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{{Short description|British medium bomber in World War II}}
{{For|the car|Bristol Blenheim (car)}}
{{Use dmy dates|date=August 2019}}
{{Use British English|date=June 2015}}
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{{Infobox aircraft
 |name= Blenheim <br /> (Types 142M, 149, 160)
 |image= File:Blenheim - RIAT 2015 (19998104414).jpg
 |image_caption= A Blenheim with the short Mk.I nose at [[RIAT]], 2015
 |aircraft_type= {{plainlist|
* [[Medium bomber]]
* [[Night fighter]]
* [[Aerial reconnaissance|Reconnaissance]]}}
 |manufacturer= [[Bristol Aeroplane Company]]
 |designer= [[Frank Barnwell]]
 |first_flight= 12 April 1935
 |introduction= 1937
 |retired= 1944 (United Kingdom) <br /> 1958 (Finland)
 |primary_user= [[Royal Air Force]]
 |more_users= [[Royal Canadian Air Force]] <br /> [[Finnish Air Force]] <br /> [[Royal Yugoslav Air Force]]
 |number_built= 4,422
 |variants= [[Bristol Beaufort]] <br /> [[Bristol Fairchild Bolingbroke]]
}}
The '''Bristol Blenheim''' is a British [[medium bomber|Light bomber]] designed and built by the [[Bristol Aeroplane Company]], which was used extensively in the first two years of the [[Second World War]], with examples still being used as trainers until the end of the war. Development began with the ''Type 142'', a civil airliner, after a challenge from the newspaper proprietor [[Harold Harmsworth, 1st Viscount Rothermere|Lord Rothermere]] to produce the fastest commercial aircraft in Europe. The ''Type 142'' first flew in April 1935, and the [[Air Ministry]] ordered a bomber development as the ''Type 142M'' for the [[Royal Air Force]] (RAF).

Deliveries of the Blenheim to RAF squadrons commenced on 10 March 1937. In service the Type 142M became the Blenheim Mk.I which would be developed into the long-nosed Type 149, the Blenheim Mk.IV, while in Canada Fairchild Canada built the Type 149 under licence as the Bolingbroke. The Type 160 Bisley was also developed from the Blenheim.

Both versions were converted into heavy night fighters by the addition of a gun pack with four Browning {{cvt|.303|in}} machine guns mounted under the fuselage. The Mk.IV was also used as a maritime patrol aircraft and both versions were also used as bombing and gunnery trainers once they had become obsolete as combat aircraft.

The Blenheim was one of the first British aircraft with an all-metal [[Monocoque#Aircraft|stressed-skin]] construction, retractable [[landing gear]], [[flap (aircraft)|flaps]], a powered [[gun turret]] and [[Variable-pitch propeller (aeronautics)|variable-pitch propeller]]s. The Mk.I was faster than the RAF's biplane fighters in the late 1930s but advances soon left it vulnerable if flown in the day, though it proved successful as a night fighter. Both Blenheim types were used by foreign operators and examples were licence built in Canada, Yugoslavia and Finland.

==Development==
===Origins===
In 1933 [[Frank Barnwell]], Bristol's chief designer, went to the United States to collect information on their latest twin-engined, low-wing monoplane airliners. When he returned he discussed one of them, the [[Lockheed Model 12 Electra Junior]], with [[Roy Fedden]] and prepared a comparable design using Fedden's [[Bristol Aquila]] engine which produced {{cvt|500|hp}}, the same power as in the Electra. [[Sir Archibald Russell]] described Barnwell's design as "close to being a replica of the Electra".<ref>A Span Of Wings, An Autobiography Sir Archibald Russell 1992, {{ISBN|1 85310 234 2}}, p.39</ref> It was designated ''Type 135''.<ref name = "moyes 3"/>

In early 1934, [[Harold Harmsworth, 1st Viscount Rothermere|Lord Rothermere]], owner of the ''[[Daily Mail]]'' newspaper, challenged the British aviation industry to build a high-speed aircraft capable of carrying six passengers and two crew members which he referred to as seeking "the fastest commercial aeroplane in Europe, if not the world".<ref name = "moyes 3"/> German firms were producing record-breaking high-speed designs, such as the [[Heinkel He 70]], and Rothermere wanted the prestige of having the fastest civilian aircraft. Rothermere also intended to encourage businesses and key figures to make greater use of civil aviation and to demonstrate to the British [[Air Ministry]] how their fighters may not be able to match modern transport aircraft, which may be easily converted to, or used as the basis for, bomber aircraft.<ref name = "moyes 3">Moyes 1966, p. 3.</ref>

Rothermere became aware of Bristol's ''Type 135'' proposal and on 3 March 1934, Barnwell issued him with a quote of the specification and performance statistics, including an estimated top speed of {{cvt|240|mph}} at {{cvt|6500|ft}}.<ref name = "moyes 3"/> The Aquila engine had been shelved in favour of the [[supercharger]]-equipped, poppet-valve [[Bristol Mercury]] engine. The Type 135 was further adapted to produce the [[Bristol Type 143|''Type 142'']] to meet the requirements outlined by Rothermere.<ref name = "moyes 3"/> In late March 1934, Rothermere ordered one ''Type 142'' aircraft, which he paid for half of the estimated £18,500 cost up front and the remainder following its first flight in the following year.<ref name = "moyes 3"/>

[[File:Bristol blenheim 1 ExCC.jpg|thumb|The first 142M with the [[United Kingdom military aircraft serials|military serial]] K7033, which served as the only [[prototype]]. It first flew in June 1936.]]
On 12 April 1935, the ''Type 142'', named ''Britain First'', conducted its first flight from [[Filton Aerodrome]], [[South Gloucestershire]].<ref name="Barnes p258">Barnes 1964, p.258.</ref><ref name = "moyes 3"/> Flight tests soon proved that the aircraft was faster than the fighters in service with the [[Royal Air Force]] (RAF), having a top speed of {{cvt|307|mph}}.<ref name="Barnes p259">Barnes 1964, p. 259.</ref><ref name = "moyes 3 4">Moyes 1966, pp. 3–4.</ref> Rothermere presented the aircraft to the nation for a formal evaluation as a bomber.<ref name = "moyes 4">Moyes 1966, p. 4.</ref> In June 1935, the Air Ministry showed interest due to its performance. On 9 July 1935, a design conference was held by Bristol at the ministry's request to convert the ''Type 142'' into a bomber.<ref name = "moyes 4"/>

The Air Ministry formalised [[List of Air Ministry Specifications|Specification B.28/35]] for prototypes of a bomber version which was designated the ''Type 142M'' (M for military) by Bristol.<ref name = "moyes 4"/> A significant change between the ''Type 142M'' bomber and its ''Type 142'' predecessor was the raising of the wing from a low-wing to a mid-wing position, which allowed for enough space under the [[Spar (aviation)|main spar]] to accommodate a bomb bay. Other modifications included the addition of a bomb-aimer's position and a [[M1919 Browning machine gun|Browning machine gun]] in the port wing along with provisions for a semi-retractable [[Anatomical terms of location#Dorsal and ventral|dorsal]] gun turret.<ref name = "moyes 4"/>

===Production===
[[File:Duxford Blenheim.jpg|thumb|Blenheim Mk.I reconstruction by the Aircraft Restoration Co at [[Duxford Aerodrome|Duxford]], for the owners, Blenheim (Duxford) Ltd. It is based on a Bolingbroke airframe with Blenheim Mk.I nose section.]]

