Editing Vickers Vimy (section)

==Design and development==
===Background===
Throughout the [[World War I|First World War]] both the [[Allies of World War I|Allied Powers]] and the [[Central Powers]] made increasingly sophisticated use of new technologies in their attempts to break through the effective stalemate of [[trench warfare]]. One key advance made during the conflict was in the use of [[fixed-wing aircraft]], which were at that time rapidly advancing in capability, [[Aviation in World War I|for combat purposes]].{{sfn|Bruce|1965|page=3}} On 23 July 1917, in response to a bombing raid by German bombers on London, the [[Air Force Board|Air Board]], having determined that existing projects were not ambitious enough, decided to cancel all orders for experimental heavy bombers then underway. A week later, following protests from the Controller of the Technical Department, the Air Board placed an order for 100 [[Handley Page Type O|Handley Page O/100]] bombers, which was accompanied by orders for prototype heavy bombers being placed with  [[Handley Page]] and [[Vickers Limited]].{{sfn|Bruce|1965|page=3}}
On 16 August 1917 Vickers was issued with a contract for three prototype aircraft{{sfn|Bruce|1965|page=3}} and [[Rex Pierson]], chief designer of Vickers' aviation division, started designing a large twin-engine biplane bomber, to be powered by either a pair of [[RAF 4]]d or 200&nbsp;hp (150&nbsp;kW) [[Hispano Suiza]] engines.{{sfn|Bruce|1965|page=3}} Pierson discussed the proposed aircraft with Major J. C. Buchanan of the Air Board to establish the rough configuration of the aircraft, which was expected to meet the requirement for a night bomber which could attack targets within the [[German Empire]].{{sfn|Jarrett|1992|page=9}}{{sfn|Bruce|1965|page=3}}

===Design===
[[File:Vickers F.B.27 Vimy side view.jpg|right|thumb|upright=1.7|Vickers F.B.27 Vimy side view]]

The Vickers F.B.27 Vimy is an equal-span twin-engine four-bay biplane, with balanced ailerons on both upper and lower wings. The engine [[nacelle]]s were positioned mid-gap and contained the fuel tanks. It has a biplane [[empennage]] with elevators on upper and lower surfaces and twin rudders. The main undercarriage consists of two pairs of wheels, each pair carried on a pair of tubular steel V-struts. There is a tail-skid and an additional skid mounted below the nose of the fuselage to prevent nose-overs.

The aircraft was designed to accommodate a three-man crew and a payload of 12 bombs.{{sfn|Bruce|1965|page=3}} In addition to the pilot's cockpit, which was positioned just ahead of the wings, there were two positions for [[Air gunner|gunner]]s, one behind the wings and the other in the nose, each with a pair of [[Scarff ring]]-mounted [[Lewis gun]]s;{{sfn|Bruce|1965|page=3}} the rear cockpit mounting was commonly not fitted during the interwar period. Provision for a maximum of four spare drums of ammunition were present in the nose position, while up to six drums could be carried in the rear position.{{sfn|Bruce|1965|page=10}}

The majority of the Vimy's payload of {{cvt|250|lb}} bombs were stowed vertically inside the fuselage between the spars of the lower centre section; a typical load consisted of 12 bombs.{{sfn|Bruce|1965|page=3}} In some variants further bombs could be stowed externally for a total of 18 bombs, if the particular engine used provided enough power.{{sfn|Bruce|1965|pages=6,10}} For [[anti-surface warfare]] in the maritime environment, the Vimy could also be armed with a pair of [[torpedo]]es. To improve bombing accuracy, the Vimy was equipped with the High Altitude Drift Mk.1a [[bombsight]]. Standard equipment also included two [[Michelin]]-built Mk.1 [[flare]] carriers.{{sfn|Bruce|1965|page=10}}

