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Bristol Blenheim Mk I: Side Plan

Bristol Blenheim Mk I: Side 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 Blenheim Mk I: Side Plan - History

Bristol Blenheim / Bolingbroke


Originally, the Bristol Blenheim was not created as a bomber or with the RAF in mind. During 1933 Bristol Chief Designer Frank Barnwell announced a proposal for a high-speed light passenger aircraft, the Bristol Type 135. The Type 135 as envisioned as a low-wing monoplane capable of carrying up to eight passengers within an all metal cantilever stressed skin fuselage, powered by two 500 hp (373 kW) nine cylinder Bristol Aquila I sleeve-valved air cooled radial engines. By 1934 work on the design had advanced to the fuselage mock-up stage and it was decided to display the mock up at the 1935 Salon Internationale de L'Aeronautique in Paris.

In 1934 Lord Rothermere, who was the owner of the Daily Mail newspaper, expressed a desire to obtain for his personal use, a fast and spacious private aeroplane, for this aviation-minded organisation had then appreciated the potential of what is today called the business or corporate aircraft. Lord Rothermere envisaged his requirements as a fast aircraft that would accommodate a crew of two and six passengers, and it just so happened that the Bristol Aeroplane Company had already drawn up the outline of a light transport in this category, the Type 135.

The new aircraft had been designed originally to be powered by two 500 hp (373 kW) Bristol Aquila I engines which were then under development. The Type 135 had an anticipated top speed of 180 mph (290 km/h) but lacked the range to meet Lord Rothermere's requirements. Frank Barnwell proposed changes that included reducing the fuselage cross section to reduce drag and replacing the 500 hp (373 kW) Bristol Aquila I engines with a couple of 640 hp (477 kW) Bristol Mercury VI radial engines driving fixed pitch four blade propellers. Design work started on the now designated Bristol Type 142 with Lord Rothermere as its principle source of funding. It would cost him £18,500 to complete the aircraft, a large sum even by todays standards. Bristol had learned of government plans to expand the RAF and with the anticipation of possible future contracts decided to fund a parallel design called the Bristol Type 143 as a private venture. The Type 143 featured a longer nose and longer undercarriage doors.

First flown at Filton on 12 April 1935, the Type 142 was to spark off much comment and excitement when during its initial trials it was found to be some 30 mph (48 km/h) faster than the prototype of Britain's most-recently procured new biplane fighter, the Gloster Gauntlet. Named Britain First, it was presented to the nation by Lord Rothermere after the Air Ministry had requested that they might retain it for a period of testing to evaiuate its potential as a light bomber. It had a number change from G-ABCZ to K-7557 and was then moved to Martlesham Heath for RAF trials. It proved so successful that in 1935 the Air Ministry issued Specification B.28/35 for a military version with similar performance. This, then was the sire of the Bristol Blenheim which was to prove an important interim weapon at the beginning of World War II.


The Bristol Mk IV dorsal turret on a Blenheim Mk IV aircraft.

Aware of Air Ministry interest in the Type 142, Bristol busied themselves with homework to evolve a military version (Type 142M) of this aircraft, and in the summer of 1935 the Air Ministry decided to accept the company's proposal, placing a first order for 150 aircraft to Specification B.28/35 in September. The new aircraft was very similar to the Type 142, but there had of course been some changes to make it suitable for the military role, primarily to accommodate a bomb aimer's station, a bomb bay and a dorsal gun turret. Little time was lost by either the Bristol company or the Air Ministry, for following the first flight of the prototype, on 25 June 1936, it was moved to Boscombe Down on 27 October 1936 for the start of official trials, with initial deliveries to RAF squadrons beginning in March 1937. In July 1937 the Air Ministry placed a follow-on order for 434 additional Blenheim Mk Is, as the type had by then been named.

Of all-metal construction, except for fabric-covered control surfaces, the Blenheim Mk I was a cantilever mid-wing monoplane, with the wing having Frise mass-balanced ailerons and split trailing-edge flaps. The fuselage nose extended only slightly forward of the engines, and both fuselage and tail unit were conventional light alloy structures. Landing gear was of the retractable tailwheel type. The tailwheel of the prototype had retracted, operated by cables linked to the main landing gear but, wisely, this feature was not carried forward into the production aircraft. The powerplant comprised two Bristol Mercury VIII engines developing 730 hp (545 kW) for take-off with a maximum power rating of 840 hp (626 kW) in level flight, mounted in nacelles on the wing leading-edge, and driving three-blade variable-pitch propellers. Accommodation was provided for a pilot, navigator/bomb-aimer, and air gunner/radio operator. A bomb bay in the wing centre-section could contain a maximum 1,000 Ibs (454 kg) of bombs, and standard armament comprised a 7.7 mm (0.303 in) machine-gun in the port wing, plus a single Vickers 'K' machine-gun in a dorsal turret.

Initial deliveries of production Blenheim Mk Is to the RAF squadrons began in March 1937. The first aircraft (K7036) to be delivered, however, crashed upon landing totally destroying the aircraft. The first RAF squadron to receive Blenheim Mk Is was No.114, then based at RAF Wyton, and it was this unit which first demonstrated the new type officially to the public at the RAF's final Hendon Display in the summer of 1937. The Blenheims were to arouse excited comment with their high speed and modern appearance, being launched on their career in an aura of emotion created by the belief that, in an unsettled Europe, the RAF was armed with the world's most formidable bomber aircraft. Production contracts soared, necessitating the establishment of new construction lines by A. V. Roe at Greengate, Middleton (Chadderton) and Rootes Securities at Speke (South Liverpool), both these factories being in Lancashire. Between them the three lines built a total of 1,355 Blenheim Mk Is which, at their peak, equipped no fewer than 26 RAF squadrons at home and overseas, the Blenheim's first overseas deployments being with No.30 Squadron in Iraq and No.11 Squadron in India, in January and July 1938 respectively.

However, by the outbreak of World War II few Blenheim Mk Is remained in service with home-based bomber squadrons, having been superseded in the bombing role by the Blenheim Mk IV, which incorporated the lessons learned from the experience which squadrons had gained in operating the Mk I. But their usefulness was by no means ended, many continuing to serve as conversion trainers and, initially, as crew trainers in OTUs. More valuable by far were some 200 which were converted to serve as night fighters, pioneering the newly conceived technique of AI (Airborne Interception) radar, carrying AI Mk III or Mk IV. The single forward-firing machine-gun was totally inadequate for this role, of course, and a special underfuselage pack to house four 7.7 mm (0.303 in) machine-guns was produced. So equipped, Blenheim Mk IFs scored the first AI success against an enemy aircraft on the night of 2-3 July 1940.

Export versions of the Blenheim Mk I were sold before the war to Finland, Turkey and Yugoslavia, and were also built under licence by these first two nations. In addition, a small number had been supplied to Romania as a diplomatic bribe in 1939, but this proved to be unsuccessful. The result, of course, was that Blenheim Mk Is fought for and against the Allies.

When, in August 1935, the Air Ministry had initiated Specification G.24/35 to find a successor to the Avro Anson for use in a coastal reconnaissance/light bomber role. Bristol had proposed its Type 149. Very similar to the Blenheim Mk I, this was based on the use of Bristol Aquila engines to confer long range with the existing fuel capacity, but proved unacceptable to the Air Ministry. Subsequently renewed interest was shown in the Type 149 for use in a general reconnaissance role, and a prototype was built, by conversion of an early Blenheim Mk I, this retaining the Mercury VIII engines and being provided with increased fuel capacity. The fuselage nose was lengthened to provide additional accommodation for the navigator/observer and his equipment, and this was to be finalised as that which graced the Blenheim Mk IV.

The Air Ministry then had misgivings about the Type 149, fearing that its introduction and manufacture would interfere with the production or urgently needed Blenheims. Instead, the Type 149 was adopted by the Royal Canadian Air Force and with the start of the British Commonwealth Air Training Plan, it was decided to produce a version in this country. Fairchild Aircraft of Longueil outside Montreal was selected to produce them under the Canadian name Bolingbroke. Quickly nicknamed the Boly, the type saw service throughout Canada. The Bristol prototype being shipped to Canada to help in the establishment of a production line. The first Bolingbroke Is had Mercury VIII engines, but after 18 of these had been built production changed to the definitive Canadian version, the Bolingbroke IV with Mercury XV engines, and equipment from both Canadian and US manufacturers. Later variants included a small number of Bolingbroke IV-Ws with American built Pratt and Whitney Twin Wasp Junior (SB4-G) 14-cylinder engines rated at 825 hp (615 kW) for take-off, and a number of Bolingbroke IV-T multi-purpose trainers.

Having blown hot and then cold over the Type 149, there was a sudden renewal of interest, primarily as an interim measure until the Type 152 torpedo-bomber, derived from the Blenheim, should become available. The decision was taken, therefore, to introduce the longer nose and stepped windscreen of the Bolingbroke, and to make provision for longer range by the introduction of increased wing fuel capacity. The Bristol designation Type 149 was retained for this changed configuration, the new RAF designation being Blenheim Mk IV. This change took place quietly on the production lines towards the end of 1938, although the first 68 Blenheim Mk IVs were built without the 'Iong-range wing'. The powerplant comprised two more powerful Mercury XV engines, and these allowed gross weight to be increased eventually by 16 per cent.

No. 90 Squadron was the initial unit to be equipped with Blenheim Mk IV s in March 1938, the first of more than 70 squadrons to operate these aircraft, and consisting of units from Army Co-operation, Bomber, Coastal, Far East Bomber, Fighter and Middle East Commands, both at home and overseas. Inevitably, such extensive use brought changes in armament and equipment, but especially the former, for the armament of the first Blenheim Mk IVs was unchanged from the initial two-gun armament of the Mk I. As finalised the number became five, the single forward-firing gun in the wing being retained, a new dorsal turret carrying two guns being adopted, and a completely new remotely-controlled Frazer-Nash mounting being added beneath the nose to hold two aft-firing machine-guns. Protective armour was also increased, but while it was not possible to enlarge the capacity of the bomb bay, provision was made for an additional 320 Ibs (145 kg) of bombs to be carried externally, under the inner wings, for short-range missions.

With so many squadrons operating the type it was inevitable that Blenheims should notch up many wartime 'firsts' for the RAF. These included the first reconnaissance mission over German territory, made on 3 September 1939. It was flown by Flying Officer A Macpherson in a Blenheim (N6215) Mk IV of No. 139 Squadron while on an armed reconnaissance over German warships at Heligoland Bight (Schillig Roads) near Wilhelmshaven. On 4 September 1939, ten aircraft from Nos. 107 & 110 Squadrons, led by Flight Lieutenant K.C. Doran of No. 110 Squadron made an attack on the same German ships. From the beginning of the war, until replaced in home squadrons of Bomber Command by Douglas Bostons and de Havilland Mosquitoes in 1942, Blenheim Mk IVs were used extensively in the European theatre. Although vulnerable to fighter attack, they were frequently used for unescorted daylight operations and undoubtedly the skill of their crews and the aircraft's ability to absorb a great deal of punishment were the primary reasons for their survival, for high speed and heavy firepower was certainly not their forte. In the overseas squadrons Blenheims continued to serve long after their usefulness had ended in Europe, and except in Singapore, where they were no match for the Japanese fighters, they proved a valuable weapon. A total of 3,298 Mk IV had been built in England when production ended, and in addition to serving with the RAF had been used by the French Free and South African air forces, and supplied in small numbers to Finland, Greece and Turkey.

