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Bristol Blenheim Mk I: Top Plan

Bristol Blenheim Mk I: Top Plan


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Blenheim Squadrons of World War Two, Jon Lake. This book looks at the entire RAF service career of the Bristol Blenheim, from its debut as a promising fast bomber, through the deadly disillusionment of the blitzkrieg, on to its work in the Middle East and Mediterranean, where the aircraft found a new lease of life. Lake also looks at the use of the Blenheim as an interim fighter aircraft and its use by Coastal Command.


Bristol Freighter

The Bristol Type 170 Freighter is a British twin-engine aircraft designed and built by the Bristol Aeroplane Company as both a freighter and airliner. Its best known use was as an air ferry to carry cars and their passengers over relatively short distances. A passenger-only version was also produced, known as the Wayfarer.

Type 170 Freighter / Wayfarer
Bristol Freighter 31 of Dan-Air operating a cargo service at Manchester Airport in 1964.
Role Cargo aircraft
National origin United Kingdom
Manufacturer Bristol Aeroplane Company
First flight 2 December 1945
Introduction 1946
Status Retired
Primary user Silver City Airways
Produced 1945–1958
Number built 214 [1]
Variants Bristol Superfreighter

The Freighter was developed during the Second World War, having attracted official attention from the British Air Ministry, which sought the development of a rugged vehicle capable of carrying various cargoes, including a 3-ton truck. Various changes to the design were made to accommodate their requirements, but being completed too late to participate in the conflict, the majority of sales of the Freighter were to commercial operators. In response to customer demand, an enlarged version to maximise vehicle-carrying capacity, known as the Bristol Superfreighter, was developed.


Bristol Blenheim

Authored By: Staff Writer | Last Edited: 06/11/2019 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

Origins of the Bristol Blenheim Light Bomber / Heavy Fighter place it in the 1930s when Lord Rothermere, owner of the "Daily Mail" newspaper, set out a challenge to produce the fastest aircraft in Europe. From this came the Bristol "Type 142" with its sleek design holding much promise. It certainly went on to impress onlookers including Royal Air Force authorities who eventually considered it for military service (indeed it proved faster that some frontline fighters of the day). Specification B.28/35 was drawn up by the Air Ministry in 1935 to cover the conversion process of the fast plane to a three-seat, twin-engined light bomber / heavy fighter form. It was known to Bristol as the "Type 142M" and named Blenheim in RAF service. An initial order of 150 in 1935 followed and this was strengthened by a 1936 order for 434 more (as the Blenheim Mk.I).

Initial users were the airmen of Squadron No.114 during March of 1937 and a stock of hundreds were available when Britain went to war in September of 1939. However, of this total many were already stationed overseas in far-off places like the Middle East and Far East so they held little value in defending the home front and in attacking Axis positions across mainland Europe. The line was continually evolved throughout its early involvement in the war and this resulted in a few more specialized designs including a night fighters and several long-range performers.

Blenheims in Action

Blenheims marked the first RAF violation of German airspace in the war when a flight crossed over into enemy territory on a reconnaissance mission near Wilhelmshaven (September 3rd, 1939). The next day, Blenheims attacked German naval positions at the Elbe Estuary but this force of ten was reduced to just five returning bombers and many of the dropped ordnance failed to detonate. The aircraft was continually pushed into action despite its shortcomings and spent time in the skies above Norway, France and the Low Countries. In these environments the aircraft proved its underperforming self and lacked suitable defensive capabilities - under-powered and under-gunned she was. This led to revisions of the armament suite, namely increasing the overall machine gun count carried. On March 11, 1940, a Blenheim claimed the RAF's first sinking of an enemy submarine (a German U-Boat).

The Blenheim equipped the first night fighter unit anywhere in the world when Squadron No.25 was given the type. During the "Battle of Britain" in the summer of 1940, a Blenheim night fighter claimed the first aerial kill while carrying radar when it downed a raiding German Dornier Do 17 Medium Bomber. The series played a crucial role in the night defense of Britain proper despite its inherent deficiencies in both performance and firepower.

The series soldiered on in anti-shipping sorties across the North Sea and in daring low-altitude runs against German infrastructure when possible. Overseas units were featured in the Middle East, Far East, North African and Mediterranean theaters (including time over Greece and Crete). Finland, becoming the first export customer of the Blenheim back in 1936 (both through direct order and local, licensed production), showcased the light bomber during its wars against the Soviet Union (the "Winter War" and the "Continuation War").

The line eventually served out its usefulness and was gradually replaced from 1942 onward by such designs as the American Douglas "Boston" and British de Havilland Mosquitoes and Bristol Beaufighters. The RAF gave up use of all Blenheims as soon as 1944.

