It is a great distinction and a highly esteemed honour to be privileged to read the forty-seventh Wilbur Wright Memorial Lecture. It is also a distinct personal pleasure to be here. Over the past 15 years I have made periodic trips to England to visit the aircraft companies, to witness the spectacular Farnborough displays of the S.B.A.C. and to attend the Anglo-American Conferences of the Royal Aeronautical Society and the Institute of the Aeronautical Sciences. This has afforded opportunities to observe and admire the rapid progress you have made in aeronautics, the brilliant achievements of British engineers and scientists and, more importantly, the chance to make and deepen warm and valued friendships. The joint meetings of the Society and the Institute are proving to be fruitful ground for the exchange of ideas and for becoming better acquainted. May I express the sincere wish that I shall have the pleasure of welcoming many of you to the Seventh Anglo-American Conference which will be held in October 1959 in New York.

For the purpose of this paper, certain fundamental parameters are assumed to be outside the control of the structures designer. It is, however, realised that the designer is often able to show that small changes in one or more of these parameters may have far-reaching effects.

These basic parameters include the aircraft size, weight, operating speed and altitude, aerodynamic characteristics and load factors. Fig. 1 shows how these combine together in various ways to give the loads acting on the structure, the temperature environment and the stiffness required to prevent aeroelastic disturbances.

Some of the aerodynamic problems that arise in flight at hypersonic speeds can be studied experimentally with wind tunnels and measuring techniques that do not differ in principle from those used for research on supersonic flow. If, however, it is required to simulate the very high temperatures of hypersonic flight, it is usually necessary to use heaters and tunnels of unconventional design, frequently having a very short running time, or to make tests with a model launched or propelled at high velocity.

The short running times sometimes involve the use of measuring techniques that differ considerably from those of conventional wind tunnel practice. Also, in the presence of high temperature, real gas effects, it is sometimes necessary to measure additional quantities in order to define the state of the gas. The paper contains a brief introductory review of these topics, and of the extent to which experimental test facilities can reproduce the conditions of full-scale hypersonic flight.

Before considering the special case of the North Atlantic, I should like to attempt some clarification of the term “Air Traffic Control” (A.T.C.). It is in fact a service for which I.C.A.O. member states have accepted responsibility dedicated primarily to avoidance of air-to-air collision hazards and secondly, to providing an expeditious traffic flow. When traffic is dense these requirements are somewhat incompatible and, of course, safety considerations are paramount; therefore the traffic flow suffers impediment in some form or other. Traffic Controllers provide service by issuing clearances which are subject to pilot acceptance. Pilots can ask for alternative clearances if they deem those offered unacceptable. Although the A.T.C. service clearly shoulders a large measure of responsibility for avoidance of air-to-air collisions, the ultimate responsibility is vested in the pilot-in-command who is authorised to take any action he considers necessary to maintain safe flight.

Recent developments in the control systems of aeroplanes have been such as to underline the need for new terms, and the need to remove any ambiguity relating to terms already in existence. The question has also been raised by the British Standards Institute in relation to the revision of the Glossary of Aeronautical Terms. The present paper examines the problem in the light of possible future developments, lists proposed terms with their definitions, and gives an outline of the underlying arguments. It is written in the spirit that in the field of systems of units, notation, and nomenclature “survival of the fittest” will always apply. The details of the nomenclature are not considered all-important, but we have tried to select the right concepts, to classify sensibly, and to produce accurate and general definitions. We expect many useful and amusing comments on nomenclature, but the other aspects are the fundamental ones, and we hope there will be some constructive criticism.

The First Fairey Memorial Lecture, “Sir Richard Fairey— An Appreciation” was given by Mr. G. W. Hall, F.R.Ae.S., on 5th March, 1959 at the Feltham Hotel, Feltham, Middlesex. This was the 34th Main Lecture of the Society to be given at a Branch and was held under the auspices of the London Airport Branch.

Mr. R. L. Lickley, F.R.Ae.S., Chairman of the London Airport Branch, opened the meeting by welcoming the President of the Society, Sir Arnold Hall, M.A., F.R.S., F.R.Ae.S. This was the first Main Lecture of the Society to be held at the London Airport Branch and they were delighted to have the President with them to preside at the Meeting.

Looking back at the pioneering period of aviation one is struck by the almost complete lack of mechanical components in the early aeroplanes. Besides the single primitive engine there were no more than about a dozen hinges on control surfaces which, together with a few pulleys and levers, formed the entire mechanical system of the aircraft. As flying speeds increased, however, the need for mechanisms grew; retracting gear for the undercarriage became necessary, wings had to be fitted with flap gear, and engines and propellers received reduction gears and pitch varying mechanisms. The advent of the turbine opened further avenues for development; thus for flight at great heights cabin pressurisation became necessary, and supersonic flight demanded powered controls and flight stabilising mechanisms. Finally, a large family of VTOL aircraft, including the helicopter, came into existence.

