Editing Bristol Beaufighter (section)

==Development==

===Origins===
[[File:Bristol Beauforts 217 Squadron in flight.jpg|thumb|upright=1.5|left|alt=Two Bristol Beauforts in flight|Bristol Beauforts in flight]]
The concept of the Beaufighter has its origins in 1938. During the [[Munich Crisis]], the Bristol Aeroplane Company recognised that the [[Royal Air Force]] (RAF) had an urgent need for a long-range fighter aircraft capable of carrying heavy payloads for maximum destruction.<ref name = "moyes 3"/> Evaluation of the [[Bristol Beaufort|Beaufort]] bomber concluded that it had great structural strength and stiffness in the wings, nacelles, [[Landing gear|undercarriage]] and tail, so that the aircraft could be readily developed further for the greater speed and manoeuvrability required by a fighter-class aircraft.<ref name = "moyes 3"/> The Bristol design team, led by [[Leslie Frise]], commenced the development of a cannon-armed fighter derivative as a private venture. The prospective aircraft had to share the same [[Jig (tool)|jigs]] as the Beaufort so that production could easily be switched from one aircraft to the other.<ref name = "moyes 3"/>

As a torpedo bomber and aerial reconnaissance aircraft, the Beaufort had a modest performance. To achieve the fighter-like performance desired for the Beaufighter, Bristol suggested that they equip the aircraft with a pair of its new [[Bristol Hercules|Hercules]] engines, capable of around 1,500&nbsp;hp, in place of the 1,000&nbsp;hp [[Bristol Taurus]] engines on the Beaufort. The Hercules was a considerably larger and more powerful engine which required larger propellers; to obtain adequate ground clearance, the engines were mounted centrally on the wing, as opposed to the underslung position on the Beaufort.<ref name = "moyes 3"/> In October 1938, the project, which received the internal name ''Type 156'', was outlined. In March 1939, the ''Type 156'' was given the name 'Beaufighter'.<ref name = "moyes 4">Moyes 1966, p. 4.</ref>

During early development, Bristol had formalised multiple configurations for the prospective aircraft, including variations such as a proposed ''Type 157'' three-seat bomber outfitted with a [[Anatomical terms of location#Dorsal and ventral|dorsal]] [[Gun turret#Aircraft|gun turret]] with a pair of cannons, and what Bristol referred to as a "sports model", with a thinner fuselage, the ''Type 158''.<ref name = "moyes 4"/> Bristol proceeded to suggest their concept for a fighter development of the Beaufort to the [[Air Ministry]]. The timing of the suggestion happened to coincide with delays in the development and production of the [[Westland Whirlwind (fighter)|Westland Whirlwind]] cannon-armed twin-engine fighter.<ref>Buttler 2004, p. 38.</ref> While there was some scepticism that the aircraft was too big for a fighter, the proposal was given a warm reception by the [[Air Staff (United Kingdom)|Air Staff]].<ref name = "moyes 3"/>

The Air Ministry produced draft [[List of Air Ministry specifications#F.11/37|Specification F.11/37]] in response to Bristol's suggestion for an "interim" aircraft, pending the proper introduction of the Whirlwind. On 16 November 1938, Bristol received formal authorisation to commence the detailed design phase of the project and to proceed with the construction of four prototypes.<ref name = "moyes 3"/> Amongst the design requirements, the aircraft had to be able to accommodate the [[Rolls-Royce Griffon]] engine as an alternative to the Hercules, and had to have maximum interchangeability between the two engines, which would feature [[Power-egg#United Kingdom|removable installations]].<ref name = "moyes 3 4"/>

