The Bristol Blenheim was a British light bomber aircraft designed and built by the Bristol Aeroplane Company that was used extensively in the early days of the Second World War. It was one of the first British aircraft to have all-metal stressed-skin construction, to utilise retractable landing gear, flaps, a powered gun turret and variable-pitch propellers.
Development
The Bristol Type 135 cabin monoplane, designed by Frank Barnwell in 1933, attracted the attention of the Press baron Lord Rothermere, who in 1934 ordered a Mercury-engined version for his own use as part of a campaign to popularise commercial aviation. The aircraft first flew in April 1935 and soon caused great interest in Air Ministry circles on account of its high performance its top speed of 307 mph(494kph) being higher than that of any RAF fighter in service. Lord Rothermere generously presented the aircraft (named 'Britain First') to the nation for evaluation as a bomber and in early 1936 the modified design was designated 'Blenheim' Mk.I. The type was ordered "off the drawing board" and first deliveries to No 114 Squadron began in March 1937. 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, to utilise retractable landing gear, flaps, powered gun turret and variable pitch propellers. A Canadian-built variant named the 'Bolingbroke' was used as an anti-submarine and training aircraft. The Blenheim Mk I outshone most biplane fighters in the late 1930s but stood little chance against the German Messerschmitt Bf109 during daylight operations, though it proved successful as a night fighter. The Mark IV variant was equally unsuccessful in its daylight bombing role, suffering major losses in the early stages of the war.
Back to Top
War time Revisions
The next major modification resulted in the Blenheim Mk III, which lengthened the nose, and thereby dispensed with the "stepless 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 takeoff and landing. 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. 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 thus creating the Blenheim Mk IV. Another modification led to a long-range fighter version as 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 and these were the first British fighters to be equipped with radar. 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.
Back to Top
In Service
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-engine fighters and within a few months, some 60 squadrons had experience of the type. 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. Blenheims continued to operate widely in many combat roles until about 1943, equipping RAF squadrons in the UK and in 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. There were orders for the Blenheim from overseas. Notably, Finland was the primary country to order the Blenheim, including a manufacturing lisence. In 1936, the Finnish Air Force ordered 18 Blenheim Mk Is from Britain and two years later, they obtained that manufacturing license for the aircraft. Another country who contracted for Blenheims was Yugoslavia. However, the Finns 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 by the Germans.
Back to Top
Synopsis
Like many aircraft designed and built prior to the war, bombers were generally faster than the biplane fighters then in service and were considered wonder weapons. The Germans fell into this category, believing that their fast flying Junkers Ju88 and Heinkel He111 could outspeed all opposition, negating the requirements for fighter escort. Each nation had to learn that bombers without escorts flying into enemy airspace controlled by a modern defence fighter force would suffer grevious losses. The Germans in the Battle of Britain, the daylight raids by Bomber Command, the daylight raids by the 8th Air Force, until escorting fighters could travel with them to Berlin and back, clearing all before them. The Blenheim was a tactical bomber which needed escorts, however, the Briitsh sent them on many a raid without them and as such, losses of the Blenheim were very high on these raids.
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.
Back to Top
Swordfish
Gladiator
Hurricane
Typhoon
Tempest
Spitfire
Mosquito
Beaufighter
Blenheim
Wellington
Halifax
Lancaster
Stirling
Sunderland
Bristol 'Blenheim'