Blenheim Production Marks and Operators

Production began with the Blenheim Mk.I and this carried a crew of three with 2 x Bristol Mercury VIII series radial piston engines of 840 horsepower each. Armament included a 7.7mm machine gun fixed to the port side wing mainplane and a 7.7mm (Vickers K) machine gun at a dorsal turret emplacement. Internally the aircraft could haul a war load of 1,000lb. Production resulted in 1,552 units built to the standard.

The Blenheim Mk.IF followed and this was evolved along the lines of a night fighter. Even as the original Mk.I bomber was being introduced back in 1937, the design was already losing out to newer aircraft - it carried an inadequate bombload for its role as a bomber and lacked the offensive punch to be considered a useful heavy fighter. As such it was outfitted with AI Mk.III or Mk.IV series radar and had its armament improved to 4 x 7.7mm machine guns all fitted to a ventral gun pack. A stock of about 200 Blenheim Mk.I bombers were converted for the night fighter role featuring this equipment. The aircraft were in action before the end of 1940 but were nothing more than interim night fighters at best.

The Blenheim Mk.II was developed as a long-range reconnaissance platform and given extra fuel stores as a result. However this mark was not adopted for serial production and only one example was ever completed.

The Blenheim Mk.IV was introduced as an upgraded model and featured 2 x Bristol Mercury XV radial piston engines of 905 horsepower each as well as the definitive lengthened, stepped nose section. The 7.7mm machine gun in the port side wing was retained but two 7.7mm machine guns now adorned the dorsal turret. A pair of remotely-controlled 7.7mm machine guns were fitted just under the nose (though sometimes a single gun was installed), rear-facing to engaging an potential trailing enemies. Armor protection was added to increase crew and aircraft survivability. The crew numbered three. The bomb load remained 1,000lb while an externally-carrying capability (eight hardpoints) could add 320lb more. 3,307 of this mark were produced making it the definitive variant of the series.

Performance for the Mk.IV included a maximum speed of 266 miles per hour, a cruising speed of 200 miles per hour, a range out to 1,460 miles and a service ceiling of 27,260 feet.

Introduced into service with the RAF in 1939, the Mk.IV form quickly superseded the once-highly-touted Mk.I series models.

The Blenheim Mk.IVF became a long-range heavy fighter and was armed similarly to the Mk.IF night fighter (4 x 7.7mm machine guns to a ventral gun pack). Mk.IV models served as the basis and were modified to the Mk.IFV standard through 60 examples.

The Blenheim Mk.V became the final production form of this aircraft series and was used in the high-altitude bomber role. Power came from a pair of Bristol Mercury XV or XXV series radial piston engines.

Operators of the Blenheim (beyond the UK) included Australia, Canada, China, Croatia, Finland, France, Greece, India, New Zealand, Poland, Portugal, Romania, South Africa, Turkey and Yugoslavia.

In all, 4,422 Bristol Blenheims of all marks were produced including 44 from Yugoslav factories (by Ikarus) and 55 by Finland. Canadian factories (Bristol Fairchild) outputted 626 of the related "Bolingbroke" bombers from 1939 to 1943. The final frontline aircraft was not retired until 1956 by the Finns. The Bristol Beaufort (introduced in 1939) was an off-shoot of the Blenheim and 1,821 were produced in the UK and Australia.


From Civil to Military

A second prototype, the Type 143, was also built. Slightly shorter and powered by twin 500 hp Aquila engines, this design was ultimately scrapped in favor of the Type 142. As development moved forward, interest in the aircraft grew and the Finnish government inquired regarding a militarized version of the Type 142. This led to Bristol beginning a study to assess adapting the aircraft for military use. The result was the creation of the Type 142F which incorporated guns and interchangeable fuselage sections which would allow it to be used as transport, light bomber, or ambulance.

As Barnwell explored these options, the Air Ministry expressed interest in a bomber variant of the aircraft. Rothermere's aircraft, which he dubbed Britain First was completed and first took to sky from Filton on April 12, 1935. Delighted with the performance, he donated it to the Air Ministry to help push the project forward.

As a result, the aircraft was transferred to the Aeroplane and Armament Experimental Establishment (AAEE) at Martlesham Heath for acceptance trials. Impressing the test pilots, it achieved speeds reaching 307 mph. Due to its performance, civil applications were discarded in favor military. Working to adapt the aircraft as a light bomber, Barnwell raised the wing to create space for a bomb bay and added a dorsal turret featuring a .30 cal. Lewis gun. A second .30 cal machine gun was added in the port wing.

