Vickers Wellington
The Vickers Wellington is a British twin-engined, long-range medium bomber. It was designed during the mid-1930s at Brooklands in Weybridge, Surrey. Led by Vickers-Armstrongs' chief designer Rex Pierson, a key feature of the aircraft is its geodetic airframe fuselage structure, which was principally designed by Barnes Wallis. Development had been started in response to Air Ministry Specification B.9/32, issued in the middle of 1932, for a bomber for the Royal Air Force.
This specification called for a twin-engined day bomber capable of delivering higher performance than any previous design. Other aircraft developed to the same specification include the Armstrong Whitworth Whitley and the Handley Page Hampden. During the development process, performance requirements such as for the tare weight changed substantially, and the engine used was not the one originally intended.
Despite the original specification, the Wellington was used as a night bomber in the early years of the Second World War, performing as one of the principal bombers used by Bomber Command. During 1943, it started to be superseded as a bomber by the larger four-engined "heavies" such as the Avro Lancaster. The Wellington continued to serve throughout the war in other duties, particularly as an anti-submarine aircraft with RAF Coastal Command.
The Wellington was the only British bomber that was produced for the duration of the war, and was produced in a greater quantity than any other British-built bomber. The Wellington remained as first-line equipment when the war ended, although it had been increasingly relegated to secondary roles. The Wellington was one of two bombers named after Arthur Wellesley, 1st Duke of Wellington, the other being the Vickers Wellesley.
A larger heavy bomber aircraft designed to Specification B.1/35, the Vickers Warwick, was developed in parallel with the Wellington; the two aircraft shared around 85% of their structural components. Many elements of the Wellington were also re-used in a civil derivative, the Vickers VC.1 Viking.
Development
Origins
In October 1932, the British Air Ministry invited Vickers to tender for the recently issued Specification B.9/32, which sought a twin-engine medium daylight bomber. In response, Vickers conducted a design study, led by chief designer Rex Pierson. Early on, Vickers' chief structures designer Barnes Wallis proposed the use of a geodetic airframe, inspired by his previous work on airships and the single-engined Wellesley light bomber. During structural testing performed at the Royal Aircraft Establishment, Farnborough, the proposed structure demonstrated not only the required strength factor of six, but reached 11 without any sign of failure, proving the geodetic airframe to possess a strength far in excess of normal levels. This strength allowed for the structure design to be further developed to reduce the size of individual members and adopt simplified standard sections of lighter construction.Vickers studied and compared the performance of various air- and liquid-cooled engines to power the bomber, including the Bristol Pegasus IS2, Pegasus IIS2, and Armstrong Siddeley Tiger radials, and the Rolls-Royce Goshawk I inline. The Pegasus was selected as the engine for air-cooled versions of the bomber, while the Goshawk engine was chosen for the liquid-cooled engine variant. On 28 February 1933, two versions of the aircraft, one with each of the selected powerplants, were submitted to the tender. In September 1933, the Air Ministry issued a pilot contract for the Goshawk-powered version. In August 1934, Vickers proposed to use either the Pegasus or the sleeve-valve nine-cylinder radial Bristol Perseus engines instead of the evaporative-cooled Goshawk, which promised improvements in speed, climb rate, ceiling, and single-engine flight capabilities without any major increase in all-up weight; the Air Ministry accepted the proposed changes.
Other refinements of the design had also been implemented and approved, such as the adoption of variable-pitch propellers, and the use of Vickers-produced gun turrets in the nose and tail positions. By December 1936, the specification had been revised to include front, rear, and midship wind-protected turret mountings. Other specification changes included modified bomb undershields and the inclusion of spring-loaded bomb bay doors. The proposal had also been developed further, a mid-wing arrangement was adopted instead of a shoulder-mounted wing for greater pilot visibility during formation flight and improved aerodynamic performance, as well as a substantially increased overall weight of the aircraft. Design studies were also conducted on behalf of the Air Ministry into the adoption of the Rolls-Royce Merlin engine.
In spite of a traditional preference of the establishment to strictly adhere to the restrictive tare weight for the aircraft established in the tender, both Pierson and Wallis firmly believed that their design should adopt the most powerful engine available. Perhaps in response to pressure from Vickers, the Air Ministry overlooked, if not openly accepted, the removal of the tare weight restriction, as between the submission of the tender in 1933 and the flight of the first prototype in 1936, the tare weight eventually rose from to. The prescribed bomb load and range requirements were routinely revised upwards by the Air Ministry; by November 1935, figures within the ministry were interested in the possibility of operating the aircraft at an all-up weight of, which aviation author C.F. Andrews described as "a very high figure for a medium bomber of those days".
During the development phase of the aircraft, as C F Andrews puts it "the political and military climate of Europe was changing rapidly. The threats of the dictators of Germany and Italy began to exert pressure on the British government to make a reappraisal of the strength of its armed forces, especially that of the Royal Air Force". By 1936, the need for a high priority to be placed on the creation of a large bomber force, which would form the spearhead of British offensive power, had been recognised; accordingly, a new command organisation within the RAF, Bomber Command, was formed that year to deliver upon this requirement.