In September 1935, the Air Ministry placed a contract for 150 aircraft directly from the drawing board, in a wider part of the rapid expansion of the RAF.<ref name = "moyes 4"/> The first example, ''K7033'', served as the sole prototype and on 25 June 1936, it made its first flight from Filton.<ref name="Mason p269">Mason 1994, p. 269.</ref><ref name = "moyes 4"/> The service name for the aircraft became ''Blenheim Mk.I'' after the [[War of the Spanish Succession]]'s [[Battle of Blenheim]]. On 10 March 1937, deliveries to the RAF started and [[No. 114 Squadron RAF|114 Squadron]] became the first to receive the Blenheim.<ref name="Mason p269"/><ref name = "moyes 4"/> On 13 January 1938, the Blenheim entered service with [[No. 30 Squadron RAF|No. 30 Squadron]], the first overseas squadron and in early 1939, the first Blenheims arrived in India.<ref name = "moyes 6">Moyes 1966, p. 6.</ref>

From July 1936 onwards, various additional orders were placed for the ''Blenheim Mk.I'', including multiple orders for the export market.<ref name = "moyes 4"/> By the end of 1936, 1,568 aircraft were on order.<ref name = "Oughton 159">Oughton 1971, p. 159.</ref> In order to meet the demand, secondary assembly lines were established at [[Chadderton]] by [[Avro]] and at [[Speke]] by [[Rootes Group|Rootes Securities]].<ref name = "moyes 4"/> The aircraft was built under licence by foreign countries, including [[Finland]], who completed a total of 55 aircraft, and [[Kingdom of Yugoslavia|Yugoslavia]], which completed 16 aircraft with a further 24 in advanced stages of completion when [[Germany invaded Yugoslavia]].<ref name = "moyes 11">Moyes 1966, p. 11.</ref> Other countries also procured the Blenheim, including [[Romania]], [[Greece]] and [[Turkey]].<ref name = "moyes 11 12">Moyes 1966, pp. 11–12.</ref><ref name = "Oughton 159"/> By September 1939, orders for the Blenheim had risen to 2,088 aircraft.<ref name = "Oughton 159"/> Total production of the ''Blenheim Mk.I'' in England was 1,351 aircraft prior to the end of the production run in 1939; production had been terminated in favour of more advanced variants.<ref name="Mason p269"/><ref name = "moyes 6"/>

===Further development===
The Blenheim production programme saw several shifts in requirements and in capacity.<ref name = "Oughton 159"/> A modified Blenheim design, given the name ''[[Bristol Bolingbroke|Bolingbroke]]'', was manufactured under licence in Canada by [[Fairchild Aircraft Ltd.|Fairchild Aircraft]].<ref name = "Oughton 157 176">Oughton 1971, pp. 157, 176.</ref> The Bolingbroke, which had been developed in response to Air Ministry Specification G.24/35 to procure a coastal reconnaissance bomber as a replacement for the [[Avro Anson]], had substantial improvements that would serve as the basis for improved variants of the Blenheim.<ref name = "Oughton 157">Oughton 1971, p. 157.</ref> Both the navigator's station and range limitations of the Blenheim Mk.I had been subject to considerable criticism, prompting the development of an improved model to rectify the shortcomings.<ref name = "Oughton 157"/> On 24 September 1937, an experimental Blenheim Mk.I, modified with an extended forward fuselage beyond its original [[stepless cockpit]], smooth-fronted nose enclosure, made its first flight from Filton.<ref name = "Oughton 157"/>

Formal work on an extended-range [[reconnaissance]] version started as the Blenheim Mk.II, which increased tankage from {{cvt|278|to|468|impgal}}. Only one Blenheim Mk.II was completed, as flight tests revealed the increase in speed to be marginal and not warranting further development.<ref name = "moyes 7"/> Another modification resulted in the Blenheim Mk.III, which lengthened the nose, dispensing with the "stepless cockpit" format of the Mk.I, introducing a true windscreen in front of the pilot, to provide more room for the bomb aimer. This required the nose to be "scooped out" in front of the pilot to maintain visibility during takeoff and landing. Both modifications were combined, along with a newer version of the Mercury engine with {{cvt|905|hp}}. The turret acquired a pair of Brownings in place of the original single Vickers K gun, creating the Blenheim Mk.IV.<ref name = "Oughton 157 158">Oughton 1971, pp. 157–158.</ref>

In early 1939, the first batch of Blenheim Mk.IVs were accepted into service; these lacked outer fuel tanks but were accepted due to the urgent demand for the type. Early Blenheim Mk.IVs were also equipped with the Mercury VIII engine, most were fitted with the more powerful Mercury XV or Mercury 25 models.<ref name = "Oughton 158 159">Oughton 1971, pp. 158–159.</ref> Further aircraft deliveries were made to the production standard and were primarily manufactured by Avro and Rootes.<ref name = "Oughton 158">Oughton 1971, p. 158.</ref> Production of the Blenheim IV continued until June 1943, when newcomers such as the [[Bristol Beaufort|Beaufort]]-derived [[Beaufighter]] had succeeded the type.<ref name = "Oughton 159"/> A total of 3,307 were produced.

A long-range fighter version, the Blenheim Mk.IF, was also developed. For this role, about 200 Blenheims were fitted with a gun pack under the fuselage for four {{cvt|.303|in|1}} Brownings.<ref name = "moyes 6"/> Later, the Airborne Intercept (AI) Mk.III or IV [[radar]] was fitted to some aircraft in use as night fighters; these were the first British fighters to be equipped with radar. The Blenheim had been selected as the first aircraft to be adapted for this role as its fuselage was sufficiently roomy to accommodate the additional crew member and radar apparatus.<ref name = "moyes 6"/> Their performance was marginal as a fighter but they served as an interim type pending availability of the more capable Beaufighter derivative. 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 [[National Rifle Association (United Kingdom)|shooting competitions]] held at [[Bisley Ranges]]), the production aircraft were renamed Blenheim Mk.V and featured a strengthened structure, pilot armour, interchangeable nose gun pack or bomb-aimer position and another Mercury variant with {{cvt|950|hp}}. The Mk.V was ordered for conventional bombing operations, with the removal of armour and most of the glazed nose section. The Mk.V (Type 160) was used primarily in the Middle East and Far East. The Blenheim served as the basis for the Beaufort [[torpedo bomber]], which led to the Beaufighter, with the lineage performing two evolutions of bomber-to-fighter.

==Design==
[[File:Bristol Bolingbroke Mk IV T Cockpit IWM Duxford.jpg|thumb|Bolingbroke Mk.IV cockpit. The Blenheim Mk.IV was similar, but had a shorter instrument console. The navigator was in the nose. The gunsight for the forward firing gun is visible.]]
[[File:Antwerp Bristol Blenheim Mk.I L6739 (G-BPIV) 06.jpg|thumb|Blenheim  dorsal gun turret which could be partially lowered to reduce drag.]]

