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The Avro 679 Manchester was a British twin-engine heavy bomber developed during the Second World War by the Avro aircraft company in the United Kingdom. Serving in the Royal Air Force and Royal Canadian Air Force, the Manchester was an operational failure because of its underdeveloped, underpowered and unreliable engines. The aircraft was the forerunner of the successful four-engined Avro Lancaster, which would become one of the most capable British strategic bombers of the war. ==Development== The Manchester was originally designed to the Air Ministry Specification P.13/36; it was the same specification that Handley Page also followed in their design of the Halifax bomber.〔Lake 2002, pp. 89–90.〕 Issued in May 1936, Specification P.13/36 called for a twin-engine monoplane "medium bomber" for "worldwide use", which was to be capable of carrying out shallow (30°) dive bombing attacks and carry heavy bombloads (8,000 lb/3,630 kg) or two 18 in (457 mm) torpedoes.〔Lewis 1974, p. 299.〕〔Bowyer 1974, p. 25.〕 Provision for catapult assisted takeoff to permit the maximum load was also part of the specification, although the need for this provision was explicitly removed in July 1938.〔Bowyer 1974, p. 29.〕 Cruising speed was to be a minimum of 275 mph at 15,000 feet.〔Mason 1994, p. 323.〕 The Air Ministry had expectations for an aircraft of similar weight to the B.1/35 specification, but being both smaller and faster. Avro had already started work on a design before the invitation to tender. They were in competition with Boulton Paul, Bristol, Fairey, Handley Page and Shorts. Vickers had the Warwick with Napier Sabre engines but did not tender it. In early 1937, the Avro design and the rival Handley Page HP.56 were accepted and prototypes of both ordered; but in mid-1937, the Air Ministry exercised their rights to order "off the drawing board". This skipping of the usual process was necessary due to the initiation of a wider expansion of the RAF in expectation of war. From 1939, it was expected that the P.13/36 would replace existing medium bombers, such as the Armstrong Whitworth Whitley, Handley Page Hampden and Vickers Wellington. The design used the Rolls-Royce Vulture 24-cylinder X-block engine, which was two Rolls-Royce Peregrine Vee cylinder blocks mounted one on top of the other, the bottom one inverted to give the "X" shape.〔Bowyer 1974, p. 26.〕 When developed in 1935, the Vulture engine had promise — it was rated at 1,760 hp (1,310 kW) but it proved woefully unreliable and had to be derated to 1,480–1,500 hp (1,100–1,120 kW). Avro's prototype Manchester ''L7246'', was assembled by their experimental department at Manchester's Ringway Airport and first flew from there on 25 July 1939, with the second aircraft following on 26 May 1940.〔〔Bowyer 1974, pp. 28-29.〕 The Vulture engine was chosen by Avro and not stipulated by the Air Ministry as is sometimes claimed; other engine layouts considered included the use of two Bristol Hercules or Bristol Centaurus radial engines.〔 The Handley Page HP.56, always intended as the backup to the Avro, was redesigned to take four engines on the orders of the Air Ministry in 1937, when the Vulture was already showing problems.〔Lake 2002, p. 90.〕 While the Manchester was designed with a twin tail, the first production aircraft, designated the Mk I, had a central fin added and twenty aircraft like this were built. They were succeeded by the Mk IA which reverted to the twin-fin system but used enlarged, taller fin and rudders mounted on a new tailplane, with span increased from 22 ft (6.71 m) to 33 ft (10.06 m). This configuration was carried over to the Lancaster, except for the first prototype, which also used a central fin and was a converted, unfinished Manchester.〔Lake 2002, p. 89.〕 Avro constructed 177 Manchesters while Metropolitan-Vickers completed 32 aircraft. Plans for Armstrong Whitworth and Fairey Aviation at Stockport/Ringway to build the Manchester were abandoned. Fairey's order for 150 Manchesters was replaced by multiple orders for the Handley Page Halifax. 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「Avro Manchester」の詳細全文を読む スポンサード リンク
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