Blackburn G . P . The Blackburn G . P seaplane , ( the second aircraft ( serial number 1416 ) was sometimes referred to as the Blackburn S . P . for Special Purpose ) , was a British twin - engine reconnaissance torpedo floatplane of the First World War , built by the Blackburn Aeroplane and Motor Co Ltd . Design and Development . The poor results obtained with the Blackburn T . B . prompted Blackburn to develop an anti - submarine floatplane designated the Blackburn G . P . ( Blackburn General Purpose ) . The large seaplane that emerged had a crew of three accommodated in a long slim fuselage . The first aircraft ( s / n 1415 ) was powered by two handed Sunbeam Nubian engines driving four bladed propellers , in nacelles sitting on the upper surface of the lower main - planes . Cooling for the engines was achieved through vertical radiator blocks attached to the rear inter - plane struts either side of the engine nacelles , which also supported the oil tanks for each engine . Construction of the aircraft was largely of wire - braced wood with fabric covering . The wings , of RAF 34 section , were built in four sections , all with dihedral but the outer sections markedly so . The outer section upper mainplane extended past the lower mainplane and was supported by cables via king - posts , above the upper surface , over the outermost inter - plane struts . To facilitate storage the outer wing sections folded to the rear for a folded span of . At the rear of the fuselage a biplane tail - unit with twin fins and rudders provided control and stability in pitch and yaw . Two bungee - sprung plywood covered main floats with twelve watertight compartments supported the aircraft through a divided strut structure which left clearance for dropping torpedoes from under the fuselage . A single tail float was also strut supported from the rear fuselage . For ground handling ashore the aircraft sat on beaching dollies under the main and tail floats . The crew sat in open cockpits , the gunner / navigator at the nose , pilot forward of the wing leading edges and a second gunner aft of the wings . The gunners could operate . 303 ( 7 . 7 mm ) Lewis machine gun s mounted on Scarff ring s . Other armament could include four 230 lb bombs on racks under the wing and / or a torpedo under the fuselage . The crew also had access to Wireless Telegraphy equipment for communications with other stations . A second G . P . was built , which was structurally stronger through the use of heavier gauge metal fittings and revised structure , with power supplied by two Rolls - Royce 190hp engines ( later to be renamed Falcon ) driving handed four bladed propellers in similar fashion to the first aircraft . Other changes included four ailerons , one on each wing , instead of just the upper mainplanes , engine nacelles raised clear of the lower mainplanes and scalloped trailing edges through the use of steel wire trailing edge members , ( a retrograde step as the wire corroded quickly causing damage to the fabric covering ) . Operational history . After initial trials the first aircraft was moved to the Marine Aircraft Experimental Station on the Isle of Grain and moored out in rough seas in a " destructive test " of mooring performance . The second aircraft carried out manufacturer ' s trials from Blackburn ' s new seaplane base at Brough and later flew to the RNAS base at Great Yarmouth for service trials . Although no more G . P . s were ordered , the aircraft formed the basis for the land based Blackburn R . T . 1 Kangaroo reconnaissance / torpedo - bomber .