Editing Bristol Mercury

{{Short description|Aircraft engine}}
{{for|another use|Bristol Mercury (newspaper)}}
{{Use dmy dates|date=December 2016}}
{{Use British English|date=December 2016}}
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{|{{Infobox aircraft begin
 |name=Mercury              
 |image=File:Bristol_Mercury_RAFM_Hendon.jpg
 |caption=Preserved Bristol Mercury VII on display at the [[Royal Air Force Museum London]]
}}{{Infobox aircraft engine
 |type=[[Reciprocating engine|Piston]] [[Aircraft engine|aero engine]]
 |manufacturer=[[Bristol Aeroplane Company]]
 |designer=[[Roy Fedden]]
 |first run=1925
 |major applications=[[Bristol Blenheim]]<br />[[Gloster Gladiator]]<br />[[Fokker D.XXI]]<br />[[Westland Lysander]]
 |number built =20,700  
 |program cost = 
 |unit cost = 
 |developed from =[[Bristol Jupiter]] 
 |developed into =[[Bristol Pegasus]] 
 |variants with their own articles =
}}
|}

The '''Bristol Mercury''' is a British nine-cylinder, air-cooled, single-row, piston [[radial engine]]. Designed by [[Roy Fedden]] of the [[Bristol Aeroplane Company]] it was used to power both civil and military aircraft of the 1930s and 1940s. Developed from the earlier [[Bristol Jupiter|Jupiter]] engine, later variants could produce 800 [[horsepower]] (600&nbsp;kW) from its [[Engine displacement|capacity]] of 1,500 [[cubic inch]]es (25 L) by use of a geared [[supercharger]].

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]]s.

==Design and development==
The Mercury was developed by the [[Bristol Aeroplane Company]] in 1925 as their [[Bristol Jupiter]] was reaching the end of its lifespan. Although the Mercury initially failed to attract much interest, the [[Air Ministry]] eventually funded three prototypes and it became another winner for the designer [[Roy Fedden]].

With the widespread introduction of [[supercharger]]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&nbsp;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 (aircraft)|propeller]]. The same techniques were applied to the original Jupiter-sized engine to produce the [[Bristol Pegasus|Pegasus]].

The Mercury's smaller size was aimed at [[fighter aircraft|fighter]] use and it powered the [[Gloster Gauntlet]] and its successor, the [[Gloster Gladiator]]. It was intended that the larger Pegasus would be for [[bomber aircraft|bomber]]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]], the [[Bristol Blenheim]].

In 1938 Roy Fedden pressed the Air Ministry to import supplies of  [[Avgas#100.2F130|100 octane aviation spirit]] from the US. This new fuel would allow aero engines to run at higher [[compression ratio]]s and [[supercharger]] 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&nbsp;lbs/sq.in (0.62 bar) and was first used in the Blenheim Mk IV.<ref>Warner 2005, pp. 100, 112, 135.</ref>

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]] produced 20,700 examples of the engine.<ref>Bridgman (Jane's) 1998, p. 270.</ref>
Outside the United Kingdom, Mercury was licence-built by [[Państwowe Zakłady Lotnicze]] in Poland and used in the [[PZL P.11]] fighters. It was also built by [[NOHAB]] in Sweden and used in the Swedish Gloster Gladiator fighters and in the [[Saab 17]] dive-bomber. In Italy, it was built by [[Alfa Romeo]] as the Mercurius. In [[Czechoslovakia]] it was built by [[Walter Engines]]. In Finland, it was built by [[Tampella]] and mainly used on [[Bristol Blenheim]] bombers.