Last of the direct developments of the Blenheim design was Bristo1's Type 160, known briefly as the Bisley, which was to enter service in the summer of 1942 as the Blenheim Mk V. Envisaged originally as a low-altitude close-support bomber, it was in fact to be built for deployment as a high-altitude bomber, powered by Mercury XV or XXV engines. Except for a changed nose, some alterations in detail and updated equipment, these aircraft were basically the same as their predecessors. Some 942 were built, all produced by Rootes at their Speke (South Liverpool) and Blythe Bridge (Stoke-on-Trent) factories, and the first unit to receive Blenheim Mk Vs was No.18 Squadron. The type was to equip six squadrons in the Middle East and four in the Far East, where they were used without distinction. This resulted from an increase in gross weight of over 17 per cent which, without the introduction of more powerful engines, had brought about a serious fall of performance. It only when the Blenheim Mk Vs were deployed in Italian campaign, contending with the advanced fighters in service with the Luftwaffe, that losses rose to quite unacceptable proportions, and the Blenheim Mk Vs withdrawn from service.

Canadian Bolingbrokes

Operational use of the Bolingbroke was limited to the Royal Canadian Air Force in Canada and the Aleutian Islands. No 8 (Bomber Reconnaissance) Squadron was the first RCAF unit to convert to the Bolingbroke, followed by one other squadron. Bolingbrokes were used primarily to fly anti-submarine coastal patrols over both the Atlantic and Pacific.

Two RCAF squadrons were assigned to the combined American-Canadian defence campaign to protect the Aleutian Islands and west coast of Alaska from Japanese attack. No. 115 Squadron arrived in the Aletuians in April of 1942 and was assigned anti-submarine patrol and maritime reconnaissance missions. In June of 1942 No. 8 Squadron deployed to the Aleutians with twelve Bolingbroke Mk IVs, making a 1,000 mile flight from RCAF Sea Island to Yakutat Island arriving on 3 June. When the squadron arrived it was ordered to paint out the Red centers to the upper wing roundels to prevent confusion with the Japanese 'meatball' insignia. Later additional recognition markings in the form of a fourteen inch Blue band was added to the rear of the fuselage. The harsh weather in the Aleutians proved a worse enemy than the Japanese and a number of Bolingbrokes were lost when thick Alaskan fogs obscured mountain tops. Normal bomb loads consisted of three 300 pound depth charges and two aircraft were maintained in an alert status at all times. The squadron is credited with sharing one submarine kill with the US Navy. A Bolingbroke Mk IV piloted by Flight Sergeant P.M.G. Thomas attacked and damaged a Japanese submarine enabling US Navy surface units to later sink it.

The majority of Bolingbrokes produced never saw combat, instead they performed as crew and operational trainers under the Commonwealth Air Training Plan, training crews for overseas units. Still others were converted to unarmed target tugs with high visibility paint schemes for training air gunners and army anti-aircraft gunners.

Specifications (Bristol Type 149 Blenheim Mk IV)

Type: Three Seat Light Bomber, Fighter & Night Fighter, Maritime Reconnaissance (Anti-Shipping/Submarine), Bombing and Gunnery Trainers & Target Tug.

Accommodation/Crew: Pilot, Navigator/Bomb-Aimer and Wireless Operator/Air Gunner. See the Blenheim Mk I for more cockpit information.

Design: Chief Designer Frank Barnwell of the Bristol Aeroplane Company Limited.

Manufacturer: The Bristol Aeroplane Company Limited based at Filton (Bristol), Bristol County, England (Mark I, IV & V Prototypes), Alexander V. Roe (Avro) Aircraft Company Limited based in Greengate, Middleton (Chadderton), Lancashire County, England (Mark I & IV), Rootes Securities Limited at Blythe Bridge (Stoke on Trent), Straffordshire County, England (Mark IV & V), Rootes Securities Limited at Speke (South Liverpool), Lancashire County, England (Mark I & V), Fairchild Aircraft Limited in Longueil, Quebec, Canada (Bolingbroke). Also built under licence by Valtion Lentokonetehdas (State Aircraft Factory) at Tampere, Finland (Mark I & IV) and Ikarus AD in Belgrade (Zemun), Yugoslavia (Mark I).

Powerplant: (100 Octane Fuel) Two Bristol Mercury XV 9-cylinder poppet-valve air-cooled radial engines developing 905 hp (675 kW) at take-off, a maximum output of 995 hp (742 kW) for level flight (5 minute usage) and a maximum ecomical cruising power output of 590 hp (440 kW) at 16,000 ft (4877 m) at 2400 rpm. (87 Octane Fuel) Two Bristol Mercury XV 9-cylinder poppet-valve air-cooled radial engines developing 725 hp (541 kW) at take-off, a maximum output of 840 hp (627 kW) for level flight (5 minute usage) and a maximum ecomical cruising power output of 590 hp (440 kW) at 16,000 ft (4877 m) at 2400 rpm.

Performance: Maximum speed 266 mph (428 km/h) at 11,800 ft (3595 m) cruising speed of 198 mph (319 km/h) service ceiling (clean) 27,260 ft (8310 m) or 22,000 ft (6706 m) fully loaded initial climb rate 1,480 ft/min (7.5 m/sec).

Fuel Capacity: Two inboard 140 Imperial gallon (636 litres) main fuel tanks and two outboard 94 Imperial gallon (427 litres) auxiliary or long range fuel tanks giving a total capacity of 468 Imperial gallons (2125 litres). Starting in early 1940 the main fuel tanks were self-sealing, but due to an initial shortage, the outboard auxiliary fuel tanks remained non self-sealing for some time.

Oil Capacity: One 11.5 Imperial gallon (52.2 litre) main oil tank and a 2.5 Imperial gallon (11.3 litre) auxiliary oil tank per engine giving a total oil capacity of 28 Imperial gallons (127.2 litres).

Range: 1,460 miles (2350 km) on internal fuel with a 1,000 lbs (454 kg) bombload. 1,950 miles (3140 km) on internal fuel without bombs.

Weights & Loadings: Empty 9,790 lbs (4441 kg), with a normal take-off weight of 13,500 lbs (6122 kg) and a maximum take-off weight of 14,400 lbs (6532 kg) fully loaded with bombs.

Dimensions: Span 56 ft 4 in (17.17 m) length 42 ft 7 in (12.98 m) height 9 ft 10 in (3.00 m) wing area 469 sq ft (43.57 sq m).

Defensive Armament: A total of three to five 7.7 mm (0.303 in) machine-guns was standard. Some Mk IV aircraft underwent various field modifications with further increased the aircrafts defensive armament. The Browning machine-guns were belt feed while the Vickers machine-guns used 50 round circular ammunition pans. The Frazer-Nash FN.54 and FN.54A turrets were jettisonable in the event of an emergency allowing the crew to use the lower fuselage emergency escape hatch.

1 × 7.7 mm (0.303 in) Browning fixed forward-firing machine-gun in the port wing.

1 x 7.7 mm (0.303 in) Lewis or Vickers "K" trainable machine-gun in a semi-retractable hydraulically operated Bristol B.Mk III dorsal turret, or

2 x 7.7 mm (0.303 in) Vickers "K" trainable machine-guns in a power-operated Bristol B.Mk IIIA dorsal turret, or

2 x 7.7 mm (0.303 in) Browning trainable machine-guns in a power-operated Bristol B.Mk IV dorsal turret.

1 × 7.7 mm (0.303 in) Browning trainable rearward-firing machine-gun in a remotely controlled Frazer-Nash FN.54 chin turret, or

2 × 7.7 mm (0.303 in) Browning trainable rearward-firing machine-guns in a remotely controlled Frazer-Nash FN.54A chin turret. The turret could rotate 20 degrees to either side with a depression of 17 degrees.

1 × 7.7 mm (0.303 in) Vickers "K" forward-firing machine-gun in a gimbal nose gun mount (optional field modification).

1 × 7.7 mm (0.303 in) Vickers "K" machine-gun in a rear firing engine nacelle mount (optional field modification).

1 × 7.7 mm (0.303 in) Vickers "K" machine-gun in a rear firing under tail mount (optional field modification).

Offensive Armament: 1,000 lbs (454 kg) of bombs internally and up to 320 lbs (145 kg) of bombs externally on two underwing racks located between the fuselage and engine nacelles. On the single Mk II aircraft produced, 500 lbs (227 kg) of bombs could be carried externally but at great expense to performance.

4 × 250 lbs (114 kg) bombs, or

2 × 500 lbs (227 kg) bombs, or

3 × 300 lbs (114 kg) depth charges carried internally.

4 × 80 lbs (36.2 kg) bombs on underwing racks, or

2 × 160 lbs (72.5 kg) bombs on underwing racks

Variants: Bristol Type 142, Bristol Type 142M, Bristol Type 143 (Aquila engined), (Type 142M) Blenheim Mk I Prototypes, (Type 142M) Blenheim Mk I, Blenheim Mk IF, Blenheim PR.Mk I, Blenheim Mk II, Blenheim Mk III, Bristol Type 149, (Type 149) Blenheim Mk IV Prototypes, (Type 149) Blenheim Mk IV, (Type 149) Blenheim Mk IVF, (Type 149) Blenheim Mk IVL, (Type 160) Bisley Mk I, (Type 160) Blenheim Mk V, Bolingbroke Mk I, Bolingbroke Mk II, Bolingbroke Mk III, Bolingbroke Mk IV, Bolingbroke Mk IV-C, Bolingbroke Mk IV-W, Bolingbroke Mk IV-T, Bolingbroke Mk IV-TT

Equipment/Avionics: Standard communications and navigation equipment.

History: First flight (Type 142 "Britain First") 12 April 1935 first flight (Type 142M) 25 June 1936 initial delivery (No. 114 Squadron RAF) March 1937 end production (VD) June 1943 withdrawn from service (Finland) 1956.

Operators: United Kingdom (RAF), Canada (RCAF), Finland, Turkey, Yugoslavia, Romania, Greece (Royal Hellenic Air Force), Free French Air Force (Forces Francaises Libre), Portugal (Arma de Aeronautica), South Africa (SAAF) and Croatia. The German Luftwaffe and the Italian Regia Aeronautica both operated captured aircraft.


