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Aviation History
1956
1956 - 0643.PDF
25 May 1956 643 Churchill (who was at that time Minister of Munitions) recordedthat John D Ryan the U.S. Undersecretary for fflShS told him that the American Navy Department claimed absolute priority for Liberty engines. Air. Churchill said: "A great pan of these precious engines on which the whole of our air offensive bombing programme depends has^ up to date, been swallowed up by American aviation." This, despite the fact that it was a British order which ensured that the Liberty went into pro- duction. Ultimately Britain received a promise that 750 Liberty engines would be delivered each month during the first half of In selecting the high-powered Liberty as the power unit for the D.H.9 replacement it seemed that the authorities were seeking to redeem themselves after their catastrophic sponsoring of the lower- powered D.H.9 in preference to the proven D.H.4 When the official request was made for the D.H.9 to be redesigned to have the Liberty, the Aircraft Manufacturing Co. were fully occupied on the design of the fine twin-engined bomber which was to be the D.H.10 and were unable to undertake any additional work. The Westland Aircraft Works were appointed parent firm for the development of the Liberty-powered D.H.9 replacement. Theirs was the responsibility for the conversion of the aircraft and the preparation of drawings for other contractors. To assist the Westland company, Mr. John Johnston, one of the Aircraft Manufacturing Company's draughtsmen, was sent to Yeovil on loan. The modified aircraft was designated D.H.9A, and design work was completed early in 1918. With the promise of so much power from the Liberty it was obviously desirable to attempt to improve all-round performance and increase the aircraft's load- carrying capabilities. This was in fact done, and there can be little doubt that, had the war lasted longer, the D.H.9A would have established itself as one of the great aircraft of the period. The new design had wings of greater span and chord than those of the D.H.9, but the same tail surfaces were used. The basic fuselage structure was similar to that of the D.H.9, but wire cross-bracing replaced the plywood cross partitions which had characterized the earlier type. The bottom of the fuselage was cross-braced from the extreme front back to the transverse mem- ber which supported the tail-skid. As on the D.H.9, the fuselage was constructed in two portions which were joined together by fishplates just behind the observer's cockpit. All structural members were of wood, the lower longi- tudinals of the forward portion being deep-section patons. The fuselage had little cross-bracing in the vertical plane: the sides of the forward portion had none at all, for a number of substantial wooden diagonals were fitted and the covering was of plywood. Three side bays of the rear fuselage were cross-braced, but the last bay was covered with plywood to form the tail box. The remainder of the rear portion of the fuselage was fabric-covered. The top-decking in front of the pilot's cockpit was rounded; behind the observer's cockpit it was flat-topped. The front of the fuselage was modified to accommodate the big vee-twelve engine: an inch-thick plywood bulkhead was built into the top of the fuselage, and two bays of bracing wires were fitted under each engine bearer. The engine installation was similar to that of the D.H.4. A large flat frontal radiator was fitted immediately behind the airscrew; it had shutters for the regula- tion of the airflow. The main fuel tanks (two of 50 gallons each) were installed immediately behind the engine, and there was a gravity tank of seven gallons' capacity in the centre-section. The pilot and observer were located close together, just behind the mainplanes. Full dual control was provided. The Westland-built Eagle-powered DM.9A, BJ664. Eagle-powered prototype C.6350 was built by Airco. The tail unit and undercarriage were virtually identical with those of the D.H.9. The incidence of the tailplane could be adjusted in flight. The steerable tail-skid was sprung by rubber cord in tension. The wings were of wooden construction, with internal wire cross-bracing and fabric covering. The ailerons were a little smaller than those of the D.H.9, and had new control horns of a flatter shape. As a refinement, all aileron control cables were carried internally within the wings. Design work was completed some time before the first Liberty engines arrived in Britain. In order to determine the D.H.9A's behaviour in flight, prototypes were assembled with the 375 h.p. Rolls-Royce Eagle VIII engine, and one such machine underwent official trials in March 1918. At least two Eagle-powered D.H.9A prototypes existed, and it is difficult to say which came first. Both were converted from D.H.9s: B.7664 was built by the Westland Aircraft Works, and C6350 apparently by the Aircraft Manu- facturing Co. The two aircraft were not identical. On the Airco-built prototype the radiator and engine cowling resembled the installation on the D.H.4, and the radiator shutters were vertical. Both starboard wings appeared to be lower mainplane panels, for each had a clear-view aperture between the spars; that in the upper wing served no useful purpose. The Westland-built machine looked much more like a produc- tion D.H.9A. The shape of radiator and cowling closely resembled those of the Liberty-powered production aircraft, and The Liberty-powered prototype C.6122.
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