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Aviation History
1956
1956 - 0679.PDF
FLIGHT, ljune 1956 > THE DE HAVILLAND D.H.9A . . . 679 Another interesting but little-known experimental D.H.9A wasH.3588, which was fitted with a special air-cooled version of the Liberty driving a Fairey-Reed metal airscrew. As the illustra-tion (p. 678) shows, the installation was an unprepossessing affair, characterized by an ugly intake, uglier outlets, and long exhaustpipes. The official photograph of the aircraft is dated April 27, 1933. Several developments of the D.H.9A design were built. Thefirst of these appeared in 1919, with the designation D.H.I5 and the official name Gazelle. This was virtually a D.H.9A airframemodified to accommodate the Galloway Atlantic engine, a vee- twelve which was rated at 500 h.p. It will be recalled (see Flight,April 6, 1956, page 386) that the Galloway company had made a version of the 230 h.p. B.H.P. engine with a cast-iron cylinderblock. The Atlantic was, in effect, two such engines united on a common crankcase. The first Atlantic engine appeared in 1918 and was put intoproduction; by October 31, 1918, twenty-five engines of this type had been delivered. However, the engine underwent a processof modification analogous to that which had transformed the 230 h.p. B.H.P. (Galloway Adriatic) into the mass-producedSiddeley Puma. The transformation produced a double Puma, with aluminium cylinder blocks, which was named SiddeleyPacific. Either the difficulties which had beset the Puma and its production had been overcome, or the authorities of the day wereincapable of learning from their mistakes, for the Pacific was ordered into production on a large scale. It is not known whether it was intended to install the Pacificin the D.H.15, but it seems most probable that the aircraft was built solely as an insurance against the possible failure of themore advanced D.H.14, or Airco Okapi, a massive biplane designed as a D.H.9A replacement and powered by the then-new and untried 600 h.p. Rolls-Rcyce Condor engine. The Armistice prevented the development of the D.H.14 by eliminat-ing the need for it, and the D.H.15 was also abandoned. In appearance the D.H.15 resembled the D.H.9A closely, forthe engine installation differed little externally from that of the Liberty. The radiator was slightly different in shape, and theAtlantic engine was fitted with long exhaust pipes which termin- ated beside the gunner's cockpit. A development of rather a different kind originated in 1920as an official design for a three-seat deck-landing naval recon- naissance aircraft based on the D.H.9A. Doubtless it was hopedto effect a substantial economy by giving carrier-borne units a modified version of the RAF.'s standard day bomber, but, as withso many adaptations of a like nature, it was not an unqualified success. The design envisaged the location of the pilot andgunner in the normal positions, and a third cockpit was provided behind the gunner's. This rearmost seat was occupied by theobserver, who also had a partially-glazed ventral trough position built on below the fuselage. The prototype aircraft was J.6585, which was apparently builtby the Armstrong Whitworth company and bore the name "Tadpole" on its nose. This machine had the Liberty engine andretained a marked resemblance to the D.H.9A. The wings, tail unit, undercarriage, and basic fuselage structure of the Nine Ackwere employed, but the incorporation of the third cockpit altered the appearance of the rear fuselage: the ventral "bath" wasimmediately conspicuous, and the top decking was modified in an ugly fashion to give depth to a cockpit which was situated at apoint where the basic fuselage was relatively shallow. The entire fuselage of the Tadpole was covered with plywood, andthe stagger was considerably reduced. Development of the design was entrusted to the WestlandAircraft Works, and the aircraft was named Walrus. The ultimate product was one of the most unprepossessing aeroplanes whichever took the air. There can be little doubt that the aircraft was somewhat under-powered with the Liberty engine. The450 h.p. Napier Lion II was substituted but its additional power can hardly have been sufficient to cope with the many drag-producing modifications which were made to the Walrus. The Lion-powered production version had a modified, jettisonableundercarriage fitted with a hydrovane, and jaws for the fore-and- aft arrester wires of the period were mounted on the underside ofthe spreader bars; emergency flotation bags, carried externally and inflated by compressed air, were fitted; and wing-foldingwas incorporated. A special valve on the main fuel tank per- mitted the rapid jettisoning of the fuel and re-sealing of the tank,which then became an additional flotation chamber. The test flying of the Walrus was performed by Capt. A. S.Keep, M.C. The aircraft was reported to be unpleasant to fly, but a batch of 36 were nevertheless ordered. One of these waslater fitted with high-lift wings, horn-balanced ailerons and elevators, and an oleo 'undercarriage. By that time the Walrushad lost all resemblance to the handsome D.H.9A from which it was descended. It will be recalled that the first aeroplane to fly with Handley D.H.15 Gazelle. Armstrong Whitworth Tadpole (Walrus prototype). Page slots was a D.H.9. That was in 1920, and in the followingyear there appeared the Handley Page X.4B, which later acquired the type number H.P.20. This remarkable aircraft consisted ofthe fuselage of a standard D.H.9A, H.634, to which a slotted cantilever monoplane wing was fitted. The X.4B was a single-seater, and was flown from what would have been the rear cockpit in a standard D.H.9A fuselage. A tall undercarriage wasfitted, and the aircraft weighed 6,500 lb loaded, a figure which gives some idea of the structure weight of that early cantileverwing, for the standard D.H.9A weighed only 4,645 lb with two 230-lb bombs and fuel for 51 hours. The ultimate D.H.9A development appeared in 1926. Knownas the D.H.9AJ, or Stag, this machine was built by the Westland Walrus. D.H.9AJ Stag.
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