World War Photos

Finnish “Pelti-Heikki” 1st production Blenheim Mk I 1936 Bristol Type 142M 1936 Bristol Type 142
Bristol Type 1 Mk IV turret Bristol 142M K7033 in flight Bristol Blenheim after Reconn Flight Wreck of Blenheim Mk IF K7177 Maleme Crete 1942
Bristol Mercury Engine Bristol Type 142 K7557 “Britain First” Blenhein Finnish Air Force Blenheim Mk II L1222 Filton 1938
Blenheim Mk I 1940 Blenheim Mk I No 90 Squadron at Bicester Blenheim Mk I K7033 Blenheim Mk.I K7037 1937
Blenheim L1545 of No. 60 Squadron RAF and Wapiti K1269 27 Sqn Crashed Blenheim Mk I L4823, Egypt 1940 Blenheim Mk IF L8372 YB-L of No. 29 Squadron RAF Debden Blenheim L1304 of No. 110 Squadron RAF
Blenheim L1426 RX-M of No. 25 Squadron RAF over Tilbury Blenheim K7133 of No. 44 Squadron RAF Waddington Blenheim L1100 of 139 Squadron on parade at Wyton in 1937 Blenheim L1132 OZ-L of No. 82 Squadron RAF 1939
Blenheim K7048 ZK-O & L1235 of No. 25 Squadron RAF Blenheim K7113 & K7054 of No. 90 Squadron RAF 1938 Blenheim K7036 114 Sqn Wyton Blenheim K7038 K7044
Blenheim K7046 of No. 114 Squadron RAF Wyton 1937 Blenheim I K7072 long nose trials as Bolingbroke 1937 Blenheim I K7175 L1328 61 Sqn Blenheim I L8391 Ismailia OTU
Blenheim I Heliopolis 1940 Blenheim I K7040 of No. 114 Squadron RAF Blenheim I K7059 of No. 90 Squadron RAF 1939 Blenheim If L1336 of No. 248 Squadron RAF
Blenheim I 62 Sqn Blenheim I No. 64 Squadron RAF Blenheim Greece Blenheim IF
Blenheim cockpit Finland Blenheim Finland Detail view of a Mercury VII engine and Rotol propeller Blenheims of No. 90 Squadron RAF: TW-F L1285, TW-H L1283, TW-J L1197 and K7050
Blenheim Mk I Bristol Aircraft Co Blenheim 82 Sqn Blenheim 84 Sqn 1940 Blenheim Mk I K7133
Blenheim 54 OTU Blenheim UF-R 601 Sqn Blenheims over Singapore Harbor 1940 Blenheim Mk I K7040 of No. 114 Squadron RAF
Blenheim 211 Sqn Albania late 1940 Blenheim 250 lb bombs, 40 Squadron RAF Blenheims Filton L1164 L1170 Blenheim Mk I flying over Singapore Harbor
Blenheima 13 Operational Training Unit Blenheims 25 Squadron Blenheims K7133 and K7130 of No. 44 Squadron RAF Blenheims I 62 Sqn

History

The Bristol Blenheim is a British three-seat light fast bomber of the Second World War. Originating as a civilian project, this twin-engine aircraft was the first cantilever-winged metal monoplane to enter service with the RAF. Faster than most of the fighters in service in 1936, it proved disappointing in the first combat trials in 1939, but was an important part of the British military system at the beginning of World War II.
In 1934, the Bristol Aeroplane Company presented at the Paris International Air Show a full-scale model of the fuselage of a twin-engine fast transport aircraft on which Frank Barnwell, head of the Bristol design office, had been working since July 1933. A low-wing cantilever monoplane of all-metal construction with a working skin, this aircraft was to carry six to eight passengers in a closed cabin at 290 km/h. As there were no engines compatible with this airframe, Bristol also announced the development of a nine-cylinder star engine of 350 hp called Aquila.
The Harmsworth brothers were owners of major English newspapers, such as The Daily Mail, The Daily Mirror and The Times. The youngest, Lord Rothermere, had always followed aviation developments closely, even serving as Secretary of State for the Royal Air Force in the Lloyd George government. When Lord Beaverbrook, another British newspaper magnate, bought the DC-1, Lord Rothermere felt compelled to inform the Bristol Aeroplane Company that he could buy a Bristol 135 if he could fly non-stop to major European cities. But the Bristol 135 did not have enough range. Frank Barnwell therefore modified his initial project.

The new project, dated April 27, 1934, was for a monoplane equipped with Bristol Mercury VI engines of 640 hp and capable of reaching 400 km/h. The Bristol 135’s wing was kept, but the fuselage was thinner thanks to a monocoque structure allowing to lodge six passengers behind the two pilots, who had an excellent field of vision because of the particular shape of the front fuselage. The main landing gear lifted backwards into the engine nacelles.

The Bristol 142 prototype made its first flight on April 12, 1935 at Filton, flown by Captain Cyril Uwins, the manufacturer’s chief pilot, with test registration R-12 and four-bladed wooden propellers. After being fitted with Hamilton Standard three-bladed variable pitch propellers, the prototype, named Britain First by its owner, underwent its certification tests at Martlesham Heath in June 1935. It as to rewach a speed of 459 km/h at full load, 48 km/h better than the last fighter ordered in series by the RAF, the Gloster Gladiator. Surprised by the result, the Air Ministry asked Lord Rothermere to study the aircraft. He offered his twin-engine aircraft to the Air Council. The unique Bristol 142 never carried the civil registration G-ADCZ that had been assigned to it.Officially taken over by the RAF in July 1935, the Bristol 142 received the British roundels and the serial number K7557 and was used for transport missions by the RAE at Farnborough until 1942.

In parallel to the Type 142, the Bristol design office developed a more basic and less expensive version to replace the Type 135. It was in fact a Bristol 142 with the Bristol Aquila III engines developed for the Type 135. The single Bristol 143 prototype made its first flight on January 20, 1936 with the temporary registration R-14 and, like the Bristol 142, was handed over to the RAF without ever having carried the civil registration G-ADEK that had been reserved for it. This aircraft was never used by the RAF, but was used as a testbed by the Bristol Aeroplane Company at Filton.

The Bristol 143 was the first to be developed for military use. As early as December 1934, this twin-engine aircraft was proposed to Coastal Command as a reconnaissance and coastal patrol aircraft. In January 1935, Finland was offered the Bristol 143F, a fighter-bomber equipped with Mercury IX engines, a Madsen 20 mm front gun and a dorsal turret. The Finnish government was negotiating the purchase of nine aircraft when the Bristol 142M project emerged.

Contrary to what has often been written, the transformation of the Bristol 142 from a twin-engine fast transport to a medium bomber was a significant engineering task: proposed on 9 July 1935 to the Ministry of Air, the project was for a two-seater bomber equipped with Aquila or Mercury engines, which was to carry 450 kg of bombs over 1,600 km. Compared to the Bristol 142, the wing was raised by 41 cm to allow the installation of a bomb bay under the longitudinal spars that could hold four 110 kg bombs or two 225 kg bombs. The horizontal stabilizer was enlarged and raised, the introduction of trim-tab on each elevator replaced the incidence adjustment device, and the vertical stabilizer was lengthened by 20 cm. The rear wheel became retractable, cabled to the main gear to avoid any hydraulic equipment at the rear of the fuselage. Finally, the front fuselage was modified (but not lengthened) to accommodate a bombardier station and a 7.7 mm Browning machine gun, and a semi-retractable dorsal turret was envisaged. Including structural reinforcements and military equipment, the empty weight was increased by 10% and the total loaded weight by 24%.
The tests carried out with the Britain First having given a precise idea of what the future aircraft would be, it did not seem necessary to the Air Ministry to go through a prototype phase and in August the B.28/35 specification was established to cover the definition of the aircraft, an order for 150 aircraft notified on plans and the new bomber named Blenheim. The RAF had high expectations of the twin-engined aircraft and intended to move very quickly, and the first two production aircraft were to be used for developmental testing.
The first production aircraft K7033 made its maiden flight on 25 June 1936 and by December a further order for 434 twin-engined aircraft was placed with the Bristol Aeroplane Company with instructions to speed up production. A year later 25 Blenheims were rolling out of the Filton factory every day, while two more assembly lines were opened, at Rootes Securities Ltd in Speke (422 aircraft ordered) and A.V.Roe & Co Ltd in Chadderton (250 aircraft ordered). In 1937 a final order for 134 aircraft was placed at Bristol.

Variants

Mk I
The first production aircraft K7033 began testing with 840hp Bristol Mercury VI-S.2 engines and during its tests at Martlesham Heath reached a speed of 452km/h at 3,657m despite weighing 900kg more than the Bristol 142 when loaded. This aircraft was quickly modified and immediately introduced into production: the engines were replaced by 840hp Mercury VIIIs, the right wing landing light was removed and the cockpit side window was modified. A little later, the propeller spinner was removed and the tailwheel became fixed. The Mk I was equipped for three men (a pilot, a navigator-bombardier and a radio gunner) and was armed with a 7.7 mm Browning machine gun in the left wing and a Vickers K of the same calibre in a hydraulically operated Bristol dorsal turret. The first aircraft to enter operational service K7035 was delivered to No 114 Sqn stationed at Wyton in early 1937, which was declared operational on 10 March 1937, just four years after Barnwell had drawn up the first Type 135 designs on paper. The Blenheim’s participation in the annual Hendon Airshow, also in 1937, caused a sensation, and the delivery of aircraft to squadrons based in Iraq or India was the subject of some spectacular flights, such as a group flight from Dhibban to Aboukir, covering 1,306 km in 3.25 hours. When the Munich crisis broke out, there were 15 RAF squadrons operating in the UK with Blenheim Mk I’s, which were replaced in the front line by Mk IV’s in September 1939. Some 200 of these were converted to night fighters, the remainder going to reinforce RAF equipment in the Middle East or being exported.
Also, a Mk I L1348 was modified as a photographic reconnaissance aircraft without being given a specific designation. The wing was reduced by 91cm, the turret removed, the glass panels at the base of the forward fuselage obscured, and various photographic equipment installed in the fuselage. With ‘souped-up’ engines, this aircraft reached 476 km/h at 2,440 m.

Mk IF
Some 200 Mk I bombers were modified as twin-engine escort fighters (hence the F for Fighter) with four fixed 7.7mm Browning machine guns housed in a belly fairing with 500 rounds per gun, the first aircraft being commissioned by No 25 Squadron in December 1938. By September 1939 six fighter squadrons were equipped or being equipped. The aircraft proved to be a poor daytime fighter, an easy target for enemy single-seaters, but an excellent night fighter, equipped successively with the AI Mk II, III and IV interceptor radars. The first night sorties took place at the end of December 1939, and the first successful interception was made on the night of 22/23 July 1940 with an AI Mk IV radar.

Mk II
A single Mk I L1222 was fitted with larger wing tanks, the structure being reinforced to allow a load weight of 6,340kg and the possibility of carrying bombs under wing.

Mk III
It seems that this designation was given to a proposed Blenheim IV which would have retained the Mk I wing (thus similar to the Blenheim IVL). Like the previous one, this model was not given a Type number and some authors continue to claim that the Bristol 149 Bolingbroke prototype K7072 was originally named Blenheim III, an error deliberately peddled during the war for propaganda purposes.

