|Three-seat light bomber|
|2 Bristol Mercury XV radial piston engines|
|Wing area||43.57 m²|
|Maximum take-off||6,532 kg|
|Maximum speed||428 km/h|
|Operative range||2,35- km|
|Service ceiling||8,310 m|
|Machine guns||5 7-7 mm|
The design had started as a civilian aircraft, a project of Lord Rothermere, owner of the Daily Mail. In order to promote British aviation, he asked the industry to deliver the fastest civilian aircraft in Europe, capable of carrying 6 passengers and 2 crew members. Bristol responded with the Type 142, and when it first flew as Britain First in 1934 it proved to be faster than any fighter the RAF had at the time.
Needless to say the Air Ministry was interested in such a plane for their own uses, and quickly sent out Specification B.28/35 for prototypes of a bomber version of the 142M (M for "military"). The main changes were to move the wing higher on the fuselage from its former low position, to allow room under the spar for a bomb-bay. The aircraft was all-metal with twin Bristol Mercury radial engines of 860hp each. It carried a crew of three – pilot, navigator/bombardier and gunner/wireless operator – and was armed with a forward firing .303 machine-gun in the wing root and a .303 in a semi-retracting dorsal turret firing to the rear. A 1,000lb bomb load was carried in the internal bay.
The plane was ordered directly from the plans, and the first production model, known at the time as the Bolingbroke, served as the first and only prototype. The name then became Blenheim I, and deliveries started in 1937. The plane would prove to be so successful that it was licensed by a number of countries, including Finland and Yugoslavia. Other countries bought it outright, including Romania, Greece, and Turkey. Total production in England amounted to 1,351 Mk.I's.
Work on an extended range reconnaissance version started as the Mk.II, which increased tankage from 278 gallons to 468, 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 However both of these modifications were instead combined, along with a newer version of the Mercury engine with 905hp and a second gun in the rear cockpit, to create the Blenheim IV.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 the fastest bomber in the world, and 3,307 would eventually be produced.
The longer range also lent itself to a Canadian need for a patrol bomber, and Fairchild started production 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 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.IV-T as trainers, and saw extensive use in the Commonwealth Air Training Plan.
Bristol Blenheim, England, 2001.|
Another modification was attempted to create a heavy-fighter version, 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 950hp. The Mk.V (Type 160) was used primarily in the Far East.
Blenheims operated widely in many combat roles until about 1943. By that point most fighters could carry similar bombloads at much higher speeds, the surviving examples when most were used for training. The Blenheim also served as the pattern for the Beaufort and, eventually, Beaufighter.