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The Handley Page Halifax was a four-engined heavy bomber model operated by the British Royal Air Force during World War II. The Halifax remained in service until the end of the war, performing a variety of duties in addition to bombing. It was a contemporary of the Avro Lancaster. The Halifax was also operated by the Royal Canadian Air Force, Royal Australian Air Force, Free French Air Force, and Polish forces, and after World War II by the Royal Egyptian Air Force, the French ''Armée de l'Air'', and the Royal Pakistan Air Force. ==Design and development== Handley Page produced the H.P.56 design to meet Air Ministry Specification P.13/36 for a twin-engine medium bomber for "world-wide use". Other candidates for the specification included the Avro 679, and designs from Fairey, Boulton Paul and Shorts; all were designed around a two-engine installation, using the Rolls-Royce Vulture, Napier Sabre, Fairey P.24 or Bristol Hercules. Most of these engines were under development. While four-engined bombers were considered for specification B.12/36 for a heavy bomber, wings mounting two engines were still in the experimental stage requiring testing at the RAE and the resulting increase in overall weight of stronger wing meant further strengthening of the whole aircraft structure.〔Buttler pp. 104〕 Following consideration of the designs by the Air Ministry in February 1937, the Avro design was selected with the Handley Page as "second string" and two prototypes of each were ordered.〔Buttler, p. 102〕 The introduction of the successful P.13/36 candidates was delayed by the necessity of ordering more Armstrong-Whitworth Whitley and Vickers Wellington bombers first. For quicker delivery Avro and HP.56 designs were ordered "off the drawing board" in mid-1937. At the end of July, Handley Page was told to redesign the HP.56 for four engines rather than two, as the Vulture was already suffering technical problems. The Avro Manchester was built with Vultures and entered RAF service, but also suffered from engine problems. The redesign increased the span from to and put on of weight. Four Merlins were specified by the Ministry in September 1937. The mockup was assessed at the end of the year and construction of the two prototypes of the HP 57 began in March 1938.〔Buttler p105〕 Modifications resulted in the definitive H.P.57, which upon acceptance was given the service name Halifax, following the practice of naming heavy bombers after major towns – in this case, Halifax in the West Riding of Yorkshire. The H.P.57 was enlarged and powered by four Rolls-Royce Merlin X engines. Such was the promise of the new model that the RAF had placed their first order for 100 Mk.I Halifaxes "off the drawing board" in January 1938 with serials already assigned to HP.56 switched to HP.57. The maiden flight of the Halifax took place on 25 October 1939 from RAF Bicester, not long after Britain declared war on Germany. Halifax production subsequently began at Handley Page's (now English Electric's) site in Samlesbury, Lancashire, with over 2,000 bombers being built by this factory during the war. The Mk.I had a 22 ft (6.7 m) long bomb bay as well as six bomb cells in the wings, enabling it to carry 13,000 lb (5,900 kg) of bombs. Defensive armament consisted of two .303 in (7.7 mm) Browning machine guns in a Boulton Paul Type C nose turret, with an additional four in a Boulton Paul Type E tail turret, and, in some aircraft, two .303 in (7.7 mm) Vickers K machine guns in beam (side, or "waist") positions. The Merlins drove constant speed wooden-bladed Rotol propellers. Subtle modifications distinguished the Mk I aircraft. Aircraft of the first batch of fifty Mk I Halifaxes were designated Mk I Series I. These were followed by 25 of the Mk I Series II with increased gross weight (from 58,000 lb/26,310 kg to 60,000 lb/27,220 kg) but with maximum landing weight unchanged at . The Mk I Series III had increased fuel capacity (1,882 gal/8,556 L), and larger oil coolers to accept the Merlin XX. A two-gun BP Type C turret mounted dorsally replaced the beam guns. Introduction of Merlin XX engines and a twin .303 in (7.7 mm) dorsal turret instead of waist guns resulted in the B Mk II Series I Halifax. The Mk II Series I (Special) achieved improved performance by removing the nose and dorsal turrets. The Mk II Series IA had a moulded Perspex nose (the standard for future Halifax variants), a four-gun Defiant-type dorsal turret, Merlin 22 engines and larger, trapezoidal-shaped vertical tail surfaces which solved control deficiencies from fin-stall with the roughly triangular-shape original surfaces, leading to rudder overbalance in the early marks. Halifax IIs were built by English Electric and Handley Page; 200 and 100 aircraft respectively. Owing to a shortage of Messier-built landing gear and hydraulics, Dowty landing gear was used. As it was incompatible with the Messier equipment this gave Halifaxes with new designations: a Mark II built with Dowty gear was the Mark V. The use of castings rather than forgings in the Dowty undercarriage speeded production but resulted in a reduced landing weight of . The Mark V were built by Rootes Group at Speke and Fairey at Stockport and were generally used by Coastal Command and for training. Some 904 had been built when Mark V production ended at the start of 1944,〔Barnes 1987〕 compared to 1,966 Mk II. The most numerous Halifax variant was the B Mk III of which 2,091 were built. First appearing in 1943, the Mk III featured the Perspex nose and modified tail of the Mk II Series IA but replaced the Merlin with the more powerful Bristol Hercules XVI radial engine. Other changes included de Havilland Hydromatic propellers and rounded wing tips. The Mk IV was a non-production design using a turbocharged Hercules powerplant. The definitive version of the Halifax was the B Mk VI, powered by the Hercules 100. The final bomber version, the Mk VII, reverted to the less powerful Hercules XVI. However, these variants were produced in relatively small quantities. The remaining variants were the C Mk VIII unarmed transport (8,000 lb/3,630 kg cargo pannier instead of a bomb bay, space for 11 passengers) and the Mk A IX paratroop transport (space for 16 paratroopers and gear). A transport/cargo version of the Halifax was also produced, known as the Handley Page Halton.〔Barnes, C H: Handley Page Aircraft since 1907, London 1976, pp. 417, 419, 423, 603〕 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「Handley Page Halifax」の詳細全文を読む スポンサード リンク
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