Editing Vickers Wellington (section)

===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 {{Convert|250|lb|abbr=on}} or {{Convert|500|lb|abbr=on}} 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 [[Anatomical terms of location#Dorsal and ventral|dorsal]] position was made.<ref name = "andrew 6"/> It had provision for a crew of four, along with a fifth position for special duties.<ref name = "andrew 6"/>

On 5 June 1936, the name "Crecy" was chosen for the type, and it was publicly displayed as such.<ref name = "andrew 7"/> 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, 1st Duke of Wellington|Arthur Wellesley, the Duke of Wellington]].<ref name = "andrew 7"/> On 12 December 1936, a corresponding [[work order|works order]] was issued for the Wellington.<ref name = "andrew 5"/>

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.<ref name = "andrew 6"/> 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.<ref name = "andrew 6 7">Andrews 1967, pp. 6–7.</ref> 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 (aeronautics)|elevator]]'s [[balanced rudder|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.<ref name = "andrew 7">Andrews 1967, p. 7.</ref> The horn balances were later deleted from the design and were not on production aircraft.<ref name = "andrew 10"/>

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 a larger bomber aircraft, the [[Vickers Warwick]]<ref name = "andrew 7 10">Andrews 1967, pp. 7, 10.</ref> 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.<ref name = "andrew 10">Andrews 1967, p. 10.</ref> Other changes made included the adoption of a retractable tailwheel and [[constant-speed propeller]]s; the Air Ministry also requested the adoption of a [[Nash & Thompson]]-design ventral turret in place of the Vickers design.<ref name = "andrew 10"/>

On 23 December 1937, the first production ''Wellington Mk I'', ''L4212'', conducted its first flight, followed by an intensive flight programme.<ref name = "andrew 10 11">Andrews 1967, pp. 10–11.</ref> 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 [[Flap (aeronautics)|flaps]] and the elevator [[trim tab]]s, were tested on ''L4212'' and resolved the problem.<ref name = "andrew 11">Andrews 1967, p. 11.</ref>