==Variants==
''Note:''<ref>List from Lumsden 2003, pp. 104–108</ref>
;Mercury I
:(1926) {{cvt|808|hp}}, direct drive. [[Schneider Trophy]] racing engine
;Mercury II
:(1928) {{cvt|420|hp}}, [[compression ratio]] 5.3:1
;Mercury IIA
:(1928) {{cvt|440|hp}}
;Mercury III
:(1929) {{cvt|485|hp}}, compression ratio 4.8:1, 0.5:1 reduction gear
[[File:Bristol (NOHAB) Mercury.jpg|thumb|Mercury license built by [[NOHAB]]]]
;Mercury IIIA
:Minor modification of Mercury III
;Mercury IV
:(1929) {{cvt|485|hp}}, 0.656:1 reduction gear
;Mercury IVA
:(1931) {{cvt|510|hp}}
;Mercury IVS.2
:(1932) {{cvt|510|hp}}
;Mercury (Short stroke)
:Unsuccessful experimental short stroke (5.0 in) version, {{cvt|390|hp}}
;Mercury V
:{{cvt|546|hp}} (became the Pegasus IS.2)
;Mercury VIS
:(1933) {{cvt|605|hp}}
[[File:Bristol Mercury.jpg|thumb|Side view showing valve gear detail.]]
;Mercury VISP
:(1931) {{cvt|605|hp}}, 'P' for [[Iran|Persia]].
;Mercury VIS.2
:(1933) {{cvt|605|hp}}
;Mercury VIA
:(1928) {{cvt|575|hp}} (became the Pegasus IU.2)
;Mercury VIIA
:{{cvt|560|hp}} (became the Pegasus IM.2)
;Mercury VIII
:(1935) {{cvt|825|hp}}, compression ratio 6.25:1, lightened engine.
;Mercury VIIIA
:Mercury VIII fitted with [[Synchronization gear|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) {{cvt|825|hp}}, lightened engine.
;Mercury X
:(1937) {{cvt|820|hp}}
;Mercury XI
:(1937) {{cvt|820|hp}}
;Mercury XII
(1937) {{cvt|820|hp}}
;Mercury XV
:(1938) {{cvt|825|hp}}, developed from Mercury VIII. Converted to run on 100 Octane fuel (previously 87 Octane).
;Mercury XVI
:{{cvt|830|hp}}
;Mercury XX
:(1940) {{cvt|810|hp}}
;Mercury 25
:(1941) {{cvt|825|hp}}, Mercury XV with crankshaft modifications.
;Mercury 26
:{{cvt|825|hp}}, Mercury 25 with modified carburettor.
;Mercury 30
:(1941) {{cvt|810|hp}}, Mercury XX with crankshaft modifications.
;Mercury 31
:(1945) {{cvt|810|hp}}, Mercury 30 with carburettor modifications and fixed pitch propeller for [[General Aircraft Hamilcar|Hamilcar X]].

==Applications==
[[File:Fokker g1.gif|thumb|right|The Mercury powered Fokker G.1]]
''Note:''<ref>List from Lumsden, the Mercury may not be the main powerplant for these types</ref>
{{div col|colwidth=22em}}
*[[Airspeed Cambridge]]
*[[Blackburn Skua]]
*[[Boulton Paul Balliol|Boulton Paul P.108]]
*[[Bristol Blenheim]]
*[[Bristol Bolingbroke]]
*[[Bristol Bulldog]]
*[[Bristol Bullpup]]
*[[Bristol Type 101]]
*[[Bristol Type 118]]
*[[Bristol Type 133]]
*[[Bristol Type 142]]
*[[Bristol Type 146]]
*[[Bristol Type 148]]
*[[Breda Ba.27]]
*[[Caproni Ca.114]]
*[[Fairey Flycatcher]]
*[[Fokker D XXI]]
*[[Fokker G.1]]
*[[General Aircraft Hamilcar|General Aircraft Hamilcar X]]
*[[Gloster Gamecock]]
*[[Gloster Gladiator]]
*[[Gloster Gauntlet]]
*[[Gloster Gnatsnapper]]
*[[Gloster Goring]]
*[[Hawker Audax]]
*[[Hawker F.20/27]]
*[[Hawker Fury]]
*[[Hawker Hart]]
*[[Hawker Hind]]
*[[Hawker Hoopoe]]
*[[Hawker F.20/27]]
*[[IMAM Ro.30]]
*[[Koolhoven F.K.52]]
*[[Letov Š-31]]
*[[Miles Martinet]]
*[[Miles Master]]
*[[PZL P.11]]
*[[PZL.50]]
*[[Saab 17]]
*[[Short Crusader]]
*[[Supermarine Sea Otter]]
*[[Valmet Vihuri]]
*[[Vickers Jockey]]
*[[Westland Interceptor]]
*[[Westland Lysander]]
{{div col end}}

==Airworthy examples==
[[The Shuttleworth Collection]] 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]], Bedfordshire.<ref>[https://www.shuttleworth.org/explore/the-collection/ The Shuttleworth Collection] Retrieved: 24 January 2022</ref>

The Aircraft Restoration Company based at [[Duxford Airfield]] also operate a Mercury powered Westland Lysander (''G-CCOM'') as well as a [[Bristol Blenheim I]] (''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.<ref>[https://www.aircraftrestorationcompany.com Aircraft Restoration Company] www.aircraftrestorationcompany.com Retrieved: 24 January 2022</ref>

The Fighter Collection, also currently based at Duxford Airfield, operate a 1939 Gloster Gladiator II (''G-GLAD'') powered by a Bristol Mercury XX.<ref>http://fighter-collection.com/cft/gloster-gladiator-g-glad/ The Fighter Collection] http://fighter-collection.com/cft/gloster-gladiator-g-glad/ Retrieved 24 January 2022.</ref>

The [[Canadian Warplane Heritage Museum]] has a Lysander IIIA in flying condition as does the [[Vintage Wings of Canada]].<ref>[http://www.warplane.com/pages/restoration_lysander_update.html Canadian Warplane Heritage Museum - Westland Lysander] www.warplane.com Retrieved: 22 September 2010</ref><ref>[http://www.vintagewings.ca/page?a=450&lang=en-CA Vintage Wings - Westland Lysander]{{Dead link|date=October 2019 |bot=InternetArchiveBot |fix-attempted=yes }} www.vintagewings.ca Retrieved: 22 September 2010</ref>

