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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 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 successful as a night fighter.〔Wheeler 1992, p. 20.〕 The Mark IV variant was equally unsuccessful in its daylight bombing role, suffering many losses in the early stages of the war.〔Wheeler 1992, p. 37.〕 ==Design and development== 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. Named 'Britain First', this first flew at Filton on 12 April 1935,〔Barnes 1964, p.258.〕 and proved to be faster than any fighter in service with the Royal Air Force at the time.〔Barnes 1964, p. 259.〕 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.〔Barnes 1964, pp. 266–267.〕 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. 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 "stepless 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.〔Gunston, Bill. ''Classic World War II Aircraft Cutaways''. London: Osprey, 1995. ISBN 1-85532-526-8.〕 The aircraft was ordered directly from the drawing board with the first production model serving as the only prototype.〔Mason 1994, p. 269.〕 The service name then became Blenheim Mk I after the famous battle during the War of the Spanish Succession. Subsequent deliveries started on 10 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.〔 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 "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. 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. 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. 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bristol Blenheim」の詳細全文を読む スポンサード リンク
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