The Bristol Blenheim was a twin-engine high performance all-metal medium bomber aircraft, powered by a pair of [[Bristol Mercury VIII]] air-cooled [[radial engine]]s, each capable of {{cvt|860|hp}}.<ref name = "moyes 16"/> Each engine drove a three-bladed [[Variable-pitch propeller (aeronautics)|controllable-pitch propeller]], and were equipped with both hand-based and electric engine starters.<ref name = "moyes 16"/> To ease maintenance, the engine mountings were designed with a split-segment to facilitate rapid engine removal without disturbing the [[carburettor]]s. A pair of fuel tanks, each containing up to {{cvt|140|impgal|l usgal}}, were housed within the centre-section of the fuselage.<ref name = "moyes 16"/>

The fuselage of the Blenheim employed a light-[[alloy]] [[monocoque]] structure using open-section [[longeron|stringers]], and was constructed in three sections.<ref name = "moyes 16"/> The wing is also built in three sections, the centre-section of which is bolted and [[rivet]]ted to the fuselage. The outer wing sections are [[Wedge (geometry)|taper]]ed in [[Chord (aeronautics)|chord]] and thickness.<ref name = "moyes 16"/> Extensive use of [[Alclad]] sheeting is made in elements such as the [[Rib (aeronautics)|ribs]], skin, [[Flap (aeronautics)|flaps]], and web reinforcement of the [[Spar (aeronautics)|spar]]s. The tail unit is of a cantilever monoplane style, using an all-metal tailplane and [[fin]] while the aerodynamically balanced [[rudder]] and [[Elevator (aeronautics)|elevator]]s use a metal frame covered with fabric.<ref name = "moyes 16"/> The [[landing gear|undercarriage]] was [[hydraulically]]-retracted, with an auxiliary hand-pump for emergency actuation; medium-pressure [[tire|tyre]]s were used, complete with [[pneumatic]]ally-actuated differentially-control brakes.<ref name = "moyes 16"/><ref name = "Oughton 177">Oughton 1971, p. 177.</ref>

The Blenheim typically carried a crew of three – pilot, navigator/bombardier and [[wireless operator|wireless (radio) operator]]/air gunner.<ref name="Barnes p266-7">Barnes 1964, pp. 266–267.</ref> The 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, essential items such as the propeller pitch control were actually placed behind the pilot where they had to be operated by feel alone.<ref name="gunston">Gunston, Bill. ''Classic World War II Aircraft Cutaways''. London: Osprey, 1995. {{ISBN|1-85532-526-8}}.</ref><ref name = "moyes 12 13">Moyes 1966, pp. 12–13.</ref> The navigator/bombardier was seated alongside the pilot, and made use of a sliding/folding seat whilst performing the bomb aiming role. Dual flight controls could be installed.<ref name = "moyes 16"/> The wireless operator/air gunner was housed aft of the wing alongside the aircraft's dorsal gun turret.<ref name = "moyes 16"/>

Armament comprised a single forward-firing [[0.303 British|{{cvt|.303|in|1}}]] Browning machine gun outboard of the port engine and a {{cvt|.303|in|1}} [[Lewis Gun]] in a semi-retracting Bristol Type B Mk.I dorsal turret firing to the rear. From 1939, the Lewis gun was replaced by the more modern {{cvt|.303|in|1}} [[Vickers K machine gun|Vickers VGO machine-gun]]. A {{cvt|1000|lb}} bomb load could be carried in the internal bomb bay set into the centre section of the fuselage.<ref name = "moyes 16"/> Like most contemporary British aircraft, the bomb bay doors were kept closed with [[bungee cord]]s 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.<ref name="gunston"/> The bomb bay could be loaded using a hand-operated [[winch]] incorporated into the fuselage.<ref name = "moyes 16"/>

To achieve its relatively high speed, the Blenheim used a very small fuselage cross-section, with its upper front glazing all at one angle in the form of a "stepless cockpit" that used no separate [[windscreen]] panels for the pilot, a notable feature of a substantial majority of German bomber designs, first conceived during the war years.<ref name="gunston"/> Both fixed and sliding window panels were present, along with a transparent sliding roof.<ref name = "moyes 16"/> Other onboard equipment included a [[radio]], [[camera]]s, navigation systems, [[electric light]]ing, [[oxygen]] apparatus, and stowage for [[parachute]]s and clothing.<ref name = "moyes 16"/>

==Operational history==
===Outbreak of war===
[[File:Bristol Blenheims 62 Squadron Singapore Feb 1941.jpg|thumb|Blenheim Mk.Is of [[No. 62 Squadron RAF]] lined up at [[Tengah Airbase|RAF Tengah]], [[Singapore]], {{Circa|February 1941}}]]
In September 1939, the month in which the Second World War broke out, the Blenheim Mk.I equipped two home-based squadrons and 11 overseas squadrons in locations such as [[Egypt]], [[Aden]], [[Iraq]], [[India]], and [[Singapore]]. Further RAF squadrons had received, or were in the process of converting to, the more capable Blenheim Mk.IV and 168 Blenheim Mk.IV aircraft had entered RAF operational strength by the outbreak of war.<ref name = "moyes 6 7">Moyes 1966, pp. 6–7.</ref><ref name = "Oughton 159"/>

On the day that war was declared on Germany, a Blenheim Mk.IV, ''N6215'', piloted by [[Flying Officer]] [[Andrew McPherson (RAF officer)|Andrew McPherson]] was the first British aircraft to cross the German coast to perform a high altitude reconnaissance mission, made on the German Navy near [[Wilhelmshaven]].<ref name = "Oughton 159"/> The following morning, 15 Blenheims from three squadrons set off on one of the first bombing missions to attack ships spotted the previous day.<ref name=Handbook>Falconer 1998, p. 212.</ref><ref name = "Oughton 159 161">Oughton 1971, pp. 159, 161.</ref> The raid was a failure, only nine aircraft attacked, and only superficial damage was done to the [[German cruiser Emden|cruiser ''Emden'']], when one of [[No. 107 Squadron RAF|No. 107]] Squadron's Blenheims crashed into the cruiser, killing 11 crewmen.<ref name=boris>{{cite magazine|last = Borisenko |first = Igor|title = Kryeser «Emden». Pyervaya zhertva Korolevskih VVS|trans-title=Cruiser Emden. First victim of the RAF|magazine= Arsenal-Kollektsya |volume = 4/2012 (4) |date = October 2012|location = Moscow |lang = ru |pages=47–49}}</ref> [[RAF Coastal Command]] were soon using the Blenheim to protect British shipping convoys off the east coast.<ref name = "Oughton 161"/>

Shortly after the conflict's start, the [[RAF Advanced Air Striking Force]] (AASF) was deployed to numerous airfields in France, allowing for shorter bombing missions against German targets.<ref name = "Oughton 161">Oughton 1971, p. 161.</ref> Several squadrons of Blenheim IVs were assigned to the AASF, being frequently used against targets in France and the [[Low Countries]] once the Battle of France had begun.<ref name = "Oughton 161 162">Oughton 1971, pp. 161–162.</ref> Blenheims were also assigned to the air component of the [[British Expeditionary Force (World War II)|British Expeditionary Force]] of the [[British Army|Army]].<ref name = "Oughton 161 162"/>