Prototype and design revision
In early 1936, an initial prototype, K4049, which was originally designated as a Type 271, was assembled. The prototype could accommodate a payload of nine or bombs, and both nose and tail gun positions were fitted with hand-operated turrets with a gun in each; provision for a third retractable gun in a dorsal position was made. It had provision for a crew of four, along with a fifth position for special duties.On 5 June 1936, the name Crecy was chosen for the type, and it was publicly displayed as such. On 15 August 1936, the aircraft was accepted for production. On 8 September 1936, the service name Wellington was adopted for the type; it fitted with Air Ministry nomenclature of naming bombers after towns and followed the Vickers Wellesley in referring to the Napoleonic War general Arthur Wellesley, the Duke of Wellington. On 12 December 1936, a corresponding works order was issued for the Wellington.
On 15 June 1936, K4049 conducted its maiden flight from Brooklands. Vickers chief test pilot Joseph Summers flew K4049 on its first flight, accompanied by Wallis and Trevor Westbrook. The aircraft soon came to be widely regarded as being an advanced design for its era and proved to have considerable merit during its flight trials. On 19 April 1937, K4049 was destroyed by an accident during a service test flight by Maurice Hare. The cause was the failure of the elevator's horn balance due to excessive slipstream exposure, leading to the aircraft inverting and rapidly descending into terrain. It was destroyed in the crash, which also resulted in the death of the navigator, Smurthwaite. The horn balances were later deleted from the design and were not on production aircraft.
Refinement of the Wellington's design was influenced by the issuing of Specifications B.3/34 and B.1/35, the latter of which led to a larger bomber aircraft, the Vickers Warwick With detail design work on both being done at same time and both aircraft using geodetic-inspired construction there was commonality in components. The production model Wellington was a complete redesign, resulting in a lengthened nose for turret and bomb aimer's position, a reshaped elevator and deepened fuselage which accommodated a larger bombload and the increased crew from four to five members. Other changes made included the adoption of a retractable tailwheel and constant-speed propellers; the Air Ministry also requested the adoption of a Nash & Thompson-design ventral turret in place of the Vickers design.
On 23 December 1937, the first production Wellington Mk I, L4212, conducted its first flight, followed by an intensive flight programme. Flight trials with L4212 confirmed the aerodynamic stability initially encountered by K4049, but also revealed the aircraft to be nose-heavy during dives, which was attributed to the redesigned elevator. Modifications, including the linking of the flaps and the elevator trim tabs, were tested on L4212 and resolved the problem.
Production
In August 1936, an initial order for 180 Wellington Mk I aircraft, powered by a pair of 1,050 hp Bristol Pegasus radial engines, was received by Vickers; it had been placed so rapidly that the order occurred prior to the first meeting intended to decide the details of the production aircraft.In October 1937, an order was placed with Gloster Aircraft Company for production of 100 Wellington Mk Is to be followed by 100 Wellington Mk II aircraft with Rolls-Royce Merlin X. Another order was placed for 64 Wellingtons to be produced by Armstrong Whitworth Aircraft at Coventry. With this flurry of orders and production having been assured by the end of 1937, Vickers set about simplifying the manufacturing process of the aircraft and announced a target of building one Wellington per day.
The geodetic design took longer to build than comparable aircraft using the more conventional monocoque approach, leading to some criticism of the Wellington. In addition it was difficult to cut holes in the fuselage for access or equipment fixtures; to aid manufacturing, the Leigh light was deployed through the mounting for the absent FN9 ventral turret.
The Gloster and AWA contracts were transferred to shadow factories in the north-west. In the late 1930s, Vickers built Wellingtons at a rate of one per day at Weybridge and 50 a month at Broughton in North Wales. Many of the employees on the production lines were only semi-skilled and new to aircraft construction. Peak wartime production in 1942 saw monthly rates of 70 at Weybridge, 130 at Broughton and 102 at Blackpool. Shadow factories were set up to produce parts for the Wellington all over the British Isles.
In October 1943, as a propaganda and morale-boosting exercise, workers at Broughton gave up their weekend to build Wellington number LN514 rushed by the clock. The bomber was assembled in 23 hours 50 minutes, and took off after 24 hours 48 minutes, beating the record of 48 hours set by a factory in California. Each Wellington was usually built within 60 hours. It was filmed for the Ministry of Information for a newsreel Worker's Week-End, and was broadcast in both Britain and America. It was the first time in aviation history that an aircraft manufacturer anywhere in the world had attempted such a feat with a metal aircraft of this scale.
A total of 180 Wellington Mk I aircraft were built; 150 for the RAF and 30 for the Royal New Zealand Air Force . In October 1938, the Mk I entered service with 9 Squadron. The Wellington was initially outnumbered by the Handley Page Hampden and the Armstrong Whitworth Whitley but outlasted both rival aircraft in service. The Wellington went on to be built in 16 variants and two post-war training conversions. The number of Wellingtons built totalled 11,462 of all versions, a greater quantity produced than any other British bomber. On 13 October 1945, the last Wellington to be produced rolled out.