Designated the Type 142M, the bomber required a crew of three: pilot, bombardier/navigator, and radioman/gunner. Desperate to have a modern bomber in service, the Air Ministry ordered 150 Type 142Ms in August 1935 before the prototype flew. Dubbed the Blenheim, the named commemorated the Duke of Marlborough's 1704 victory at Blenheim.


Restorations

During the early 1970s Ormond Haydon-Ballie, a young RAF Flight Lieutenant was seconded to the RCAF.

Whilst in Canada amongst other aircraft he discovered several derelict ‘Bolingbrokes’ (Bristol Blenheims built under licence in Canada).

In 1973 he purchased two complete airframes, 9896 and 10038 both built in Canada and having seen wartime service, he also gathered together as many engines and spare parts and had then shipped to the UK in 1974, and through a bit of wrangling got them stored at the old RAF station at Duxford in building number 66 which was immediately christened ‘Blenheim Palace’, which it is still known as today.

As the maintenance of Haydon-Baillie’s flying aircraft took priority work on the Blenheims was very low key and was dealt a terrible blow in July 1977 when he was killed in a flying accident in Germany.

In July 1978 Graham Warner was being shown around Duxford and amongst other items saw the Blenheims for the first time and after much thought and speaking to Haydon-Baillie’s team over a period of time decided to take the project on.


The aircraft was painted in the ‘camouflage pattern A’ and the chosen markings of V6028 GB-D, of 105 Squadron, 2 Group, RAF Bomber Command, the aircraft in which Wing Commander Hughie Idwal Edwards won the Victoria Cross on 4th July 1941.

On the 22nd May 1987, a Bristol Blenheim took to the skies for the first time in over forty years to become the sole airworthy example.

This first flight followed a meticulous restoration which took twelve years, a small fortune, and some 40,000 voluntary man-hours to complete.

Just four weeks later on 21st June 1987 the aircraft was destroyed in an accident at Denham, not due to any mechanical fault, and mercifully with no loss of life.

The 2nd restoration.

To aid the raising of the necessary funds ‘The Blenheim Appeal Fund’ was launched with donations going towards the rebuild.

It was also decided to restore the proper historic importance of the Blenheim.

The components for the second restoration arrived at Duxford in February 1988 from Strathallan.

At a press conference on 29th June 1988 it was announced that a ‘Blenheim Society’ was to be formed, with a newsletter to keep supporters informed of the progress on the restoration.

From lessons learned on the first project a different system was used on this project, each major component was assembled and systems installed whilst in the workshop. The project was completed in 1993, and the aircraft first flew in May of that year.

From the beginning it was decided the aircraft should be repainted over a period of time in various schemes to represent the different commands and squadrons in which the Blenheim served.


The aircraft was built as a Mk IVF and painted all black as night fighter Z5722 WM-Z, the personal aircraft of the CO of 68 Squadron, Wing Commander the Hon Max Aitken DSO, DFC CzMC.
His widow Lady Aitken gave her blessing to use these markings.

The aircraft was also given the name ‘Spirit of Britain First’ after the first Blenheim.


The aircraft was then painted in the markings of a Coastal Command Mk IVF L8841 QY-C, of 254 Squadron.

Here the aircraft is painted to represent Mk IV Bomber
R3821 UX-N, of 82 Squadron.

In 2003 this aircraft had a landing accident, once again due to no mechanical failure of the aircraft.

Blenheim Duxford Ltd., was formed and took over the responsibility for the aircraft, and it was decided to repair the aircraft representing a Mk IF, L6739 YP-Q, of 23 Squadron, using the nose rescued by Ralph Nelson.


Ralph Nelson (a Bristol employee) and the Blenheim Mk I nose which he converted into an electric car.

Text from ‘Spirit of Britain First’ by Graham Warner ISBN 1-85260-533-2


Bristol Blenheim

The Bristol Type 142M/149 Blenheim was a high-speed light bomber used extensively in the early days of World War II, built by Bristol Aeroplane Company.

The design had started as a civilian aircraft, a project of Lord Rothermere, owner of the Daily Mail. In order to promote British aviation, he asked the industry to deliver the fastest civilian aircraft in Europe, capable of carrying 6 passengers and 2 crew members. Bristol responded with the Type 142, and when it first flew as Britain First in 1934 it proved to be faster than any fighter the RAF had at the time.

