Westland PV . 7 The Westland PV . 7 was a private venture submission to a 1930s British specification for a general purpose military aircraft with two crew . It was a single - engined , high - wing monoplane of promise , but was destroyed early in official tests . Design and development . The Air Ministry specification G . 4 / 31 called 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 . Nine manufacturers responded with designs and while some gained contracts for single prototypes , such were the potential rewards that others , like Westland , built aircraft as private ventures . Contenders were the Armstrong Whitworth A . W . 19 , Blackburn B - 7 , Bristol 120 , Fairey G . 4 / 31 , Handley Page HP . 47 , Hawker P . V . 4 , Parnall G . 4 / 31 , Vickers Type 253 and the Westland PV . 7 . Only Westland and Handley Page submitted monoplane designs . The Ministry expressed a preference for an air cooled engine and all manufacturers apart from Armstrong - Whitworth and Blackburn chose the nine cylinder Bristol Pegasus radial . The Westland PV . 7 was a large , tall single - engined high - wing monoplane with separate cockpits for two crew . The constant chord wings were all metal , built around two spars with ribs and inter - spar rods for stiffening . Leading edge Handley Page slats were fitted outboard and the inboard trailing edges carried 4 ft 9 in ( 1 . 45 m ) span split flaps that opened symmetrically above and below the wing to act as dive brakes . Ailerons extended Immediately outboard of the flaps , almost to the wing tips . The wings met the top of the fuselage , with the pilot ' s head between them and behind the line of the outer leading edge , so at the centre the wings were thinned and tapered on the leading edge to improve his view . Originally his cockpit was open , but as it was only 6 ft ( 1 . 83 m ) behind the propeller it was very draughty and was eventually glazed in , with entry via an opening upper panel and extending rearwards above the wing . On each side a pair of parallel , cranked lift struts joined the lower fuselage to about mid span , reinforced by struts from the crank - point to the upper fuselage . The main lift struts had a wide chord airfoil section and themselves contributed to lift . The main undercarriage legs were fitted to these struts at the crank - point , each axle supported by a pair of V - struts to the lower fuselage . There was a castoring tailwheel under the tailplane . The fuselage was mostly constructed from square section duralumin tube with some steel at critical points and alloys formers and stringer to shape it . It was mostly fabric covered , though there was some metal sheet in the forward part and a plywood decking around the rear cockpit . The tail unit was metal framed and fabric covered , with a narrow parallel chord braced tailplane and elevators . The fin and rudder were broad , the latter extending to the base of the fuselage . Initially both elevators and rudder were horn balanced . The second crew member ' s large cockpit was just behind the trailing edge , enclosed in a multi - piece , segmented glazed cover that could be folded away forward when gunnery using the Scarff ring mounted Lewis machine gun was necessary . From there he could access the bomb aimer ' s position , lit by two small underwing windows on each side , lying prone on the fuselage floor . Part of the reason for the tall , split axle undercarriage was to allow a torpedo of up to 1 , 100 lb ( 500 kg ) to be held in crutches between the legs ; alternatively two 500 lb ( 227 kg ) bombs could be carried in under - fuselage racks . The pilot had control of a port side , forward firing Vickers machine gun . The PV . 7 was powered by a Bristol Pegasus IIIM3 engine within a Townend ring , which produced 722 hp ( 538 kW ) and drove a two bladed wooden propeller . It flew for the first time on 30 October 1933 , with Harald Penrose , Westland ' s regular test pilot at the controls . Early flights showed the need to glaze the cockpit and lighten the ailerons , and later tests at higher speed revealed that the wing twisted under aileron loads . This latter problem required significant re - working of the wing structure , specifically the replacement of the inter - spar rods with torsionally stiffer tubes . Flight testing also showed that the rudder was aerodynamically over - balanced , causing oscillations cured by removal of the horn balance entirely . The PV . 7 featured in the New Types Park at the 1934 Hendon RAF Display at the end of June , then went to the RAF Martlesham Heath for official testing . Since this was to be done by Service pilots , Westland cancelled their insurance cover as any damage would be paid for by the government . The initial reaction of the RAF pilots was encouraging . On 25 August , at the request of the Air Ministry Penrose flew the aircraft again , making tests of its behaviour with the centre of gravity far aft . After he had taken off , a telegram arrived at Martlesham saying that this test should not proceed as the airframe would be over - stressed , but Penrose was not in radio contact and went ahead . In a high speed dive the Westland calculations were confirmed by the collapse of the port wing . Penrose was lucky to escape by parachute , as the upper hatch had jammed and he had to squeeze out of a small side window , becoming the first British pilot to bale out of an aircraft with an enclosed cockpit . It was the end of Westland ' s G . 4 / 31 hopes , though ; the Air Ministry would not pay for the loss of an aircraft flown by a civilian , and the company could not afford to build a replacement . In the end , none of the aircraft originally submitted to the specification was built in quantity , for although the Vickers 253 was declared winner and ordered , it was replaced by the slightly later and much superior Vickers Wellesley .