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Aviation History
1925
1925 - 0562.PDF
SEPTEMBER 3, 1925 THE JUNKERS G.24.L This side view gives a good idea of the cabin, and the men standing in front ofthe machine give scale to the picture the machine may be fitted with more powerful engines, one combination being that found on the Swedish-built machine which visited Croydon, and which was equipped with three 230 h.p. Junkers engines of the L.2 type. An unusual and interesting feature of the design of the G.24 is that the machine, apart from changes in individual engine units, can be used either as a single-engined, twin- engined, or three-engined monoplane, the wings being so designed that when the two-wing engine units are removed, with their length of wing surfaces, the two end pieces of the wings can be moved inwards a corresponding amount, the wing surface being thus somewhat decreased and the machine turned into an ordinary single-engined low-wing monoplane. If desired a more powerful engine can then be fitted in the nose, and among those given as possible power plants for this purpose is the 450 h.p. Napier "Lion." Conversely, if the machine is preferred as a twin-engined type, the central engine unit can be removed, a streamline nose being fitted in its place, and the machine then becomes a normal twin-engined monoplane, again with a choice of engines within certain limits of power, and subject to structural considerations. It might have been thought that all these changes repre- sented the maximum possible in the matter of adapting any- given type of machine to a variety of purposes and conditions, but there is a further series of changes possible by which the machine is turned into a seaplane. This has actually been done, and, we understand, very successfully done, and two photographs published on another page show the machine converted in this way. Presumably, the same changes to twin and single engine could be made in the seaplane type, so that it would seem that in the G.23 and all its modifications, Professor Junkers has produced a type with almost endless possibilities. The following description should be taken to refer to the Swedish-built machine that visited Croydon, and which is now in use on the Amsterdam-Hamburg-Copenhagen-Malmo service of the Aero Transport Co., of Stockholm. In constructional design the Junkers G.24.L is similar to the smaller, single-engined Junkers machines which are already familiar to readers of FLIGHT. That is to say, all- metal construction is employed, even to the fuselage and wing covering, which is in the form of corrugated sheet Duralumin. A feature of the wing construction of all Junkers machines, and which has been retained in the G.24, is the use of tubular spars and the entire absence of wing ribs. The tubular wing spars are placed against the top and bottom wing surfaces at fairly close intervals, and are con- nected by lengths of corrugated strip, riveted to the sides of the tubes. It would appear to be impossible to calculate the strength of such a wing by ordinary methods, but we believe that the Junkers Company have, as a result of a great number of sand loading tests, succeeded in evolving empirical formulae, which enables the strength of the wing in bending and torsion to be calculated very accurately. The wing structure is, of course, to a great extent redundant, and the argument advanced against criticism of the wing design is, that a large number of the corrugated strips could probably be broken without materially decreasing the strength of the wing, as the loads would be taken up by the other members, much as in our better known biplane structures, the incidence bracing takes over the function of a front or rear lift wire, should one of the latter break. The wing engines are mounted on engine bearers built integral with the wing structure, the entire section of wing being built as a separate unit and removed with the engine, so that the effect of removing the two wing engines and re- placing the two end sections is to shorten the wing span by an amount equal to the width of the two wing-engine sections. From the photographs it will be noticed that the wing engines are carefully cowled-in, with the fairing THE JUNKERS G.24.L :'••• Three-quarter rear view. Note how the wing engine cowling is faired into the wing surface 562
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