Needless to say the Air Ministry was interested in such a plane for their own uses, and quickly sent out Specification B.28/35 for prototypes of a bomber version of the 142M (M for "military"). The main changes were to move the wing higher on the fuselage from its former low position, to allow room under the spar for a bomb-bay. The aircraft was all-metal with twin Bristol Mercury VIII radial engines of 860 hp (640 kW) each. It carried a crew of three &ndash pilot, navigator/bombardier and gunner/wireless operator &ndash and was armed with a forward firing 0.303-in machine-gun in the wing root and a 0.303-in (7.7-mm) machine-gun in a semi-retracting dorsal turret firing to the rear. A 1,000-lb (454-kg) bombload was carried in the internal bay.

The plane was ordered directly from the plans, and the first production model, known at the time as the Bolingbroke, served as the first and only prototype. The name then became Blenheim I, and deliveries started in 1937. The plane would prove to be so successful that it was licensed by a number of countries, including Finland and Yugoslavia. Other countries bought it outright, including Romania, Greece, and Turkey. Total production of the Blenheim in England amounted to 1,351 Mk.I's.

After France fell to Germany in June 1940, the Free French air force was formed at RAF Odiham in the guise 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.

Work on an extended range reconnaissance version started as the Mk.II, which increased tankage from 278 to 468 gallons, but only one was completed. Another modification resulted in the 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 a second gun in the rear cockpit, to create the Blenheim IV. When it was introduced in 1939, the Mk.IV (Type 149 to Bristol) was one of the fastest bomber in the world (slower only than the Dornier Do 215), and 3,307 would eventually be produced.

The longer range also lent itself to a Canadian need for a patrol bomber, and Fairchild started production of Blenheim Mk.IV there with the original name as the Bolingbroke. After a small run of British-like planes as the Mk.I, Fairchild switched production to the Bolingbroke Mk.IV with American instruments and equipment. These versions also included anti-icing boots and a dinghy. Some of these planes served as bombers during the Aleutians campaign, but most of the 150 served in the intended role as patrol bombers on the Atlantic coast. Another 450 were completed as the Mk.IVT as trainers, and saw extensive use in the Commonwealth Air Training Plan. 676 Bolingbrokes were made.

Another modification was attempted to create a heavy fighter version. In this purpose, about 200 Blenheims were fitted as Mk.IF variant, with an underbelly gun-pack with four 0.303-in machine guns. Some of them were also fitted with a radar AI Mk.III or IV, being the first British fighters with radar. Their performance was rather poor as a fighter, but they served before an advent of more sophisticated machines. Radar-equipped Blenheim Mk.IF scored the first victory on July 2/3, 1940, over Dornier Do 17 bomber. About 60 of Mk.IV's were also equipped with a gun pack as Mk.IVF, but they were used by the Coastal Command rather to protect convoys from German long-range bombers.

The last bomber variant was conceived as ground attack aircraft, using a solid nose containing four more Browning machine-guns. Originally known as the Bisley, the production aircraft were renamed Blenheim V and featured a strengthened structure, pilot armour, interchangeable nose gun pack or bombardier position, and yet another new Mercury with 950 hp (710 kW). The Mk.V (Type 160) was used primarily in the Far East.

Blenheims operated widely in many combat roles until about 1943. By that point most fighters could carry similar bombloads at much higher speeds, and the surviving examples were relegated to training duty. Bristol's intended successor to the Blenheim, the Buckingham, was considered inferior to the Mosquito, and did not see combat.

The Blenheim also served as the pattern for the Beaufort and, eventually, Beaufighter.


Bristol Blenheim in 1/32 Scale

The Bristol Blenheim was a solid product of the mid 1930s. A cantilever low wing monoplane featuring stress skin construction, it was a world class airplane in its day, but its day was rapidly fading by the time WW II erupted. Soldiering on till the end of the war and beyond, it performed a variety of tasks, for a variety of countries until its military career ended May 20, 1958 when a Finnish target towing Blenheim landed for the last time. Several Finnish units flew the Blenheim in hard combat against the Soviet Union's forces, both in the Winter War of 1939-1940 and the Continuation War 1941-1944 and thirty-one were lost on operations. A truce with the USSR was signed on September 4, 1944 and it required the Finns to help oust their erstwhile allies, the Germans, from Finnish territory. The Blenheims were back in a shooting war and another two were lost before operations ceased on March 13, 1945 when the last sortie was flown - an uneventful anti-submarine patrol. Though on alert, no more war missions were flown and the last German soldiers were withdrawn from Finland by April 27, 1945.

