World interest in the development of a satisfactory fully automatic all weather landing system has increased considerably in the past year or so. Statistics on accidents reveal the disquieting fact that a very large percentage occur in the landing phase, either in poor visibility or in conditions where limited or misleading visual clues conspire to affect a pilot's judgment of the required vertical descent path. Factors such as the changed performance characteristics of large turbo-jet aircraft, higher approach and landing speeds and differences in the approach attitude of new aircraft all add to the pilot's difficulties during the landing operation.

Ten years ago it seemed that the solid propellant rocket engine could make only a limited contribution to rocketry. Although it was simpler and more compact than its liquid propellant rival it suffered from three serious drawbacks. The nozzle was uncooled and so the burning time had to be short, the entire propellant container was subjected to the full combustion pressure and temperature and therefore the inert weight of the engine was high and, since the specific impulse of solid propellants is in general lower than that of liquid propellants (because solids are partially reacted systems) the engine performance was consequently poor, and finally, no means were available for controlling the magnitude and duration of the rocket thrust. These facts were the foundation of the opinion, still held by some people, that solid propellant engines were only suitable as boosters or short burning time sustainers for small missiles.

The object of this paper is to give a brief account of the development of the study of hypersonic flow over the past three decades, and to stress some of the ways in which hypersonic flow differs from supersonic flow. In some of the early work on the subject a wrong emphasis was given to the study of flows with attached shock waves and to the nature of the shock boundary layer interaction problem, and it is only quite recently, mainly as a result of experimental work, that it has become possible to obtain a balanced picture of the important features of hypersonic flow fields. In the present paper real gas effects are not taken into account; in general, the inclusion of these effects will not markedly alter the picture given.

This paper is concerned primarily with some of the practical difficulties encountered in connection with the prediction of kinetic heating temperatures. Attention will be concentrated upon methods for estimating temperatures and heat transfer rates for practical aircraft designed to fly at Mach numbers up to about five.

One factor common to all kinetic heating calculations is the variation of temperature through the thickness of the boundary layer, with consequent variation of viscosity. At Mach numbers above about 3, these temperature variations also lead to considerable variations of other properties of air—which are commonly assumed to remain constant—even in classical compressible flow aerodynamics. These factors complicate the aerodynamic equations.

Flutter calculations were made on a fixed root model wing carrying a localised mass. Modes were calculated for the wing for certain conditions of restraint at the localised mass position, the choice of modes being based on observation of the behaviour of wind tunnel models under fluttering conditions. The general agreement between the calculations and experimental results was good and justified the extension of the calculations to conditions of localised mass loading that were not covered by experiment. The extended calculations show that there is an optimum spanwise position for a localised mass from the flutter point of view and, that this optimum position is related to the nodal line position in the overtone torsion mode of the bare wing. For values of localised mass parameters likely to occur in practice, flutter speeds can be estimated from calculations in a very limited number of modes, the choice of modes depending on the localised mass loading.

To anyone who knew Barnwell, however little, it is a great honour and pleasure to be invited to give this lecture as a tribute to his memory. I was too young and too remote to have known him well, but he was the first leading aeroplane designer that I ever met. Some older members of our Society will recall the aeroplane known as the Bristol Bagshot; and a few will remember that in its early flights it was found to suffer from an unexpected, and at that time new, form of control trouble. This occurred shortly after I had started work in the old Airworthiness Department at Farnborough, and the investigation of this new trouble, later to become known as “ Reversal of Aileron Control,” was put upon the new recruit. As a result I came to know Russell, as lively a young man at Bristol then as now, and was taken by him to see Barnwell. I was struck then, as afterwards, that here was a designer of insight and great kindliness who had learnt to combine engineering with the humanities to an unusual degree; and, as I realised afterwards, he had also learnt how to encourage and get the best out of the young men around him. And so I, like so many others, came to admire him.

Fretting is examined in its engineering aspects and then considered on a more theoretical basis. The mechanism of fatigue initiation by fretting is discussed, and also some of the methods proposed for the prevention of fretting. Some attention is also given to the fatigue life of joints when fretting does not occur. The difficulties that have been encountered in understanding fretting and assessing its consequences are thought to have a rather special significance. It is considered that there is now sufficient knowledge to put the whole subject tentatively on a rational basis, but more research is required to remove some of the uncertainties that still remain.