Bristol began building an initial prototype by taking a partly-built Beaufort out of the production line, which sped progress; Bristol had promised series production in early 1940 on the basis of an order being placed in February 1939. Designers expected that maximum re-use of Beaufort components would speed the process, but the fuselage required more work than expected and had to be redesigned.<ref>Buttler 2004, p. 40.</ref> Perhaps in anticipation of this, the Air Ministry had requested that Bristol investigate the prospects of a "slim fuselage" configuration.<ref name = "moyes 3 4">Moyes 1966, pp. 3–4.</ref> Since the "Beaufort cannon fighter" was a conversion of an existing design, development and production was expected to proceed more quickly than with a new one. Within six months the first F.11/37 prototype, ''R2052'', had been completed.<ref name = "moyes 4"/> A total of 2,100 drawings were produced during the transition from Beaufort to the prototype Beaufighter; more than twice as many were made during later development, from the prototype to the production Beaufighter. Two weeks before the prototype's first flight, an initial production contract for 300 aircraft under Specification F.11/37 was issued by the Air Ministry, ordering the type "off the drawing board".<ref name = "moyes 4"/>

===Prototypes and refinement===
On 17 July 1939, ''R2052'', the first, unarmed, prototype, conducted its [[maiden flight]], a little more than eight months after development had formally started.<ref name = "moyes 4"/> The rapid pace of development was partly due to the re-use of many elements of the Beaufort design, and frequently identical components. ''R2052'' was initially operated by Bristol for testing while it was based at [[Filton Aerodrome]].<ref name = "moyes 4"/> Early modifications to ''R2052'' included stiffening of the elevator control circuit, increased fin area and lengthening of the main [[oleo strut]] of the undercarriage to better accommodate weight increases and hard landings.<ref name = "moyes 4 5">Moyes 1966, pp. 4–5.</ref>

During the pre-delivery trials, the first prototype ''R2052'', powered by a pair of two-speed [[supercharged]] Hercules I-IS engines, had achieved 335&nbsp;mph (539&nbsp;km/h) at 16,800&nbsp;ft (5,120 m) in a clean configuration.<ref name = "moyes 5">Moyes 1966, p. 5.</ref> The second prototype, ''R2053'', which was furnished with Hercules I-M engines (similar to Hercules II) and was laden with operational equipment, had attained a lower speed of 309&nbsp;mph at 15,000&nbsp;ft. According to aviation author Philip Moyes, the performance of the second prototype was considered disappointing, particularly as the Hercules III engines of the initial production aircraft would likely provide little improvement, especially in light of additional operational equipment being installed; it was recognised that demand for the Hercules engine to power other aircraft such as the [[Short Stirling]] bomber posed a potential risk to the production rate of the Beaufighter. This sparked considerable interest in the adoption of alternative engines for the type.<ref name = "moyes 4 5"/>

[[File:252 Squadron RAF Beaufighter cockpit at Chivenor IWM CH 17305.jpg|thumb|left|Cockpit of a Beaufighter Mk.IF]]
[[Roy Fedden]], chief designer of the Bristol engine division, was a keen advocate for the improved Hercules VI for the Beaufighter but it was soon passed over in favour of the rival Griffon engine, as the Hercules VI required extensive development.<ref name = "moyes 5"/> Due to production of the Griffon being reserved for the [[Fairey Firefly]], the Air Ministry instead opted for the [[Rolls-Royce Merlin]] to power the Beaufighter until the manufacturing rate of the Hercules could be raised by a new [[shadow factory]] in [[Accrington]]. The standard Merlin XX-powered aircraft was later called the ''Beaufighter Mk.IIF''; the planned slim-fuselage aircraft, alternatively equipped with Hercules IV and Griffon engines, the ''Beaufighter Mk.III'' and ''Beaufighter Mk.IV'' respectively, were not built.<ref name = "moyes 5"/>