Mk IV
From 1935 Frank Barnwell worked on various evolutions of the Type 142M. To meet the M.15/35 specification the Type 150 was a Bristol Perseus VI powered torpedo bomber carrying a torpedo in the belly hold. The G.24/35 specification was covered, as we have seen, by the Type 149 Bolingbroke, but in April 1935 development began on a new version of the Blenheim to meet both the G.24/35 (twin-engined multipurpose) and M.15/35 (torpedo bomber) specifications. This project led to the Bristol 152 Beaufort, but Coastal Command could not wait and the Beaufort’s development was in danger of being disrupted by the accidental death of Frank Barnwell in a light aircraft he had built himself and which was making its second flight.

The Air Ministry took a renewed interest in the Bolingbroke and decided to revive production of the aircraft, which retained the Type 149 but was christened Mk IV. The Blenheim IV was a Blenheim Mk I with the front fuselage of the Bolingbroke and the wing of the Blenheim II, with new wing tanks to increase range. There was no prototype and the Mk I was upgraded to the Mk IV at the end of 1938 by simply modifying 68 Mk I airframes on the production line.

Blenheim IVL: 68 Mk I airframes modified on the production line, thus without the wing tanks of the standard model.
Blenheim IVF: Night fighter corresponding to the Mk IF, the armament being identical. Approximately 60 examples were modified in this way, used mainly by thirteen RAF fighter squadrons.
Blenheim IV: Standard model with Mercury XV engine of 920 hp at take-off. As with the Mk I the payload capacity was 454 kg, but an additional 145 kg could be carried under the wing. The defensive armament was in principle identical to that of the Mk I, but from the first fights it appeared necessary to improve the defensive armament of this bomber. Standard modifications introduced during production included the installation of a Vickers K machine gun pivoted in the nose cone and a Browning machine gun installed in a glass gondola under the front fuselage, at the location of the crew escape hatch, and firing towards the rear. The last production aircraft received a Bristol B.I Mk.IIIA dorsal turret with two Vickers K or B.I Mk IV with two Browning guns. A remote-controlled Frazer-Nash twin with two rear-firing Browning guns was finally fitted under the nose of some aircraft. More or less effective modifications were also made in squadrons, such as fixed rear-firing machine guns installed either in the engine nacelles or in the rear fuselage tip.

Mk V
In January 1940, Bristol proposed to the Air Ministry a version of the Type 149 Blenheim IV specially adapted for tactical support, with the nose section modified to accommodate four 7.7mm Browning machine guns (1,000 rounds each). This project took into account the experience gained during the first months of the conflict in Europe, as the aircraft could also be used as a fighter or as a trainer. As the Air Staff was already considering this type of aircraft, the B.6/40 specification was written around this definition to allow the order of two Bristol 160 Bisley Mk I prototypes, which were built by Rootes Securities, Bristol’s main subcontractor on the Blenheim programme.
In addition to the modified front fuselage, the cockpit was armoured, the windscreen redesigned, a Bristol B.X dorsal turret equipped with two Browning machine guns was installed and the engines were changed to Mercury XVIs for better low-level performance. While the prototypes were being built, the programme was modified to allow an alternative use as a very high altitude bomber. It was therefore decided to make an interchangeable nose cone: for high-altitude missions, it was glazed on the left side to accommodate a bomber-navigator and received a lower fairing to allow it to sit, but also to accommodate a Frazer-Nash barbette with two rear-firing Browning machine guns. The engines became Mercury XV or XXV of 830 hp, insufficient for an aircraft whose total weight reached 7,700 kg.
The designation Blenheim V replaced the Bisley designation before the first Bristol 160 AD657 took to the air at Filton on 24 February 1941 with the nose of the ground attack version, the second prototype AD661 being equipped as a high altitude bomber. The low-altitude version was soon abandoned and 940 production aircraft with Mercury 25 or 30 engines were built by Rootes Securities Ltd at Blythe Bridge until June 1943. The first examples were delivered to No 18 Sqdn in the summer of 1942, with the aircraft entering operations in November in North Africa. The Blenheim V had a very short career, ending in late 1943 in the Far East. A number of them were modified in dual control without a dorsal turret for Fighter Command’s OTUs, some of them in service in the Mediterranean were transferred in 1942 to Turkey and some to Portugal, which already had a number of Mk IVs interned after forced landings on its territory.

Bolingbroke
To meet the G.24/35 twin-engine multi-role specification (coastal reconnaissance and bombing), the Type 149 was a slightly modified Mk I with Aquila AE-3M engines allowing a greater range. After extending the front of the fuselage by 91 cm to install the radionavigator in front of the pilot, 150 were ordered in November 1936 under the name Bolingbroke. In 1937, a Blenheim I K7072 was taken off the line and converted into the Bristol 149 Bolingbroke prototype (not Mk III).
The first step was to move the bomber’s windscreen and cockpit forward by 90cm without changing the pilot’s position. But before the start of the flight tests it was realised that the pilot would have a serious lack of visibility. The windscreen was therefore moved back to its original position and the glass roof of the front seat lowered below the pilot’s line of vision. Thus modified, it took to the air on 24 September 1937, but the forward visibility on landing was still poor. The upper left section was therefore lowered, giving a very characteristic look to the front of the aircraft.
The Royal Canadian Air Force wished to adopt the aircraft and negotiations began for overseas production, plans to build the Bolingbroke at Filton for RAF use being abandoned in favour of continuing production of the Mk I for overseas units. The Bolingbroke prototype K7072 was therefore shipped to Canada to facilitate the start of production at Fairchild Aircraft Ltd in Longueuil.
Bolingbroke I: 18 aircraft produced to plans supplied by Bristol Aeroplane Company, substantially identical to K7072 with Mercury VIII engines.
Bolingbroke II: A Mk I rebuilt to Mk IV standard after an accident.
Bolingbroke III: It was envisaged that the Bolingbroke could be fitted with skis or floats instead of the original landing gear to suit Canadian conditions. But in fact the idea was abandoned after the modification of a Bolingbroke I �” with two EDO floats.
Bolingbroke IV: Production version redesigned to North American standards for use by the Canadian or American air forces. 125 were built with Mercury XV engines.
Bolingbroke IVC: A Mk IV completed with 990hp Wright R-1820-G3B Cyclone nine-cylinder star engines.
Bolingbroke IVW: 15 aircraft delivered with 14-cylinder Pratt & Whitney Twin Wasp R1830 1200 hp star engines.
Bolingbroke IVT: 517 aircraft for training bombers, gunners, twin-engine pilots, and even target towing.


Bristol Blenheim Mk.I L6739

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.


Bristol Blenheim Mk I: Side Plan - History

    The fact that a heavy twin-engined fighter such as the Beaufighter was available as soon as the late autumn of 1940 was largely due to the foresight and enterprise of the Bristol Aeroplane Company in envisaging the probable need for a high-performance long-range fighter capable of undertaking duties of a more aggressive nature than those foreseen by official specifications. At the end of 1938, L. G. Frise and his design team began the design of what was virtually a fighter variant of the Beaufort general reconnaissance and torpedo-bomber. The initial proposal was framed, as far as possible, to meet the requirements of specification F.11/37, and envisaged an aeroplane using a large proportion of Beaufort components, including the wings, tail assembly and undercarriage, a pair of Hercules radial engines and carrying a battery of four 20-mm. Hispano cannon. The economy of the proposal was of obvious appeal to the government, struggling to meet the vast requirements of a major rearmament program, and, as the Type 156, four prototypes were ordered.

To the Japanese, the Beaufighter became known as "The Whispering Death" because of the speed at which one could suddenly strike and turn for home.

    The Beaufighter prototype (R2052) had two-speed supercharged Bristol Hercules radials which were mounted well ahead of the wing leading edges to alleviate vibration. This necessitated cutting down on other weight forward of the c.g. and resulted in the Beaufighter's characteristic stunted fuselage nose. The main fuselage and the engine mountings were, in fact, the only entirely new components. The outer wings, including the ailerons, flaps and tanks the whole of the retractable landing gear and hydraulic systems and the aft section of the fuselage, complete with tailplane, elevators, fin, rudder and tail wheel, were identical to those of the Beaufort, while the center section, with tanks and flaps, was similar apart from certain fittings. Official trials commenced at an all-up weight of 16,000 lb. after the first prototype's delivery to the RAF on April 2, 1940, and a maximum speed of 335 mph was attained at 16,800 feet.

    As production continued, additional versions appeared differing in engines installed and in other ways. Beaufighters were used in many theaters of war and for varied duties, performing particularly well in the Western Desert thanks to their long range. Coastal Command of the RAF received several torpedo-carrying versions which were responsible for sinking a great deal of enemy shipping. The last and most numerous was the superb Mk X, which could carry a large torpedo or bombs and rocket projectiles, and claimed among its victories several German submarines.

    The Beaufighter IF was soon bearing the brunt of the action against German night bombers, weighing up to 20,800 lb., it attained a maximum speed of 323 mph at 15,000 feet, had a range of 1,500 miles at 194 mph, an initial climb rate of 1,850 ft./min., and a service ceiling of 28,900 feet. Although the Beaufighter IF handled well, it was tricky under certain conditions. There was a strong tendency to swing on takeoff and the danger of a roll-over in the event of an engine cutting suddenly. On landing, the Beaufighter's large flap area pulled the aircraft up rapidly, but there was a tendency to veer from the straight which, if unchecked, resulted in a ground loop, the c.g. being so far aft. The first few Beaufighter Is were delivered without the wing-mounted machine-guns, and initially it was found that when the cannon were fired, the recoil caused the nose to dip enough for the pilot to lose his target. The seriousness of this fault was such that thought was given to alternative armament and, with one pair of cannon and the wing-mounted machine-guns supplanted by a Boulton Paul turret containing four 0.303 machine guns and mounted just aft of the pilot's cockpit, the Beaufighter V was produced. Only two examples (R2274 and R2306) were completed, both being converted Merlin engined Mark IIs, and these were used experimentally by No. 29 Squadron during the early months of 1942, but the installation of the turret drastically reduced performance, and the Beaufighter V was abandoned.

The Beaufighter had two qualities which the Bristol Blenheim lacked -- speed and firepower.

    The Beaufighter T.F.X was the final major production variant and passed through several important modification stages without any change in its Mark number. These included, in particular, the introduction of A.I.Mk.VIII radar in a "thimble" nose—this radar having been found suitable for ASV use—and a large dorsal fin (after a trial installation on a Beaufighter 11, T3032) to give the required directional stability and linked with an increase in elevator area to improve longitudinal stability. Before deliveries of the Beaufighter X could begin, a batch of sixty Beaufighter VIs with Hercules XVI engines and provision for torpedo-carrying was built. These were designated Beaufighter VI (I.T.F.)—interim torpedo fighter—and were converted to Mark Xs when more Hercules XVII engines became available.

    To the Japanese, the Beaufighter became known as "The Whispering Death" (not be confused with "Whistling Death F4U Corsair) which gives some idea of the speed at which one could suddenly appear, strike and turn for home. Beaufighters were also flown by the air forces of Australia, New Zealand and, in small numbers, the US. In Britain they remained flying as target tugs throughout the 1950s.

