Bristol Blenheim

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Bristol Blenheim (Types 142M, 149, 160)
Bristol Blenheim, England, 2001.
Type	Light bomber/fighter
Manufacturer	Bristol Aeroplane Company
Designed by	Frank Barnwell
Maiden flight	1935
Introduced	1937
Retired	1944 (RAF), 1956 (Finland)
Status	Retired
Primary user	Royal Air Force
Number built	4,422

The Bristol Blenheim was a British high-speed light bomber and fighter used extensively in the early days of the Second World War, built by Bristol Aeroplane Company. It was the first British aircraft to have all-metal stressed skin construction and one of the first to utilize retractable landing gear, flaps, powered gun turret and variable-pitch propellers.

[edit] Design and development

The Type 135 civil twin design was on Bristol drawing boards by July 1933. In 1934, this design was offered to Lord Rothermere, owner of the Daily Mail who had wished to promote British aviation. He had asked the industry to deliver the fastest civilian aircraft in Europe, capable of carrying six passengers and two crew members. Bristol further refined their original design to produce the Type 142. When it first flew as Britain First at Filton on 12 April 1935, it proved to be faster than any fighter the Royal Air Force had at the time.

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

[edit] Operational history

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

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

To achieve its relatively high speed, the Blenheim had a very small fuselage. 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 bungees 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 rather mediocre.^[1]

The concept of a fast bomber was realized definitively with the de Havilland Mosquito.

[edit] Variants

Work on an extended range reconnaissance version started as the Blenheim Mk.II, which increased tankage from 278 to 468 gallons, but only one was completed. Another modification resulted in the Blenheim Mk.III, which lengthened the nose to provide more room for the bombardier. This required the nose to be "scooped out" in front of the pilot to maintain visibility during takeoff and landing. However both of these modifications were instead combined, along with a newer version of the Mercury engine with 905 hp (675 kW) and a second gun in the rear cockpit, to create the Blenheim IV. When it was introduced in 1939, the Mk.IV (Type 149 to Bristol) was one of the fastest bombers in the world, second only to the Dornier Do 215. 3,307 would eventually be produced.

The longer range also lent itself to a Canadian need for a patrol bomber and Fairchild Aircraft Ltd. (Canada) of Quebec, Canada, started production of the Blenheim Mk.IV as the Bolingbroke, irreverently nicknamed the "Bolly." After a small run of aircraft constructed to British specifications, as the Bolingbroke Mk.I, Fairchild switched production to the Bolingbroke Mk.IV with American instruments and equipment. These versions also included anti-icing boots and a dinghy. Some of these aircraft served as bombers during the Aleutians campaign, but most of the 150 served in the intended role as patrol bombers on the Atlantic coast. Another 450 were completed as the Bolingbroke Mk.IV T as trainers and saw extensive use in the Commonwealth Air Training Plan. One of the final variants was the Bolingbroke Mk.IV W which was powered by two 895-kW (1,200-hp) Pratt & Whitney R-1830 Twin Wasp engines. 676 Bolingbrokes were produced in total.

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

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

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

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

Blenheim cockpit. Note the asymetry of the instrument console, which indicates the "scooped out" area of the nose in front of the pilot.

[edit] Units using the Blenheim

Main article: List of Bristol Blenheim operators

Users of the Blenheim included the Royal Air Force, Fleet Air Arm, Royal Canadian Air Force, Royal New Zealand Air Force and South African Air Force.

Additional nations which purchased and flew the Blenheim were Australia, Croatia, Finland, France, Greece, Portugal, Romania, Turkey and Yugoslavia.

[edit] Specifications (Bristol Blenheim Mk.IV)

General characteristics

• Crew: 3
• Length: 42 ft 9 in (13 m)
• Wingspan: 56 ft 4 in (17.17 m)
• Height: 12 ft 10 in (3.91 m)
• Wing area: 469 ft² (43.6 m²)
• Empty weight: 9,790 lb (4,440 kg)
• Loaded weight: 14,400 lb (6,530 kg)
• Powerplant: 2× Bristol Mercury XV radial engines, 920 hp (690 kW) each

Performance

• Maximum speed: 266 mph (231 knots, 428 km/h)
• Range: 1,950 mi (1,690 nm, 3,140 km)
• Service ceiling: 31,500 ft (9,600 m)
• Rate of climb: 1,500 ft/min (7.6 m/s)
• Wing loading: 30.7 lb/ft² (150 kg/m²)
• Power/mass: 0.13 hp/lb (210 W/kg)

Armament

• Guns:
  
  • 1× .303 in (7.7 mm) Vickers K machine gun in the nose
  • 2× .303 in Browning machine guns in chin turret
  • 2× .303 in Browning machine guns in dorsal turret
• Bombs:
  
  • 4× 250 lb (110 kg) bombs or
  • 2× 500 lb (230 kg) bombs internally, and
  • 8× 40 lb (18 kg) bombs externally

[edit] Survivors

Bolingbroke in a Manitoba junk yard, 2006

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

Bolingbroke IV at the British Columbia Museum of Flight, Victoria, British Columbia

Today, only a single Bolingbroke IVT remains airworthy. Although actually a RCAF training variant, it is painted to represent a Blenheim IV in RAF wartime service. It is owned and operated by the Aircraft Restoration Company at Duxford, UK, and has been flying since May 1993. A number of other Bolingbrokes survived the war but were summarily consigned to the scrap heap. Postwar, enterprising farmers often bought surplus aircraft such as these for the scrap metal content or even the fuel remaining in the tanks. A number of museum examples in Canada can be traced back to this period.

[edit] References

[edit] External links

• RAF Bristol Blenheim history
• Bristol Blenheim / Bolingbroke
• Blenheim I
• Blenheim IV
• Blenheim armament
• No 211 Squadron RAF

[edit] Related content

Comparable aircraft

• De Havilland Mosquito
• Potez 630

Designation sequence

• Type 26 - Type 105 - Type 130 - Type 142 - Type 143 - Type 149 - Type 152 - Type 156 - Type 160 - Type 163 - Type 164 - Type 166

Related lists

• List of aircraft of the RAF
• List of bomber aircraft