In May 1940, AASF and BEF Blenheims participated in the [[Battle of France]], being sent against German forces advancing towards [[Brussels]], resulting in many aircraft sustaining heavy damage or being lost to enemy fire.<ref name = "Oughton 162">Oughton 1971, p. 162.</ref> German attacks upon the French airfields also damaged a considerable number of Blenheims on the ground. On 14 May, a combined force of [[Fairey Battle]]s and Blenheims was dispatched on a counter-attack on German forces breaking through defensive lines but 40 out of 71 aircraft were lost in this sortie. This is the worst losses proportionally taken by the RAF.<ref name = "Oughton 162"/> Further action by Blenheims of Bomber Command that day sustained 25% losses despite heavy British fighter cover.<ref name = "Oughton 162"/> Shortly thereafter, the heavily depleted squadrons were withdrawn to Britain.<ref name = "Oughton 162 164">Oughton 1971, pp. 162, 164.</ref> Around 50 Blenheims supported the [[Dunkirk evacuation]] by harassing enemy forces.<ref name = "Oughton 164">Oughton 1971, p. 164.</ref>

Rapid advances in technology in the late 1930s rendered the Blenheim obsolescent by 1939. In particular, it had become heavier as extra service equipment was installed that was found to be necessary through operational experience. This, coupled with the rapid performance increases of the fighters that would oppose it, had eclipsed the Blenheim's speed advantage.<ref>Warner 2005, p. 158.</ref> In January 1941, the [[Air Staff (United Kingdom)|Air Staff]] classified the Blenheim as inadequate in terms of performance and armament for current operations.<ref name = "Oughton 170"/>

The light armament was unable to deter fighter opposition. Squadrons were forced to improvise a better defensive armament, until officially sanctioned modifications were introduced in early 1940.<ref name = "Oughton 164"/> The Blenheim also proved to be vulnerable to [[anti-aircraft artillery]], especially around the rear fuselage. Flexible, [[Self-sealing fuel tank|self-sealing]] liners had been fitted to the fuel tanks but they were still not fully protected against the {{cvt|20|mm|order=flip}} [[MG FF cannon]] carried by the ''Luftwaffe''{{'}}s [[Messerschmitt Bf 109]] and [[Bf 110]] fighters.<ref>Warner 2005, pp. 155–158.</ref>

===Home front===
Blenheim squadrons were still in demand after their withdrawal from France as part of the British action during the [[Norwegian campaign]].<ref name = "Oughton 164 166">Oughton 1971, pp. 164, 166.</ref> Typically operating from bases in northern Britain, such as [[RAF Lossiemouth]], flying for extended periods over the [[North Sea]] led to the weather posing almost as much of a risk as enemy combatants, particularly as most of the Blenheim IVs lacked heating or [[deicing]] systems and in response, some aircraft were fitted with boilers on the starboard engine exhaust.<ref name = "Oughton 166">Oughton 1971, p. 166.</ref> Heavy losses occurred, caused by both enemy action and engine failures due to [[Icing conditions|icing]].<ref name = "Oughton 166"/>

After the [[fall of France]] in June 1940, the [[Free French Air Force]] was formed at [[RAF Odiham]], [[Hampshire]], in the form of ''Groupe Mixte de Combat'' (GMC) 1, consisting of a mixed bag of Blenheims and [[Westland Lysander]] liaison/observation aircraft, which were later dispatched to North Africa and saw action against Italian and German forces.<ref name = "moyes 7">Moyes 1966, p. 7.</ref>

Blenheim units operated throughout the [[Battle of Britain]], often taking heavy casualties, although they were never accorded the publicity of the fighter squadrons. From July to December 1940, Blenheims raided German-occupied airfields both in daylight and at night. Although most of these raids were unproductive, there were some successes; on 1 August five out of twelve Blenheims sent to attack [[Haamstede]] and Evere (Brussels) were able to bomb, damaging (50 per cent, 40 per cent and 10 per cent) three Bf 109Es of II./JG 27 at Leuwarden and apparently killing a ''Staffelkapitän'' identified as ''[[Hauptmann]]'' Albrecht von Ankum-Frank. Two other 109s were claimed by Blenheim gunners.<ref>Ramsay 1989, p. 552.</ref>{{ref label|Note6|f|f}} 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.<ref>Ramsay 1989, p. 555.</ref>

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 [[Aalborg]] in north-western [[Denmark]] by twelve aircraft of [[No. 82 Squadron RAF|82 Squadron]]. One Blenheim returned early (the pilot was later charged but was killed on another operation before a [[court martial]] was held) while the other eleven, which reached Denmark, were shot down, five by flak and six by Bf 109s.<ref>Warner 2005, p. 255.</ref> Blenheim units had also 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.<ref>Warner 2005.</ref>

[[File:Wreckage of an RAF Bristol Blenheim downed on 15 February 1941 (2189-023-004-001).jpg|thumb|Wreckage of a Blenheim shot down over the Occupied Netherlands on 15 February 1941]]
On 12 August 1941, an action described by ''[[The Daily Telegraph]]'' in 2006 as being the "RAF's most audacious and dangerous low-level bombing raid, a large-scale attack against power stations near Cologne" took place.<ref name=Telegraph-2006-04-10>[https://www.telegraph.co.uk/news/obituaries/1515268/Wing-Commander-Tom-Baker.html "Obituary of Wing Commander Tom Baker."] ''[[The Daily Telegraph]]'', 10 April 2006.</ref> The raid was a low-level daylight raid by 54 Blenheims under the command of Wing Commander Nichol of [[No. 114 Squadron RAF|114 Squadron]]. They hit their targets (Fortuna Power Station in [[Bergheim, North Rhine-Westphalia|Oberaußem-Fortuna]] and the Goldenberg Power Station in [[Hürth-Knapsack]]), but twelve 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%. The England cricketer [[Squadron leader]] [[Bill Edrich]] was awarded the [[Distinguished Flying Cross (United Kingdom)|DFC]] for his part in the raid.<ref name=Telegraph-2006-04-10/><ref>David Frith 1987, p. 365.</ref><ref>Gardner. James. [http://www.nationalarchives.gov.uk/theartofwar/prop/the_fighting_forces/INF3_0850.htm "Bristol Blenheims" (Pencil and watercolour on board, 1941).] ''[[The National Archives (United Kingdom)|National Archives]]''. Retrieved: 22 July 2008.</ref>

From 5 September 1940 Blenheims of Bomber Command began a bombing campaign targeting German-occupied ports along the [[English Channel]], alongside heavier bomber types.<ref name = "Oughton 166 167">Oughton 1971, pp. 166–167.</ref> Bomber Command Blenheims also performed anti-shipping patrols due to Coastal Command's own strike squadrons being heavily depleted throughout the latter half of 1940.<ref name = "Oughton 167">Oughton 1971, p. 167.</ref> On 11 March 1940, a Blenheim IV, ''P4852'', became the first RAF aircraft to sink a [[U-boat]], having scored two direct hits on {{GS|U-31|1936|2}} in the [[Schillig Roads]].<ref name = "Oughton 170">Oughton 1971, p. 170.</ref> In April 1941, a campaign aiming to completely close off the Channel to enemy shipping was launched using an initial flight of Blenheims stationed at [[RAF Manston]]. Between April and June that year, a total of 297 Blenheims of [[No. 2 Group RAF|No 2. Group]] attacked German shipping at sea, losing 36 aircraft, while Coastal Command launched 143 attacks in the same period, losing 52 aircraft; by the end of the year, 698 ships had been attacked and 41 of these sunk for the loss of 123 aircraft.<ref name = "Oughton 170"/>

