercury 30 with carburettor modifications and fixed pitch propeller for Hamilcar X.

Applications

''Note:'' * Airspeed Cambridge *

Blackburn Skua The Blackburn B-24 Skua was a carrier-based low-wing, two-seater, single- radial engine aircraft by the British aviation company Blackburn Aircraft. It was the first Royal Navy carrier-borne all-metal cantilever monoplane aircraft, as well as t ...

* Boulton Paul P.108 *

Bristol Bolingbroke The Bristol Fairchild Bolingbroke is a maritime patrol aircraft and trainer used by the Royal Canadian Air Force during the Second World War. Built by Fairchild-Canada, it was a license-built version of the Bristol Blenheim Mk IV bomber. De ...

Bristol Bulldog The Bristol Bulldog is a British Royal Air Force single-seat biplane fighter designed during the 1920s by the Bristol Aeroplane Company. More than 400 Bulldogs were produced for the RAF and overseas customers, and it was one of the most fam ...

Bristol Bullpup The Bristol Type 107 Bullpup was a British fighter aircraft built in the 1920s. It was not selected for squadron service and only the single prototype was built Background The design of the Bullpup was an outcome of a series of design studie ...

Bristol Type 101 The Bristol Type 101, was a British two-seat fighter prototype of the 1920s. Development Designed as a private venture, the 101 was a single-bay biplane, two-seat design of mixed construction. The fuselage was a spruce box-girder covered wi ...

Bristol Type 118 The Bristol Type 118 was a general-purpose military aircraft, a two-seat biplane built by the Bristol Aeroplane Company in the early 1930s, powered by a Bristol Mercury radial engine and aimed at overseas markets. The Type 120 was a Bristol Peg ...

Bristol Type 133 The Bristol Type 133 was a single-seat, single-engine monoplane fighter armed with four guns, using stressed-skin construction and with a retractable undercarriage. It was built by The Bristol Aeroplane Co. to meet Specification F.7/30. The s ...

Bristol Type 142 The Bristol Blenheim is a British light bomber aircraft designed and built by the Bristol Aeroplane Company (Bristol) which was used extensively in the first two years of the Second World War, with examples still being used as trainers until ...

Bristol Type 146 The Bristol Type 146 was a British single-seat, eight-gun fighter monoplane prototype built to a mid-1930s Air Ministry contract. Powered by a radial engine, it was outclassed by Merlin-engined fighters and only one was built. Design and deve ...

Bristol Type 148 The Bristol Type 148 was a two-seat, single-engine low-wing monoplane built in 1937 to an Air Ministry specification for an army cooperation aircraft. It lost in the competition to the Westland Lysander and did not progress past the two prototy ...

* Breda Ba.27 * Fairey Flycatcher * Fokker D XXI * Fokker G.1 * General Aircraft Hamilcar X *

Gloster Gamecock The Gloster Gamecock was a biplane fighter designed and produced by the British aircraft manufacturer Gloster. The Gamecock was a development of the earlier Grebe Mk III, an early interwar fighter procured by the Royal Air Force (RAF). Work ...

* Gloster Gnatsnapper *

Gloster Goring The Gloster Goring was a single-engined two-seat biplane designed to meet 1926 Air Ministry specifications for a day/torpedo bomber. It was not put into production and the one aircraft built served later as an engine testbed. Development Early ...

Hawker Audax The Hawker Hart is a British two-seater biplane light bomber aircraft that saw service with the Royal Air Force (RAF). It was designed during the 1920s by Sydney Camm and manufactured by Hawker Aircraft. The Hart was a prominent British aircra ...

* Hawker F.20/27 *

Hawker Fury The Hawker Fury is a British biplane fighter aircraft used by the Royal Air Force in the 1930s. It was a fast, agile aircraft, and the first interceptor in RAF service capable of speed higher than 200 mph (321 kmh). It was the fighter co ...

Hawker Hart The Hawker Hart is a British two-seater biplane light bomber aircraft that saw service with the Royal Air Force (RAF). It was designed during the 1920s by Sydney Camm and manufactured by Hawker Aircraft. The Hart was a prominent British aircra ...

* Hawker Hind *

Hawker Hoopoe The Hawker Hoopoe was a British prototype naval fighter aircraft designed and built in 1927 by Hawker Aircraft. Service trials found the aircraft to be unsatisfactory, and it was superseded by the same company's Nimrod design. Design and deve ...

* Hawker F.20/27 * IMAM Ro.30 * Koolhoven F.K.52 * Letov Š-31 *

Miles Martinet The Miles M.25 Martinet was a target tug aircraft of the Royal Air Force (RAF) and Fleet Air Arm (FAA) that was in service during the Second World War. It was the first British aircraft to be designed specifically for target towing. Work o ...

Miles Master The Miles M.9 Master was a British two-seat monoplane advanced trainer designed and built by aviation company Miles Aircraft Ltd. It was inducted in large numbers into both the Royal Air Force (RAF) and Fleet Air Arm (FAA) during the Second W ...

* PZL P.11 *

Short Crusader The Short Crusader also called the Short-Bristow Crusader and Short-Bristol Crusader was a British racing seaplane of the 1920s, built by Short Brothers to compete in the 1927 Schneider Trophy race. Background Although inline engines had a cle ...

Supermarine Sea Otter The Supermarine Sea Otter was an amphibious aircraft designed and built by the British aircraft manufacturer Supermarine. It was the final biplane flying boat to be designed by Supermarine; it was also the last biplane to enter service with bo ...

