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The Bristol Blenheim was a Britishmarker light bomber aircraft designed and built by the Bristol Aeroplane Company that was used extensively in the early days of the Second World War. It was later adapted into a successful long-range and night fighter. It was one of the first British aircraft to have all-metal stressed-skin construction, to utilise retractable landing gear, flap, powered gun turret and variable pitch propellers. A Canadian-built variant named the Bolingbroke was used as an anti-submarine and training aircraft.

Design and development

Blenheim Mk IV cockpit.
Note the asymmetry of the instrument console, indicating the position of the scooped out area of the nose in front of the pilot.
The ring and bead gunsight for the forward firing guns is visible.


In 1934, Lord Rothermere, owner of the Daily Mail newspaper, issued a challenge to the British aviation industry to build a high-speed aircraft capable of carrying six passengers and two crew members. At the time, German firms were producing a variety of high-speed designs that were breaking records, and Rothermere wanted to recapture the title of fastest civilian aircraft in Europe. Bristol had been working on a suitable design as the Type 135 since July 1933, and further adapted it to produce the Type 142 to meet Rothermere's requirements.

When it first flew as Britain First at Filtonmarker on 12 April 1935, it proved to be faster than any fighter in service with the Royal Air Force at the time. The Air Ministry was obviously interested in such an aircraft and quickly sent out Specification B.28/35 for prototypes of a bomber version; the Type 142M (M for military). The main changes were to move the wing from a low-wing to a mid-wing position, allowing room under the main spar for a bomb bay. The aircraft was all-metal with two Bristol Mercury VIII air-cooled radial engines, each of 860 hp (640 kW). It carried a crew of three - pilot, navigator/bombardier and telegraphist/air gunner. Armament comprised a single forward-firing .303 in (7.7 mm) Browning machine gun outboard of the port engine and a .303 in (7.7 mm) Lewis Gun in a semi-retracting Bristol Type B Mk I dorsal turret firing to the rear. From 1939 onwards, the Lewis gun was replaced by the more modern .303 in (7.7 mm) Vickers VGO machine gun of the same calibre. A 1,000 lb (450 kg) bomb load could be carried in the internal bay.

To achieve its relatively high speed, the Blenheim had a very small fuselage cross-section. Pilot's quarters on the left side of the nose were so cramped that the control yoke obscured all flight instruments while engine instruments eliminated the forward view on landings. Most secondary instruments were arranged along the left side of the cockpit, with essential items like propeller pitch control actually placed behind the pilot where they had to be operated by feel alone. Like most contemporary British aircraft, the bomb bay doors were kept closed with bungee cords and opened under the weight of the released bombs. Because there was no way to predict how long it would take for the bombs to force the doors open, bombing accuracy was consequently poor.

The aircraft was ordered directly from the drawing board with the first production model serving as the only prototype. The name then became Blenheim Mk I after a historic German village where the British had won a great victorymarker. Subsequent deliveries started in March 1937, with 114 Squadron being the first squadron to receive the Blenheim. The aircraft would prove to be so successful that it was licensed by a number of countries, including Finlandmarker and Yugoslaviamarker. Other countries bought it outright, including Romaniamarker, Greecemarker and Turkeymarker. Total production of the Blenheim Mk I in England amounted to 1,351 aircraft.



Work on an extended-range reconnaissance version started as the Blenheim Mk II, which increased tankage from 278 gal (1,264 L) to 468 gal (2,127 L), but only one was completed. Another modification resulted in the Blenheim Mk III, which lengthened the nose to provide more room for the bombardier. This required the nose to be "scooped out" in front of the pilot to maintain visibility during takeoff and landing. However both of these modifications were instead combined, along with a newer version of the Mercury engine with 905 hp (675 kW) and the turret acquired a pair of Brownings instead of the Vickers K; creating the Blenheim Mk IV. In total, 3,307 would eventually be produced.

Another modification led to a long-range fighter version; the Blenheim Mk IF. For this role, about 200 Blenheims were fitted with a gun-pack under the fuselage for four .303 in (7.7 mm) Brownings. Later, the Airborne Intercept (AI) Mk III or IV radar would be fitted to some aircraft in use as night fighters, becoming the first British fighters equipped with radar. Their performance was marginal as a fighter, but they served as an interim type, pending availability of the Beaufighter. About 60 Mk IVs were also equipped with the gun pack as the Mk IVF and were used by Coastal Command to protect convoys from German long-range bombers.

