GB365280A - Improvements in or connected with sheet metal spars particularly adapted for use in aircraft structures - Google Patents

Abstract

365,280. Metal spars for aircraft. STEEL WING CO., Ltd., Gloster Works & Aerodrome, Hucclecote, and EMBY, D. H., Old Vicarage, Ampney Crucis, near Cirencester, both in Gloucestershire. Dec. 20, 1930, Nos. 38440/30 and 25833/31. [Class 4.] Metal spars for aircraft have booms formed from two or more metal strips so corrugated and bent that the borders of the strips coincide and are fixed together while other parts of the strips are spaced apart, two such looms being connected together by distancing struts and diagonal bracing embraced by the outer borders of the booms. Fig. 1 shows a spar having booms each formed from two strips a, b having coterminal edges a3, a4 and central portions a<5> with intermediate portions spaced as shown. The edges a<3>, a<4> and central portions a<5> are secured together by hollow rivets those securing the former passing through spacing tubes. Vertical struts c bent as shown and provided with liners c<6> at their ends are secured to the edges a<3>, a<4> by bolts d passing through distance tubes d<1> or by separate rivets. Diagonal bracing e of channel section expanded at the ends and fitted with strengthening pieces e<2> are secured to the booms also by the bolts d or rivets which secure the struts. Lightening holes c<5> are formed in the struts c. Various modified booms are described. The strip a may be in two parts with flat overlapping central portions, upturned at the edges to interengage, or the strip b may be of channel section with rounded corners, or strips with polygonal instead of curved corrugations may be used. Fig. 8 shows a boom made from four pieces overlapping at the centre and Fig. 9 a boom made with three strips two of which fit closely together. A boom formed from two strips so bent as to form rectangular hollow spaces at the corners also is described with an additional strip secured over the central flat portion. Figs. 10 and 12 show other modifications. The spacing of the rivets bracing the edges a<3>, a<4> together is varied to suit the load on the spar and the thickness or number of the strips forming a boom may be varied for the same purpose.