Valmet Vihuri Valmet Vihuri ( Finnish for ''Gale'') was a Finnish advanced two-seat fighter trainer aircraft, serving in the Finnish Air Force between 1953 and 1959. Only a few airframes have survived, as in the Central Finland Aviation Museum in Finland. Hi ...

Vickers Jockey The Vickers Type 151 Jockey was an experimental low-wing monoplane interceptor fighter powered by a radial engine. It was later modified into the Type 171 Jockey II, which had a more powerful engine and detail improvements. Only one was built; ...

Westland Interceptor The Westland Interceptor was a fighter developed by the British company Westland Aircraft to Air Ministry Specification ''F.20/27''. When tested in 1929 and 1930, it showed unsatisfactory handling characteristics and was rejected by the RAF in ...

Westland Lysander The Westland Lysander is a British army co-operation and liaison aircraft produced by Westland Aircraft that was used immediately before and during the Second World War. After becoming obsolete in the army co-operation role, the aircraft' ...

Airworthy examples

The Shuttleworth Collection The Shuttleworth Collection is a working aeronautical and automotive collection located at the Old Warden Aerodrome, Old Warden in Bedfordshire, England. It is the oldest in the world and one of the most prestigious, due to the variety of old ...

operates two Bristol Mercury powered aircraft: A Westland Lysander III (''G-AZWT'') and a Gloster Gladiator I (''G-AMRK'') which can be seen during flying displays at

Old Warden Aerodrome Old Warden Aerodrome is located east southeast of Bedford, in Bedfordshire, England. The privately owned aerodrome serves The Shuttleworth Collection The Shuttleworth Collection is a working aeronautical and automotive collection located ...

, Bedfordshire. The Aircraft Restoration Company based at

Duxford Airfield Duxford Aerodrome is located south of Cambridge, within the civil parish of Duxford, Cambridgeshire, England and nearly west of the village. The airfield is owned by the Imperial War Museum (IWM) and is the site of the Imperial War Muse ...

also operate a Mercury powered Westland Lysander (''G-CCOM'') as well as a

Bristol Blenheim I The Bristol Blenheim is a British light bomber aircraft designed and built by the Bristol Aeroplane Company (Bristol) which was used extensively in the first two years of the Second World War, with examples still being used as trainers until t ...

(''G-BPIV'') light bomber fitted with two Bristol Mercurys, which can be seen at air displays at IWM Duxford as well as across the UK. The Fighter Collection, also currently based at Duxford Airfield, operate a 1939 Gloster Gladiator II (''G-GLAD'') powered by a Bristol Mercury XX. The

Canadian Warplane Heritage Museum The Canadian Warplane Heritage Museum is an aviation museum located at the John C. Munro Hamilton International Airport in Mount Hope, Ontario, Canada. The museum has 47 military jets and propeller-driven aircraft on display. Displayed is a c ...

has a Lysander IIIA in flying condition as does the

Vintage Wings of Canada Vintage Wings of Canada is a not for profit, charitable organization, with a collection of historically significant aircraft. The facility is located at the Gatineau-Ottawa Executive Airport, Quebec, Canada. It was founded by former Cognos ...

Engines on display

*A Bristol Mercury VII is on display at the

Royal Air Force Museum London The Royal Air Force Museum London (also commonly known as the RAF Museum) is located on the former Hendon Aerodrome. It includes five buildings and hangars showing the history of aviation and the Royal Air Force. It is part of the Royal Air Fo ...

.RAF Museum - Bristol Mercury
Retrieved: 4 August 2009 *Another example of a Bristol Mercury VII is on display at the

Shuttleworth Collection The Shuttleworth Collection is a working aeronautical and automotive collection located at the Old Warden Aerodrome, Old Warden in Bedfordshire, England. It is the oldest in the world and one of the most prestigious, due to the variety of old ...

. *A sectioned Bristol Mercury is on display at the

Fleet Air Arm Museum The Fleet Air Arm Museum is devoted to the history of British naval aviation. It has an extensive collection of military and civilian aircraft, aero engines, models of aircraft and Royal Navy ships (especially aircraft carriers), and paintin ...

RNAS Yeovilton Royal Naval Air Station Yeovilton, or RNAS Yeovilton, (HMS ''Heron'') is an airfield of the Royal Navy and British Army, sited a few miles north of Yeovil, Somerset. It is one of two active Fleet Air Arm bases (the other being RNAS Culdrose) ...

Specifications (Mercury VI-S)

References

Notes

Bibliography

* Bridgman, L, (ed.) (1998) ''Jane's Fighting Aircraft of World War II.'' Crescent. *Gunston, Bill. ''World Encyclopedia of Aero Engines: From the Pioneers to the Present Day''. 5th edition, Stroud, UK: Sutton, 2006. * Lumsden, Alec. ''British Piston Engines and Their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. . * Warner, G. ''The Bristol Blenheim: A Complete History''. London: Crécy Publishing, 2nd edition 2005. . *White, Graham. ''Allied Aircraft Piston Engines of World War II: History and Development of Frontline Aircraft Piston Engines Produced by Great Britain and the United States During World War II''. Warrendale, Pennsylvania: SAE International, 1995.

External links

Recorded sound of the Mercury V S2 engine
used in PZL P.11c (

MP3 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the United States and elsewhere. Origin ...

format) {{Walter aeroengines Aircraft air-cooled radial piston engines Mercury 1920s aircraft piston engines