The Vimy was powered by a range of different engines. Owing to engine supply difficulties, the prototype Vimys were tested with a number of different engine types, including [[Sunbeam Maori]]s, [[Salmson 9 (water-cooled engine)|Salmson 9Zm]] water-cooled [[radial engine|radial]]s, and [[Fiat A.12]]bis engines, before production orders were placed for aircraft powered by the 230&nbsp;hp (170&nbsp;kW) [[Siddeley Puma|BHP Puma]], 400&nbsp;hp (300&nbsp;kW) Fiat, 400&nbsp;hp (300&nbsp;kW) [[Liberty L-12]] and the 300&nbsp;hp (270&nbsp;kW) [[Rolls-Royce Eagle|Rolls-Royce Eagle VIII]] engines, with a total of 776 ordered before the end of the First World War. Of these, only aircraft powered by the Eagle engine, known as the Vimy IV, were delivered to the RAF.{{sfn|Mason|1994|page=96}} Due to the number of engine types used there are multiple conflicting official reports on the production numbers of each sub-variant of the Vimy.{{sfn|Bruce|1965|page=5–6}}

Design and production of the prototypes was extremely rapid; the detailed design phase of what had become internally designated as the Vickers '''F.B.27''' and the manufacture of the three prototypes was completed within four months.{{sfn|Bruce|1965|page=3}}

===Prototypes===
By the time the first prototype had been completed the RAF 4D was not sufficiently developed, so it was fitted with the alternative Hispano Suiza engine.{{sfn|Bruce|1965|page=3}} On 30 November 1917 the first prototype, flown by Captain Gordon Bell, made its [[maiden flight]] from [[RAF Joyce Green|Royal Flying Corps Station Joyce Green]], [[Kent]].{{sfn|Mason|1994|page=95}} In January 1918 the first prototype was dispatched to [[RAF Martlesham Heath]], [[Suffolk]], for the official trials of the type. Reportedly, the F.B.27 quickly made a positive impression: it was able to take off with a greater payload than the [[Handley Page O/400]] despite having about half the effective engine power.{{sfn|Bruce|1965|page=3}} The engines proved to be unreliable during these trials, leading to the aircraft's return to Joyce Green on 12 April 1918.{{sfn|Bruce|1965|page=3}}

The first prototype was extensively modified, receiving new [[Salmson water-cooled aero-engines]] in place of the Hispano Suizas; other changes included the adoption of an alternative exhaust stack configuration, a 3-degree dihedral on the mainplanes, and a modified tail unit.{{sfn|Bruce|1965|page=3}} Following these modifications, the prototype was used for several years, surviving the war and being allocated a civil registration. In August 1919 the prototype was flown from [[Brooklands]] to [[Amsterdam]] in the Netherlands as part of Vicker's exhibit at the [[Eerste Luchtverkeer Tentoonstelling Amsterdam]].{{sfn|Bruce|1965|page=3}}

During early 1918 the second prototype was completed.{{sfn|Bruce|1965|page=4}} Unlike the first, it had plain [[Elevator (aeronautics)|elevators]] and [[aileron]]s which had an inverse taper; the tops of the wings and tailplanes also differed. The defensive armament was increased, giving the rear gunner two separate guns; these changes would be standardised on production aircraft.{{sfn|Bruce|1965|page=4}} The second prototype was powered by a pair of [[Sunbeam Maori]] engines, which were found to have an unreliable cooling system during initial testing at Joyce Green. On 26 April 1918 the aircraft was dispatched to RAF Martlesham Heath for official tests, but testing was interrupted by its loss in a crash following an engine failure.{{sfn|Bruce|1965|page=4}}

During the first half of the 1918 the third prototype was also completed.{{sfn|Bruce|1965|page=4}} It was powered by a pair of 400&nbsp;hp (300&nbsp;kW) [[Fiat A.12]] engines, and had a redesigned nose section and [[nacelle]]s which were similar to production aircraft. On 15 August 1918 the third prototype was sent to RAF Martlesham Heath for performance tests; testing was delayed by the need to replace a cracked [[Propeller (aeronautics)|propeller]].{{sfn|Bruce|1965|page=4}} On 11 September 1918 it was lost when its payload of bombs detonated owing to a hard landing, the result of a pilot-induced [[Stall (fluid mechanics)|stall]].{{sfn|Bruce|1965|page=4}}

It was decided to construct a fourth prototype to test the [[Rolls-Royce Eagle|Rolls-Royce Eagle VIII]] engine.{{sfn|Bruce|1965|page=6}} On 11 October 1918 this was flown from Joyce Green to Martlesham Heath to conduct official trials. Aside from being powered by the Eagle engine, it was identical to the earlier prototypes except for having a greatly increased fuel capacity and reshaped and enlarged rudders.{{sfn|Bruce|1965|pages=6–7}} By the time the fourth prototype commenced flying trials, mass production of the Vimy had already begun.{{sfn|Bruce|1965|page=7}}