The tendency in the past has been to assume that when wakes or non-uniform total head profiles are fed into an axial compressor then substantially constant static pressure prevails at the entry, the variations in total head appearing as variations in velocity. This variation in velocity causes variation in incidence on the early stage blade rows and thus can give rise to excitation of blade vibration. This assumption is implicit, for instance, in References 1 and 2, but we think has been a common assumption by most of the people working in this field.

Where the compressor is fed by a duct of substantially parallel walls for a reasonable length ahead, such an assumption appeared justifiable. Such a duct when given an air flow test with its outlet discharging, for instance, to atmosphere instead of to the compressor, then the distribution assumed would normally be obtained and in fact many surveys of such ducts have been represented in this fashion. The object of this note is to show that, in fact, this distribution will not normally occur when the compressor is present and we may normally expect much more nearly a constant velocity into the compressor with attendant static pressure distributions to match with the total head variations ahead of the intake, with of course, the attendant curved flow to support the static pressure gradients.

The use of models for structural test investigations in the presence of kinetic heating effects is examined. The principal features of the complex process to be represented are discussed under the classifications external air flow, internal heat transfer, elastic response. Of these the second is found to influence most model design, and an analysis of a typical structure is included to illustrate the various contributions to internal heat transfer.

When considering the problems of take-off and landing from the pilot's point of view, the most important fact to remember is that he is a human being. This drawback immediately limits his capabilities in the operation of an aeroplane because the control of a pilot's actions is through the computer we call the brain. This computer, although extremely efficient in almost all functions, has nevertheless serious limitations when it comes, first, to speed of computation, and secondly, the number of functions it can compute at one time.

Until now the speed of operation of aircraft has been compatible with the speed of computation of the human brain that is governing the pilot's reactions. Also the size and complexity of the aircraft and the operation have been compatible with the number of functions the brain can compute at one time

Air dissolves in aircraft fuels to an extent directly proportional to the ambient pressure, so that when fuel which has been stored at sea-level atmospheric pressure is taken up to a high altitude, there is a tendency for air to come out of solution. In certain circumstances, which are later described in detail, air bubbles can be liberated very violently from fuels in aircraft tanks at high altitude and a thick foam can form on the surface for a short time.

The production of fuel foams by degassing has posed a certain problem; foams, being intimate mixtures of air and fuel, may well be inflammable; furthermore, the rising of air bubbles through fuel can result in the accumulation of electrical charge in the foam giving rise to the possibility of a source of ignition.

Figure 1 illustrates a structural problem which occurs in naval architecture, and which may also be of interest in the structural design of aircraft. Compressive loading is applied to one transverse edge of a stiffened flat sheet and reacted, not by equal compressive loads on the opposite transverse edge, but by shear forces along the two longitudinal edges. These shear forces, and the complementary shear forces acting on the transverse edges, arise from the connection of the stiffened sheet to adjacent structure. This situation arises, for example, at a ship's transverse bulkhead. The lower edge of the bulkhead is subjected to vertical loads applied by the ship's bottom structure, and these loads are transmitted upwards and outwards to the vertical edges of the bulkhead, thence to be diffused into the side shell plating.

When a body moves through air at very high speed at such a height that the air can be considered as a continuum, the distinction between sharp and blunt noses with their attached or detached bow shocks loses its significance, since, in practical cases, the bow wave is always detached and fairly strong. In practice, all bodies behave as blunt shapes with a smaller or larger subsonic region near the nose where the entropy and the corresponding loss of total head change from streamline to streamline due to the curvature of the bow shock. These entropy gradients determine the behaviour of the hypersonic flow fields to a large extent. Even in regions where viscosity effects are small they give rise to gradients of the velocity and shear layers with a lower velocity and a higher entropy near the surface than would occur in their absence. Thus one can expect to gain some relief in the heating problems arising on the surface of the body. On the other hand, one would lose farther downstream on long slender shapes as more and more air of lower entropy is entrained into the boundary layer so that the heat transfer to the surface goes up again. Both these flow regions will be discussed here for the simple case of a body of axial symmetry at zero incidence. Finally, some remarks on the flow field past a lifting body will be made. Recently, a great deal of information on these subjects has appeared in a number of reviewing papers so that little can be added. The numerical results on the subsonic flow regions in Section 2 have not been published before.