    When the last Beaufighter (SR919) left the Bristol Aeroplane Company's Weston-super-Mare works on September 21, 1945, a total of 5,562 aircraft of this type had been produced in the United Kingdom. Of these some 1,063 were Mark Vls and 2,231 were Mark Xs. During its operational career it had played a prime role in defeating the Luftwaffe's night "blitz" of 1940-1941, and it had operated in every major campaign of the war, carrying out the last operational sortie of the European war, a strike against German shipping in the Skagerrak, and serving with distinction in the Pacific until the capitulation of Japan. The Beaufighter may have been the product of improvisation, but it was a remarkably successful one.

Shown above is a 3-view of the Beaufighter I with experimental A.I.Mk.VIII radar "thimble" nose.

Specifications:
Bristol Beaufighter T.F.X
Dimensions:
Wing span: 57 ft. 10 in. (17.64 m)
Length: 41 ft. 4 in. (12.59 m)
Height: 15 ft. 10 in. (4.84 m)
Weights:
Empty: 15,592 lb (7,072 kg)
Maximum: 25,400 lb. (11,521 kg)
Disposable Load: 9,808 lb. (4,448 kg)
Performance:
Maximum Speed: 305 mph (490 km/h) @ sea-level.
320 mph (514 km/h) @ 10,000 ft. (3,048 m)
Service Ceiling: 19,000 ft. (5,791 m) (without torpedo)
Range: 1,400 miles (2,253 km) with torpedo and normal fuel.
1,750 miles (2,816 km) with torpedo and long-range tanks.
Powerplant:
Two Bristol Hercules XVII fourteen-cylinder two-row sleeve-valve radial engines rated at 1,725 hp (1,286 kW) @ 2,900 rpm for take-off and
1,395 hp (1,040 kW) @ 2,400 rpm at 1,500 ft. (457 m).
Armament:
Four 20 mm Hispano cannon in the fuselage nose and six .303 in. machine-guns in the wings and one .303 in. Vickers "K" or Browning gun in the dorsal position. One 18-in. torpedo externally under fuselage. Eight rocket projectiles could be carried as alternative to the wing guns.

© The Aviation History On-Line Museum. All rights reserved.
Created November 27, 2001. Updated January 6, 2013.


Bristol Blenheim Mk I: Side Plan - History

J ust one minute after Britain's formal declaration of war against Germany took effect on September 3, 1939, a Blenheim IV of 139 Squadron took off to fly the RAF's first sortie of the war, a photo-reconnaissance operation. The next day, Blenheims made the first Bomber Command attack by bombing enemy warships.

F rom these earliest operations until early 1942, the Blenheim IV served in a variety of roles. Squadrons were based in France in the early months of the war, other squadrons based in Britain were assigned to intercept enemy shipping, and Blenheim enabled Bomber Command to carry on offensive operations over Europe for almost two years before they were replaced by superior aircraft. Blenheim IV's also served in North Africa, the Middle East, and in the far East against the Japanese.

A fighter version of the Blenheim IV carried four machine guns in the bomb bay. These aircraft were involved in the defence of London and served with Coastal Command in anti-shipping, reconnaissance, and a variety of other roles.

A pilot, navigator/bomb-aimer, and wireless operator/gunner comprised the crew of the Blenheim IV. The navigator sat in the nose of the aircraft at a plotting table situated just below the distinctively scalloped port side of the canopy.

T he Bolingbroke was the Canadian-built version of the Blenheim IV and the first of over 600 assembled at Longueuil, Quebec entered service with the Royal Canadian Air Force in November, 1939. Bolingbroke squadrons flow patrols off the Atlantic coast and the Pacific where one was involved in the first successful RCAF attack on Japanese submarine. Two squadrons were assigned to the combined American-Canadian campaign to protect the Aleutian Islands and the west coast of Alaska from Japanese attack.

H owever, the majority of Bolingbrokes never saw combat, instead they performed as crew and operational trainers under the British Commonwealth Air Training Plan at various stations across Canada. Others were converted to target tugs, training air gunners and army anti-aircraft gunners.

T he Boly was the first modern, all aluminium aircraft built in Canada and appeared on both skis and floats for its various roles.

O ur museum's aircraft is Bolingbroke #9987 and was donated by Harry and Anne Whereatt of Assiniboia, Saskatchewan. It served with #3 Bombing and Gunnery School at MacDonald, Manitoba as part of the BCATP. In 1946 almost 150 Bolingbrokes were sold as surplus out of the MacDonald base. This aircraft was purchased by Mr. Whereatt from a farmer in southern Manitoba and then towed to his home near Assiniboia.

A s the museum's primary focus is to honour those associated with Bomber Command during World War II, this aircraft has been restored as a Bomber Command Blenheim IV. On August 12, 2000 it was dedicated to the memory of Barry Davidson, a Calgary pilot who was shot down while flying a #18 squadron Blenheim IV on July 6, 1940. P/O Davidson and his two crewmembers had taken off from West Raynham to attack aerodromes in France.


Bristol Blenheim – Specifications, Facts, Drawings, Blueprints

It was the newspaper magnate Lord Rothmere who asked the Bristol company to build him a fast executive aircraft to carry a pilot and six passengers at 240 mph, appreciably faster than any Royal Air Force (RAF) fighter in 1934. The result was the Type 142, the first modern stressed-skin monoplane in Britain with retractable landing gear, flaps and, after a wait, imported American variable-pitch propellers.

Its performance staggered even the designer, Barnwell, for on Air Ministry test it reached 307 mph. The inevitable result was the Bristol Blenheim bomber, to produce which Barnwell designed a new fuselage with mid-wing and bomb beneath it. Pilot and nav/bomb-aimer sat in the neat glazed nose, and a part-retractable dorsal turret was added behind the wing.

The Bristol Blenheim first appeared in production form as the short-nosed Blenheim Mk I, whose prototype (K 7033) first flew on 25 June 1936. The Blenheim I was ordered in what were huge quantities to a company almost devoid of work. Ultimately 1,134 were built, many of which made gallant bombing raids early in the war and were then converter to IF fighter configuration (some having the AI Mk III, the first operational fighter radar in the world). The fast bomber excited intense foreign interest and many were exported to Finland, Turkey, Jugoslavia, Lithuania, Romania and Greece. To provide a nav/bomb-aimer station ahead of the pilot the nose was then lengthened 3 ft and this type was name Bolingbroke, a name retained for all the variety of Blenheims built in Canada (the Bolingbroke Mk III being a twin-float seaplane).

Most of the Blenheim Bristol bombers were serving in the Middle and Far East, home squadrons of the RAF having already begun to re-equip with the Mk IV.

A revised asymmetric nose was adopted for production in the speedy Mk IV, which later acquired a fighter gun pack (IVF) or a manual rear-firing chin gun (IVL), finally having a two-gun chin turret. With Mercury XV engines replacing the 840 hp Mercury VIIIs of the Blenheim I, the Mk IV was better armed and had a slightly improved performance over its predecessor. One thousand nine hundred and thirty Mk IVs were completed.

The performance of the final Blenheim Bristol British variant, the Mk V, was disappointing. This version was redesigned to meet Specification B.6/40, and in 1941 one Mk VA day bomber prototype and one close-support Mk VB were built by Bristol. Rootes Securities Ltd built nine hundred and forty-two examples, mostly as the Mk VD (a ‘tropical’ version of the VA), but including a proportion of Mk VC dual-control trainers. Combat losses of the Mk VD were heavy, and it was quickly replaced by US Baltimores and Venturas.

During their career the Blenheim Bristol aircraft served with every operational command of the RAF and in every theatre of war.


The Bristol Blenheim, Latest Model Arrivals and Additional Sale Offers.

The Bristol Blenheim is a British light bomber aircraft designed and built by the Bristol Aeroplane Company that was used extensively in the first two years of the Second World War. It was adapted as an interim long-range and night fighter, pending the availability of the Beaufighter. It was one of the first British aircraft to have all-metal stressed-skin construction, retractable landing gear, flaps, a powered gun turret and variable-pitch propellers.

A Canadian-built variant named the Bolingbroke was used as an anti-submarine patrol aircraft and trainer. The Blenheim Mk I outran most biplane fighters in the late 1930s but stood little chance against the German Messerschmitt Bf 109 during daylight operations, though it proved very successful as a night fighter. The Mark IV variant was equally unsuccessful in its daylight bombing role, suffering many losses in the early stages of the war.

In 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. 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 in Europe. Bristol had been working on a suitable design as the ‘Type 135’ since July 1933, and further adapted it to produce the Type 142 to meet Rothermere’s requirements.

K7557 Britain First in flight circa 1935

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

Bristol Blenheim prototype K7033

To achieve its relatively high speed, the Blenheim had a very small fuselage cross-section, with its upper front glazing all at one angle in the form of a “step-less 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. 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, with essential items like propeller pitch control actually placed behind the pilot where they had to be operated by feel alone. Like most contemporary British aircraft, the bomb bay doors were kept closed with bungee cords and opened under the weight of the released bombs. Because there was no way to predict how long it would take for the bombs to force the doors open, bombing accuracy was consequently poor.

The aircraft was ordered directly from the drawing board with the first production model serving as the only prototype. The service name then became Blenheim Mk I after the famous battle during the War of the Spanish Succession. Subsequent deliveries started on 10th March 1937, with 114 Squadron being the first squadron to receive the Blenheim. The aircraft was built under license by countries including Finland and Yugoslavia, which built 60 aircraft. Other countries bought it, including Romania, Greece and Turkey. Total production of the Blenheim Mk I in England was 1,351 aircraft.

Bristol Blenheim Mk IV

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

Bristol Blenheim Mk IVFs of No. 254 Squadron RAF flying from Aldergrove in Northern Ireland

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

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

Bristol Blenheim MK V

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

On the day that war was declared on Germany, a Blenheim piloted by Flying Officer Andrew McPherson was the first British aircraft to cross the German coast and the following morning 15 Blenheims from three squadrons set off on one of the first bombing missions. With the rapid advances in technology which had taken place in the late 1930s, by then the aircraft was already obsolescent. The Blenheim was regarded as a pleasant aircraft to fly, although it did have some characteristics which could catch even experienced pilots by surprise. It had become heavier as extra service equipment was installed much of this was found to be needed through operational experience. This, coupled with the rapid performance increases of fighters, had eclipsed the Blenheim’s speed advantage.

Blenheim Mk1F, Singapore, April 1941.

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

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

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

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

There were also some missions which produced an almost 100% casualty rate amongst the Blenheims. One such operation was mounted on 13th August 1940 against a Luftwaffe airfield near Aalborg in north-western Denmark by 12 aircraft of 82 Squadron. One Blenheim returned early (the pilot was later charged and due to appear before a court martial, but was killed on another operation) the other 11, which reached Denmark, were shot down, five by flak and six by Bf 109s.

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

The view from a Blenheim bomber as it finishes its bomb run over the other Cologne power station with bombs exploding on target.

