A brief survey is made of the way the flow develops about wings with leading edges swept at about 50° as the stream Mach number rises from a subsonic to a supersonic value. The shock pattern which occurs may be complex. Three aspects of the wing flow are discussed in more detail, including the possible conditions for shock-induced separation of the surface boundary layer. The effect of the changing flow pattern on the overall wing lift, drag and pitching moment is commented upon.

As man's conquest of the air was gathering momentum in the 1920s, there came a longing among explorers of the Arctic, to overfly the icy waters which had hitherto taken such a heavy toll in men and ships. Men who, like Wilkins, had already made their mark in sailing through the ice and walking over the eternal snows, looked to the aeroplane or airship as a wonderful observation platform and as a means of quicker travel. And of the great of many nations who tried their skill and courage in the early attempts to fly across the Arctic, George Hubert Wilkins stands out as greatest of them all.

There are three practical aspects to the problem of man powered flight: aerodynamics, physiology and engineering. There are many more impracticable aspects to man powered flight, including the philosophical, the fanatical and the sceptical, which unfortunately have not yet been included in the lectures of the Man Powered Aircraft Group but which will no doubt find their places.

The engineering aspects are fortunately fairly clearly defined, although there is likely to be a slight threat of interference with the aerodynamic problems.

The first basis for the design of any power-driven mechanism is an exact knowledge of the characteristics and capabilities of the power unit available. Without such information no designer is able to start on the initial sketch of the mechanism. The man powered aircraft is no exception and its designers have suffered in the past by insufficient knowledge about man's power. This may seem remarkable because until about two centuries ago almost all the world's work was done by muscle-power, and much of the muscle was human.

A polar-controlled missile is one in which manoeuvre is carried out by rotations about roll and pitch axes, that is, in the manner of a conventional aeroplane. This paper discusses some problems in the application of this form of control to homing missiles.

In comparison with the alternative Cartesian configuration, this method presents some special design problems. In the former case, it is often possible to resolve the motion into two planes and consider the pitch and yaw control systems as independent two-dimensional problems. This simplification is not possible in the case of polar control and it is usually necessary to consider the whole three-dimensional system. The equations of motion which result are, in general, not susceptible to analysis. Because of this, the design of control systems requires extensive use of simulators.

This note is devoted to the analysis of the initial buckling of an elastic sheet reinforced by a uniform non-buckling grid of stringers and skew ribs. The stringers and ribs enter the analysis through their influence on the stresses in the unbuckled sheet. Combinations of the following loadings in the plane of the reinforced sheet are considered: —

1. (i) uniform direct loading normal to the ribs,

2. (ii) uniform shear loading relative to axes perpendicular and parallel to the ribs.

In a recent article, H. Werlé, has described how the free spiral vortices on delta wings with leading edge separation suddenly expand if the incidence is increased beyond a critical value. His description conforms to a great extent with the results, arrived at during an English investigation of the same phenomenon (called the vortex breakdown), but the interpretations of the observations, suggested by the two sources, are different. Against this background it is felt that some further comments and some pertinent high speed observations, may be of interest.

In a Technical Note in the June Journal (p. 354), Dr. A. L. M. Grzedzielski discusses some aspects of the Matrix Force Method of Structural Analysis and in particular has raised objections to the concept of initial strains and its use by the present writers as an artifice in the treatment of cut-outs and modifications in structures. Dr. Grzedzielski asserts that the idea of initial strains is not valid if the flexibility matrix of the unassembled structural elements is other than purely diagonal. Unfortunately this assertion is just not true.