The last bomber variant was conceived as an armoured ground attack aircraft, with a solid nose containing four more Browning machine guns. Originally known as the Bisley, (after the shooting competitions held at Bisleymarker), the production aircraft were renamed Blenheim Mk V and featured a strengthened structure, pilot armour, interchangeable nose gun pack or bombardier position, and yet another Mercury variant, this time with 950 hp (710 kW). The Mk V was ordered for conventional bombing operations, with the removal of armour and most of the glazed nose section. The Mk V, or Type 160, was used primarily in the Middle East and Far East.

The Blenheim would serve as the basis for the Beaufort torpedo bomber, which itself led to the Beaufighter, the lineage performing two complete circles of bomber to fighter.

Operational history

Bristol Blenheim Mk IV bombers at RAF Tengah, Singapore, June 1941.


The Blenheim was regarded as a pleasant aircraft to fly, although it did have some characteristics which could catch even experienced pilots by surprise. Unfortunately, with the rapid advances in technology which had taken place in the late 1930s, by the start of the Second World War, the Blenheim was obsolescent. The aircraft had become heavier as extra service equipment was installed; much of this was found to be needed through operational experience. This, coupled with the rapid performance increases of fighters, had eclipsed the Blenheim's speed advantage.

Although the rear gunner was housed in a turret, the turret could only traverse a total of 180 degrees, leaving the forward arc open to attack. The light armament of one .303 in (7.7 mm) Vickers VGO in the turret and one .303 in (7.7 mm) Browning machine gun in the port wing was seldom able to deter fighter opposition. Squadrons were forced to use several different improvisations in an attempt to provide better defensive armament, until officially sanctioned modifications were able to be introduced in early 1940. The Blenheim also proved to be vulnerable to flak, especially around the rear fuselage. Flexible, self-sealing liners had been fitted to the fuel tanks but they were still not fully protected against the 20 mm MG FF cannon carried by the Luftwaffe s Bf 109s and Bf 110s.

After France fell to Germany in June 1940, the Free French Air Force was formed at RAF Odihammarker in the form of Groupe Mixte de Combat (GMC) 1, consisting of a mixed bag of Blenheims and Westland Lysander liaison/observation aircraft, which eventually went to North Africa and saw action against the Italians and Germans.

The Battle of Britain

The Blenheim units operated throughout the battle, often taking heavy casualties, although they were never accorded the publicity of the fighter squadrons.

The Blenheim units raided German occupied airfields throughout July to December 1940, both during daylight hours and at night. Although most of these raids were unproductive there were some successes; on 1 August five out of 12 Blenheims sent to attack Haamstedemarker and Everemarker (Brusselsmarker) were able to bomb, destroying or heavily damaging three Bf 109s of II./JG 27 and apparently killing a Staffelkapitan identified as Hauptmann Albrecht von Ankum-Frank. Two other 109s were claimed by Blenheim gunners. Another successful raid on Haamstede was made by a single Blenheim on 7 August which destroyed one 109 of 4./JG 54, heavily damaged another and caused lighter damage to four more.

There were also some missions which produced an almost 100% casualty rate amongst the Blenheims; one such operation was mounted on 13 August 1940 against a Luftwaffe airfield near Aalborgmarker in north-eastern Denmarkmarker by 12 aircraft of 82 Squadron. One Blenheim returned early (the pilot was later charged and due to appear before a court martial but was killed on another operation), the other 11, which reached Denmark, were shot down, five by flak and six by Bf 109s. It is a testament to the courage of the men in these units that they continued to operate throughout these months with little respite and with little of the publicity accorded to Fighter Command.

As well as the bombing operations, Blenheim-equipped units had been formed to carry out long-range strategic reconnaissance missions over Germany and German-occupied territories. In this role, the Blenheims once again proved to be too slow and vulnerable against Luftwaffe fighters and they took constant casualties.

Cologne power stations raid

The action on 12 August 1941 was described by the Daily Telegraph in 2006 as the "RAF's most audacious and dangerous low-level bombing raid, a large-scale attack against power stations near Cologne."Staff. Obituary of Wing Commander Tom Baker, Daily Telegraph, 10 April 2006.

The raid was a low-level daylight raid by 54 Blenheims under the command of Wing Commander Nichol of No. 114 Squadron RAF. The Blenheims hit their targets (the Fortuna Power Station in Knapsackmarker and the Goldenburg Power Station in Quadrath) but 12 of the Blenheims were lost during the raid, 22% of those that took part which was far above the sustainable loss rate of less than 5%.