Finnish Blenheims were divided into six Series, labeled, oddly enough, I through VI. The break down is as follows:

  • Series I- 18 machines numbered BL-104 - BL-121, British built Mk I
  • Series II - 15 machines numbered BL-146 - BL-160, Finnish built Mk II
  • Series III - 12 machines numbered BL-122 - BL-133, British built Mk IV
  • Series IV- 12 machines numbered BL-134 - BL-145, British built Mk I
  • Series V - 30 machines numbered BL-161 - BL-190, Finnish built Mk II
  • Series VI - 10 machines numbered BL-196 - BL-205, Finnish built Mk IV, using some Yugoslavian components.

One Series III airplane was lost during delivery for a total of 97 Blenheims in Finnish service.

The Model

My 1/32 Bristol Blenheim model represents a Mk. II of the second Finnish Series. The main inspiration for this project came rather obliquely from a desire for more space to store unbuilt kits. Somehow, I had managed over time to acquire two Revell Beaufighter. The Beaufighter is a big kit in a big box, and I thought that maybe I could use a few parts from one of these to make a Blenheim, and cram the leftovers into the remaining box, thereby gaining a little space. (Never mind that if the want for more space was the driving force, it would have been easier, quicker and probably more fun to have built a few kits "outtadabox". Rationality is not exactly the battle cry of the scratchbuilder!). I also thought that this would be an easy way to build a big Blenheim. Grrrr. As it turned out, I DID painfully extract a set of wings, but pure scratchbuilding would have been a lot less hassle.

Two photos showing nicely the conversion work necessary on the fuselage.

The Blenheim wing was smaller in span, chord, and maximum airfoil thickness. The location and size of the engine nacelles and control surfaces also differed as well as the location of the outer panels which governed dihedral. The only other kit parts used were the cowl nose rings and props, and these were just basically blanks to cut down in all dimensions.

The fuselage, clear parts, and engine nacelles were home made vacuum forms, done in the kitchen using the oven, a shop vac and a crude homemade plywood suction box. The male molds were hacked out of balsa wood. (note: if you want to know more about on how to make masters for scratchbuilt vac models click here)

A view of the wing quilting process. The layers of paint can be clearly seen here, and the effect, while subtle, is effective.

A shot of the interior, showing the wooden wingspar box and crew positions.

Tail surfaces were plastic skinned wooden affairs. The landing gear was made from various diameters of wire-cored Plastruct tube and bamboo skewers. The skis were made from a slab of steamed and curved basswood, faced on the tops and bottoms with sheet plastic. I put the airplane on skis because it's a little something different, and also it rid me of the need to go on a torturous wheel-hunting safari.

Some photos show special fairings under the nacelles on some ski-equipped machines, but not all. I chose to leave these off because one day, I may find a set of suitable wheels! Interior details were the usual mix of things we're all familiar with - plastic sheet, sprue, Evergreen plastic strips, paper, and wire.

The front office. The crew is bundled up properly for flying at altitude in a cold environment.

A crew was added because despite having a tremendous amount of research material, some areas remained a bit murky, and a crew helped hide my information gaps! These guys were made from Airfix multi-pose sets.

The engines were scrap box items, modified with bullet shaped crankcases and detailed with an assortment of sprue rods. Most of my methods and techniques would be familiar to anyone who has a couple of more involved conversions under their belt. One thing that has to be taken into account in a model of this size is strength. Much internal bracing was added to keep the fuselage from twisting and splitting. The entire central area in the fuselage bottom where the bomb bay would be is a mass of wood blocks, bamboo sticks and epoxy putty to provide a solid heart to support the wing spars.

If I did anything unusual, it's in the external detailing. There is a LOT of surface area on a 1/32 Blenheim, and it would've looked too naked if it was just smoothed and painted. To remedy this, I added the quilted texture, sometimes called "oil-canning", that results from sheet metal being attached to an under frame. First, I drew the locations of all structural members - ribs, spars, formers, bulkheads etc. on the surface with pencil, and then simply hand painted the resultant blocks within the pencil lines. This raised the area around the lines, and wasn't really that difficult or tedious. I spent maybe four hours on the entire airframe, and that's including about three coats. A little sanding followed by a couple of heavy airbrushed coats to blend it all, and the effect was quite realistic. It's a very subtle effect, but when the light is right, it looks just like sheet metal riveted to a framework! (I don't know if this will even show up in the photos). Having done this, I thought I might as well add the other bit of prominent surface detail - the stitching on the fabric covered control surfaces, and so this was done using a fine paint brush and white glue.

The rear part of the model showing the rudder, rear flying surfaces and the turret.

Fuselage before being glued together.

