Boulton Paul P . 32 The sole Boulton & Paul P . 32 was a British three - engined biplane built to an Air Ministry specification for a long range night bomber . A lack of engine availability slowed construction and by the time it went for tests the thinking on bomber types had moved on . Design and development . The Air Ministry specification B . 22 / 27 of 1927 called for a three - engined long range night bomber . Boulton & Paul tendered the P . 32 and obtained an order for one prototype . de Havilland also received a prototype order for their DH . 72 , an aircraft of similar size and layout . Both were twin finned three bay biplanes with two engines on the lower wings and one on the upper centre section . The centre engine position was driven by the specification ' s requirement for a clear view from a bomb aimer ' s position in the nose . The P . 32 was a metal framed aircraft , using steel for the main members and duralumin elsewhere . Its unstaggered , foldable wings were straight edged with constant chord and rectangular tips , a Boulton & Paul characteristic seen also in , for example the Sidestrand . Both wings carried ailerons , but only the lower one had dihedral . Two of the uncowled three 550 hp ( 410 kW ) Bristol Jupiter XF radial engines were mounted on the top of the lower wing just within the inner bay , their three - bladed propellers close to the fuselage sides . The third engine was similarly mounted on the upper wing , above the fuselage ; the wide interplane gap just gave airscrew clearance . These engines were replaced with 575 hp ( 429 kW ) Jupiter XFBMs , enclosed in Townend ring s and driving four bladed airscrews as soon as these medium supercharged models became available . The square section , slab sided fuselage held either four or five crew , though more seats The specification called for a gunner / bomb aimer in the nose . In the P . 32 he could use the bombsight when sitting facing forward and , by rotating his seat , take up his third role as navigator at a chart table . There was a walkway aft , which passed in turn the pilot ' s and second pilot ' s open cockpits in tandem on the port side , the wireless / camera operator ' s internal position near the leading edge , the dorsal gunner ' s cockpit and the tail gunner ' s station in the extreme , slightly drooped tail . The second pilot was optional ; he might be an instructor or a relief . The dorsal gun could be manned either by the wireless operator or the tail gunner . Each of the three gun positions had a Lewis gun on a Scarff ring . Bombs were held in a recessed but not enclosed bay below the fuselage ; more could be mounted below the inner wing . The monoplane horizontal stabiliser carried servo assisted elevators and a pair of fins with horn balanced rudders . These were also servo assisted , with the servo surfaces mounted well behind the rudders ' trailing edges on outriggers . The main undercarriage was unusual in that on either side pairs of wheels were fitted on a long axle so that the inner one was close to the fuselage and the outer one beyond the engine and inner bay . The P . 32 was initially fitted with a pair of tailskids , soon replaced with a tailwheel with a little faired leg . Like its de Havilland competitor , the P . 32 ' s completion was delayed by a series of design changes requested by the Air Ministry but especially by the unavailability of engines from Bristol . The Bristol Mercury Vs originally specified were never fitted . It first flew at Mousehold Heath on 23 October 1931 , joining the DH . 72 for evaluation by the A & EE at RAF Martlesham Heath that November . It appeared at the Hendon display in 1932 , painted in the standard dull green , but it seems the Ministry saw no future for this class of intermediate weight bombers , for none were ordered and no performance figures from Martlesham tests have survived for either the P . 32 or the DH . 72 .