A considerable amount of theoretical investigation has been undertaken recently, into the stress concentrations arising in the vicinity of cut-outs in aircraft pressure cabins. Papers which analyse the stress concentrations around circular, elliptical, and square reinforced cut-outs, under various loading conditions have been presented by Mansfield, Hicks and Wittrick.

In all of these investigations, the problem of the cut-out in a cylinder has been reduced to a problem of an infinite plane sheet containing a hole, and the effects of the curvature have been generally assumed to be insignificant.

The theoretical study of heat transfer in ducts and passages which are not circular is difficult. In addition to geometrical and hydrodynamic problems, thermal aspects such as non-uniformity of heat transfer at the section boundary, increase the number of variables to be taken into account. The popular and perhaps simplest technique for the prediction of heat transfer in forced turbulent convection in non-circular ducts, is to use the more easily determined equation for an equivalent circular section. The form of the equation, which is used to correlate experimental data for the simpler case of heat transfer in the circular section, may be derived from considerations of similarity or alternatively by dimensional analysis. (Reference may be made to the classical work of W. Nusselt at the early part of the present century for the derivation of such an equation.) The equivalent circular pipe is equivalent in two respects. It is a pipe which has the same pressure drop and same heat transfer as the non-circular duct under consideration for the same conditions. The diameter of the equivalent pipe which replaces the non-circular section will be discussed later.

A survey is made in retrospect and prospect of the field of VTOL aircraft. The helicopter and the new VTOL aircraft, although historically separated and differing in appearance, belong to the same family of VTOL aircraft. The dominant parameter in this family is the disc loading, giving the two fundamental types of actuator disc—open disc or rotor and buried disc or fan. Noise and vibration criteria are discussed. The rotor is subject to fundamental aerodynamic limitations, which give speed limits for the pure rotor as well as the rotor compounded with a fixed wing. Rotors are subject to scale effects which limit the economic size of helicopters. Engine requirements for helicopters are discussed. There are three basic types of helicopter. Their characteristics, economics and uses are examined.

Following upon an experiment on the subjective effects of jet engine noise we have recently undertaken a similar experiment, this time on the subjective aspects of helicopter noise. The purpose of the earlier experiment was to determine the reliability of various methods of rating based on spectrum analysis, so far as comparisons between jet- and piston-engined aircraft are concerned. The main objective of the present experiment was to find if these methods are applicable to the pulsating types of noise characteristic of helicopters.

The basic objective of air traffic control in military flying is, of course, the same as in any other flying; to enable all aircraft to fly safely throughout each flight with the maximum freedom to attain their purpose efficiently. In practice, this necessarily involves the imposition of conditions and restrictions, and it is one of the main aims in the development of air traffic services to increase both the safety and flexibility of aircraft operation with the minimum restrictions. In progressing this we fully recognise the needs of civil aviation and, contrary to some public misconceptions of civil/military conflict in air traffic control, a joint approach is made at all levels to resolve A.T.C. requirements.

In a recent technical note, Squire discussed the approximate solution of certain second-order linear differential equations by the method attributed variously to Riccati, Madelung, Wentzel, Kramers and Brillouin (the W.K.B. method), and others. The problem of eigenvalues, frequently met with in this type of equation, does not, however, appear to have received much attention by this method, and in this note a simple formula is developed which appears to give excellent numerical results in many cases.

The process of atomisation is of primary importance in several branches of engineering, such as in the combustion of liquid fuels, in the chemical industry, in operations involving drying, evaporation, absorption, and so on, in fire-fighting and the production and dissipation of fogs and in agriculture.

In agriculture, the spraying of small drops is employed in the dissemination of insecticides, herbicides, etc., for the purpose of crop protection, and the spraying of large drops is used for overhead irrigation.

Since the advent of the atomiser, a hundred years ago, the engineer has been in advance of theory in his practice of atomisation. For lack of fundamental data he has had to rely upon laborious hit and miss experiments to obtain a design suitable to a particular requirement. Thus the atomiser has been a fruitful avenue for the inventor. Its small size and apparent simplicity has, however, deceived many into the belief that the problem is simple. Research over the last thirty years has proved this to be anything but true, and even now our knowledge is still extremely limited.

MR. Hazell has outlined some of the future improvements both in performance and in experimental facilities—such as attitude measurement or control— which it is hoped to be able to offer for Upper Atmosphere Research in the sounding rocket Skylark. I propose to try to look further ahead and, in particular, into the future possibilities in the United Kingdom of upper atmosphere and space research in earth satellites.

But before doing this I should like to rehearse briefly some of the arguments which suggest that sounding rockets and earth satellites will have a complementary part to play in upper atmosphere and space research in the future.