====Fighter operations====
[[File:Bristol Blenheim Mk IVFs of No. 254 Squadron RAF flying from Aldergrove in Northern Ireland, May 1941. CH2992.jpg|thumb|Formation of Blenheim IVFs in flight]]
The Bristol Blenheim was used by both Bomber and [[Fighter Command]]s. About two hundred Mk.I bombers were modified into Mk.IF long-range fighters with [[No. 600 Squadron RAF|600 Squadron]] (Auxiliary Air Force) based at [[RAF Hendon|Hendon]], the first squadron to take delivery in September 1938. By 1939, at least seven squadrons were operating them as fighters, increasing to about 60 squadrons within a few months. The Mk.IF proved to be slower and less manoeuvrable than expected, and by June 1940 daylight Blenheim losses caused concern for Fighter Command. The Mk.IF was relegated mainly to [[night fighter]] duties where [[No. 23 Squadron RAF|23 Squadron]], which had already operated them at night, soon relegated them to night intruder operations as they were not effective as night fighters.

In the German night-bombing raid on London on 18 June 1940, Blenheims accounted for five German bombers, thus proving that they were better-suited for night fighting. In July, No. 600 Squadron, by then based at [[RAF Manston]], had some of its Mk.IFs equipped with [[AI Mark IV radar#Mk. III|AI Mk.III]] radar. With this radar equipment, a Blenheim from the [[Fighter Interception Unit]] (FIU) at [[RAF Ford]] achieved the first success on the night of 2–3 July 1940, accounting for a [[Dornier Do 17]] bomber.<ref name = "moyes 6"/>  The Blenheim was replaced by the faster and more heavily armed [[Bristol Beaufighter]] in 1940–1941.

===Mediterranean and Middle East===
[[File:Bristol Blenheim - Egypt - Royal Air Force Operations in the Middle East and North Africa, 1939-1943. CM18.jpg|thumb|Armourers of No. 113 Squadron preparing to load a Blenheim Mk.I prior to a raid on [[Tobruk]], [[Libya]], {{Circa|1942}}]]
On 11 June 1940, only hours after Italy's entry into the war on Germany's side, several Blenheim IVs bombed Italian positions.<ref name = "Oughton 170"/> In mid-1940, reinforcement ferry routes were established throughout Africa, starting in [[Takoradi]] on the [[Gold Coast (British colony)|Gold Coast]]. By the end of 1940, a total of three RAF squadrons equipped with Blenheim IV aircraft were performing anti-shipping, bombing, and reconnaissance missions in support of Allied ground forces in North Africa.<ref name = "Oughton 167"/>

By July 1941, it had been recognised that, in response to the increasing intensity of combat in [[North Africa]] and in the [[Middle East]] theatres, additional squadrons were urgently required.<ref name = "Oughton 170"/> In the latter half of 1941, several Blenheim squadrons were flown out to [[Malta]], many being stationed there into early 1942 before mainly being absorbed in the [[Western Desert]] air operations.<ref name = "Oughton 170"/> As Bomber Command gradually took Blenheims out of the Northern Europe theatre, they were often dispatched to other areas such as North Africa.<ref name = "Oughton 175">Oughton 1971, p. 175.</ref> Upon the outbreak of the [[Pacific War]] in December 1941, some Blenheim squadrons in the Middle East were relocated from the theatre to the Far East in response to the new threat from Japanese forces.<ref name = "Oughton 170 173">Oughton 1971, pp. 170, 173.</ref>

===South East Asia===
[[File:Blenheims flying low.jpg|thumb|Blenheims of [[No. 60 Squadron RAF]] flying low to attack a Japanese [[Coastal trading vessel|coaster]] off [[Akyab]], [[Burma]] on 11 October 1942]]

Blenheims continued to operate widely in many combat roles until about 1943, equipping RAF squadrons in the UK and at British bases in [[Aden]], India, [[British Malaya]], Singapore, and the [[Dutch East Indies]]. Many Blenheims were lost to [[Empire of Japan|Japanese]] fighters during the [[Malayan Campaign]] and the battles for [[Battle of Singapore|Singapore]] and [[Battle of Palembang|Sumatra]].<ref name = "Oughton 170"/> By that point, the day bomber role was more effectively carried out by fighter-bombers, and the surviving examples were relegated to training duties. Nonetheless, the Blenheim played a role in preventing India from falling and in [[Burma Campaign|recapturing Burma]], destroyed over 60 aircraft on the ground in raids on [[Bangkok]] early in the campaign.<ref name="Blenheim Squadrons of World War 2">Lake 1998, pp. 89–90.</ref>

One Blenheim pilot, Squadron Leader [[Arthur Scarf]], was posthumously awarded the [[Victoria Cross]] for an attack on [[Singora]], [[Thailand]], on 9 December 1941. Another bomber of [[No. 60 Squadron RAF]] was credited with shooting down Lt Col [[Tateo Katō]]'s [[Nakajima Ki-43]] fighter and badly damaging two others in a single engagement on 22 May 1942, over the [[Bay of Bengal]]. Katō's death was a severe blow to the [[Imperial Japanese Army Air Force]].<ref name="Japanese Army Air Force Aces 1937-45">Sakaida 1997, p. 27.</ref>

The Air Ministry's replacement for the Blenheim as a medium day bomber, another Bristol design, the [[Bristol Buckingham|Buckingham]], was overtaken by events and changes in requirements, and considered inferior to the [[de Havilland Mosquito]], and as such did not see combat. The final ground-attack version – the Blenheim Mk.V – first equipped 139 Squadron in June 1942. Eventually thirteen squadrons – mainly in the Middle East and Far East – received this variant but generally operated them only for a few months.<ref>Jefford 2001</ref>

One Blenheim Mk.IV left in Java by the retreating British forces in 1942 ended up in the hands of the fledgling [[Indonesian Air Force]] (AURI). They repaired it, installed {{cvt|950|hp|kW}} [[Nakajima Sakae]] engines, painted it in their colours, and flew it around [[Yogyakarta]] on at least three occasions.<ref name=GS76>{{cite magazine | editor-last1 = Green | editor-first1 = William | editor-last2 = Swanborough | editor-first2 = Gordon | magazine = Air Enthusiast Quarterly | volume = 2 | year = 1976 | pages = 155–156 | title = Pentagon over the islands }}</ref>

