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IN the August, 1929, issue of Aircraft ENGINEERING appeared the first technical description of his single‐spar wing, contributed by Mr. H. J. Stieger himself. The Mono‐Spar wing had then only just made its appearance, and a specimen, showing the principles of the invention, was then creating great interest at the Olympia Aero Show, on a stand which was visited by every aeronautical engineer who came to the exhibition. The Air Ministry had already shown its interest in the wing, and official tests carried out on an experimental wing to its order were referred to by Mr. Stieger in his article.

No. 325,041. Aircraft spars. —Chorlton, A. E. L., 55, Lower Belgrave Street; Haig, R. A. de H., 5, Clarendon Street, and Stieger, H. J., 76, Somerset Road, Wimbledon, all in London. Dec. 7, 1928, Nos. 36,131/28 and 18,692/29. [Classes 4 and 20 (iv).]

THE relative merits of the monoplane and the biplane have often been argued, and the respective advantages which, up to the present, have been claimed on either side still leave the solution of the question in doubt. Until now the bias in this country has been towards the biplane, but, as the knowledge with regard to methods of obtaining torsionally stiff structures grows, the pendulum is bound to swing the other way.

THE increasing use of low‐wing monoplanes has emphasized the susceptibility of this type of aeroplane to detrimental wing‐fuselage interference. This interference was first indicated by the inferior aerodynamic characteristics of the low‐wing as compared with the high‐wing monoplane.

ONE of the outstanding problems in design of stressed‐skin structures is that of ensuring adequate rigidity to guard against instability failure or buckling of the parts of the structure which have to carry compressive loads. Such structures consist usually of a scries of longitudinal members or stringers with intersecting transverses or frames. Apart from the waving of the skin itself in the panels thus formed, which must usually be tolerated and which remains modcrate in extent so long as the stiffening members themselves do not deflect, and docs not impair the ability of the structure as a whole to continue to take increasing load, there are two possible forms of buckling. The stringers alone may bow between adjacent frames, which remain fixed, or longer waves involving both stringers and frames may occur. The strength to resist the first type of failure can be estimated with reasonable accuracy by treating the stringers as struts of length equal to the frame spacing, and gives a design criterion for the stringers. It is fairly evident that for this rather elementary treatment of the stability problem to be adequate it is necessary that the frames themselves should have a certain minimum rigidity. It is in determining this minimum rigidity that the question arises of the possibility of the second type of buckling, which will be specially considered here. Whether this will, in any practical case, be sufficient to fix the size of frame required, cannot of course be stated in general terms, as this will depend on the local loads which the various frames may have to carry. Fig. 1 shows the type of deformation involved, for the special case of the side of a monocoque fuselage, which may be subjected to compression due to lateral bending under the action of rudder and inertia loads. The mode of waving is specified by the longitudinal wave‐length (two frame spaces in the illustration) and by the transverse wave length, which may be the full width of the panel or something less than this.

A casing 1 encloses conical chambers 6, 7 and has an end portion 50 enclosing a double frustoconical chamber 52, 53, the space between which and the casing is filled with sound absorbent material such as asbestos or coke, or sheet asbestos may be wrapped round the frusta. The conical passage 53 leads to an eccentric aperture 4 in the base 2 of the chamber 6 and, likewise, the chamber 6 leads to an eccentric aperture in the base of chamber 7. Behind each eccentric aperture is located a deflecting plate 10 comprising two portions 11, 12 of which 11 is inclined to the longitudinal axis of the silencer casing, while the portion 12 is parallel thereto. The deflectors may whirl the gases in the same or in opposite directions. The chamber 52, 53 allows initial expansion of the gases. Specification 366,257 is referred to.

THE General Aircraft Company's S.T.10 monoplane was the winner of this year's King's Cup Race. Fitted with two Pobjoy Niagara radial engines which develop 90 h.p. at 3,500 r.p.h. for a weight of 145 lb. it maintained an average speed in the final round of 13·16 m.p.h. piloted by Flt.‐Lt. Schofield.

