During the past hundred years much data on the fatigue behaviour of a wide range of materials has been accumulated and it is now well known, as a result of service failures and laboratory tests, that stress concentrators whether mechanically formed or inherent in the material, can cause serious reductions in endurance.

The work described in this note forms part of a project being conducted at the Aeronautical Research Laboratories, Melbourne, Australia on the effect of stress concentrations on the fatigue properties of materials. The primary aim of the project is to establish a series of fatigue curves for different materials under a wide range of theoretical stress concentration factors and to attempt to find a basis on which to assess the notch sensitivity of different materials. The first investigation was carried out on 24S-T aluminium alloy and tests on two additional aluminium alloys, annealed copper and an alloy steel are in progress.

The chemist regards magnesium as a highly reactive metal for such reasons as the inflammability of its powder or foil in air, its active displacement of hydrogen gas from many aqueous chloride solutions and its position near the reactive end of the electrode-potential series. All these suggest that the metal would be unsuitable for constructional engineering. Yet engineers use alloys, rich in magnesium, up to 98 per cent. of the metal, for an increasing number of services, although the alloying elements do not, as a rule, greatly cut down, and may even increase, the corrosion rate. Their industrial use is possible because the liability to corrode, reckoned over a reasonably prolonged period, is not a definite property of a metal such as conductivity which is subject only to relatively small changes with alteration of environment, but is highly specific to metal-liquid and metal-gas systems. Moreover, these systems may undergo important changes with time owing to the intervention of films of corrosion products, and the rate of attack may be governed by the physical characteristics of these films which will vary with the adjacent liquid and gases. Thus in stagnant caustic alkalies magnesium may be reckoned as almost incorrodible because of the intervention of a film of hydroxide of the self-healing type which, in these conditions, is highly impervious to magnesium ions; but in the presence of alkali chlorides the corrosion product is physically different and rapid corrosion occurs. Many dilute acids attack magnesium rapidly but hydrofluoric acid scarcely at all, no doubt owing to the formation of a protective film of fluoride.

A meeting of the Society was held in the Lecture Hall of the Institution of Mechanical Engineers, Storey's Gate, St. James's Park, Westminster, London, S.W.I, on Thursday, March 22nd, 1945, at which a paper by Mr. R. H. Bound, F.R.Ae.S., F.S.E., M.I.M.E., A.M.I.A.E., on “Hydraulics for Aircraft,” was read and discussed. In the chair, the President, Sir Roy Fedden.

In section 8 the author's apparatus for the study of skin friction, based on direct application of the momentum theorem, has been described (Fig. 99). In a paper published in 1914, this idea was further developed and it was shown that it is possible to calculate approximately in this way the skin friction and the distribution of air velocities in different régime.

Reinforced rectangular plates find frequent application in the field of aeroplane structures, ship structures and allied fields. The stability of a structural element, if its critical load in compression is rather low, is normally influenced by its own weight. Usually the ratio of the body forces of the stiffened plate to the critical load is a considerable amount and the influence of the body forces of the plate and the ribs on the critical load of the stiffened plate is discussed here.

In this note (following Timoshenko), the extensional deformation of the middle surface during buckling is neglected, which greatly simplifies the analysis. Although it leads to an under-estimation of the critical load (of the order of 10 per cent at most) it is not likely to influence the general conclusions. Strain energy method of analysis is used.

In A. H. Stratford's interesting note in the August Journal, he assumes that an airline is presented with an aircraft of given performance, and must decide what is the best range for it to fly. Surely the practical case is the exact opposite: that an operator wishes to carry passengers or freight between two given points, and must choose between perhaps three or four available types of aircraft. Moreover, it is up to the operator to tell the manufacturers which feature he wants improved (e.g. fuel consumption, take-off distance, and so on), when he is ready to order replacements.

Secondly, Mr. Stratford wishes to replace the usual concept of direct operating cost per payload ton mile by that of per cent, profit, as a measure of the efficiency of operation over a certain route. While this may be a more realistic approach to the problem of a private airline company, operating over a single route, its merit is not so obvious for the large national or subsidised airlines, which are often required to fly unprofitable routes.

The dangers and other disadvantages of using air pressure in the strength testing of pressurised fuselages are reviewed. A technique in which water is used instead of air is described, and its advantages considered. References are made to future test methods, and particularly to the need for the application of pressure combined with aerodynamic and inertia loads.

In the early days of aviation in 1910 when Rolls, Egerton, Ogilvie and Grace were flying the open machines at the Aero Club's flying ground at Eastchurch, Grace made the interesting statement that in a few years aircraft design would develop under a continuous flow of invention in the same way as the motor car was then developing. Had Grace lived he would have been astonished at the truth of his prophecy, for the subject known at the Patent Office under the head of “Aeronautics“ has developed into one of the greatest industries in the world, and by the end of the year 1930 the abridgments on Aeronautics had become one of the stoutest volumes in the patent classification. In spite of this growth which marked out the subject for a department of its own, for some inscrutable reason the Patent Office then decided to mix up aircraft with ships and thenceforth have published these two subjects in a single group instead of keeping them separate as before that time.

The Society's All-Day Discussion on Aircraft Design Philosophy was extremely well supported and at one stage there were more than 350 members and visitors present. As is inevitable on these occasions there was insufficient time available for all those who wished to make a contribution to do so, even though the four lecturers had reduced their contributions to a bare minimum by presenting summarised versions of their papers.

With such an all-embracing title as Aircraft Design Philosophy it was obvious that some main channel of exploration would have to be chosen; that which evolved during the planning of this event was structural safety, as will be apparent from the discussion. The preparation of a summary of discussions presents a number of problems.

A Meeting of the Royal Aeronautical Society was held in the Great. Hall of the Institution of Civil Engineers, Great George Street, Westminster, London, S.W.1, on Wednesday, 19th December, 1945, at which a paper by Professor N. Feather, Ph.D., F.R.S., entitled “ Atomic Disintegration ” was presented and discussed. In the Chair, the President, Sir Frederick Handley Page, C.B.E.

The idea of the disintegration of the atom appeared first—as a notion seriously entertained by a scientist of repute—in the hypothesis put forward by Rutherford and Soddy in 1903, in an attempt to explain the phenomena of radioactivity as known at that time.

In certain types of aeroplane the empennage is carried on two tail booms emanating from the main body. In some cases the booms and tail plane form what is virtually a portal and in these circumstances a fairly simple approximation may be found for the stresses resulting from fin and rudder side loads. The method adopted follows the treatment given in the author’s paper, “The Stressing of Rigid Jointed Frames.”