Avro 529 The Avro 529 was a twin - engined biplane long - range bomber of the First World War . Two prototypes were built but no production ensued . Development . The Avro 529 was Avro ' s second twin - engined aircraft and their second attempt at a heavy bomber . Their first in both categories was the Pike , developed in early 1916 to Royal Flying Corps ( RFC ) guidelines for a short - range bomber . The Pike arrived too late to secure orders from the RFC who would order the Handley - Page O / 100 and for the Royal Naval Air Service ( RNAS ) who had ordered the Short Bomber . Nonetheless , after trials of the Pike , the Admiralty ordered two prototypes of an enlarged Pike for a long range bomber role . This was the Type 529 . Like the Pike , it was a large twin - engined biplane of the then - standard wood and canvas construction . It had three - bay wings without sweepback , dihedral or stagger , partly to facilitate wing folding . The vertical tail was different to that of the Pike : it had a small , roughly triangular fin and a rudder with a round balance surface above the fin , a reminder of Avro ' s " comma " rudder form . The fuselage was rectangular in cross - section and seated three in separate cockpits . The pilot sat just forward of the wing leading edge , there was a gunner ' s position ( with emergency dual control ) mid - way between the trailing edge and the tail and the front gunner / bomb - aimer ' s position was in the nose . Both gunners ' positions were provided with a . 303 in ( 7 . 7 mm ) Lewis Gun mounted on a Scarff ring . The landing gear used two main wheels on split axles , plus a tail - skid . The two prototypes differed from each other chiefly in their powerplants . The first , just known as the Avro 529 had a pair of uncowled Rolls - Royce Falcon water - cooled in - line engines mounted midway between the wings . Each produced 190 hp ( 140 kW ) and drove four - bladed , opposite - handed wooden airscrews . It carried 140 gal ( 636 L ) of fuel in a tank in the centre fuselage . The second machine , designated Type 529A had a pair 230 hp ( 170 kW ) BHP in - line water - cooled engines , cowled and mounted in nacelles on the lower wing . These drove wooden , two - bladed airscrews . In this aircraft fuel was held in a pair of 60 gal ( 273 L ) , one in each nacelle . Fuel was pumped from these to 10 gal ( 45 L ) tanks above the engines by wind - driven pumps , and fed to the motors under gravity . The type 529A had slightly different wings to the first prototype , 13 in ( 33 cm ) greater in span , smaller in area and hence of higher aspect ratio . It was about 8 % lighter . Another difference between the two prototypes were the arrangements for the bomb - aimer . In the first machine , this was done from the seat of the front cockpit , but in the 529A there was provision for a prone bomb - aimer ' s position with a small window , noticeable in side view . From there , he communicated with the pilot by Gosport tube . The 529A could carry 20 50 lb ( 20 kg ) bombs racked nose up inside the fuselage between the lower wing spars . The Type 529 was , even with the B . H . P . engines rather low powered , but seems to have handled well apart from poor elevator control . There was no production order and the type was not developed further .