Gases to be silenced are caused to partake of a whirling motion close to the inner surface and past the reticulations of the reticulated wall of a chamber arranged within an outer casing. Substantially the whole of the gases flow past the reticulations from a relatively restricted inlet to an outlet, and the whirling motion may be imparted by a deflector plate or curved vane or by a tangential inlet. A casing 1 has at one end a portion 50 terminating in a hemispherical cap 51 with inlet 54, and at the other end a plate 3 with eccentric outlet 5 and a pipe 9 attached thereto. The interior of portion 50 is separated from the interior of the rest of the casing by a plate 2 having an eccentric aperture 4 behind which is a deflector plate 10. Within the portion 50 are hollow conical frusta 52, 53 abutting at their larger ends. The small end of frustum 52 is connected to the inlet 54, while the small end of frustum 53 is connected to the aperture 4. Within the casing 1 are a pair of frustoconical chambers 6, 7 with reticulated walls, the smaller end of chamber (5 entering the larger end of chamber 7 eccentrically, and the smaller end of chamber 7 terminating in the outlet pipe 9. The deflector plate 10, adapted to whirl the gases, is located close to the wall of chamber 6 and comprises a portion 11 inclined to the longitudinal axis of the casing with an edge in contact with the internal surface of chamber 6, and a portion 12 arranged parallel to the axis of the chamber. A similar plate is located behind the entrance to chamber 7. The spaces between the frusta 52, 53 and the outer casing are filled with sound‐absorbing material 57 such as asbestos or coke, or, alternatively, sheet asbestos may be wound round the frusta. The space between the chambers 6, 7 and the casing serves as a cushioning space and may also be filled with sound‐absorbing material such as steel wool, or fibrous asbestos or with material adapted to absorb poisonous gases. An opening 13 may be provided for the removal of solid matter. In a modification (Fig. 2) the inlet pipe 59 is secured to an end plate 58 forming the base of the conical chamber 60, the smaller end of which passes through an eccentric opening in diaphragm 2 into a cylindrical reticulated chamber 15 supported by a diaphragm 16, and is extended by a pipe 62 adapted to direct the gases on to a portion 20 of a deflector plate on the side remote from an aperture 21. The gases then pass through aperture 21 and flow along the inner surface of the chamber with a gyratory motion. A second deflector plate 22, similar to the first, is situated in the chamber 15. In both constructions, the second deflector plate may produce whirling in the same or an opposite direction to the first. In a modification, the reticulated chambers are of spherical form. In Fig. 4 gases enter the chambers 38 tangentially by a pipe 39 and leave by pipes 40, 41. In Figs. 5 to 8 (not shown) different arrangements and combinations of chambers within the casing are described, and in two of the forms, suitable for aircraft, the casing is conical and provided at its rearward or smaller end with a number of perforations to give a gradual outlet. Specification 366,257 is referred to in the Provisional Specification.

THE article published in this issue on the installing and installation‐testing of the Rolls‐Royce “R” engine fitted in the Supermarine S.6 B. seaplane, which made the Schneider Trophy the permanent property of Great Britain and also set up a new world's speed record, is of far more than mere historical interest.

IN setting out to study the exhibits at a great international exhibition such as that recently held at Olympia, one is naturally inclined in the first place to walk round the exhibition as a whole, so as to form some general impressions before examining the individual stands in detail. In the same way it is proposed in this article to make a general review of the exhibition as a whole before embarking on detailed comments on particular items of interest which were to be found at the various stands. It is by no means an easy matter to analyse the general tendencies of design as demonstrated at the Exhibition for the principal reason that there is so little to go upon in the way of existing standards. No less than nine years have passed since the previous International Aero Exhibition at Olympia, and during that long period there has been no general exposition of British aircraft design. It is true that there has been a succession of International Aero Exhibitions in Paris and that last year, for the first time since the war, there was an International Aero Exhibition at Berlin, but British design has been very poorly represented at any of these or the several other exhibitions held on the Continent.