The problem discussed is that of the elastic local instability of a uniformly compressed thin-walled strut composed of a number of flat component plates. The strut is essentially “ open ” in cross-sectional form, while reinforcing flanges are attached to the extreme edges. An overall stability equation, based on the small deflection theory of plate bending, is derived from the conditions which must hold at the common and extreme longitudinal edges of the strut.

It is shown that the critical compression stress induces a mode of buckling which involves a whole number of sinusoidal half-waves in the longitudinal direction. Furthermore, the number of half-waves is common to all component plates of the strut. The general’ stability equation—a zero determinant of high order—lends itself to expansion in terms of 4th order minors, which may again be expressed in terms of seven basic functions. A knowledge of these functions is sufficient for the solution of any problem, however complex, within the scope of the general analysis.

Application of the basic functions to the solution of three different problems yields results which indicate the need for considerable care in the design of thin-walled struts with reinforcing flanges. In struts of this type a longer wavelength of buckling is possible than is commonly associated with local instability problems.

A simple method is given for calculating, in incompressible flow, the spanwise and chordwise loadings on thin swept wings with symmetrical aerofoil sections and of moderate and large aspect ratios. The present note is based on, and continues, the investigation described in an earlier paper. The design of swept wings with given spanwise and chordwise load distributions, obtained by modifying the plan form of the wing or by adding camber and twist, is briefly considered, as well as the design of swept wings which give minimum induced drag.

This problem arose in connection with the stabilisation of the spar flanges of an aeroplane, where the spar passes through the fuselage. The fore-and-aft stabilisation of a compression flange in these circumstances may often be effected by means of intermediate supports, which are necessarily flexible, and the reliability of any calculations of buckling load is somewhat doubtful, mainly due to the difficulty of estimating the stiffness of the supports. In view of this it was decided in a recent design to consider a continuous support for the spar flange in the form of a thin horizontal web riveted to the flange and to the sides of the fuselage, and having a small member attached to its other edge.

The supersonic flow past a combination of a thin wing and a slender body of revolution is discussed by means of the linearised equation of motion. The exact equation is first established so that the linearised solution can be fed back and the order of the error terms calculated. The theory holds under quite general conditions which should be realised in practice.

The wing-body combination considered consists of a wing symmetrically situated on a pointed body of revolution and satisfying the following fairly general conditions. The wing leading edge is supersonic at the root, and the body is approximately cylindrical downstream of the leading edge. The body radius is of an order larger than the wing thickness, but is small compared with the chord or span of the wing.

It is found that if the wing and body are at the same incidence, and the aspect ratio of the wing is greater than 2 (M2-1)-½, where M is the main stream Mach number, the lift is equivalent to that of the complete wing when isolated. If the wing only is at incidence then the lift is equivalent to that of the part of the wing lying outside the body.

The presence of the body has a more significant effect on the drag. If, for example, the body is an infinite cylinder of radius a, and the wing is rectangular with aspect ratio greater than 2(M2-1)-½, then the drag of the wing is decreased by a factor (1-2a/b), where 2b is the span of the wing.

When these conditions do not hold the results are not quite so simple but are by no means complicated.