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Aviation History
1932
1932 - 0365.PDF
FLIGHT, APRIL 22, 1932 The Stieger ST. 4 Built by General Aircraft, Limited, of Croydon, and incorporating the Monospar System of Construction invented by Mr. H. J. Stieger, this machine is a four seater fitted with two Pobjoy "i?" Engines. That the Stieger System does give low structure weight appears to be proved by the fact that the ratio of gross weight to tare weight of the ST. 4 reaches the high value of 1-84 so that the machine carries as normal disposable load 84 per cent, of its own weight IN presenting to our readers an illustrated description of the Stieger ST-4 monoplane this week, we are faced with a slight difficulty arising out of the fact that, at the moment of writing, the machine is not entirely finished. In consequence it is not possible, for one thing, to publish photographs of the machine in its completed form, and, secondly, actual performance figures, etc., are not available. However, as the machine is cer tainly an unusually interesting one, both from the de signer's and from the user's point of view, we have thought that the best procedure would be to deal with the ST.4 this week mainly from the structural aspect, leaving the subject of the practical or operational features for a subsequent article. In order, however, to give our readers a slightly better idea of how the ST.4 will appear when finished, we have had blocks made of some photo graphs of a scale model, and these will be found in the description which follows. series of Warren girder ties around the periphery of the girder. In point of fact, the fuselage girder of the earlier machine approached less to the monospar principle than does that of the new machine, the pyramid bracing being compressed into the cross-sectional area of the girder, while in the new type the struts and diagonal tie rods of the monospar wing system are repeated in the fuselage structure (rear portion). In fact, the fuselage structure of the first machine resembled more nearly the Breguet type of construction, with a box section single spar in the bottom of the fuselage. To anyone who had an opportunity of examining closely the details of the first small experimental machine designed by Mr. Stieger, the far greater simplicity of the ST.4 is apparent instantly. Not only the fuselage, but the wing structure is much simpler, and must have been far less costly to build. This, of course, is the usual and natural process of development of all types of aircraft, but is, Before turning our attention to the structural details perhaps, slightly more obvious in the new ST.4. the ST.4 it may be of assistance to our readers if we The ST.4 is a twin-engined low-wing monoplane of the mention quite briefly that the machine is designed as a full cantilever type. Great care has been taken to keep fourseater twin-engined monoplane, ability to maintain the aerodynamic design "clean," and an order to avoid height with one engine out of action having been kept too great interference between fuselage and wing roots, the prominently in view during de sign. By clean aerodynamic de sign, low structure weight, and light engines, it is thought that this desirable quality has been attained, although definite proof in the form of actual test flights must still be awaited. A cruis ing speed of approximately 115 m.p.h. (185 km./h.) has been aimed at. Structural Design In the design of the machine to be marketed shortly by General Aircraft, Ltd., of Croy don, Mr. Stieger has applied his monospar principle of construc tion not only to the wing, but also, to some extent, to the fuselage. Perhaps some of our readers may remember that some thing of the sort was done in the case of the first experimental machine designed by Mr. Stieger and the Mono-spar Company, and built by the Gloster Aircraft Co., Ltd., at Brockworth. That machine (see FLIGHT of July 10, 1931) was purely experimental, and the details, although some what similar in general principle, differed very materially from the present type. Both wing and fuselage were of monospar con struction, but the wing spar as well as the fuselage girder em ployed a different formation of the structure. The spar, it may be recollected, had a single flat duralumin web, with triangular holes stamped out for lightness, while the booms were built up to form a tube of somewhat irregu lar contour. The fuselage girder was of square cross section, and consisted of four " D "-section APPEAR : A composite photograph of a scale model of the ST.4. booms held apart by tubular AS 11 J™"-J? the pob]oy engines will not be of the totally-enclosing type. struts, and braced by duralumin The actual cowiing (FLIGHT Photo.) sheet stamped out to form a B2
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