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Aviation History
1919
1919 - 0797.PDF
JUNE 19, 1919 THE, CAPRONI BOMBING TRIPLANE CA-4-19I5 # THE Caproni triplane represents a type designed and built by the famous Italian constructor since 1915. This machine was created at that time for the night bombing of important military and naval bases, railway stations and war plants. As in the preceding types of machines by the same constructor, the type CA-4 triplane has for its distinctive characteristic the number and arrangement of the motors, originated by the famous Italian constructor. There are three motors, one driving a pusher screw mounted in a central nacelle, the other two are each mounted in the nose of a. fuselage and drive a tractor screw. These two fuselages and tie central nacelle are attached to the spars of the middle wing, whilst the centre section of the lower plane carries the bomb rack, also designed by Engineer Caproni. (Normally the crew of the machine consists of two pilots, seated side by side, and a gunner—who operates a i^ in. gun and btwo Fiat machine guns—located in the central nacelle, and a gunner or observer in each of the fuselages, which are also fitted with Fiat machine guns. Each of the crew can pass from one cockpit to another, a foot walk covered with veneer wood being provided on the middle plane between the central nacelle and the fuselages for this purpose. The CA-4 triplane has been successively equipped with three different types of motors. At first, three Isotta- trailing edges. On the linen, above and below the wing, maple batten strips are screwed in correspondence to the ribs. For the interplane struts, ash, spruce and seamless steel tubes are employed, and some of the struts have adjustable ends. The bracing is, as usual, with steel cables and wires. As on all Caproni bombing machines, the stabiliser, elevator, rudders and ailerons are constructed of steel tubing. The stabiliser is solidly braced to the fuselage by means of cables and steel tube struts. There are three balanced rudders and a one-piece elevator. Ailerons are fitted to all three planes. Dual control is fitted, so that the machine can be controlled by either pilot at will. The control system for the ailerons and elevator is a combination of the wheel and stick type, and the rudders are operated by a foot bar of the usual pattern. The petrol is fed from three tanks, one each on the fuselages and one in the central nacelle. Three wind-driven centrifugal pumps deliver the petrol from the tanks to a central distri butor, and thence to the carburettors of the engines. Both pilots have close at hand the necessary devices for controlling the petrol supply. For testing the motors on the ground two small gravity tanks are provided, but these are excluded from the main system when the machine is in [flight. In cases This three-engined 1,200 h.p. Caproni triplane, has a span of about 103 ft., and carries a useful load of several tons Fraschini 8-cylinder vertical 240-250 h.p. engines were used ; later three Fiat A/i2-bis6-cylinder vertical engines were fitted, and [finally three Liberty 12 Navy type (low compression) engines were adopted. With an aggregated useful military load [of 6,600 lbs. the performance of this triplane, equipped with Liberty engines, has been considerably better than those obtained with the other types of motors, especially in climbing. In jthe official tests, at full load and fully armed, a speed of 98 |m.p.h. at 6,560 ft. was reached. The average rates of climb attained (with Liberty motors) at full military loads were : 3,280 ft. in 6 mins., 6,560 ft. in 14 mins., and 10,000 ft. in 25 mins. The ceiling is at about 16,000 ft. The total weight of the machine, empty, is 11,100 lbs., and with full military load, 17,700 lbs. With a complete fuel load of 550 gals, the bomb rack is supposed to be loaded with 2,500 lbs. of bombs, but practically in almost all bombing raids the load of bombs exceeded 3,000 lbs. Each of the three planes is built up in seven sections, the corresponding sections in upper, middle and lower planes being of equal span, as follows. Centre sections, 5 ft. 6 ins. ; intermediate sections (two), 13 ft. 1 in. each, and outer sections 18 ft. 3 ins. The wing spars are of box spar section, and the ribs, double ribs and box ribs are of white wood and ash. Between ribs the spars are wrapped with strong linen. The connection between the two subsequent sections is obtained with the male and female box fitting system. The covering is 'linen, nailed on the rib >flanges and on the leading and •__Courtesy Aerial Agt U.S.A.). of emergency the pilot on the left can operate a hand-pump, which is capable of feeding the three engines from the central tank. Each engine has its own oil tank and a radiator for cooling jthe oil. The engine radiators are mounted either in the nose of the respective fuselage or nacelle, or else above in each engine, [as shown in the [photographs. All the radiators are of the honeycomb type, and are fitted with shutters. The central nacelle is perfectly streanuined. Two main longerons with steel tube compression struts between them, wire braced, form the frame on which a set of ribs are fastened, giving the shape of the nacelle. Birch veneer and walnut are employed in the construction of these ribs—a similar form of construction to that employed for flying boat hulls. The front upper part of the nacelle is formed by a cowling made of plywood with interposed layers of fabric. The two pilots are seated behind the front gunner, and behind them again is the petrol tank. At the rear of the latter, which is of the same circular section as that of the nacelle, is a short foot-way allowing free access to the engine at the rear. The engine is enclosed by cowling. The two fuselages are flat-sided and of the usual girder construction—four «ash longerons, compression struts, and wire bracing. All the fittings to which the diagonals are fastened are manufactured from the same set of dies, and are extremely simple, light and free from welding. Their applica tion is such that the longerons are not pierced by bolts or screws. The engine housing is cowled with sheet aluminium. The petrol and oil tanks are situated just behind the engine. 797
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