An attempt is made to assess the rate at which failures occur within a group of similar structures, or structural components, when each structure is subjected to the same set of applied loads. The structures are similar in every respect except for small inherent differences in strength from one structure to another. On infrequent occasions the applied loads may be so intense as to destroy the weaker members of the group. For the problem in which the structural strengths are distributed within the group in a “normal” fashion, and when the frequency of severe loads diminishes exponentially, it is found that the rate at which failures occur within the group of structures is governed by two simple non-dimensional parameters. Numerical values of these parameters are studied more fully.

For supersonic wings it is known that the presence of a tip reduces the lift and the performance compared with the corresponding values for the two-dimensional wing. It appeared from some work by K. Stewartson that the addition of a vane at the wing tip might counteract this effect. The purpose of this paper is to determine the effect due to the presence of the vane. For this purpose a wing in the form of a semi-infinite wedge whose leading edge is swept back is supposed placed at incidence to the flow, with a symmetric triangular vane with diamond-shaped base attached to it, its vertex being at the tip of the leading edge, and its plane of symmetry parallel to the flow. The problem is of the “conical field” type and is solved by the method of S. Goldstein and G. N. Ward.

The problem is divided into its anti-symmetrical and symmetrical parts. The results obtained in Ref. 1 are applied to determine the field in each case, both outside and inside the Mach cone of the vertex.

The effects of distortion on the longitudinal stability of swept wing aircraft at high speeds (sub-critical Mach numbers) are considered on a quasi-static basis. The method is based on the theory of Gates and Lyon but involves some extension of this theory.

The treatment of wing distortion is considered in some detail and the effects of built-in twist and camber and wing weight are included, using the so-called superposition method. The application of the analysis of Lyon and Ripley for investigating fuselage, tail and control circuit distortion is suggested, but means of modifying and simplifying this procedure where desirable are put forward.

The analysis is illustrated by means of a simple example of a swept wing fighter aircraft for which wing, fuselage and tail distortion effects are considered, and the results are discussed with reference to the individual and combined distortion effects, as well as the effect of compressibility.