====First attack on the Japanese carrier force====
On 9 April 1942, nine Blenheims from [[No. 11 Squadron RAF|11 Squadron]] attacked the [[1st Air Fleet]] (''Kidō Butai''); the [[Imperial Japanese]] main [[carrier battle group]] (Admiral [[Chūichi Nagumo]]). The Blenheims approached undetected by the [[Mitsubishi A6M Zero|A6M2 Zero]] [[combat air patrol]] (CAP) fighters and surprised the Japanese carrier battle group.<ref name="Parshall_145">Parshall, p. 145</ref> While the bombers attacked fleet carrier {{ship|Japanese aircraft carrier|Akagi||2}} from an altitude of {{convert|11000|ft}}, they missed.<ref name="Shores_1993_426">Shores 1993, p. 426–427</ref><ref name="Parshall_145"/> Four of the Blenheims were shot down over the carriers by CAP ''Zeroes'' (two of which were claimed by ace-fighter pilot [[Kaname Harada]] from {{ship|Japanese aircraft carrier|Soryu||2}}) and by other Japanese aircraft returning from the earlier attack on {{HMS|Hermes|95|6}}, shooting down two ''Zeroes'' in return.<ref name="Shores_1993_426"/><ref>{{Cite book |last=Shores |first=Christopher |title=Bloody Shambles: Volume Two: The Defence of Sumatra to the Fall of Burma |publisher=Grub Street |year=1993 |isbn=978-0948817670}}</ref> This was the first time a Japanese carrier force had faced a concerted air attack in the [[Pacific War]].<ref name="Parshall_145"/>

===Finland===
[[File:Bristol Blenheim Mk. IV of the Finnish Air Force.jpg|thumb|Blenheim BL-129 of Finnish Air Force [[No. 44 Squadron, Finnish Air Force|LeLv 44]] ]]
In 1936, the Finnish Air Force became the first export customer for the Blenheim, ordering 18 Blenheim Mk.Is, which were delivered from Britain between June 1937 and July 1938.<ref name = "moyes 11"/> Two years later, Finland obtained a manufacturing licence for the Blenheim. Before any aircraft could be manufactured at the ''[[Valtion lentokonetehdas]]'' (State Aeroplane 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 and were delivered from the RAF's own stocks.<ref name = "moyes 11"/>

In the aftermath of the Winter War, 55 Blenheims were constructed in Finland, the final aircraft being completed in September 1944; this brought the total number of Blenheims in Finnish service to 97 (75 Mk.Is and 22 Mk.IVs).<ref name="Backwoods">Perttula, Pentti.(1999) [https://web.archive.org/web/20010331180939/http://www.sci.fi/~ambush/faf/blenheim.html ''Bristol Blenheim."] ''Backwoods Landing Strip: Finnish Air Force Aircraft'', ''FAF in Colour''. Retrieved: 27 June 2009.</ref><ref name = "moyes 11"/> The Finns also received 20 half-completed ex-Yugoslavian Mk.IV Blenheims captured by Germany, together with manufacturing tools, production equipment, and a huge variety of spare parts, although some of these had been damaged or otherwise destroyed through [[sabotage]]. Yugoslavia had ceased production of the Mk.I and commenced a production run of Mk.IVs just prior to the April 1941 invasion.<ref>Ciglic and Savic 2002, p. 62.</ref><ref name = "moyes 11"/> The British-made Blenheims had RAF green interiors, RAF seat belts and instruments on imperial units, while Finnish-made Blenheims had medium grey interiors, Finnish-style seat belts and metric instruments.<ref name="ReferenceA">Raunio, Jukka: Lentäjän näkökulma IV, Forssan Kirjapaino OY, 1998</ref>

[[File:Blenheim-luonetjarvi.jpg|thumb|Blenheim I (BL-111) coming in for a landing on Luonetjärvi Airfield, March 1944. BL-111 was a Series I aircraft with doorless bomb bays.]]
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.<ref name="Backwoods"/> The Finnish Blenheims were divided on six series (''sarja''):

:Series I (BL-104..BL-121): 18 British-made Blenheim I bombers with doorless bomb bays. Arrived in 1938
:Series II (BL-146..BL-160): 15 Finnish-made Blenheim I bombers with deepened bomb bay doors. In service by 1941.
:Series III (BL-122..BL-133): 12 British-made Blenheim IV bombers ("long-noses"). Arrived in January 1940.
:Series IV (BL-134..BL-145): 12 British-made Blenheim I bombers. Arrived in February 1940.
:Series V (BL-161..BL-190): 30 Finnish-made Blenheim I bombers. In service by 1943.
:Series VI (BL-196..BL-205): 10 Finnish-made Blenheim IV bombers. In service by 1944.
:Series VII (BL-191..BL-195): six Finnish-made Blenheim I bombers, was cancelled in 1944.

Series I with doorless bomb bays could carry {{cvt|800|kg|order=flip}} bomb load in the bomb bay and up to {{cvt|100|kg|order=flip}} in wing cells. Series II, V and VI could carry {{cvt|800|kg|order=flip}} load on bomb bay and {{cvt|172|kg|order=flip}} on wing cells and fuselage racks. Series III and IV had the original RAF bomb bays and racks and could carry only {{cvt|1000|lb}} load on bomb bay and {{cvt|200|lb}} on wing cells. The bomb bays, bomb bay doors and bomb racks of various series were modified on major overhauls to host bigger bombs.<ref name="ReferenceA"/><ref>Keskinen, Kalevi, Stenman, Kari: Suomen Ilmavoimien Historia 10: Bristol Blenheim, 2004</ref>

After the war, Finland was prohibited from flying bomber aircraft by the [[Paris Peace Treaty]], with Finland's Blenheims being placed into storage in 1948. However, in 1951, five Blenheims were re-activated for use as [[target tug]]s, with the last flight of a Finnish Blenheim taking place on 20 May 1958.<ref name="StenmanAE p35">Stenman ''Air Enthusiast'' Summer 1994, p. 35.</ref> The usual nickname of Blenheim in the Finnish Air Force was ''Pelti-Heikki'' ("Tin Henry").

==Variants==
[[File:Bristol Blenheim ExCC.jpg|thumb|Bristol Blenheim Mk.I in flight]]
[[File:Blenheim 2.jpg|thumb|Bolingbroke IVT in the Commonwealth Air Training Plan Museum, Brandon, Manitoba]]

;Blenheim Mk.I : Three-seat twin-engined light bomber, powered by two {{cvt|840|hp}} Bristol Mercury VIII radial piston engines, armed with a {{cvt|0.303|in|1}} machine gun in the port wing, plus a {{cvt|0.303|in|1}} Vickers K gun in the dorsal turret, maximum bombload {{cvt|1000|lb}}. 1,552 built. Company designation '''Type 142M'''.
;Blenheim Mk.IF : Long-range heavy fighter version, armed with four {{cvt|0.303|in|1}} machine guns in a special gun pack under the fuselage. About 200 Blenheim Mk.Is were converted into Mk.IF fighters, with a number of those converted to night fighters with the addition of AI Mk.III or Mk.IV airborne interceptor radar.
;Blenheim Mk.II : Long-range reconnaissance version with extra fuel tankage. One built.
;Blenheim Mk.III : Prototype for Mk.IV with lengthened nose.
;Blenheim Mk.IV/Bolingbroke I: Improved version, fitted with protective armour and extended nose, powered by two {{cvt|905|hp}} Bristol Mercury XV radial piston engines, armed with a {{cvt|0.303|in|1}} machine gun in the port wing, plus two {{cvt|0.303|in|1}} machine-guns in a powered operated dorsal turret, and two remotely controlled rearward-firing {{cvt|0.303|in|1}} machine guns mounted beneath the nose, maximum bombload {{cvt|1000|lb}} internally and {{cvt|320|lb}} externally. 3,307 built. Company designation '''Type 149'''
;Blenheim Mk.IVF : Long-range fighter version, armed with four {{cvt|0.303|in|1}} machine guns in special gun pack under the fuselage. About 60 Blenheim Mk.IVs were converted into Mk.IVF fighters.
;Blenheim Mk.V/Bisley Mk.I: High-altitude bomber, powered by two Bristol Mercury XV or XXV radial piston engines. Company designation '''Type 160'''