In February 1940, an order was placed for three Beaufighters, converted to use the alternative Merlin engine. The Merlin engine installations and [[nacelle]]s were designed by [[Rolls-Royce Limited|Rolls-Royce]] as a complete "[[power egg]]"; the design and approach of the Beaufighter's Merlin installation was later incorporated into the design for the much larger four-engined [[Avro Lancaster]] bomber.<ref name="white 64"/> Success with the Merlin-equipped aircraft was expected to lead to production aircraft in 1941.<ref name="white 64"/> In June 1940, the first Merlin-powered aircraft conducted its first flight. In late 1940, the two Merlin-equipped prototypes (the third having been destroyed in a bombing raid) were delivered.<ref name = "moyes 5 10">Moyes 1966, pp. 5, 10.</ref> Flight tests found that the Merlins left the aircraft underpowered, with a pronounced tendency to swing to port, making take-offs and landings difficult and causing a high accident rate&nbsp;– out of 337 Merlin-powered aircraft, 102 were lost to accidents.<ref name="white 64">White 2006, p. 64.</ref><ref name = "moyes 10"/>

On 2 April 1940, ''R2052'' was delivered to the RAF; it was followed by ''R2053'' two weeks later.<ref name = "moyes 5"/> On 27 July 1940, the first five production Beaufighters were delivered to the RAF along with another five on 3 August 1940. These production aircraft incorporated aerodynamic improvements, reducing [[aerodynamic drag]] from the engine nacelles and tail wheel; the oil coolers were also relocated on the [[leading edge]] of the wing.<ref name = "moyes 5"/> The armament of the Beaufighter had also undergone substantial changes, the initial 60-round capacity spring-loaded drum magazine arrangement being awkward and inconvenient; alternative systems were investigated by Bristol.<ref name = "moyes 5 6"/>

Bristol's proposed [[recoil]]-operated ammunition feed system was rejected by officials, which led to a new system being devised and tested on the fourth prototype, ''R2055''. The initial rejection was later reversed, upon the introduction of a new electrically driven feed derived from [[Manufacture d'armes de Châtellerault|Châtellerault]] designs brought to Britain by [[Free French]] officers, which was quite similar to Bristol's original proposal.<ref name = "moyes 6"/> The initial 50 production aircraft were approved for completion with a cannon-only armament. The design of the cannons and the armament configuration was revised on most aircraft. The addition of six [[M1919 Browning machine gun#Browning 03 Mark II|.303 Browning]] [[machine gun]]s made the Beaufighter the most heavily armed fighter aircraft in the world, capable of delivering a theoretical weight of fire of up to {{convert|780|lb|kg|abbr=on}} per minute; the practical rate of fire was much lower due to gun overheating and ammunition capacity.<ref name = "moyes 6"/>

Further armament trials and experimental modifications were performed throughout the Beaufighter's operational life. By mid-1941, 20 Beaufighters were reserved for test purposes, including engine development, stability and manoeuvrability improvements and other purposes.<ref name = "moyes 5 11 13">Moyes 1966, pp. 5, 11, 13.</ref> In May 1941, the Beaufighter Mk.IIs ''R2274'' and ''R2306'' were modified to the ''Beaufighter Mk.III'' standard; removing the six wing guns and two inboard cannons to install a [[Boulton-Paul]]-built four-gun turret behind the pilot, to overcome the effect of recoil and nose-down tendency when firing the usual armament, was found to obstruct the emergency egress of the pilot.<ref name = "moyes 11"/> The fourth prototype, ''R2055'', had its regular armament replaced by a pair of {{nowrap|40 mm}} guns for attacking ground targets, a [[Vickers S]] gun mounted on the starboard fuselage and a [[Rolls-Royce 40mm Cannon|Rolls-Royce BH]] gun mounted on the port fuselage; these trials also led to the Vickers gun being installed on an anti-tank [[Hawker Hurricane]] IID.<ref name = "moyes 5 11 13"/>

