Tension bolts are widely used in engines, in machinery of various kinds, and in structures. They have unique advantages in their contribution to ease of assembly and dismantling. They also give a comparatively rigid and compact joint, and from the standpoint of static strength are extremely efficient. Unfortunately they have not got a good reputation from the standpoint of fatigue. Some designers go to considerable trouble to avoid them. Others accept their limitations and ensure safety by care in detail design and by adopting conservative figures for design stresses. Where necessary, a limitation is placed on working life, at the expiration of which the nut and bolt are replaced by new ones.

Early in 1946, when work on guided weapons had only just begun in the United Kingdom, it became clear that there was a future need for a long Range, preferably over land, for the testing and development of guided weapons. Such a Range could not be located in the British Isles, and a survey throughout the British Commonwealth indicated that Australia was most likely to provide a suitable site. Therefore, a party of Ministry of Supply and Ministry of Aircraft Production personnel under the leadership of Lieut. General (now Sir John) Evetts carried out a preliminary survey in 1946, selected a site in South Australia which appeared most suitable and submitted a detailed report to the Ministry of Supply.

Aircraft have been used for agricultural purposes for at least thirty years. Probably the first country to use them to any extent in agriculture was the United States where there are now probably some 7,000 or more aircraft in more or less continuous employment on some aspect of agricultural aviation.

Up to the present, although many countries, since the end of the Second World War, have employed aircraft on agricultural work, the total world employment of aircraft on this activity has been small in comparison to that obtaining in the U.S.A.

The aviation industry has not yet given much attention to the development of rotary winged machines as specialist agricultural tools which would help to make farming easier, more efficient and more productive. The emphasis is, and naturally has been, on the development of the immediately bigger markets for military aircraft. It is understandable, if unfortunate, that the farmer has to wait his turn well down in the queue of various armed forces specialists. He is waiting for aviation to turn the focus, some day, of its technical knowledge and research resources onto the way that the versatility, manoeuvrability and usefulness of the helicopter can be used to grow more food, timber, wool and other natural products.

A method for providing lateral control at supersonic speeds by means of control surfaces located on nacelles or on the fuselage is described. These surfaces are arranged so that they affect the pressures over adjacent wings, and hence produce a rolling moment. The note includes the results of calculations and of a limited number of measurements which enable the effectiveness of such controls to be estimated.

Several methods are available for the solution of problems of forced vibration of systems with nonlinear elastic characteristics. Of these, the Martienssen, Den Hartog and Rauscher methods may be applied even if the restoring force characteristic is only known graphically, while the Duffing and Perturbation methods are only applicable when the restoring force characteristic is expressed in a convenient mathematical form. Successive approximations are used in the Duffing, Perturbation and Rauscher methods and therefore any desired degree of accuracy can be obtained. The Den Hartog and Martienssen methods give a two-term and one-term solution respectively.

Two methods are given concerning the following problems of linear algebra over the field of complex numbers (or, less rigorously, linear problems with complex coefficients): the solving of a system of linear algebraic equations, the inversion of a matrix and the evaluation of a determinant. The second method is especially suitable for use with computers. In addition to the usual numerical checking, the second method also provides an effective form check.

Accurate representation of a model field in an electrolytic tank requires, among other things, that the electrical conductivity of the liquid should be everywhere constant. Einstein and Sander and Yates have discussed the importance of other possible inaccuracies, and have shown that by correct probe design, circuit design and choice of electrode materials, these may be made very small. This note describes very briefly some experiments, carried out in two shallow electrolytic tanks, which demonstrate that the principal error can be that introduced by variations of conductivity produced by non-uniformity of temperature distribution in the electrolyte. The point is of particular importance since the results also showed that the mechanical design of the tank can have a vital bearing on the achievement of uniform temperature.

Figure 1 is a set of S-N curves for DTD. 150, taken from Rotol Structures Department Report No. 337. It is difficult to estimate N accurately on the flat part of the curve, and estimates of fatigue life by different people can be very different. Fig. 1, although based on scanty test results, is typical of S-N curves.

I wish to thank Mr. Wingham for his clearly relevant criticism of the proposed noseplane layout. I would suggest that the trouble which Mr. Wingham forsees might be avoided by mounting the noseplane as low as possible, as shown in the figure, with careful detail attention to engine positioning, alignment and air intake configuration. Also, the servo-plane would be relatively small and, trailing the air stream, cause little disturbance—surely, too, the high rear mounted mainplane now shown would exert a major smoothing effect on the general air flow pattern—per Jetstar and Caravelle?