Long-range fighter

The Bristol Blenheim was used by both Bomber and Fighter Command. Some 200 Mk I bombers were modified into Mk IF long-range fighters with 600 Squadron based at Hendonmarker, the first squadron to take delivery of these variants in September 1938. By 1939, at least seven squadrons were operating these twin-engine fighters and within a few months, some 60 squadrons had experience of the type. The Mk IF proved to be slower and less nimble than expected, and by June 1940, daylight Blenheim losses was to cause concern for Fighter Command. It was then decided that the Mk IF would be relegated mainly to night fighter duties where No. 23 Squadron RAF who had already operated the type under night time conditions had better success.

Night fighter

In the German night bombing raid on London, 18 June 1940, Blenheims accounted for five German bombers thus proving they were better suited in the nocturnal role. In July, No. 600 Squadron, by then based at RAF Manstonmarker, had some of its Mk IFs equipped with AI Mk III radar. With this radar equipment, a Blenheim from the Fighter Interception Unit (FIU) at RAF Fordmarker achieved the first success on the night of 2-3 July 1940, accounting for a Dornier Do 17 bomber. More successes came and, before long, the Blenheim was to prove invaluable in the night fighter role. Gradually, with the introduction of the Bristol Beaufighter in 1940-1941, its role was supplanted by its faster, better armed progeny.

Eastern service

Blenheims continued to operate widely in many combat roles until about 1943, equipping RAF squadrons in the UK and in British bases in Egypt, Iraq, Adenmarker, India, British Malaya, Singapore, and the Dutch East Indiesmarker. Many Blenheims were lost to Japanesemarker fighters during the Malayan campaign, battles for Singaporemarker, and Sumatra. By that point, most fighters could carry similar bombloads at much higher speeds and the surviving examples were relegated to training duties. Bristol's intended successor to the Blenheim, the Buckingham, was considered inferior to the Mosquito, and did not see combat.

The final ground attack version - the Blenheim Mk V - first equipped 139 Squadron in June 1942. Eventually 13 squadrons - mainly in the Middle East and Far East - received this variant but operated them generally only for a few months.

Finland



In 1936, the Finnish Air Force ordered 18 Blenheim Mk Is from Britain and two years later, they obtained a manufacturing license for the aircraft. Before any aircraft could be manufactured at the Valtion lentokonetehdas (State Airplane Factory) in Finland, the Winter War broke out, forcing the Finns to order more aircraft from the UK. A further 24 British-manufactured Blenheims were ordered during the Winter War. After the Winter War, 55 Blenheims were constructed in Finland, bringing the total number to 97 aircraft (75 Mk Is and 22 Mk IVs).

The Finns obtained large supplies of ex-Yugoslavian spares from the Germans during the war.

The Finnish Blenheims flew 423 missions during the Winter War, and close to 3,000 missions during the Continuation War and Lapland War. Blenheim machine gunners also shot down eight Soviet aircraft. Thirty-seven Blenheims were lost in combat during the wars.

After the war, Finland was prohibited to fly bomber aircraft. However, some of the Finnish Blenheims continued in service as target tugs until 1958.

Variants

Blenheim Mk I
Three-seat twin-engined light bomber, powered by two 840 hp (630 kW) Bristol Mercury VIII radial piston engines, armed with a 0.303 in (7.7 mm) machine gun in the port wing, plus a 0.303 in (7.7 mm) Vickers K gun in the dorsal turret, maximum bombload 1,000 lb (450 kg). 1,552 built. Company designation Type 142M.
Blenheim Mk IF
Night fighter version, equipped with an AI Mk III or Mk IV airborne interceptor radar, armed with four 0.303 in (7.7 mm) machine guns in a special gun pack under the fuselage. About 200 Blenheim Mk Is were converted into Mk IF night fighters.
Blenheim Mk II
Long-range reconnaissance version with extra fuel tankage. Only one Blenheim Mk II was built.
Blenheim Mk III
Blenheim Mk IV
Improved version, fitted with protective armour, powered by two 905 hp (675 kW) Bristol Mercury XV radial piston engines, armed with a 0.303 in (7.7 mm) machine gun in the port wing, plus two 0.303 in (7.7 mm) machine-guns in a powered operated dorsal turret, and two remotely controlled rearward-firing 0.303 in (7.7 mm) machine gun mounted beneath the nose, maximum bombload 1,000 lb (450 kg) internally and 320 lb (150 kg) externally. 3,307 built.
Blenheim Mk IVF
Long-range fighter version, armed with four 0.303 in (7.7 mm) machine guns in special gun pack under the fuselage. About 60 Blenheim Nk IVs were converted into Mk IVF fighters.
Blenheim Mk V
High-altitude bomber version, powered by two Bristol Mercury XV or XXV radial piston engines.