The action against Cologne power stations on 12th August 1941 was described by the Daily Telegraph in 2006 as the “RAF’s most audacious and dangerous low-level bombing raid, a large-scale attack against power stations near Cologne.” The raid was a low-level daylight raid by 54 Blenheims under the command of Wing Commander Nichol of No. 114 Squadron RAF. The Blenheims hit their targets (Fortuna Power Station in Oberaußem-Fortuna and the Goldenberg Power Station in Hürth-Knapsack) but 12 of the Blenheims were lost during the raid, 22% of those that took part, which was far above the sustainable loss rate of less than 5%. The England cricketer Sqn Ldr Bill Edrich was awarded the DFC for his part in the raid.

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

Bristol Blenheim MkIVF Night Fighter

In the German night-bombing raid on London on 18th 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 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 2nd–3rd July 1940, accounting for a Dornier Do 17 bomber. More successes came, and before long the Blenheim proved itself invaluable as a night fighter. Gradually, with the introduction of the Bristol Beaufighter in 1940–1941, the Blenheim was supplanted by its faster, better-armed descendant.

Bristol Blenheim Mk.IV, V6149, 13th Hellenic Squadron, Egypt

Blenheims continued to operate widely in many combat roles until about 1943, equipping RAF squadrons in the UK and on British bases in Egypt, Iraq, Aden, India, British Malaya, Singapore, and the Dutch East Indies. Many Blenheims were lost to Japanese fighters during the Malayan Campaign, battles for Singapore, and Sumatra. By that point, the traditional daylight light bomber role was more effectively carried out by suitable fighter-bombers, and the surviving examples were relegated to training duties. Nonetheless, the Blenheim played a role in preventing India from falling and recapturing Burma, destroying over 60 aircraft on the ground in raids on Bangkok early in the campaign.

Arthur Scarf VC

One Blenheim pilot, Squadron Leader Arthur Scarf, was posthumously awarded the Victoria Cross for an attack on Singora, Thailand, on 9th 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 22nd May 1942, over the Bay of Bengal. Katō’s death was a severe blow to the Imperial Japanese Army Air Force.

The Air Ministry’s replacement for the Blenheim as a daylight bomber, another Bristol design, the 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 13 squadrons – mainly in the Middle East and Far East – received this variant but operated them generally only for a few months.

Bristol Blenheim Mk I Finnish Air Force

In 1936, the Finnish Air Force ordered 18 Blenheim Mk Is from Britain and two years later, they obtained a manufacturing license for the aircraft. Before any aircraft could be manufactured at the Valtion lentokonetehdas (State 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. After the Winter War, 55 Blenheims were constructed in Finland, bringing the total number to 97 aircraft (75 Mk Is and 22 Mk IVs)

The Finns also received 20 half-completed ex-Yugoslavian Mk IV Blenheims captured by Germany, together with manufacturing tools and production equipment, as well as a huge variety of spare parts. Yugoslavia had ceased production of the Mk I and commenced a production run of Mk IVs just prior to the April 1941 invasion.

Bristol Blenheim Mk I Finnish Air Force

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

After the war, Finland was prohibited 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 tugs, with the last flight of a Finnish Blenheim taking place on 20 May 1958.

Bristol Blenheim/ Bolingbroke Survivors.

An airworthy Blenheim had been rebuilt from a scrapped Bolingbroke over a 12-year period, only to crash at an air show at Denham within a month of completion in 1987.

Bristol Blenheim crash at Denham 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 19th August 2003 the crash was feared to have made it a write-off, but after extensive repair and conversion to the Mark I “Short nose” version by The Aircraft Restoration Company (ARC or ARCo) at Duxford, was displayed to the public on 30th May 2014, and first flew for 29 minutes on 20th November 2014, following restoration at the Imperial War Museum Duxford, Cambridgeshire, England.

The only flying Blenheim (Mk.1 L6739) displaying at Duxford in 2015.(the subject of Corgi Aviation Archives latest model below).

In Canada, a number of other Bolingbrokes survived the war but were summarily consigned to the scrap heap. Post-war, 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 colour. 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.

Front view of a Bristol Bolingbroke Mark IV at British Columbia Aviation Musuem,Canada

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.

BL-200 (bearing the Hakaristi) at the Aviation Museum of Central Finland.

In the summer of 1996, a Bristol Blenheim Mk IVF was recovered from the sea, a few kilometres off Rethymnon, Crete. The aircraft belonged to No. 203 Squadron RAF and was downed by friendly fire on 28th April 1941. The Blenheim was moved to the Hellenic Air Force Museum for restoration.

A salvaged Bristol Blenheim Mk IV F Hellenic Air Force Museum.

In Arizona, the Pima Air Museum has a Bristol Bollingbroke IVT (RCAF #10076) on static display.

In Belgium, the Royal Museum of the Armed Forces and Military History has Bristol Fairchild Bolingbroke IV-T (9895) on static display.

New Corgi Aviation Archive Bristol Blenheim.

Corgi’s new model of Imperial War Museum’s Bristol Blenheim Mk.I, L6739 (G-BPIV) is now available to pre-order and is already proving to be a very popular model. Please click on the image or link below to order your now.

Latest Model Arrivals at Sywell

More models have arrived at Sywell this week and are being dispatched to those of you that have already pre-ordered these models. Please click on the images below to go straight to the model of your choice.

This aircraft recently made a visit to Sywell and I managed to get some great shots of it. It really is a beautifully restored aircraft ! I include a couple of them here…

DH Dragon Rapide G-AHAG Scillonia Airways at Sywell Aerodrome.

DH Dragon Rapide G-AHAG Scillonia Airways taking on fuel at Sywell Aerodrome

Latest Sale Offers added to “Offers of the Week”

I have added some additional models to the “Offers of the Week” section on the website. Please click on the link HERE to see them all or on any of the images and links below to go straight to the model of your choice.

That’s it for this week. A busy weekend ahead with Flying Legends at Duxford and The Royal International Air Tattoo at Fairford. Let’s hope for some kind weather !

Thank you for taking time to read this week’s Newsletter.

Find Us At Sywell Aerodrome

Flying Tigers is now based at the historic Sywell Aerodrome, in Northamptonshire. We hope to welcome many of you to our new premises over the coming months. See map.

Bristol Blenheim IV

As the Allied Ground and Air Forces faced defeat in May 1940 the RAF had to use its light bomber force in desperate daylight raids against German army bridgeheads in France and the Low Countries. The Blenheim Ivs and Fairey Battles used in these attacks suffered crippling losses. In fact no higher loss, in operations of a similar size, has ever been suffered by the Royal Air Force.

The Blenheim IV, with its redesigned and longer nose, superseded the Blenheim I on the production lines in 1938. The original short nose Blenheim I had been developed from a civil aircraft and was one of the first new high performance monoplanes ordered under RAF Expansion Plans.

After the fighting in France was over Coastal and Bomber Command Blenheim Ivs began day and night attacks against German occupied ports and installations in frantic attempts to disrupt their invasion plans. These attacks continued through into 1941 and on 4 July Wg Cdr H.I. Edwards was awarded the Victoria Cross for his part in a daylight bombing attack on Bremen while flying a Blenheim IV.

A number of night fighter conversions were made from early Blenheim Is and later Blenheim IVs but their lack of speed precluded any great success.


Plane

Originally, the Bristol Blenheim was not created as a bomber or with the RAF in mind. During 1933 Bristol Chief Designer Frank Barnwell announced a proposal for a high-speed light passenger aircraft, the Bristol Type 135. The Type 135 as envisioned as a low-wing monoplane capable of carrying up to eight passengers within an all metal cantilever stressed skin fuselage, powered by two 500 hp (373 kW) nine cylinder Bristol Aquila I sleeve-valved air cooled radial engines. By 1934 work on the design had advanced to the fuselage mock-up stage and it was decided to display the mock up at the 1935Salon Internationale de L'Aeronautique in Paris.

In 1934 Lord Rothermere, who was the owner of the Daily Mail newspaper, expressed a desire to obtain for his personal use, a fast and spacious private aeroplane, for this aviation-minded organisation had then appreciated the potential of what is today called the business or corporate aircraft. Lord Rothermere envisaged his requirements as a fast aircraft that would accommodate a crew of two and six passengers, and it just so happened that the Bristol Aeroplane Company had already drawn up the outline of a light transport in this category, the Type 135.

The new aircraft had been designed originally to be powered by two 500 hp (373 kW) Bristol Aquila I engines which were then under development. The Type 135 had an anticipated top speed of 180 mph (290 km/h) but lacked the range to meet Lord Rothermere's requirements. Frank Barnwell proposed changes that included reducing the fuselage cross section to reduce drag and replacing the 500 hp (373 kW) Bristol Aquila I engines with a couple of 640 hp (477 kW) Bristol Mercury VI radial engines driving fixed pitch four blade propellers. Design work started on the now designated Bristol Type 142 with Lord Rothermere as its principle source of funding. It would cost him £18,500 to complete the aircraft, a large sum even by todays standards. Bristol had learned of government plans to expand the RAF and with the anticipation of possible future contracts decided to fund a parallel design called the Bristol Type 143 as a private venture. The Type 143 featured a longer nose and longer undercarriage doors.

First flown at Filton on 12 April 1935, the Type 142 was to spark off much comment and excitement when during its initial trials it was found to be some 30 mph (48 km/h) faster than the prototype of Britain's most-recently procured new biplane fighter, the Gloster Gauntlet. Named Britain First, it was presented to the nation by Lord Rothermere after the Air Ministry had requested that they might retain it for a period of testing to evaiuate its potential as a light bomber. It had a number change from G-ABCZ to K-7557 and was then moved to Martlesham Heath for RAF trials. It proved so successful that in 1935 the Air Ministry issued Specification B.28/35 for a military version with similar performance. This, then was the sire of the Bristol Blenheim which was to prove an important interim weapon at the beginning of World War II.


The Bristol Mk IV dorsal turret on a Blenheim Mk IV aircraft.

Aware of Air Ministry interest in the Type 142, Bristol busied themselves with homework to evolve a military version (Type 142M) of this aircraft, and in the summer of 1935 the Air Ministry decided to accept the company's proposal, placing a first order for 150 aircraft to Specification B.28/35 in September. The new aircraft was very similar to the Type 142, but there had of course been some changes to make it suitable for the military role, primarily to accommodate a bomb aimer's station, a bomb bay and a dorsal gun turret. Little time was lost by either the Bristol company or the Air Ministry, for following the first flight of the prototype, on 25 June 1936, it was moved to Boscombe Down on 27 October 1936 for the start of official trials, with initial deliveries to RAF squadrons beginning in March 1937. In July 1937 the Air Ministry placed a follow-on order for 434 additional Blenheim Mk Is, as the type had by then been named.

