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Aviation History
1940
1940 - 1907.PDF
JULY 4, 1940 ASSISTING TAKE-OFF and ALIGHTING Hydroplane Launching Gear for Stepless Flying Boats By F. W. KING /% SSISTED take-off is bound to come. It is the only /~\ way in which a worth-while increase in payload proportion can be obtained. But assisting take- off solves only half the problem. Except for the special cases of the bomber and the long-range aircraft where the loading is substantially reduced before alighting, it is the alighting case which sets the limit to wing-load- ing. Before the high loadings which assisted take-off makes possible can be employed for ordinary operation, some provision must be made for safe alighting with high minimum flying speeds. The solution of the alighting problem is easy. It has been staring the aeronautical world in the face since 1931. The outstanding lesson of the Schneider Trophy Race of that year was that an aircraft can be put down perfectly safely at speeds in excess of no m.p.h.—on water. Nature does it too. Swans, geese, ducks— Nature's examples of high wing-loading—alight on water. Water is a shock-absorber which has not to be carried in flight. Seaplane Float Structure The combination of assisted take-off with water- alighting solves both halves of the problem; Wing- loads and payloads can go up enormously. It is pos- sible to unite the aerodynamic efficiency of the land aeroplane with structural simplicity of the flying boat, and to achieve with the combination an alighting tech- nique capable of dealing with far higher speeds than either. A boat hull built for alighting only could dis- pense with the steps and chines and planing bottom of present flying boats. Its hull might be no larger than the fuselage of a land aeroplane. It would have no undercarriage. Obviously, if aircraft are to be operated from water bases, it is desirable to employ a method of assisting take-off capable of operation from water. An arrange- ment for this is shown in Fig. 1. The aircraft is mounted for launching on a float-supported structure similar to that of a twin-float seaplane. Extra thrust is provided by any number of aero engine and airscrews mounted on the floats. With the airscrews placed as shown, immediately behind the wings of the aircraft, the indraught induces lift which, operating during the early part of the take-off run, enables the floats to hydroplane earlier. The " Crouch-Bolas effect" is obtained for the take-off run without any complication on the aircraft. The arrangement would be convenient in operation as the aircraft could be mounted for launching without external assistance. The method is shown in Fig. 2. The floats for the launching gear provide convenient tankage for refuelling, this would eliminate the separate tender. Servicing operations could be performed very conveniently from the decks of the floats. As air-drag has not to be considered, the floats may be designed purely for water-performance. This would produce a form simpler and cheaper than seaplane floats. It is claimed that a launching device constructed in S ENGINES WITH TRACTOR AND PUSHER AIRSCREWS r TRAVELLINGHYDRAULIC JACK WITH VACUUM PLATES Fig. 1. General arrangement of the hydroplane launching gear. this way would be cheaper than any existing device for assisted take-off and would be capable of launching almost any type of aircraft with the minimum of adapta- tion. There are no limits to size in either direction. The proposed method of holding and releasing by means of large suction plates avoids the imposition of concentrated loads and the necessity for special fittings on the aircraft. The engines might conveniently be engines which had already completed their term of life in the air. Vacuum Plates Used in conjunction with the stepless flying boat, the method would make possible enormous savings in air- craft operation. Sheltered harbours and creeks, lakes and inland waterways of suitable size constitute cost- less aerodromes. The complete elimination of the undercarriage cheapens the airframe and reduces its weight. The small hull is of simple form easily con- structed from cheap materials. It is particularly suit- able for plastics. With extra power provided for take- off, engines might be smaller and lighter. Diesel engines become possible. For the same reason, the v.p. airscrews may be replaced by lighter and cheaper fixed screws. From the pilot's point of view assisted take-off by this method may differ little from ordinary take-off technique. As shown in the diagrams, the vacuum plates are applied to the undercarriage of the wings and are hinged on a line near the eg, of the aircraft. By this practice it is possible for the pilot to control the attitude of aircraft during the take-off run by the normal elevator control. Thus, although the speed and course of the launching gear is under the control of its attendant, the take-off may be completely under the control of the pilot. Obviously a very simple de- vice may enable the pilot to break the vacuum and effect release at the desired moment. No complicated inter-connection of controls is necessary. Porpoising and diving tendencies during the alight- ing run may be obviated by making the hull long on
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