Vickers Type 253 The Vickers Type 253 was a single engined two seat biplane general purpose military machine built to a 1930 government specification . It won a production contract , but this was transferred to the same company ' s monoplane equivalent , the Wellesley . Only one Type 253 was built . Development . In April 1932 the Air Ministry awarded a contract to Vickers for a single prototype aircraft under Air Ministry specification G . 4 / 31 for a Westland Wapiti replacement , a multi role aircraft capable of carrying out level bombing , army co - operation , dive bombing , reconnaissance , casualty evacuation and torpedo bombing . Vickers ' entrant to this competition was the Type 253 , though often known by the specification as the Vickers G . 4 / 31 . The Ministry had also ordered prototypes of other designs and some manufacturers had offered private ventures ( aircraft built with their own money ) . The Type 253 was in competition with the Handley Page HP . 47 . Fairey G . 4 / 31 , Westland PV . 7 , Armstrong Whitworth A . W . 19 , Blackburn B - 7 , Hawker P . V . 4 and the Parnall G . 4 / 31 . The Ministry preferred an air cooled engine and Vickers choice was the radial Bristol Pegasus . The Vickers Type 253 used a Pegasus IIM3 engine , enclosed by a drag reducing Townend ring , to power a two bay , unstaggered biplane , with a lower wing smaller in span and chord . Both wings were of constant chord , but the centre sections were mildly forward swept and the lower centre section carried anhedral out to the inner interplane struts . Both sets of interplane struts leaned outwards , the outer ones more so . Both wings carried ailerons and the upper planes had leading edge slats . The wings joined the fuselage top and bottom with no gap , the pilot sitting just ahead of the leading edge in an open cockpit and the observer sited well behind the trailing edge . A conventional tail carried balanced rudder and elevators . The split axle fixed undercarriage was neatly mounted , the main legs fixed to the front spar under the inner interplane struts and braced rearwards to the wing roots . Construction was the common one of canvas over a metal frame , but the fuselage frame was quite novel . It was designed by Vickers ' chief structural engineer , Barnes Wallis and was a step along the road to his geodetic frames , where the distinction between main and secondary members was largely lost . The Type 207 fuselage frame had four light alloy longerons , each made in sections that were screwed together . These longerons were joined by a pair of oppositely handed helical channel members , forming a diagonal tubular mesh . Wing construction was less radical , and indeed less novel than that of the earlier Type 207 , which had thick RAF 34 section wings built of complex webbing informed by Wallis ' earlier airship experience ; the Type 253 reverted to the thinner RAF15 section and a more familiar two spar design . Mutt Summers took the Type 253 on its first flight on 16 August 1934 at Brooklands . It then went , after some modifications to the Aeroplane and Armament Experimental Establishment at Martlesham Heath for trials in the specification competition . In February 1935 the sole 253 flew with an uprated Pegasus IIIM3 . The Type 253 won the competition and an order for 150 aircraft . However , on 19 June 1935 , Summers flew the Type 246 monoplane that Vickers had built to the same specification as a private venture , which was to become the prototype Type 287 Wellesley . It was immediately apparent that the monoplane offered better performance and a greater payload , so the Type 253 order was cancelled and replaced with one for the Wellesley in September 1935 .