Advanced textbooks of strength of materials dealing with the shear centre give examples of the simplest sections only (e.g., Ref. 1, Art. 8). Numerous articles in the technical press are devoted to the subject, and the method to find the shear centre of any open section is now well established (Ref. 2). However, the number of readily usable solutions for sections common in practice, is small. Consideration in this paper is given to a more complicated section, fairly common in practice, and a formulae is derived for the location of its shear centre. The section is a lipped channel, symmetrical about one axis, and the paper is followed by a diagram that enables the shear centre position for various ratios of lip to leg and leg to web to be read off.

Measurements of momentum in regions of turbulent mixing show that an analogy exists between the processes of turbulent and molecular balance which enables a rational application of the differential equation of thermal conduction to the propagation of turbulent momentum to be made. This fact forms the basis of a new phenomenological theory of free turbulent flows.

In modern aircraft, the flying performance, design of the airframe, engines, armament, or the military purpose are the features of principal interest, while the efficiency of the undercarriage is usually known only to a limited number of specialists. Shock-absorber legs, wheels and brakes are now such highly developed structural components that they deserve special attention. In the following, modern types of wheels and bra kes are described in detail and following, modern types of wheels and brakes are described in de the theoretical basis for the calculation of the landing process discussed.

The rocket goes far back into history. In the Thirty Years’ War, it played a conspicuous part in the capture of Philippsburg in 1645. During the Napoleonic Wars, General .Congreve used rocket projectiles to force the fall of Boulogne (1806) and of Copenhagen (1807). The latter town, for instance, received a total of 120,000 rockets. It may be concluded, therefore, that in former times, this type of projectile must have played the part of modern artillery.

The chief aim of the vibration engineer is to prevent the occurrence of structural failure due to excessive vibration. A secondary aim of only slightly less importance is to ensure comfort for personnel by the elimination of physiologically unpleasant vibrations; this consideration is a vital factor in the effective design of operational aircraft. The technique of vibration research is largely a matter of detecting and avoiding resonant conditions, and any method of predicting natural frequencies by calculation is welcome if only because it offers the possibility of reducing the practical testing programme.

Economical organisation and practically inexhaustible supplies of raw material in our country create exceptionally favourable conditions for the rapid development of the plastics industry. The raw material is drawn from the by-products of various branches of the chemical and agricultural industries.

By their technical properties, plastics present many advantages over many other materials. Some of them are as strong as metal, as transparent as glass, and as light as wood. Plastics are endowed with high dielectric properties, great thermo-stability, and low conductibility for sound and heat; they can be machined, pressed, moulded, and have a pleasing exterior.

It is just one hundred years ago, towards the end of March, 1843, that the invention or design of the first power-driven aeroplane, Henson's so-called “Aerial Steam Carriage,” was made public to the world at large. The centenary marks an important step in the history of heavier-than-air flight, and in view of the development arrived at in the aeroplane of to-day—its great size, immense power, long range, and astonishing speed—the event assumes, in retrospect, a greater interest and significance than has been hitherto accorded to it. It is fitting, therefore—the more so in that the ‘inventor’ was an Englishman—that this notable occasion should not be allowed to pass unnoticed in the pages of the Royal Aeronautical Society's Journal. There is, moreover, the additional reason that the Society can claim an indirect connection with Henson's project, in as much as John Stringfellow, who was closely associated with Henson in their joint struggles to produce a model flying-machine, was one of the Society's most active and enthusiastic members in its early years.

It has long been realised that there is a precise analogy between the properties of vibrating mechanical systems and those of alternating current electric circuits. It was from this analogy that the concept of “ mechanical impedance ” (more appropriately termed “ dynamic stiffness ”) was derived, thus enabling the theory of certain types of mechanical vibration, notably torsional motion, to be put on a more rational basis.

By means of analogous elements it is possible to represent a mechanical vibrating system, provided it includes no bending elements, by an equivalent electric circuit. The author has been unable to discover any full description of the process, and the object of the present paper is to set out the principles underlying the procedure and to illustrate them briefly by examples.

Airscrew blade stresses caused by periodic displacement of the airscrew shaft and the possibility of their elimination by elastic connection of motor and airscrew. are investigated.

In cases of tapered struts with hinged or built-in ends where the exact determination of the buckling load is complicated it may be useful to apply a method of successive approximations.

Let us first consider a bar of the length l with hinged ends under the action of the compressive force P. The differential equation of the bending line becomes

where v is the deflection at the section u, v with the moment of inertia I (u) and E is Young's modulus. At the ends of the bar the deflection v is equal to zero (Fig. I).

Multitudes of young- men are starting to study navigation. As a rule it is only after many months of painful work that they come to see what it is all about –many of them never get to that point at all.

In none of the books on navigation have I been able to find a simple picture, defining each step in the reasoning that enables us to navigate by the stars. Hence this effort. As set out here the principles can be grasped by anyone.