Operators

Bolingbroke IVT in the Commonwealth Air Training Plan Museum, Brandon, Manitoba






Survivors

Bolingbroke in a Manitoba junk yard, 2006
BL-200 in Aviation Museum of Central Finland.
There are currently no Blenheim or Bolingbroke aircraft that are airworthy. Two examples of the type are owned by the Aircraft Restoration Company in Duxfordmarker, Cambridgeshire. The first airworthy Blenheim had been rebuilt from a scrapped Bolingbroke over a 12-year period, only to be destroyed within a month of completion. A replacement Bolingbroke Mk IVT was rebuilt to flying status in just five years and painted to represent a Blenheim Mk IV in RAF wartime service. It began appearing at air shows and exhibitions in the UK, flying since May 1993 and was used in the 1995 film version of Shakespeare's Richard III. This aircraft crashed on landing 18 August 2003, and is presently undergoing an extensive repair.

In Canada, a number of other Bolingbrokes survived the war but were summarily consigned to the scrap heap. Postwar, enterprising farmers often bought surplus aircraft such as these for the scrap metal content, tires for farm implements, and even for the fuel remaining in the tanks. Some surviving examples in Canada of the Bolingbroke can be traced back to this period. The Canadian Warplane Heritage Museummarker in Hamiltonmarker, Ontariomarker has been rebuilding a Bolingbroke to what is hoped to be airworthy status. The Commonwealth Air Training Plan Museum in Brandonmarker, Manitobamarker has restored the exterior of one Bolingbroke, painting it in the Air Training Plan yellow color. This particular aircraft is on display at a location ( ) on the Trans-Canada Highway in Brandon.

In Finland, the sole surviving original Blenheim in the world, a Mk IV registered as BL-200 of the Finnish Air Force, has been completely restored and is now on show at the Aviation Museum of Central Finland at Tikkakoski Aviation Museum of Central Finlandmarker. [12340]

In Greece a Bristol Blenheim Mk IVF was recovered from the sea and moved to the Hellenic Air Force Museummarker for restoration.

Specifications (Blenheim Mk IV)



See also

References

Notes

Bibliography

  • Air Ministry Pilot's Notes: Blenheim. London: OHMS/Air Data Publications, 1939.
  • Air Ministry Pilot's Notes: Blenheim V. London: OHMS/Air Data Publications, 1942.
  • Barnes, C.H. Bristol Aircraft Since 1910. London: Putnam, 1970. ISBN 0-85177-804-6.
  • Boiten, T. Bristol Blenheim. London: The Crowood Press, 1998. ISBN 1-86126-115-2.
  • Bowyer, C. Bristol Blenheim. London: Ian Allen, 1984. ISBN 0-7110-1351-9.
  • Donald, David. The Complete Encyclopedia of World Aircraft. New York: Barnes & Noble, 1997. ISBN 0-7607-0592-5.
  • Keskinen, Kalevi et al. Suomen Ilmavoimien Historia 10, Bristol Blenheim (in Finnish). Loviisa, Finland: Painoyhtymä Oy, 2004. ISBN 952-99432-1-0.
  • Jefford, C.G., RAF Squadrons. Shrewsbury: Airlife Publishing, 2nd edition, 2001. ISBN 1-84037-141-2.
  • Lake, Jon. Blenheim Squadrons of World War II. London: Osprey Publishing, 1998. ISBN 1-85532-723-6.
  • Mackay, Ron. Bristol Blenheim in Action. Carrollton, Texas: Squadron/Signal Publications, 1998. ISBN 0-89747-209-8.
  • March, Daniel J., ed. British Warplanes of World War II. London: Aerospace, 1998. ISBN 1-874023-92-1.
  • Marttila, Jukka. Bristol Blenheim - Taitoa ja tekniikkaa (in Finnish). Vantaa, Finland: Blenimi-Publishing, 1989. ISBN 952-90017-0-3.
  • Mason, Francis K. The British Bomber Since 1914. London: Putnam Aeronautical Books, 1994. ISBN 0-85177-861-5.
  • Mondey, David. The Hamlyn Concise Guide to American Aircraft of World War II. London: Aerospace Publishing Ltd, 1996. ISBN0-7858-1361-6.
  • Thomas, A. Bristol Blenheim (Warpaint No. 26). London: Hall Park Books, 2000. ISBN 1-84176-289-X.
  • Warner, G. The Bristol Blenheim: A Complete History. London: Crécy Publishing, 2nd edition 2005. ISBN 0-85979-101-7.


External links




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