Initial deliveries of production Blenheim Mk Is to the RAF squadrons began in March 1937. The first aircraft (K7036) to be delivered, however, crashed upon landing totally destroying the aircraft. The first RAF squadron to receive Blenheim Mk Is was No.114, then based at RAF Wyton, and it was this unit which first demonstrated the new type officially to the public at the RAF's final Hendon Display in the summer of 1937. The Blenheims were to arouse excited comment with their high speed and modern appearance, being launched on their career in an aura of emotion created by the belief that, in an unsettled Europe, the RAF was armed with the world's most formidable bomber aircraft. Production contracts soared, necessitating the establishment of new construction lines by A. V. Roe at Greengate, Middleton (Chadderton) and Rootes Securities at Speke (South Liverpool), both these factories being in Lancashire. Between them the three lines built a total of 1,355 Blenheim Mk Is which, at their peak, equipped no fewer than 26 RAF squadrons at home and overseas, the Blenheim's first overseas deployments being with No.30 Squadron in Iraq and No.11 Squadron in India, in January and July 1938 respectively.

However, by the outbreak of World War II few Blenheim Mk Is remained in service with home-based bomber squadrons, having been superseded in the bombing role by the Blenheim Mk IV, which incorporated the lessons learned from the experience which squadrons had gained in operating the Mk I. But their usefulness was by no means ended, many continuing to serve as conversion trainers and, initially, as crew trainers in OTUs. More valuable by far were some 200 which were converted to serve as night fighters, pioneering the newly conceived technique of AI (Airborne Interception) radar, carrying AI Mk III or Mk IV. The single forward-firing machine-gun was totally inadequate for this role, of course, and a special underfuselage pack to house four 7.7 mm (0.303 in) machine-guns was produced. So equipped, Blenheim Mk IFs scored the first AI success against an enemy aircraft on the night of 2-3 July 1940.

Export versions of the Blenheim Mk I were sold before the war to Finland, Turkey and Yugoslavia, and were also built under licence by these first two nations. In addition, a small number had been supplied to Romania as a diplomatic bribe in 1939, but this proved to be unsuccessful. The result, of course, was that Blenheim Mk Is fought for and against the Allies.

When, in August 1935, the Air Ministry had initiated Specification G.24/35 to find a successor to the Avro Anson for use in a coastal reconnaissance/light bomber role. Bristol had proposed its Type 149. Very similar to the Blenheim Mk I, this was based on the use of Bristol Aquila engines to confer long range with the existing fuel capacity, but proved unacceptable to the Air Ministry. Subsequently renewed interest was shown in the Type 149 for use in a general reconnaissance role, and a prototype was built, by conversion of an early Blenheim Mk I, this retaining the Mercury VIII engines and being provided with increased fuel capacity. The fuselage nose was lengthened to provide additional accommodation for the navigator/observer and his equipment, and this was to be finalised as that which graced the Blenheim Mk IV.

The Air Ministry then had misgivings about the Type 149, fearing that its introduction and manufacture would interfere with the production or urgently needed Blenheims. Instead, the Type 149 was adopted by the Royal Canadian Air Force and with the start of the British Commonwealth Air Training Plan, it was decided to produce a version in this country. Fairchild Aircraft of Longueil outside Montreal was selected to produce them under the Canadian name Bolingbroke. Quickly nicknamed the Boly, the type saw service throughout Canada. The Bristol prototype being shipped to Canada to help in the establishment of a production line. The first Bolingbroke Is had Mercury VIII engines, but after 18 of these had been built production changed to the definitive Canadian version, the Bolingbroke IV with Mercury XV engines, and equipment from both Canadian and US manufacturers. Later variants included a small number of Bolingbroke IV-Ws with American built Pratt and Whitney Twin Wasp Junior (SB4-G) 14-cylinder engines rated at 825 hp (615 kW) for take-off, and a number of Bolingbroke IV-T multi-purpose trainers.

Having blown hot and then cold over the Type 149, there was a sudden renewal of interest, primarily as an interim measure until the Type 152 torpedo-bomber, derived from the Blenheim, should become available. The decision was taken, therefore, to introduce the longer nose and stepped windscreen of the Bolingbroke, and to make provision for longer range by the introduction of increased wing fuel capacity. The Bristol designation Type 149 was retained for this changed configuration, the new RAF designation being Blenheim Mk IV. This change took place quietly on the production lines towards the end of 1938, although the first 68 Blenheim Mk IVs were built without the 'Iong-range wing'. The powerplant comprised two more powerful Mercury XV engines, and these allowed gross weight to be increased eventually by 16 per cent.

No. 90 Squadron was the initial unit to be equipped with Blenheim Mk IV s in March 1938, the first of more than 70 squadrons to operate these aircraft, and consisting of units from Army Co-operation, Bomber, Coastal, Far East Bomber, Fighter and Middle East Commands, both at home and overseas. Inevitably, such extensive use brought changes in armament and equipment, but especially the former, for the armament of the first Blenheim Mk IVs was unchanged from the initial two-gun armament of the Mk I. As finalised the number became five, the single forward-firing gun in the wing being retained, a new dorsal turret carrying two guns being adopted, and a completely new remotely-controlled Frazer-Nash mounting being added beneath the nose to hold two aft-firing machine-guns. Protective armour was also increased, but while it was not possible to enlarge the capacity of the bomb bay, provision was made for an additional 320 Ibs (145 kg) of bombs to be carried externally, under the inner wings, for short-range missions.

With so many squadrons operating the type it was inevitable that Blenheims should notch up many wartime 'firsts' for the RAF. These included the first reconnaissance mission over German territory, made on 3 September 1939. It was flown by Flying Officer A Macpherson in a Blenheim (N6215) Mk IV of No. 139 Squadron while on an armed reconnaissance over German warships at Heligoland Bight (Schillig Roads) near Wilhelmshaven. On 4 September 1939, ten aircraft from Nos. 107 & 110 Squadrons, led by Flight Lieutenant K.C. Doran of No. 110 Squadron made an attack on the same German ships. From the beginning of the war, until replaced in home squadrons of Bomber Command by Douglas Bostons and de Havilland Mosquitoes in 1942, Blenheim Mk IVs were used extensively in the European theatre. Although vulnerable to fighter attack, they were frequently used for unescorted daylight operations and undoubtedly the skill of their crews and the aircraft's ability to absorb a great deal of punishment were the primary reasons for their survival, for high speed and heavy firepower was certainly not their forte. In the overseas squadrons Blenheims continued to serve long after their usefulness had ended in Europe, and except in Singapore, where they were no match for the Japanese fighters, they proved a valuable weapon. A total of 3,298 Mk IV had been built in England when production ended, and in addition to serving with the RAF had been used by the French Free and South African air forces, and supplied in small numbers to Finland, Greece and Turkey.

Canadian Bolingbrokes

Operational use of the Bolingbroke was limited to the Royal Canadian Air Force in Canada and the Aleutian Islands. No 8 (Bomber Reconnaissance) Squadron was the first RCAF unit to convert to the Bolingbroke, followed by one other squadron. Bolingbrokes were used primarily to fly anti-submarine coastal patrols over both the Atlantic and Pacific.

Two RCAF squadrons were assigned to the combined American-Canadian defence campaign to protect the Aleutian Islands and west coast of Alaska from Japanese attack. No. 115 Squadron arrived in the Aletuians in April of 1942 and was assigned anti-submarine patrol and maritime reconnaissance missions. In June of 1942 No. 8 Squadron deployed to the Aleutians with twelve Bolingbroke Mk IVs, making a 1,000 mile flight from RCAF Sea Island to Yakutat Island arriving on 3 June. When the squadron arrived it was ordered to paint out the Red centers to the upper wing roundels to prevent confusion with the Japanese 'meatball' insignia. Later additional recognition markings in the form of a fourteen inch Blue band was added to the rear of the fuselage. The harsh weather in the Aleutians proved a worse enemy than the Japanese and a number of Bolingbrokes were lost when thick Alaskan fogs obscured mountain tops. Normal bomb loads consisted of three 300 pound depth charges and two aircraft were maintained in an alert status at all times. The squadron is credited with sharing one submarine kill with the US Navy. A Bolingbroke Mk IV piloted by Flight Sergeant P.M.G. Thomas attacked and damaged a Japanese submarine enabling US Navy surface units to later sink it.

The majority of Bolingbrokes produced never saw combat, instead they performed as crew and operational trainers under the Commonwealth Air Training Plan, training crews for overseas units. Still others were converted to unarmed target tugs with high visibility paint schemes for training air gunners and army anti-aircraft gunners.

Accommodation/Crew: Pilot, Navigator/Bomb-Aimer and Wireless Operator/Air Gunner. See the Blenheim Mk I for more cockpit information.

Design: Chief Designer Frank Barnwell of the Bristol Aeroplane Company Limited.

Manufacturer: The Bristol Aeroplane Company Limited based at Filton (Bristol), Bristol County, England (Mark I, IV & V Prototypes), Alexander V. Roe (Avro) Aircraft Company Limited based in Greengate, Middleton (Chadderton), Lancashire County, England (Mark I & IV), Rootes Securities Limited at Blythe Bridge (Stoke on Trent), Straffordshire County, England (Mark IV & V), Rootes Securities Limited at Speke (South Liverpool), Lancashire County, England (Mark I & V), Fairchild Aircraft Limited in Longueil, Quebec, Canada (Bolingbroke). Also built under licence by Valtion Lentokonetehdas (State Aircraft Factory) at Tampere, Finland (Mark I & IV) and Ikarus AD in Belgrade (Zemun), Yugoslavia (Mark I).

Powerplant: (100 Octane Fuel) Two Bristol Mercury XV 9-cylinder poppet-valve air-cooled radial engines developing 905 hp (675 kW) at take-off, a maximum output of 995 hp (742 kW) for level flight (5 minute usage) and a maximum ecomical cruising power output of 590 hp (440 kW) at 16,000 ft (4877 m) at 2400 rpm. (87 Octane Fuel) Two Bristol Mercury XV 9-cylinder poppet-valve air-cooled radial engines developing 725 hp (541 kW) at take-off, a maximum output of 840 hp (627 kW) for level flight (5 minute usage) and a maximum ecomical cruising power output of 590 hp (440 kW) at 16,000 ft (4877 m) at 2400 rpm.

Performance: Maximum speed 266 mph (428 km/h) at 11,800 ft (3595 m) cruising speed of 198 mph (319 km/h) service ceiling (clean) 27,260 ft (8310 m) or 22,000 ft (6706 m) fully loaded initial climb rate 1,480 ft/min (7.5 m/sec).

Fuel Capacity: Two inboard 140 Imperial gallon (636 litres) main fuel tanks and two outboard 94 Imperial gallon (427 litres) auxiliary or long range fuel tanks giving a total capacity of 468 Imperial gallons (2125 litres). Starting in early 1940 the main fuel tanks were self-sealing, but due to an initial shortage, the outboard auxiliary fuel tanks remained non self-sealing for some time.

Oil Capacity: One 11.5 Imperial gallon (52.2 litre) main oil tank and a 2.5 Imperial gallon (11.3 litre) auxiliary oil tank per engine giving a total oil capacity of 28 Imperial gallons (127.2 litres).

Range: 1,460 miles (2350 km) on internal fuel with a 1,000 lbs (454 kg) bombload. 1,950 miles (3140 km) on internal fuel without bombs.

Weights & Loadings: Empty 9,790 lbs (4441 kg), with a normal take-off weight of 13,500 lbs (6122 kg) and a maximum take-off weight of 14,400 lbs (6532 kg) fully loaded with bombs.