Once I decided to go ahead with this insanely impractical project, I knew exactly which version my model would represent! Since I've always found the history of the Finnish Air Force to be among the most interesting stories around, and because the long nose Mk IV is more well known, I decided out of some perverted sense of contrariness to make my model as an early all-glass short-nose Finnish example. This presented a few difficulties, chiefly the lack of accurate drawings showing the top view of the nose. I derived mine from a couple of good, almost straight down overhead photos, and with a little empirical playing around with cardboard and tape, the facets all seemed to fit. Another major difficulty was in tracking down which instrument panel would be seen in my Blenheim. I found three distinctly different panels used on Finnish machines, and making a semi-educated guess, based on subliminal clues, I picked one design.

The photo has been lightened and contrast has been added so it shows the subtle effect of the oil canning technique if you study it carefully.

My other quandary was interior color. The British built airplanes kept the standard British interior green color for a long time, but Finnish manufactured airplanes seemed to have some shade of gray. A friend of mine in Finland, Tony Manninen, inquired around and e-mailed the answer - a light gray.

I also settled early on one particular machine, chosen because multiple photographs of it were available, and it displayed a certain "typicality". I wanted my model to represent the "Every Blenheim". Pouring over a mass of photos, I picked BL-155, an airplane with a combat record, and one that survived the war, being cashed out in 1952. When it came time to spray the camouflage, I found that the Finnish patterns were pretty standard, but that some airplanes had hard edged color demarcations and others were quite loose and fuzzy, while some airframes had a mix! This is what I went for - some fuzzy, some hard edged. The yellow areas were hard masked, and home- sprayed decals were used.

I hope you enjoy the photos of my Blenheim. When I started this model I had no plans to ever display her innards, so consequently, very little exists to document her construction progress. I shot a few crude photos for my own purposes, and directly scanned her intimate fuselage contents, and that's about it.

References

An exact bibliography would be next to impossible, but three main sources stand out:

  1. Bristol Blenheim Suomen Ilmavoimien Historia #10 by Kalevi Keskinen, Kari Stenman, and Klaus Niska. This 1983 book is the bible of Finnish Blenheimery. It covers EVERY Blenheim in Finnsh service and is loaded with pictures and color profiles.
  2. Battle of Britain Aircraft by Ray Rimell, a 1990 Argus book that explains in detail how to build the top twelve BoB airplanes in 1/72, but also contained some truly nice scale drawings of a Mk IV by A.L. Bentley. Though I built the Mk II, almost everything aft of the cockpit is applicable.
  3. Air Enthusiast Quarterly #54 Summer 1994 has a well done synopsis of the Blenheim's Finnish combat history and some nice photos, by Kari Stenman

A lot of my sources were just magazines or books that had a picture here or there. When a Blenheim Mk. IV was being restored to flying condition in the '80s, most major aviation magazines covered this work, and lots of skeletal photos taken during the period were available. These were very useful and armed with my other books and magazines, I knew what was appropriate for my Mk.II and what wasn't. Unfortunately, what was also useful was the coverage provided in these same magazines when the airplane crashed in 1985. The cycle started again with the effort to get the beast back in the air, so another round of great restoration material started popping up! To get an idea of what I had gathered, look at the photo of the model sitting on its pyramid of Blenheim Lore!

To Aidrian Bridgeman-Sutton for the loan of materials, and Tony Manninen for obtaining some key information, a big thanks! I couldn't have done it without ya!

This article first appeared in one of the issues of Internet modeler - a virtual modeling magazine.

Related Content

This article was published on Wednesday, July 20 2011 Last modified on Saturday, May 14 2016

© Large Scale Planes 1999&mdash2021. All trademarks and copyrights are held by their respective owners. Member items are owned by the member. All rights reserved.


Contents

Origins [ edit | edit source ]

In early 1934, 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 – he referred to the ambition as seeking "the fastest commercial aeroplane in Europe, if not the world".[1] At the time, German firms were producing a variety of record-breaking high-speed designs, such as the single-engined Heinkel He 70, and Rothermere wanted to recapture the title of fastest civilian aircraft, as well as to purchase such an aircraft himself. 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 fighter aircraft may not be able to match modern transport aircraft, which may be easily converted to, or used as the basis for, a bomber aircraft.[1]

Since July 1933, Frank Barnwell, Bristol's chief designer, had been working on a small twin-engine low-wing monoplane design, initially intended to be powered by the sleeve-valve Bristol Aquila radial engine, designated as the Type 135.[1] Rothermere became aware of Bristol's proposal and, in response to his inquiry, on 3 March 1934, Barnwell issued him with a quote of the specification and performance statistics of the design, including an estimated top speed of 240 mph at an altitude of 6,500 feet.[1] By this point, proposed use of the Aquila engine had been shelved in favour of the supercharger-equipped, poppet-valve Bristol Mercury engine. Deeming it suitable for the issued challenge, the design of Type 135 was further adapted to produce the Type 142 in order to meet the requirements outlined by Rothermere.[1] In late March 1934, Rothermere placed an order for a single Type 142 aircraft, under which he paid for half of the estimated £18,500 cost up front and the remainder upon the aircraft's first flight in the following year.