=== Production ===

Since the performance of the first prototype was satisfactory it was decided to start production before the evaluation of either of the other prototypes.{{sfn|Bruce|1965|page=4}} On 26 March 1918 the first production contract, for 150 aircraft, was issued; these were built at Vickers' works in [[Crayford]] in the [[London Borough of Bexley|Bexley]]. Production of the type by additional manufacturers was envisaged early on; in May 1918 follow-up contracts were issued to [[Clayton & Shuttleworth]], [[Morgan & Co]], and the [[Royal Aircraft Establishment]] (RAE), in addition to a separate production line at Vickers' [[Weybridge]] complex.{{sfn|Bruce|1965|pages=4–5, 7}} At one point over 1,000 aircraft had been ordered under wartime contracts. The type had received the official name of ''Vimy'', after the [[Battle of Vimy Ridge]].{{sfn|Bruce|1965|page=5}}

By the end of 1918 a total of 13 aircraft had been completed by Vickers; 7 at Crayford and 6 at Weybridge.{{sfn|Bruce|1965|page=7}} Production continued after the signing of the [[Armistice of 11 November 1918]], which led to Vickers ultimately completing 112 aircraft under wartime contracts. The majority, if not all, of Vimys ordered from Morgan & Co were completed, while [[Westland Aircraft]] manufactured 25 of the 75 units that they were contracted for.{{sfn|Bruce|1965|page=7}} The numbers produced by the RAE are obscured by changes in serial number allocation and the apparent adoption of a piecemeal approach to manufacturing, which came into effect shortly after the end of the war; in February 1920, the RAE completed their final Vimy.{{sfn|Bruce|1965|pages=7–8}}

Production aircraft used several different types of engines, leading to various mark numbers being applied to the Vimy to distinguish between the emerging subtypes.{{sfn|Bruce|1965|page=5}} The use of different engines was often because of availability; relatively few engines from [[Rolls-Royce Limited]] were used in the Vimy during 1918 owing to low output levels from that manufacturer, while other manufacturers also struggled to keep up with engine demand that year. At one point, there was considerable enthusiasm for powering the Vimy with American [[Liberty L-12]] engines, because of their plentiful supply at the time, but all orders for the Liberty-equipped Vimy were terminated in January 1919 and no examples were ever completed.{{sfn|Bruce|1965|page=5}} The [[Siddeley Puma|BHP Puma]] was also intended for use on the Vimy, but it was cancelled without any aircraft being fitted with the engine.{{sfn|Bruce|1965|page=5}}

Use of the Vimy extended beyond its original use as a bomber. A model with greater internal space was developed, known as the ''Vimy Commercial'' within the civil market.{{sfn|Bruce|1965|page=12}} It saw service with the RAF; known as the [[Vickers Vernon]], it became the first dedicated troop transport to be operated by the service. The Vimy was also used as an [[air ambulance]] for transporting wounded troops to medical facilities, while some examples were configured to perform record-breaking long-distance flights.{{sfn|Bruce|1965|page=12}} From 1923 to 1925 limited production batches of the Vimy were manufactured by Vickers. Between 1923 and 1931, at least another 43 early production aircraft were reconditioned to extend their service lives; at least one Vimy was reconditioned four times.{{sfn|Bruce|1965|page=9}}

By October 1918 only three aircraft had been delivered to the [[Royal Air Force]] (RAF), one of which had been deployed to France for use by the [[Independent Air Force]]. It had been envisioned that the Vimy would be able to conduct long-range bombing missions into Germany, having the ability to reach [[Berlin]] from bases in France, but the [[Armistice of 11 November 1918]] brought an end to the conflict before the Vimy could be used on any offensive operations.{{sfn|Thetford|1992|page=32}}{{sfn|Bruce|1965|page=7}} After the war, the RAF rapidly contracted in size, which slowed the introduction of the Vimy.{{sfn|Bruce|1965|page=8}} The Vimy only reached full service status in July 1919 when it entered service with [[No. 58 Squadron RAF|58 Squadron]] in Egypt, replacing the older Handley Page 0/400.{{sfn|Andrews|Morgan|1988|page=90}}