Natural frequencies of free flexural vibration of rectangular plates may, in many cases, be considerably increased by attaching to the plate one or more elastic stiffening ribs parallel to one edge, or by casting or machining the plate and stiffeners integrally.

Hoppmann has determined by a semi-empirical method the natural frequencies of an integrally stiffened simply-supported square plate, using the concept of a homogeneous orthotropic plate of uniform thickness having elastic compliances which are equivalent to those of the stiffened plate. Filippov has obtained the exact solution for the fundamental frequency of a simply-supported square plate having a number of equally spaced stiffeners and has considered the effect of point loads applied to the stiffeners in a direction perpendicular to the plane of the plate.

Automatic navigation systems for aircraft often use gyroscopes to measure the changes in the direction of motion of the aircraft they are controlling. These measurements are fed back to the mechanisms moving the control surfaces of the aircraft.

Such a system is usually designed, in the first instance, assuming the aircraft structure to be rigid and such that the system is then stable.

Now suppose the aircraft structure, considered elastic, is disturbed in flight by, say, a gust. Normal modes of vibration of the structure will be excited, the resulting oscillations will be detected by the gyroscope and fed as error signals to the control surface actuators. If the actuators are capable of following these error signals, the control surfaces will also oscillate, exciting the structure further and so completing the cycle. This cycle may be unstable.

The flight plan of the supersonic transport demands efficient aerodynamics and propulsion over a wide range of speed and altitude. As an example, the typical trans-Atlantic flight shown in Fig. 1 demonstrates that apart from cruising efficiently at, say, M = 2·2 for 2.500 n.m. at altitudes from 50,000 ft. to 65,000 ft., the aircraft must also be efficient at subsonic speeds. This is particularly true on the portion of the flight after the normal stage length, i.e. the diversion and hold, since the fuel required here must be carried the whole way and the “ growth factor” on aircraft size is large.

I would like to preface my remarks by gratefully acknowledging the inspiration I have received from my colleagues and others with whom the problems I shall talk about have been discussed, and by making it clear that, although my views are naturally coloured by the work on which I am engaged, they must not necessarily be taken as the official views of the Air Registration Board.

The supersonic aeroplane, due to its novelty, presents the three main types of airworthiness problem in a more pressing form. These are: knowledge of the environment; knowledge of what the aeroplane must be able to do in that environment (which includes a clear idea of acceptable risk); and obtaining, before passenger service, the necessary confidence that the intended safety level will be achieved. I can only touch on a few of the individual problems.

The General Elastic Analysis of the bending of a bi-metallic strip subjected to uniform heating has been made by Timoshenko. In this note we extend the theory to that of a tri-metal strip. General formulae for curvature and bending stresses have been developed. These formulae reduce to simple expressions if a particular choice of material constants and thicknesses is made. These latter formulae indicate that the curvature can be independent of the coefficient of linear expansion of the middle material and that it is possible to have the stresses at the inter-surfaces equal if a proper choice of the ratios of the coefficients of linear expansion of the three materials is made.

It has been recorded in the Annual Reports that String-fellow made a trip to California with Frederick Marriott, who had been the publicity agent for Henson's project of 1843 and the subsequent experiments of Henson and Stringfellow. Marriott, who had become editor of the San Francisco News Letter, began to interest the Californians in a project of a large aeroplane partly lifted by gas, a project which had been suggested in previous years without number.

What is the normal practice of a reasonably good farmer in the matter of fertiliser application to both arable and grass crops? First, there is such a wide disparity between the practice of a good farmer and the rest that it can only be hoped that all will soon be brought up to the good standard. A recent survey showed that about 50 per cent of temporary grass and 70 per cent of permanent grassland in England and Wales still receive no nitrogen fertiliser.

Normal application to both temporary and permanent grassland (for light and medium soils) is three to five cwt. of a compound (12: 12: 18) plus two applications of nitrogen, or expressed as straight fertilisers:

The words “automatic techniques” used in the title of this paper are interpreted as applying to all aspects of the Air Traffic Control complex, in which the latest electronic and electromechanical developments and techniques might prove beneficial. Navigational capability, communications efficiency, data processing, planning and dynamic displays, and conflict detection can all be improved, for example, by equipment incorporating various degrees of automation. While it is easy to list such improvements, it is much more difficult to relate their value specifically to a particular Air Traffic Control problem at a particular centre, and to recommend in which respects money or effort expended by the Government responsible would bring them the greatest or most immediate benefit. In fact, experience shows that each case differs and requires special study and consideration so that any difficulties currently existing or foreseen can be expressed in terms that facilitate rational engineering solutions.