Bristol Blenheim

Bristol Blenheim, England, 2001

The Bristol Type 142M Blenheim was a high-speed light bomber used extensively in the early days of World War II, built by Bristol Aeroplane Company. It was the first British aircraft to have an all-metal stressed skin construction and one of the first to utilize retractable landing gear, flaps, powered gun turret, and variable-pitch propellers.

History

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

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

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

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

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 (Gunston 1995).

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

Variants

Work on an extended range reconnaissance version started as the Mk.II, which increased tankage from 278 to 468 gallons, but only one was completed. Another modification resulted in the Mk.III, which lengthened the nose to provide more room for the bombardier. This required the nose to be "scooped out" in front of the pilot to maintain visibility during takeoff and landing. However both of these modifications were instead combined, along with a newer version of the Mercury engine with 905 hp (675 kW) and a second gun in the rear cockpit, to create the Blenheim IV. When it was introduced in 1939, the Mk.IV (Type 149 to Bristol) was one of the fastest 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 started production of Blenheim Mk.IV there with the original name as the Bolingbroke. After a small run of British-like planes as the Mk.I, Fairchild switched production to the Bolingbroke Mk.IV with American instruments and equipment. These versions also included anti-icing boots and a dinghy. Some of these planes served as bombers during the Aleutians campaign, but most of the 150 served in the intended role as patrol bombers on the Atlantic coast. Another 450 were completed as the Mk.IVT as trainers, and saw extensive use in the Commonwealth Air Training Plan. 676 Bolingbrokes were 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 rather poor as a fighter, but they served before an advent of more sophisticated machines. A radar-equipped Blenheim Mk.IF scored the first victory on the night of 2/3 July, 1940, over a Dornier Do 17 bomber. About 60 of Mk.IV's were also equipped with a gun pack as Mk.IVF, but they were used by 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 duty. Bristol's intended successor to the Blenheim, the Buckingham, was considered inferior to the Mosquito, and did not see combat.

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

Units using the Blenheim

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

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

Specifications (Bristol Blenheim IV)

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