==Operators==
[[File:Bristol Blenheim Mk IV (BL-200).jpg|thumb|Blenheim IV BL-200 (with the [[Western use of the swastika in the early 20th century#Finland|Finnish Hakaristi]] markings) at the Aviation Museum of Central Finland]]
{{Main|List of Bristol Blenheim operators}}
{{colbegin}}
* {{AUS}}
* [[File:Canadian Red Ensign (1921–1957).svg|25px]] [[Canada]]
* {{flag|Independent State of Croatia}}
* {{FIN}}
* {{FRA}}
* {{flagcountry|Kingdom of Greece}}
* {{flag|India|British}}
* {{IDN}}<ref name=GS76/>
* {{NZL}}
* {{POL}}
* {{POR}}
* {{flag|Romania}}
* {{flag|South Africa|1928}}
* {{TUR}}
* {{UK}}
* {{flagcountry|Kingdom of Yugoslavia}}
{{colend}}

==Surviving aircraft==
[[File:Bristol Blenheim restoration, Duxford Military Vehicles Day and MAFVA Nationals 2012. (7425392456).jpg|thumb|A Bristol Blenheim undergoing restoration at [[Imperial War Museum Duxford]], 2012]]
In Finland, the sole surviving Blenheim (all other survivors are Bolingbrokes), a Mk.IV serialed BL-200 of the Finnish Air Force, is on display at the [[Aviation Museum of Central Finland]] at Tikkakoski.<ref>[http://www.k-silmailumuseo.fi "Keski-Suomen Ilmailumuseon (The Aviation Museum of Central Finland)."] ''k-silmailumuseo.fi''. Retrieved: 21 July 2010.</ref>

An airworthy Blenheim was rebuilt from a scrapped Bolingbroke over a 12-year period, only to crash at an airshow at [[Denham Aerodrome|Denham]] within a month of completion in 1987.

A replacement Bolingbroke Mk.IVT was rebuilt to flying status over five years and painted to represent a Blenheim Mk.IV in wartime RAF service. It began flying in the UK in 1993, and was used in the 1995 film version of [[Shakespeare's]] ''[[Richard III (1995 film)|Richard III]]''. This aircraft crashed on landing at Duxford on 18 August 2003,<ref>{{cite web|title=Airfield to examine safety after crash |date=19 August 2003 |url=http://news.bbc.co.uk/1/hi/england/cambridgeshire/3162809.stm |publisher=BBC |access-date=2 October 2017}}</ref> but after extensive repair and conversion to the Mark I "Short nose" version, was displayed and flown again in 2014, at the [[Imperial War Museum Duxford]], England.<ref>[https://www.facebook.com/media/set/?set=a.872552412755500.1073741870.386907504653329&type=1 "The Blenheim Flys – November 20th 2014."] ''Facebook''. Retrieved: 25 April 2015.</ref> The aircraft appeared in the 2017 [[Christopher Nolan]] film ''[[Dunkirk (2017 film)|Dunkirk]]''.

In summer 1996, a Bristol Blenheim Mk.IVF was recovered from the sea, off [[Rethymnon]], Crete. The [[No. 203 Squadron RAF]] aircraft was downed by friendly fire on 28 April 1941. The Blenheim was moved to the [[Hellenic Air Force Museum]] for restoration.<ref>[http://www.haf.gr/en/history/museum/exhibition.asp "Μουσείο Πολεμικής Αεροπορίας (Hellenic Airforce Museum)."] {{webarchive|url=https://web.archive.org/web/20120318075955/http://www.haf.gr/en/history/museum/exhibition.asp |date=18 March 2012 }} ''haf.gr.'' Retrieved: 18 April 2012.</ref>

The [[Kent Battle of Britain Museum]] in [[Hawkinge]] began a project to rebuild a Blenheim IVF using the remains of four Bolingbrokes in 2018. The [[Historic Flying Limited|Aircraft Restoration Company (ARC)]] provided surplus parts from its own Blenheim restoration.<ref>{{Cite web | url=http://www.kbobm.org/blenheim_project.html | title=Blenheim Project: Kent Battle of Britain Museum }}</ref>

The [[Royal Museum of the Armed Forces and Military History]] in [[Brussels]] exhibits a Bolingbroke painted as a [[No. 139 Squadron RAF]] Blenheim XD-A that crash landed in May 1940 in Belgium.

A [[Bristol Bolingbroke|Bolingbroke]] is being restored for museum display at [[Aerospace Bristol]].{{cn|date=August 2024}}

==Specifications (Blenheim Mk.IV)==
[[File:Bristol Blenheim.png|thumb|3-view drawing of the Blenheim Mk.I(F), with scrap views showing the Mk.IV and Mk.V variants]]
{{Aircraft specs
|ref=''British Warplanes of World War II'',<ref name="Marchp43">March 1998, p. 43.</ref> ''The Bristol Blenheim I''<ref name = "moyes 16">Moyes 1966, p. 16.</ref>
|prime units?=imp
|crew=3
|length ft=42|length in=7
|span ft=56|span in=4
|height ft=9|height in=10
|wing area sqft=469
|airfoil= RAF-28 (18%)<ref name="Selig">{{cite web |last1=Lednicer |first1=David |title=The Incomplete Guide to Airfoil Usage |url=https://m-selig.ae.illinois.edu/ads/aircraft.html |website=UIUC Applied Aerodynamics Group  |access-date=28 May 2019}}</ref>
|empty weight lb=9790|gross weight lb=14400
<!-- Powerplant -->
|eng1 number=2|eng1 name=[[Bristol Mercury XV]]|eng1 type=9-cylinder air-cooled radial piston engines|eng1 hp=920
|prop blade number=3
|prop name=[[Hamilton Standard]] variable-pitch propellers, built under license by de Havilland
|prop dia ft=10|prop dia in=6
<!-- Performance -->
|max speed mph=266|max speed note=at {{cvt|11800|ft}}|cruise speed mph=198
|range miles=1460
|ceiling ft=27260
|time to altitude={{cvt|6500|ft}} in 4 minutes 10 seconds
|wing loading lb/sqft=30.7
|power/mass={{cvt|0.13|hp/lb|kW/kg}}
<!--Armament-->
|guns=<br>
:* 1 × {{cvt|.303|in|1}} [[M1919 Browning machine gun|Browning machine gun]] in port wing
:* 1 or 2 × {{cvt|.303|in|1}} Browning guns rear-firing in under-nose fairing or [[Nash & Thompson]] FN.54 turret
:* 2 × {{cvt|.303|in|1}} Browning guns in dorsal turret
|bombs=<br>
:* {{cvt|1200|lb}} total
:* 4 × {{cvt|250|lb}} General Purpose bombs ''or''
:* 2 × {{cvt|500|lb}} GP bombs internally and 8 × {{cvt|40|lb}} GP bombs externally
 
