Bristol Mercury

For the 1917 14-cylinder radial engine see Cosmos Mercury

The Bristol Mercury is a nine-cylinder air-cooled single-row piston radial engine. The Mercury was used mainly on British military aircraft in the 1930s and 1940s. A number were also built in Europe under licence.

At least one Bristol Mercury remains airworthy in 2009.

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

The Mercury's smaller size was aimed at fighter use, and it powered the Gloster Gauntlet and its successor, the Gloster Gladiator. It was intended that the larger Pegasus would be for bombers, but as the power ratings of both engines rose the Mercury found itself being 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 100 octane aviation spirit from the USA. This new fuel would allow aero engines to run at higher compression ratios and supercharger boost pressure than the existing 87 octane fuel thus increasing the available 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 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 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 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,

Variants

Note:

Mercury I

(1926) 808 hp, direct drive. Schneider Trophy racing engine.

Mercury II

(1928) 420 hp, compression ratio 5.3:1.

Mercury IIA

(1928) 440 hp

Mercury III

(1929) 485 hp, compression ratio 4.8:1, 0.5:1 reduction gear.

File:Bristol (NOHAB) Mercury.jpg

Mercury license built by NOHAB

Mercury IIIA

Minor modification of Mercury III.

Mercury IV

(1929) 485 hp, 0.656:1 reduction gear.

Mercury IVA

(1931) 510 hp.

Mercury IVS.2

(1932) 510 hp.

Mercury (Short stroke)

Unsuccessful experimental short stroke (5.0 in) version, 390 hp.

Mercury V

546 hp (became the Pegasus IS.2)

Mercury VIS

(1933) 605 hp, see specifications section.

File:Bristol Mercury.jpg

Side view showing valve gear detail.

Mercury VISP

(1931) 605 hp, 'P' for Persia.

Mercury VIS.2

(1933) 605 hp.

Mercury VIA

(1928) 575 hp (became the Pegasus IU.2)

Mercury VIIA

560 hp (became the Pegasus IM.2)

Mercury VIII

(1935) 825 hp, compression ratio 6.25:1, lightened engine.

Mercury VIIIA

Mercury VIII fitted with gun synchronisation gear for the Gloster Gladiator

Mercury VIIIA

535 hp, second use of VIIIA designation, (became the Pegasus IU.2P)

Mercury IX

(1935) 825 hp, lightened engine.

Mercury X

(1937) 820 hp.

Mercury XI

(1937) 820 hp.

Mercury XII

(1937) 820 hp

Mercury XV

(1938) 825 hp, developed from Mercury VIII. Converted to run on 100 Octane fuel (previously 87 Octane).

Mercury XVI

830 hp.

Mercury XX

(1940) 810 hp

Mercury 25

(1941) 825 hp. Mercury XV with crankshaft modifications.

Mercury 26

825 hp. As Mercury 25 with modified carburettor.

Mercury 30

(1941) 810 hp, Mercury XX with crankshaft modifications.

Mercury 31

(1945) 810 hp, Mercury 30 with carburettor modifications and fixed pitch propeller for Hamilcar X.

Applications

Note: Template:Multicol

• Airspeed Cambridge
• Blackburn Skua
• 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
• Fairey Flycatcher
• Fokker D XXI
• Fokker G.1
• General Aircraft Hamilcar X
• Gloster Gamecock
• Gloster Gladiator
• Gloster Gauntlet

File:Fokker g1.gif

The Mercury powered Fokker G.1

• 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
• Miles Martinet
• Miles Master
• PZL P.11
• Saab 17
• Short Crusader
• Supermarine Sea Otter
• Valmet Vihuri
• Vickers Jockey
• Westland Interceptor
• Westland Lysander

Survivors

A Bristol Mercury powered Westland Lysander remains airworthy in 2009 at the Shuttleworth Collection, Old Warden, England and is flown at home air displays throughout the summer months.

Engines on display

A Bristol Mercury VII is on display at the Royal Air Force Museum (London).

See also

Related development

• Bristol Jupiter
• Bristol Pegasus

Related lists

• List of aircraft engines

References

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. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
• 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.

Further reading

• Gunston, Bill. Development of Piston Aero Engines. Cambridge, England. Patrick Stephens Limited, 2006. ISBN 0-7509-4478-1

External links

Wikimedia Commons has media related to:

Bristol Mercury

• Recorded sound of the Mercury V S2 engine used in PZL P.11c (mp3 format)

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Bristol Mercury".