===Production===
[[File:Royal Air Force Fighter Command, 1939-1945. CE21.jpg|thumb|upright=1.3|Ground crew loading ammunition for the cannon of an RAF Beaufighter Mk.VI night fighter]]
Large orders for the Beaufighter were placed around the outbreak of the Second World War, including one for 918 aircraft shortly after the arrival of the initial production examples.<ref name = "moyes 5"/> In mid-1940, during an official visit to Bristol's Filton facility by the Minister of Aircraft Production, [[Lord Beaverbrook]], the minister spoke of the importance of the Beaufighter to the war effort and urged its rapid service entry.<ref name = "moyes 5"/> While the aircraft's size had once caused scepticism, the Beaufighter became the highest performance aircraft capable of carrying the bulky early aircraft interception radars used for night fighter operations, without incurring substantial endurance or armament penalties, and was invaluable as a night fighter.<ref name = "moyes 5"/>

For the maximum rate of production, sub-contracting of the major components was used wherever possible and two large shadow factories to perform final assembly work on the Beaufighter were established via the [[Ministry of Aircraft Production]]; the first, operated by the [[Fairey Aviation Company]], was at [[Stockport]], [[Greater Manchester]] and the second shadow, run by Bristol, was at [[Weston-super-Mare]], [[Somerset]].<ref name = "moyes 5"/> Output of the Beaufighter rose rapidly upon the commencement of production.<ref name = "moyes 5"/>

Through 1940–41, the manufacturing rate of the Beaufighter steadily rose.<ref name = "moyes 10"/> On 7 December 1940, the 100th Filton-built aircraft was dispatched; the 200th Filton-built aircraft followed on 10 May 1941. On 7 March 1941, the first Fairey-built Beaufighter Mk.I performed its first test flight; the first Weston-built aircraft reached the same milestone on 20 February 1941.<ref name = "moyes 10"/> The volume of production involved, along with other factors, had led to a shortage of Hercules engines being expected, jeopardising the aircraft's manufacturing rate.<ref name = "moyes 5"/> The next variant, the ''Beaufighter Mk.II'', used the Merlin engine instead.<ref name = "moyes 10"/> On 22 March 1941, the first production Beaufighter Mk.II, ''R2270'', conducted its maiden flight; squadron deliveries commenced in late April 1941.<ref name = "moyes 10"/>

By mid-1941, manufacture of the Beaufighter varied to meet the demands of [[RAF Fighter Command]] and [[RAF Coastal Command]].<ref name = "moyes 11"/> Early aircraft were able to be outfitted and perform with either command but later, the roles and equipment diverged, leading to the production of distinct models, distinguished by the [[suffix]]es ''F'' for Fighter Command and ''C'' for Coastal Command.<ref name = "moyes 11"/> Often, one command opted for modifications and features that the other did not. This occurred with the [[bellows]]-type [[Air brake (aeronautics)|dive brake]] that became standard for Coastal Command Beaufighters for its usefulness in torpedo-bombing.<ref name = "moyes 11 13">Moyes 1966, pp. 11, 13.</ref>

Production of the earlier Beaufort in Australia and the great success of British-made Beaufighters used by the [[Royal Australian Air Force]] (RAAF), contributed to the Australian government deciding in January 1943 to manufacture Beaufighters under the [[Department of Aircraft Production]] (DAP) organisation at [[Fishermans Bend]], [[Melbourne]], [[Victoria (Australia)|Victoria]] from 1944.<ref name = "moyes 14">Moyes 1966, p. 14.</ref> The DAP Beaufighter was an attack and torpedo bomber known as the "Mk.21". Design changes included Hercules VII or XVIII engines and some minor changes in armament. By September 1945, when British production ended, 5,564 Beaufighters had been built by Bristol and the Fairey Aviation Company at Stockport and [[Manchester Airport|RAF Ringway]] (498); also by the Ministry of Aircraft Production (3336) and [[Rootes Group|Rootes]] at [[Blythe Bridge]] (260). When Australian production ceased in 1946, 364 Mk.21s had been built.<ref>Franks 2002, p. 171.</ref><ref>Hall 1995, p. 24.</ref>