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Aviation History
1937
1937 - 2125.PDF
JULY 29, 1937. FLIGHT. c was resumed. Mr. R. Falkland Carey, who had designed the Waygood-Otis catapult, designed a new one, which followed in a general way the lines of the American cata pults, with the motion of the ram transmitted to the launch ing carriage by wire ropes over pulleys. The Carey cata pult was designed to launch aircraft up to 7,000 lb. weight, the run being 34ft. and the speed 45 m.p.h. The mean acceleration was 2 g. Compressed air was used. Simultaneously with the design of the Carey catapult, the R.A.E., Farnborough, proceeded with the design of an entirely different type. The speed, run and acceleration were the same as for the Carey, but no cables and pulleys were used, the launching carriage being attached directly to the smallest of the series of telescopic tubes which formed the ram Again compressed air was used as the motive power, the pressure in the bottles being 2,000 lb./sq. in. Two of these catapults were built by MacTaggart Scott. Cordite Introduced In 1928 the R.A.E. catapult was modified to use cordite instead of compressed air, and in later developments of it the forward half of the structure is hinged so as to stow alongside the rear half when the catapult is not in use. Larger versions will launch aircraft up to 8,000 lb. weight at 55 m.p.h., the run being 50ft. In recent times the wire-ropes-over-pulleys type of cata pult has come into favour, two Admiralty designs particu larly being used extensively by the Navy. One of these was built by MacTaggart Scott and the other by Ransome and Rapier. The latter is known as the "slider" type from the fact that a subsidiary sliding structure is made to move along the main structure, and carries the actual launching carriage, which in turn runs along the sliding structure. The MacTaggart Scott type has its main structure divided into three portions, the two end portions sliding inside the centre portion for stowage. This catapult will launch air craft up to 8,000 lb. at a speed of 57 m.p.h., 7,000 lb. at 60 m.p.h., and 6,000 lb. at 63 m.p.h. The corresponding Mechanisation : A De Havilland Queen Bee wireless-controlled target aeroplane is catapulted, pilotless, from H.M.S. Neptune. mean accelerations are 2.15 g, 2.38 g, and 2.62 g. The launching run is 50ft. 6in. In Germany considerable catapult development has taken place, notably by the Heinkel firm, in connection with the " mother ships " used on the South Atlantic air route and, more recently, on the North Atlantic experiments. The most recent of these ships, the Friesenland, belonging to the Deutsche Luft Hansa, has a Heinkel catapult capable of launching aircraft up to 37,000 lb. gross weight, which is probably the most powerful catapult hitherto constructed. If, however, catapults of this size can be used successfully on a vessel, there would not appear to be any reason why catapults of even greater power should not be used ashore. It will usually be found that space is nothing like so cramped on land as on board ship, so that a much longer starting run can be permitted. This means that either the power required can be smaller, or the take-off spead greater, or that the acceleration can be reduced to a much smaller figure. On military aircraft it is usually possible to design the structure to be strong enough to stand an acceleration of 3 g-4 g. It has been found that the crew can stand an acceleration of 5 g without very much discom fort, mainly due to the fact that the acceleration is in a horizontal direction, as distinct from certain aerobatic manoeuvres in which the acceleration is usually in a direc tion parallel with the pilot's spine. In this connection it is interesting to note that experiments have shown that accelerations of 5.2 g sustained for less than 1 second were no more unpleasant than accelerations of 3 g for i£ seconds. The " Accelerator " Type Some years ago the R.A.E. developed a totally different type of catapult, which has been variously described as a field catapult and an accelerator. It is not a catapult in the sense that the aircraft is not secured to a launching carriage but runs along the surface of the aerodrome on its own wheels. In order to reduce the angle of incidence of the wings, the tail is carried on a trolley, which is, of course, arrested when the aircraft leaves the ground under the control 61 the pilot. The Farnborough accelerator has an interesting power unit, in which two compressed-air engines are used, each developing 2,000 b.h.p. at 2,500 r.p.m. The engines drive, through a 6: 1 gearing, a cable K.W EpF ""* : fi 11 M3H|* "Tin • JJ^W^^T • l*,**'5SSr*i,. m. "PPW* m,
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