Editing Avro Manchester (section)

==Development==
The Manchester has its origins in a design produced by Avro to fulfil the British [[Air Ministry]]'s [[List of Air Ministry Specifications|Specification P.13/36]]. This was the same specification to which [[Handley Page]] had also produced their initial design for what would become the [[Handley Page Halifax|Halifax]] bomber.<ref>Lake 2002, pp. 89–90.</ref> 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 bomb loads ({{cvt|8000|lb}}) or two {{cvt|18|in}} [[torpedo]]es.<ref name ="Lewis bomber">Lewis 1974, p. 299.</ref><ref name = "Bowyer 25">Bowyer 1974, p. 25.</ref> Provisions to conduct catapult assisted takeoffs, which would permit the carriage of the maximum payload, was another requirement, although this provision was removed in July 1938.<ref name = "Bowyer 29">Bowyer 1974, p. 29.</ref> The envisioned cruising speed of the bomber was to be a minimum of {{cvt|275|mph}} at {{cvt|15000|ft}}.<ref name="Mason bomber p323">Mason 1994, p. 323.</ref> The Air Ministry had expectations for an aircraft of similar weight to the [[Vickers Warwick|B.1/35]] specification but smaller and faster.

Avro had already started work on a corresponding design prior to having received a formal invitation to tender. The company was in competition with [[Boulton Paul Aircraft|Boulton Paul]], [[Bristol Aeroplane Company|Bristol]], [[Fairey Aviation Company|Fairey]], Handley Page and [[Short Brothers|Shorts]]. Vickers also had its Warwick, which had [[Napier Sabre]] engines but eventually chose against tendering 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 right to order the types "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 another great European war. From 1939, it was expected that the P.13/36 would begin replacing the RAF's medium bombers, such as the [[Armstrong Whitworth Whitley]], [[Handley Page Hampden]] and [[Vickers Wellington]].

The Avro design used the [[Rolls-Royce Vulture]] 24-cylinder [[X engine|X-block engine]], which was two [[Rolls-Royce Peregrine]] [[V engine|Vee]] [[cylinder block]]s mounted one on top of the other, the bottom one inverted to give the "X" shape.<ref name = "Bowyer 26">Bowyer 1974, p. 26.</ref> When developed in 1935, the Vulture engine had promise — it was rated at {{cvt|1760|hp}} but it proved woefully unreliable and had to be derated to {{cvt|1480|–|1500|hp}}. Avro's prototype Manchester ''L7246'', was assembled by their experimental department at Manchester's [[Manchester Airport|Ringway Airport]] and first flew on 25 July 1939, with the second aircraft following on 26 May 1940.<ref name="Lewis bomber"/><ref>Bowyer 1974, pp. 28–29.</ref> The Vulture engine was chosen by Avro and not stipulated by the Air Ministry as is sometimes claimed; other engine layouts considered were the use of two [[Bristol Hercules]] or [[Bristol Centaurus]] [[radial engine]]s.<ref name = "Bowyer 26"/>{{efn|The historian Francis Mason claimed that the engine selection was a part of the specification as does aviation author Chaz Bowyer.<ref name="Mason bomber p323"/><ref>Bowyer 1974, pp. 25–26.</ref> Buttler states the Ministry specified prototypes with Hercules and Vulture engines and Sinnott rebuts the assertion.<ref>Buttler, 2004 p102-103</ref><ref>Sinnott 2001, pp. 165–171.</ref>}} The Handley Page HP.56, always intended as the back-up 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.<ref>Lake 2002, p. 90.</ref>{{efn|Handley Page's aborted HP.56 proposal would become the four engine HP.57 that entered service as the Handley Page Halifax, a significantly more successful aircraft than the Manchester.}}

[[File:Aircraft of the Royal Air Force 1939-1945- Avro 679 Manchester. CH17300.jpg|thumb|Avro Manchester Mk I (note additional central tail fin)]]

While the Manchester was designed with a [[twin tail]], the first production aircraft, 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 with enlarged and taller fins and [[rudder]]s mounted on a new [[tailplane]], with span increased from {{cvt|22|ft}} to {{cvt|33|ft}}. 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.<ref name = "lake 89">Lake 2002, p. 89.</ref> Avro constructed 177 Manchesters while [[Metropolitan-Vickers]] completed 32 aircraft. Plans for [[Armstrong Whitworth]] and [[Fairey Aviation]] at  Ringway (now [[Manchester Airport]]) to build the Manchester were abandoned. Fairey's order for 150 Manchesters was replaced by orders for the Halifax.