Patent GB-447520-A (GB)
Title: Improvements in or relating to spars for aircraft wings
IPC: B64C3/18
Filed: 1935-05-31
Abstract: 447,520. Aircraft structures. SHORT BROS. (ROCHESTER & BEDFORD), Ltd., and GOUGE, A., Rochester, Kent. May 31, 1935, No. 15822. [Class 4] A spar for use in the construction of aircraft parts such as wings and fuselages comprises upper and lower booms of T-section, the heads of the T's being shaped so as to extend parallel to the body contour and the legs being so arranged that the legs in the upper and lower booms are co-planar, tubular bracing members, end fittings in the bracing members each having an extended web and gusset plates attaching each of said webs to the leg of the boom. As applied to a cantilever wing structure, Fig. 1, upper and lower front booms a, b and upper and lower rear booms c, d are interconnected to form front and rear girders of a single rectangular spar, each boom being constituted by aT-section element extruded to approximately the correct form and then milled to conform with the wing contour and to give the necessary taper. The upper and lower booms of each girder are interconnected by bracing members in Warren girder formation, each member comprising a tubular element, Fig. 3, into the ends of which are fitted plug attachments, g, Fig. 4, of the type described in Specification 447,617, [Group X]. Members g are extruded or built up in an H- section comprising flanges g<1> curved to fit the tube to which they are riveted and a web g2 extended to form a tab g<3> adapted for attachment to the leg of the T-section boom by means of gusset plates h, h<1> The latter may be of non-uniform depth to accommodate for the differing thicknesses of the leg and of the tabs or may be of uniform thickness and either secured to the tabs through the intermediary of packing pieces or be joggled inwardly at the points of junction of leg and tab. The tube members may be cut away as shown at e<1>, e2, Fig. 4, to give accessibility for riveting. The girders are interconnected by transverse ribs with or without longitudinal stringers. Metal covering sections i, j are riveted to the heads of the T-section booms a, c and b, d, respectively. To obtain flush rivets, rivet holes a<3>, Fig. 6, in the heads of the booms are outwardly flared at a<4>, rivets k of comparatively soft metal, being inserted from the inner side of the head to project through holes in the covering plate which holes are only of sufficient size to accommodate the shank of the rivet. The arrangement is stated to be such as to cause the rivet head to assume the form shown in Fig. 7, when flattened and the edges of the rivet hole in the covering plate to be driven into flared hole a<4>. The wing nose comprises a metal plate l supported by riblets projecting forwardly from the front girder. Plate l is riveted to extended 'edges of plates i, j. Flush rivets are obtained by bending in the edges of the rivet holes in the plates i, j, as at i<4>, Fig. -8, and making the rivet shank to fit tightly in the corresponding hole in sheet l. The annular depression around each rivet is filled with composition and the wing varnished or painted to obtain a smooth surface.