Heat addition in the external flow around a supersonic aircraft may produce a field of increased pressure and thereby a propulsive and a lifting force. Less specifically, such effects could be produced by alternative processes involving the gradual expenditure of energy stored in an aircraft, and, according to the process, could be available at hyper-, super-, or subsonic speeds. A generalised study is made of associated effects on cruising range. Results are presented as performance “frameworks,” within which future experimental or analytic data should define regions of feasibility for particular systems.

The paper presents a solution to the buckling of infinitely long plates when they are reinforced by transverse stiffeners possessing both torsional and flexural rigidity. The cases of both edges being clamped and simply-supported are dealt with. Numerical results are presented for the ratio of torsional rigidity to flexural rigidity as obtained with a thin-walled circular tube. When the stiffeners are completely rigid, in which case the individual panels are clamped along the transverse edges, the results obtained are in agreement with existing solutions for isolated rectangular plates.

The stress concentration factors for a family of square holes, with varying degrees of curvature at the corners, and with varying amounts of compact uniform reinforcement on the boundary, have been computed for each of four loading cases. Poisson's ratio was assumed to be 1/3.

A method is described for the determination of the oscillatory aerodynamic coefficients for a helicopter rotor in forward flight. The method treats the blades and the recirculating wakes on a three-dimensional basis, but certain approximations are made so that the problem is tractable. In particular it is assumed that the downwash effect of a wake sheet beneath the rotor can be represented by concentrating the doublet distribution in the sheet in a single line of doublets.

A simple method is presented for calculating the heat transfer rate through a compressible laminar boundary layer. The temperature of the wall is assumed to be uniform, the viscosity being proportional to the absolute temperature with a ratio which may vary in an appropriate manner with position along the wall; the Prandtl number is arbitrary but greater than about 0·5.

The method assumes, following Lighthill, that heat transfer rates are determined mainly by the form of the velocity field in regions close to the wall. After applying the Ulingworth-Stewartson transformation the velocity is expanded in powers of the distance Y normal to the wall, three terms being retained. The first term, proportional to the skin friction, is zero near to a position of boundary layer separation. The second term is proportional to the pressure gradient and also to the wall temperature. Accordingly it can become close to zero when the wall is sufficiently cooled. The third term becomes important only when the first two are simultaneously close to zero and is proportional to the heat transfer rate. Since the three terms cannot, in fact, ever be all zero at the same position they form a uniformly valid non-trivial approximation to the velocity close to the wall.

With this velocity profile, and following similarity arguments first given by Liepmann, it is possible to reduce the integrated thermal energy equation to a first-order ordinary differential equation for the heat transfer rate, which is easily solved.

A comparison with an accurate solution of Poots, for a particular pressure gradient and wall temperature, yields agreement to within 1 per cent at one third of the distance from leading edge to separation and 3 per cent at twice this distance, with the error rising to 16 per cent at separation where the heat transfer rate is, of course, very low. The modesty of this error is very encouraging.

The fatigue properties of unmachined extrusions of high-strength aluminium-copper alloys are known to be lower than those of conventional fully-machined test pieces. Work described in this note has shown that the removal of a layer of metal 0·025 in. thick from the surface of B.S. L65-type extrusions results in an increase in fatigue properties to values approaching those obtained from the conventional laboratory test pieces. Because the removal of material from the surface is not always a practical proposition, other methods of improving strength have been examined and the effect of surface compressive stresses has been shown to be beneficial. Sufficient compressive stress can be induced by surface-rolling to increase the fatigue properties to those of conventional specimens, but this method can only be easily applied to round sections and it is suggested that shot-peening or vapour-blasting could be used for more complicated sections.

The fatigue life of a pin-jointed connection can be optimised by using a moderately high degree of interference between the loading pin and plate. Where a joint has to be assembled in confined conditions, difficulty may be experienced in inserting the interference-fit pin and one possible solution is to use a pre-assembled interference-fit bush in the plate, leaving only a light interference-fit pin to be pressed in on assembly of the joint. It is shown that a relatively thick bush of diametral ratio 4/3 will give a reduction in shear stress concentration factor for the plate comparable with that obtained with a solid pin, but that maximum benefit is not obtained with a thinner bush of diametral ratio 8/7. Where thin bushes are essential in order to maintain the ultimate tensile and fatigue strengths of the plate and /or the ultimate and fatigue strengths of the pin, the shear stress concentration factor for the plate is reduced as the modular ratio of bush to plate is increased and as the interference fit of the loading pin in the bush is increased.

Curie and Skan have modified the approximate methods of Thwaites and Stratford to predict separation properties of laminar boundary layers for flow over an impermeable surface. The work of Curie and Skan has been extended by Curle to include the estimation of laminar skin friction for the whole flow. The purpose of the following note is to compare the approximate methods of Curie and Skan and Curle with the numerical results given by the author for flow past a circular cylinder. It is found that there is remarkable agreement between these approximate methods and the exact numerical solutions. This indicates that these methods can be used widely, both on account of their simplicity and their accuracy.