:* Finnish Blenheim IV Series VIs carried a {{cvt|1800|lb|-1}} load in the bomb bay and {{cvt|379|lb}} on wing cells and fuselage racks.
|avionics= * T1082 (transmitter) and R1083 (receiver) radio sets
}}

==See also==
{{External media|topic= |width=18% |float=right |video1=[https://www.youtube.com/watch?v=aM60r3kEmaQ Period news report on the Blenheim] |video2=[https://www.youtube.com/watch?v=tGtv79u2y7Q Footage and images of Blenheim operations] |video3=[https://www.youtube.com/watch?v=pS6F0mxVP5E Preserved Blenheim MK.IF taking off and performing multiple flypasts in 2015]}}
{{aircontent
|related=
* [[Bristol Beaufort]]
* [[Bristol Beaufighter]]
* [[Bristol Fairchild Bolingbroke]]
|similar aircraft=
* [[Bloch MB.170]]
* [[Dornier Do 17]]
* [[Kawasaki Ki-48]] ''Sokei''
* [[Lockheed Hudson]]
* [[PZL.37 Łoś]]
* [[Tupolev SB]]
|lists=
* [[List of bomber aircraft]]
* [[List of aircraft of the United Kingdom in World War II]]
* [[List of aircraft of World War II]]
}}

==References==
===Citations===
{{Reflist}}

===Bibliography===
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* {{cite book |title=Air Ministry Pilot's Notes: Blenheim V |publisher=HMSO (reprint by Air Data Publications) |location=London |year=1942}}
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* {{cite book |last1=Ciglić |first1=Boris |last2=Savić |first2=Dragan |title=Croatian Aces of World War II |series=Osprey Aircraft of the Aces – 49 |publisher=Oxford |location=London |year=2002 |isbn=1841764353}}
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* {{cite book |last=Jefford |first=C.G. |title=RAF Squadrons: A Comprehensive Record of the Movement and Equipment of All RAF Squadrons and Their Antecedents Since 1912 |publisher=Airlife Publishing |location=Shrewsbury, UK |edition=2nd |year=2001 |isbn=1840371412}}
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* {{cite book |editor-last=March |editor-first=Daniel J. |title=British Warplanes of World War II |publisher=Aerospace |location=London |year=1998 |isbn=1874023921}}
* {{cite book |last=Marttila |first=Jukka |title=Bristol Blenheim – Taitoa ja tekniikkaa |publisher=Blenimi-Publishing |location=Vantaa, Finland |year=1989 |isbn=9529001703 |language=fi}}
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* {{cite book |last=Ognjević |first=Aleksandar M. |title=Bristol Blenheim: The Yugoslav Story: Operational Record 1937–1958 |publisher=Leadensky Books |location=Zemun, Serbia |year=2014 |isbn=978-8691762506}}
* {{cite book |last=Oughton |first=James D. |title=Bristol Blenheim Mk.IV |series=Aircraft in Profile No 218 |publisher=Profile Publications Ltd |location=Leatherhead, Surrey, UK |year=1971}}
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* {{cite book |last=Sakaida |first=Henry |title=Japanese Army Air Force Aces 1937–45 |publisher=Osprey Publishing |location=Oxford, UK |year=1997 |isbn=1855325292}}
* {{cite magazine |last=Stenman |first=Kari |title=From Britain to Finland: Supplies for the Winter War |magazine=Air Enthusiast |issue=94 |date=July–August 2001 |pages=56–59 |issn=0143-5450}}
* {{cite magazine |last=Stenman |first=Kari |title=Staying Power: The Bristol Blenheim in Finnish Service |magazine=Air Enthusiast |issue=54 |date=Summer 1994 |pages=26–35 |issn=0143-5450}}
* {{cite book |last=Thomas |first=A. |title=Bristol Blenheim (Warpaint No. 26) |publisher=Hall Park Books |location=London |year=2000 |isbn=184176289X}}
* {{cite book |last=Warner |first=Graham |title=The Bristol Blenheim: A Complete History |publisher=Crécy Publishing |location=London |edition=2nd |year=2005 |isbn=0859791017}}
* {{cite magazine |last=Warner |first=Graham |title=Spirit of Britain First: A Pictorial Tribute to Britain's Airworthy Blenheim |magazine=Air Enthusiast |issue=65 |date=September–October 1996 |pages=68–69 |issn=0143-5450}}
* {{cite book |last=Wheeler |first=Barry C. |title=The Hamlyn Guide to Military Aircraft Markings |publisher=Chancellor Press |location=London |year=1992 |isbn=1851525823}}

==Further reading==
* {{cite journal |last1=Stuart |first1=Robert |date=2014 |title=Air Raid Colombo, 5 April 1942: The Fully Expected Surprise Attack |url=http://www.rcaf-arc.forces.gc.ca/en/cf-aerospace-warfare-centre/elibrary/journal/2014-vol3-iss4-06-air-raid-colombo-5-april-1942.page |journal=Royal Canadian Air Force Journal |volume=3 |issue=4 |publisher=[[Department of National Defence (Canada)|Department of National Defence of Canada]] |access-date=1 May 2022}}
* {{cite journal |last1=Stuart |first1=Rob |date=2006 |title=Leonard Birchall and the Japanese Raid on Colombo |url=http://www.journal.forces.gc.ca/vo7/no4/stuart-eng.asp |journal=Canadian Military Journal |volume=7 |issue=4 |publisher=[[Department of National Defence (Canada)|Department of National Defence of Canada]] |access-date=1 May 2022}}

==External links==
{{Commons category}}
* [https://web.archive.org/web/20090531102957/http://www.raf.mod.uk/history_old/blen1.html RAF Bristol Blenheim history]
* [http://www.211squadron.org/ No. 211 Squadron RAF]
* [https://web.archive.org/web/20080424000034/http://www.blenheimsociety.org.uk/ Blenheim Society]
* [http://www.arc-duxford.co.uk/ Aircraft Restoration Company]
* [https://web.archive.org/web/20110720183435/http://www.ilmasotakoulunkilta.fi/IlmaSK/ilmaskmma.nsf/sp?open&cid=Content7FCEC-2 Finnish Mk.IV Blenheim restoration]
* [http://www.flightglobal.com/pdfarchive/view/1937/1937%20-%201665.html "Up in the Blenheim, a civilian pilot's impressions..."; ''Flight'', 24 June 1937]
* [http://www.flightglobal.com/pdfarchive/view/1938/1938%20-%201413.html "How the Bristol Blenheims are erected"; ''Aircraft Engineer'' (supplement to ''Flight''), 19 May 1938]
* [http://www.flightglobal.com/pdfarchive/view/1945/1945%20-%202254.html "In the air IV – Flying the Blenheim"; ''Flight'', 15 November 1945]

{{Bristol aircraft}}
{{RAF WWII Strategic Bombing}}

{{Authority control}}

[[Category:Bristol Aeroplane Company aircraft|Blenheim]]
[[Category:1930s British bomber aircraft]]
[[Category:1930s British fighter aircraft]]
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[[Category:Aircraft first flown in 1935]]
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[[Category:Aircraft with retractable conventional landing gear]]