On 12 April 1935, the Type 142, which had been given the name Britain First, conducted its maiden flight from Filton Aerodrome, South Gloucestershire.[2][1] Flight tests soon proved that the aircraft was in fact faster than any fighter in service with the Royal Air Force (RAF) at the time, having demonstrated a top speed of 307 mph.[3][4] Rothermere presented the aircraft to the nation for a formal evaluation at a potential bomber.[5] By June 1935, the Air Ministry had become interested in the project due to its high performance. On 9 July 1935, a design conference was held by Bristol at the ministry's request into the question of converting the Type 142 into a suitable medium bomber.[5]

Based upon talks from the conference, the Air Ministry quickly formalised Specification B.28/35 for prototypes of a bomber version the Type 142M (M for military).[5] One principal change between the Type 142M bomber and its Type 142 predecessor was the repositioning of the wing from a low-wing to a mid-wing position, which allowed for more internal space within the fuselage underneath the main spar to accommodate a sizable bomb bay. Other modifications included the addition of a bomb-aimer's position and a Browning machine gun in the nose along with provisions for a semi-retractable gun turret in the dorsal position.

Production [ edit | edit source ]

In September 1935, an initial contract for 150 aircraft was placed. The Air Ministry had chosen to order the type directly from the drawing board, having been urgently sought as one piece of a wider and rapid expansion of the RAF.[5] The first aircraft built of this production model, K7033, served as the only prototype on 25 June 1936, K7033 conducted its first flight from Filton.[6][5] The service name for the aircraft became Blenheim Mk I after the famous battle during the War of the Spanish Succession. On 10 March 1937, production deliveries to the RAF formally started 114 Squadron became the first squadron to receive the Blenheim.[6][5] On 13 January 1938, the Blenheim entered service with No. 30 Squadron, the first overseas squadron to receive the type in early 1939, the first Blenheims arrived in India.[7]

From July 1936 onwards, various additional orders were placed for the Blenheim Mk I, including multiple orders for the export market.[5] By the end of 1936, 1,568 aircraft were on order.[8] In order to meet the demand, secondary assembly lines were established at Chadderton by Avro and at Speke by Rootes Securities.[5] The aircraft was built under licence by overseas countries, including Finland, who completed a total of 55 aircraft, and Yugoslavia, which completed 16 aircraft with a further 24 in advanced stages of completion when Germany invaded Yugoslavia.[9] Other countries also procured the Blenheim, including Romania, Greece and Turkey.[10][8] By September 1939, orders for the Blenheim had risen to 2,088 aircraft.[8] 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.[6][7]

The Blenheim production program saw several shifts in requirements and in capacity.[8] A modified Blenheim design, given the name Bolingbroke, was manufactured under licence in Canada by Fairchild Aircraft.[11] The Bolingbroke, which had been developed in response to Air Ministry Specification G.24/35 to procure a coastal reconnaissance/light bomber as a replacement for the Avro Anson, had substantial improvements that would serve as the basis for improved variants of the Blenheim.[12] According to aviation author James D. Oughton, both the navigator's station and range limitations of the Blenheim Mk I had been subject to considerable criticism, thus an improved model of the aircraft was desired in order to rectify these shortcomings.[12] 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.

Further development [ edit | edit source ]

Formal 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). Only one Blenheim Mk II was completed, as flight tests revealed the increase in speed to be marginal and not warranting further development.[13] 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 905 hp (675 kW). the turret acquired a pair of Brownings in place of the original single Vickers K gun, creating the Blenheim Mk IV.

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.[15] Further aircraft deliveries were made to the production standard and were primarily manufactured by Avro and Roots.[16] Production of the Blenheim IV continued until June 1943, when newcomers such as the Beaufort-derived Beaufighter had succeeded the type.[8] 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 .303 in (7.7 mm) Brownings.[7] 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.[7] 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 shooting competitions held at Bisley), 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 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 (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.


Mk1 Bristol Blenheim

The Bristol Blenheim is a truly unique aircraft and was a milestone in the history of British aviation as the first stressed skin aeroplane accepted by the RAF. It bore the brunt of the early war bombing effort and its crews paid a heavy price defending the nation, Winston Churchill paid homage to their bravery comparing them to the 'Charge of the Light Brigade'. At the start of the war the RAF had 1089 Blenheim bombers in service, more than any other aircraft however, this is now the only flying example left in the world and serves as a lasting memorial to those who crewed them.