In his classic paper, The Expanding Domain of Aeroelasticity, Collar indicated how various types of problems (involving at least two of the three kinds of force—aerodynamic, elastic and inertial), which had hitherto been dealt with in their own “watertight compartments,” were tending to coalesce into a single subject which might be defined as “the dynamics of a deformable aeroplane.” The title of the subject, as Collar pointed out, at once suggests (to the mathematician at least) the formal solution of the problems which it comprises.

I should like to thank Mr. Hafner for his paper on “ Safe Mechanisms ” published in the May Journal (p. 273). There is much scope for thought and invention along the lines he suggests and such thought will result in increased safety.

In Section 3.1 on page 276 “ Safety Standard,” it is suggested that accident statistics should be quoted on an hourly basis and not per mile. A man expects to live three score years and ten; it is, therefore, the risk of spending a proportion of this time in a given occupation which is significant. It is then possible to compare the relative risks of lying in bed, train travel, air travel, space travel and so on.

The title of this lecture is “The Operation of Naval Aircraft and Aircraft Carriers”, but its sub-title should be “New Aircraft into Old Carriers”, because I am going to talk about just one phase of the Aircraft and Carrier problem: that of converting our wartime designed Carriers so that they can operate our new Aircraft coming into service, particularly the Scimitar, Sea Vixen and N.A.39.

Work on rocket propulsion was begun by the de Havilland Engine Co. in 1946, almost exactly a year after the end of the Second World War. For about the first year activities were confined largely to a general appreciation of rocket problems and techniques and to an assessment of the experience which had been obtained elsewhere. At that time “elsewhere” meant almost exclusively Germany, from where many technical reports were then becoming available.

In 1946 the policy in this country regarding guided weapons was, to say the least, obscure and the part which the liquid propellant rocket engine was to play in that field, even more obscure. It was not surprising, therefore, that the de Havilland Engine Co., being already well established in the field of aircraft propulsion, should very soon tend to concentrate its rocket propulsion efforts to manned aircraft applications. They were encouraged in this policy by the successful German use of the Me. 163 and of rocket take-off units fitted to the He.lll, Ju.88 and other aircraft. In particular, it was foreseen that the defence requirements of the United Kingdom might necessitate at an early date the use of a fast climbing rocket-propelled fighter.

Over the past years many questions which come under the broad heading of cloud physics have been put to the Meteorological Office by aircraft firms and others, questions on the water and ice crystal contents of clouds and the size distribution of raindrops are examples. These questions have invariably been easy to ask and at first sight the answers would appear to be straightforward, but almost equally invariably these simple questions have proved difficult to answer with precision and in many cases estimates only have been possible. This may well appear surprising and it is the purpose of this paper to indicate some of the difficulties encountered.

Aircraft operate within a domain of altitude and Mach number, the limitations to which are prescribed by the present state of technical knowledge. With the perfection of the aircraft gas turbine we have witnessed the boundaries of flight recede beyond the sonic barrier and are now approaching the stage where the vastly improved propulsiorl technique will permit cruising supersonic flight. Several excellent papers referring to this subject have been given.

It is necessary to start this paper with a disclaimer. Neither the author nor his firm have been concerned with the development of Drone aircraft for more than a few years. Others in the field have more, certainly longer, experience; the choice of the present author is probably because he has been associated with the development of the most ambitious target aircraft so far produced in Britain—the Canberra Mk. 10.

The early history of work on automatic flight was discussed by Dr. G. W. H. Gardner in the 46th Wilbur Wright Memorial Lecture*. Credit is due to the Royal Aircraft Establishment for the development of more modern Drones and associated equipment, and indeed, of the whole control system which is now used for Aberporth and in Australia. Much credit is also due to the Australian authorities for the working up of the target service which they now provide at Woomera and for the development of the Jindivik target. The Fairey Aviation Company Ltd. and Flight Refuelling Ltd. have respectively been concerned with the droning of the Fairey Firefly and the Gloster Meteor aircraft which are also used as targets for British missiles.