Dimensions: Span 56 ft 4 in (17.17 m) length 42 ft 7 in (12.98 m) height 9 ft 10 in (3.00 m) wing area 469 sq ft (43.57 sq m).

1 × 7.7 mm (0.303 in) Browning fixed forward-firing machine-gun in the port wing.

1 x 7.7 mm (0.303 in) Lewis or Vickers "K" trainable machine-gun in a semi-retractable hydraulically operated Bristol B.Mk III dorsal turret, or

2 x 7.7 mm (0.303 in) Vickers "K" trainable machine-guns in a power-operated Bristol B.Mk IIIA dorsal turret, or

2 x 7.7 mm (0.303 in) Browning trainable machine-guns in a power-operated Bristol B.Mk IV dorsal turret.

1 × 7.7 mm (0.303 in) Browning trainable rearward-firing machine-gun in a remotely controlled Frazer-Nash FN.54 chin turret, or

2 × 7.7 mm (0.303 in) Browning trainable rearward-firing machine-guns in a remotely controlled Frazer-Nash FN.54A chin turret. The turret could rotate 20 degrees to either side with a depression of 17 degrees.

1 × 7.7 mm (0.303 in) Vickers "K" forward-firing machine-gun in a gimbal nose gun mount (optional field modification).

1 × 7.7 mm (0.303 in) Vickers "K" machine-gun in a rear firing engine nacelle mount (optional field modification).

1 × 7.7 mm (0.303 in) Vickers "K" machine-gun in a rear firing under tail mount (optional field modification).

4 × 250 lbs (114 kg) bombs, or

2 × 500 lbs (227 kg) bombs, or

3 × 300 lbs (114 kg) depth charges carried internally.

4 × 80 lbs (36.2 kg) bombs on underwing racks, or

2 × 160 lbs (72.5 kg) bombs on underwing racks

Variants: Bristol Type 142, Bristol Type 142M, Bristol Type 143 (Aquila engined), (Type 142M) Blenheim Mk I Prototypes, (Type 142M) Blenheim Mk I, Blenheim Mk IF, Blenheim PR.Mk I, Blenheim Mk II, Blenheim Mk III, Bristol Type 149, (Type 149) Blenheim Mk IV Prototypes, (Type 149) Blenheim Mk IV, (Type 149) Blenheim Mk IVF, (Type 149) Blenheim Mk IVL, (Type 160) Bisley Mk I, (Type 160) Blenheim Mk V, Bolingbroke Mk I, Bolingbroke Mk II, Bolingbroke Mk III, Bolingbroke Mk IV, Bolingbroke Mk IV-C, Bolingbroke Mk IV-W, Bolingbroke Mk IV-T, Bolingbroke Mk IV-TT

Equipment/Avionics: Standard communications and navigation equipment.

History: First flight (Type 142 "Britain First") 12 April 1935 first flight (Type 142M) 25 June 1936 initial delivery (No. 114 Squadron RAF) March 1937 end production (VD) June 1943 withdrawn from service (Finland) 1956.

Operators: United Kingdom (RAF), Canada (RCAF), Finland, Turkey, Yugoslavia, Romania, Greece (Royal Hellenic Air Force), Free French Air Force (Forces Francaises Libre), Portugal (Arma de Aeronautica), South Africa (SAAF) and Croatia. The German Luftwaffe and the Italian Regia Aeronautica both operated captured aircraft.

Number Still Airworthy: One

Bristol Blenheim Mk IV

Typical Blenhiem Specifications
Manufacturer:
Bristol
Length: 43 ft 1 in
Wing Span: 56 ft
Height: 9 ft 10 in
Speed: 170 to 303 mph at 15,000 ft
Range: up to 1,900 miles
Ceiling: 20,000 ft
Armament: two .303 in mg turret mounted, one .303 in mg remote control nose blister mount
Bomb Load: 1,000 lbs
Weight: 14,000 lbs

No. 18 Squadron was a medium bomber squadron that spend a large part of the Second World Wars overseas, starting in France in 1939-40 and then serving on Malta, in North Africa, in Sicily and in Italy.

Up until May 1939 the squadron had been equipped with the Hawker Hind. It then received the Bristol Blenheim Mk I, the start of a relationship with the Blenheim that would last until the spring of 1943.

At the outbreak of the Second World War No. 18 Squadron was sent to France as part of the Air Component of the BEF. There it took part in the first ten days of the disasterous campaign of May 1940, before retreating to Britain.

This was followed by the squadron's wartime stay in Britain, lasting for seventeen months. During this period the squadron was engaged in attacks on the German invasion barges during 1940, before "leaning over the channel" in 1941 to attack German installations.

In October 1941 the squadron's aircraft flew to Malta, where they took part in raids against Axis shipping. By January 1942 the squadron was down to five aircraft, and was withdrawn to Egypt.

The squadron then reformed in Britain with new aircraft and new crews but many of the same ground crews. Most of 1942 was spent in Britain, before the squadron was moved to North Africa, in November.

The squadron remained in the Mediterranean theatre for the rest of the war, accompanying the Allied armies as they advanced from Algeria to Tunisia, across to Sicily and then finally to Italy. While based in North Africa, the squadron was re-equipped with the Boston bomber. While based in Italy, the squadron was used against targets in northern Italy and the Balkans.

Group and Duty
September 1939-May 1940: Air Component, France
May 1940-October 1941: Attacks on Channel Ports, France and the Low Countries
October 1941-January 1942: Malta
May-November 1942: United Kingdom
November 1942-August 1943: North Africa
August-October 1943: Sicily
October 1943-end of war: Italy

United Kingdom
12 September 1936-30 September 1939: Upper Heyford

France
30 September 1939: Beauvraignes
16 October 1939: Meharicourt
17 May 1940: Poix
19 May 1940: Crecy and Abbeville

United Kingdom
20-26 May 1940: Watton
26 May-12 June 1940: Gatwick
12 June-8 September 1940: West Raynham
8 September 1940-3 April 1941: Great Massingham
3 April-13 July 1941: Oulton
13 July-16 August 1941: Horsham St. Faith
16-27 August 1941: Manston
27 August-12 October 1941: Horsham St. Faith

Malta
12 October 1941-21 March 1942

Egypt
10 January-5 February 1942: Helwan
5-14 February 1942: L.G.05
14 February-21 March 1942: Fuka

United Kingdom (with new crews)
13-15 May 1942: Dundonald
15-20 May 1942: Ayr
20 May-23 August 1942: Wattisham
23 August-11 November 1942: West Raynham
11-30 November 1942: Bilda

Algeria and Tunisia
30 November- 5 December 1942: Canrobert
5-17 December 1942: Setif
17 December 1942-7 March 1943: Canrobert
7 March-17 April 1943: Oulmene
17 April-7 June 1943: Souk el Arba
7 June-3 August 1943: Grombalia

Sicily
3-9 August 1943: Gela West
9-24 August 1943: Comiso
24 August-7 October 1943: Gerbini

Italy
7-30 October 1943: Brindisi
30 October 1943-16 February 1944: Foggia
16 February-14 June 1944: Marcianise
14-25 June 1944: Nettuno/ La Blanca
25 June-18 July 1944: Tarquinia
18 July-18 October 1944: Cecina
18 October 1944-7 March 1945: Falconara
7 March-13 May 1945: Forli
13 May 1945-12 September: Aviono

Although not at Wattisham for very long, 18 Squadron is one of the few that is still active today.

Northolt was the site for the birth of 18 Squadron on 11 May 1915, which was formed from Nr 4 Reserve Squadron. A brief move to Norwich (Mousehold) for training was made on 16 August, the squadron acquiring a gamut of aeroplanes such as Bristol Scouts, Shorthorns and Martinsydes but eventually was sent to the Western Front and the horrors of the Great War flying the Vickers FB Gunbus. Flying tactical reconnaissance missions, it saw action over the trenches of the Somme flying from bases such as St Omer, Bertangles and Auchel. DH4s were provided in 1917 and DH9As shortly before the war's end. Disbandment came on 31 December 1919 at Weston-on-the-Green.

The first of many reformations for the squadron came on 20 October 1931 when two Hawker Harts were supplied to the fledging unit at Upper Heyford in Oxfordshire. Forming the backbone of the RAF's light bomber fleet in the thirties, the Hart was to be a common sight in the Oxford skies for the first half of the decade, especially so in the colours of 18 Squadron. Hinds replaced the Harts in 1936, hardly a giant leap in capability, but were to remain in service for two years before Blenheims were available. At this time a brief move to Bircham Newton in Norfolk was made, but by September of that year the squadron was back at Upper Heyford. At Bircham 'C' Flight was detached to Worthy Down to form the nucleus of 49 Squadron.

The start of the war saw 18 Squadron provide aerial reconnaissance over France for the British Expeditionary Force, flying from an airfield near Amy. Such was the devastating effect of the Battle of France that most of the squadron was lost in those frenetic months, the unit being withdrawn to England in the early summer of 1940. Returning to Lympne in Kent, the surviving Blenheims were quickly dispersed to less vulnerable locations, most going to Watton in Norfolk.

Reformed at Gatwick (yes, now the airport) and equipped with Blenheim IVs, coded 'WV', the squadron moved to West Raynham on 12 June, staying here for three months before moving all of a mile to the nearby satellite airstrip of Great Massingham. The first squadron to use Massingham, from here the unit flew night missions against enemy airfields and also provided diversionary raids for the heavy bomber fleet. In April '41 it moved to north Norfolk and another rudimentary airfield at Oulton, satellite airfield for Horsham St Faiths. From here and the parent airfield, still using the redoubtable Blenheim, by now the Mk IV, tactics changed to the anti-shipping role. Detachments were sent to Manston for Operation Channel Stop as with other light bomber units, and during this time on 19 August the squadron made a 'humanitarian' mission by dropping a new metal leg to the captured Wing Commander Douglas Bader in St Omer! Carried by Blenheim R3843 WV-F, naturally enough this mission was titled 'Operation Leg'.

In July, the squadron departed for pastures new in the beautiful island of Malta to bolster the defence of the beleaguered population but returned to Oulton in the November, for rest and recuperation. A month later came departure for Wattisham, although the squadron was somewhat depleted with some crews still in the Mediterranean. As mentioned before, its stay at Wattisham was brief as by August 1942 it had moved back to Great Massingham. Provided now with Blenheim VDs (commonly known as the Bisley), it left for the Middle East in October.

Algeria was the destination, from here the squadron mounted raids on German targets in Tunisia but suffered heavy losses in the early daylight missions. A switch to night missions was made and also a change of aircraft, from the Blenheim to the Boston III. A move to Sicily in August 1943 and onwards into Italy in October saw the squadron see out the war mounting raids on Northern Italy and the Balkans from bases such as Brindisi, still in use today. Immediately after VE day the squadron moved to Aviano, where today much military action is seen, then post-war it moved to Hassini in Greece, where disbandment came on 31 March 1946.


Watch the video: 2021 Airfix 148 Bristol Blenheim first impressions. (July 2022).


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