==Engines on display==
*A Bristol Mercury VII is on display at the [[Royal Air Force Museum London]].<ref>[http://navigator.rafmuseum.org/results.do?view=detail&db=object&pageSize=1&id=33278 RAF Museum - Bristol Mercury] Retrieved: 4 August 2009</ref>
*Another example of a Bristol Mercury VII is on display at the [[Shuttleworth Collection]].
*A sectioned Bristol Mercury is on display at the [[Fleet Air Arm Museum]], [[RNAS Yeovilton (HMS Heron)|RNAS Yeovilton]].
*Bristol Mercury V is in running condition mounted on last PZL P.11 fighter at the [[Polish Aviation Museum|Muzeum Lotnictwa Polskiego]] in [[Kraków]].
* A Tampella Mercury is displayed next to [[Valmet Vihuri]] at [[Finnish Air Force Museum]].

==Specifications (Mercury VI-S)==
[[File:Bristol MercuryVII.JPG|thumb|right|Bristol Mercury VII on display at the [[Shuttleworth Collection]]]]
{{pistonspecs|
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|ref=''Lumsden''<ref>Lumsden 2003, p.105.</ref>
|type=Nine-cylinder single-row supercharged air-cooled [[radial engine]]
|bore={{convert|5.75|in|mm|0|abbr=on}}
|stroke={{convert|6.5|in|mm|0|abbr=on}}
|displacement=1,520 in<sup>3</sup> (24.9 L)
|length=47 in (1,194 mm)
|diameter=51.5 in (1,307 mm)
|width=
|height=
|weight=966 lb (438 kg)
|valvetrain=Overhead valve, 4 valves per cylinder – 2 intake and 2 [[sodium]]-filled exhaust
|supercharger=Single-speed [[centrifugal type supercharger]]
|turbocharger=
|fuelsystem=[[Claudel-Hobson]] [[carburetor|carburettor]]
|fueltype=87 [[octane rating|Octane]] [[petrol]]
|oilsystem=
|coolingsystem=Air-cooled
|power=<br />
* 612 hp (457 kW) at 2,750 rpm for takeoff
* 636 hp (474 kW) at 2,750 rpm at 15,500 ft (4,730 m)
|specpower=0.4 hp/in<sup>3</sup> (18.35 kW/L)
|compression=6:1
|fuelcon=
|specfuelcon=0.49 lb/(hp·h) (300 g/kWh)
|oilcon=
|power/weight=0.63 hp/lb (1.04 kW/kg)
|reduction_gear=[[Farman Aviation Works|Farman]] [[epicyclic gearing]], 0.5:1, left hand tractor
}}

==See also==
{{aircontent
<!-- other related articles that have not already linked: -->
|see also=

<!-- designs which were developed into or from this aircraft: -->
|related=
*[[Bristol Jupiter]]
*[[Bristol Pegasus]]
<!-- aircraft that are of similar role, era, and capability this design: -->
|similar aircraft=

<!-- relevant lists that this aircraft appears in: -->
|lists=
*[[List of aircraft engines]]
<!-- For aircraft engine articles.  Engines that are of similar to this design: -->
|similar engines=
*[[BMW 114]]
*[[BMW 132]]
*[[Bramo 323]]
*[[Pratt & Whitney R-1340]]
*[[Shvetsov ASh-62]]
*[[Wright R-1820]]
<!-- See [[WP:Air/PC]] for more explanation of these fields. -->
}}

==References==

===Notes===
{{reflist}}

===Bibliography===
* Bridgman, L, (ed.) (1998) ''Jane's Fighting Aircraft of World War II.'' Crescent. {{ISBN|0-517-67964-7}}
*Gunston, Bill. ''World Encyclopedia of Aero Engines: From the Pioneers to the Present Day''. 5th edition, Stroud, UK: Sutton, 2006.{{ISBN|0-7509-4479-X}}
* Lumsden, Alec. ''British Piston Engines and Their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. {{ISBN|1-85310-294-6}}.
* Warner, G. ''The Bristol Blenheim: A Complete History''. London: Crécy Publishing, 2nd edition 2005. {{ISBN|0-85979-101-7}}.
*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. {{ISBN|1-56091-655-9}}

==Further reading==
* {{Cite book |last=Gunston |first=Bill |year=2006 |title=Development of Piston Aero Engines |edition=2nd |location=Cambridge |publisher=Patrick Stephens Limited |isbn=0-7509-4478-1 |oclc=}}

==External links==
{{Commons category|Bristol Mercury}}
* [https://web.archive.org/web/20110514001151/http://republika.pl/rola1/files/pzl11_start_run_01.mp3 Recorded sound of the Mercury V S2 engine] used in [[PZL P.11c]] ([[MP3]] format)

{{Bristol aeroengines}}
{{Alfa Romeo aeroengines}}
{{Walter aeroengines}}

[[Category:Aircraft air-cooled radial piston engines]]
[[Category:Bristol aircraft engines|Mercury]]
[[Category:1920s aircraft piston engines]]