The restoration wouldn't have been possible without the ARC Volunteers who put in over 25,000 man hours to help the rebuild and the Blenheim Society whose relentless fund raising helped to keep the project afloat.

The Mk1 Nose of our Blenheim has a particularly interesting history. It began life as a Bristol Blenheim Mk1 built under license by AVRO and issued to 23 Squadron on 2nd September 1939, serial number L6739. It served as a night fighter throughout the Battle of Britain before being struck off charge in December 1940 after which it went back to Bristol's and was left in their scrapyard. After the war an innovative electrician by the name of Ralph Nelson, who was working at Bristol's, was given permission to buy the nose which he then went on to convert into an electric car. After mounting it to the chassis of an Austin 7 he fitted an electric motor of his own design and registered it as a 'Nelson' with the index JAD347. Ralph drove the car for 10 years before it suffered a fire which damaged the systems beyond repair, however, he had heard of the ongoing 2nd Blenheim restoration at Duxford and donated the car to the project in 1992.

Thankfully Ralph had kept most of the original systems such as the control column, rudder pedals, trim system and fittings including the seat and frame, so after hours of reverse engineering and a huge amount of fabrication work we where able to turn the much loved car back into the Blenheim nose you see today. If you have a chance to see it up close in the future look for the tax disc in one of the front windows, we decided to leave it in as a lasting legacy of Ralph and his car for which this project wouldn't have been possible without.


Aircraft Nut

Global Aviation Resource reports that May 30th the Imperial War Museum Duxford the Aircraft Restoration Company’s Bristol Blenheim appeared in public as a complete aircraft for the first time since its long-term rebuild began in the summer of 2003.

Unfortunately, the Blenheim crash-landed again in August 2003 this time at Duxford. While the aircraft suffered considerable damage, she wasn’t broken beyond repair. The Blenheim’s crew didn’t give up on her and formed a trust to ensure her continued operation in the UK. They contracted ARCo to provide two full-time engineers to support the restoration project undertaken by Blenheim Duxford Ltd. (and supported by The Blenheim Society).

The Blenheim has undergone a thorough rebuild inside Duxford’s Hangar 3, and more recently in ARCo’s workshop. Interestingly, the team has decided to rebuild the aircraft to Mk.I standard. The bulk of the aircraft is nearly identical to a Mk.IV, except for the forward fuselage which is radically different. The Mk.I is essentially extinct (as are British-built Blenheim IVs, with no complete examples known to exist), but a few forward fuselages survive. One of these ended up at Duxford a few decades ago.

Ralph Nelson, a Bristol employee, had converted it into a peculiar automobile during 1946, using the chassis and power train from an Austin 7

The Mk.I fuselage comes from Blenheim L6739, a Battle of Britain night-fighter veteran. The Blenheim Society obtained the “car” intending to rebuild it into a fully operational nose section for a potential swap with the Mk.IV nose. The team had already begun this process before the 2003 accident, so it seemed logical to blend what they had already completed into G-BPIV’s restoration once that began. They rolled out the freshly restored “Blenheim Mk.I” in night fighter camouflage just a few days ago, and will eventually mark her as L6739. ARCo ran one of the aircraft’s Bristol Mercury engines on May 23rd, and expect to run the other very soon. If all goes well, she will be flying again very soon and delighting air show audiences again across the UK

There are currently no Blenheim or Bolingbroke aircraft that are airworthy. One airworthy Blenheim had been rebuilt from a scrapped Bolingbroke over a 12-year period, only to crash at an airshow at Denham within a month of completion in 1987.

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 at Duxford on 19 August 2003 the crash was feared to have made it a write-off, but it is presently undergoing an extensive repair and conversion to the Mark I "Short nose" version by The Aircraft Restoration Company (ARC or ARCo) at Duxford, most of the work being done by volunteers.

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, tyres 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 Museum in Hamilton, Ontario is rebuilding a Bolingbroke to airworthy status. The Commonwealth Air Training Plan Museum in Brandon, Manitoba 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. A restored Bolingbroke is on static display at the British Columbia Aviation Museum in Victoria, British Columbia. The Canadian Museum of Flight at Langley Airport, Langley, British Columbia has on display the restored nose and cockpit section of a Bolingbroke, and holds the rest of an entire airframe in storage pending future restoration and display.

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 display at the Aviation Museum of Central Finland at Tikkakoski.



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