I am very appreciative of the honour that has been accorded me in being invited to deliver the Second Lanchester Memorial Lecture: appreciative, but all too conscious of my own inadequacy. This is especially true, since in the first Lecture we heard a tribute to a very great man from another such: and the prospect of following von Karman to this lectern is one to deter perhaps all but the most foolhardy. Since von Karman’s address discussed very fully the contributions of Lanchester to aeronautics, little is left for subsequent lecturers on this subject, and I have therefore chosen to speak of a problem which has been my special interest and concern throughout my professional life, namely, aeroelasticity—a field in which, as in so many others, Lanchester was a pioneer.

The Kinship of the English-speaking peoples, our common heritage of democratic ideals, and our close military alliance have created a unique relationship between the British Commonwealth and the United States. I know we both value it highly.

I am mindful of this in, saying that I feel that I am among friends here and that I appreciate your warm hospitality. Incidentally, my father received the same warm hospitality from you a quarter of a century ago when he delivered the twenty-third Wilbur Wright Memorial Lecture in 1935.

So much has been written, both of fact and fancy, about satellites and space travel in the past few years that the selection of material suitable for presentation to the members of a learned Society concerned mainly with purely aeronautical matters is a hazardous and difficult task. I propose in this paper to tackle it by restricting the subject severely to a description of the general characteristics of near earth satellites and the scientific exploration made possible by their use as observing platforms. The later sections of the paper have a bearing on the possibilities and engineering problems of space probes and space travel; I leave it to others to speculate on the likely time scale and types of such activities and attempt instead to make sure that the basic factors involved are made reasonably clear. To set the background it is important to review briefly the actual practical achievements up to the present time.

A study of engineering problems encountered in the design of transparencies for supersonic aircraft is presented with a special emphasis on the effects of kinetic heating. The paper is written primarily with optical transparencies in mind but many of the general principles discussed are equally applicable to the design of radomes for elevated temperature applications.

The first parts of the paper consider briefly the methods of calculating temperature distribution in transparent panels subjected to kinetic heating (or cooling) and this leads naturally to discussion of the effects of the non-uniform temperature distribution, differential expansion and the edge restraints preventing thermal deformations. Methods of calculating thermal stresses are suggested through the concept of the “ self-equilibrating ” temperature distribution; the main attention, however, being concentrated on the derivation of simple engineering formulae rather than on the mathematical rigour of the solution.

The choice of design cases for combined pressure and thermal loading is considered and it is shown that, in general, deceleration manoeuvres combined with outward pressure constitute the design criteria for transparencies. The effects of various parameters on the magnitude of thermal stresses are analysed; these include the effects of altitude, temperature, deceleration and material properties. It is shown that, for given material and panel geometry, the thermal stresses depend mainly on the following parameters: total temperature change, acceleration (or deceleration), and the Biot number based on the panel thickness.

Practical design aspects are also considered, such as choice of materials, strength, panel geometry, mounting of panels and the fail-safe design. Finally, testing of transparencies under pressure and thermal loading is briefly discussed, together with possible methods of strain measurements, and a tentative proving procedure for transparencies is suggested.

Claude Grahame-White, who died on 19th August 1959, in Nice, after a short illness, was perhaps the outstanding British pilot in those golden years of flying 1909-1914. He did more than anyone to stimulate interest in flying in those early days and, in the 1916 edition of the then well-known “Representative Subjects of the King” published by Dod's Peerage Publishers, was described as “a pioneer of aviation, not only as an aeroplane pilot but as a constructor, and one of the chief originators of this new Industry in England—an industry which now promises to equalise in importance, and eventually eclipse, even such a great industry as that of shipbuilding”.

An X-ray back reflection technique has been used to measure the surface residual stresses resulting from the cold and hot forming of certain high strength aluminium alloys. The alloys examined were to specifications DTD 683, DTD 687 and B.S.S. L65, and the residual stresses have been related to the residual strain in bending of these alloys. The results show that, apart from the degree of straining, the residual stresses are affected by the heat treatment (cold or hot quench) and the amount (if any) of controlled stretching that the alloy has had between solution treatment and precipitation.

A centrifugal compressor rotor is quite robust, but the blading of an axial compressor looks horrifyingly fragile and very susceptible to damage by objects sucked into the engine. The introduction of axial compressor engines into airline service brings this again to the attention of designers and service engineers. The object of this paper is to outline the problem, and to describe one experimental approach to assessing the relative merits of different blade materials from the damage point of view.

A guided missile system is a very complex assembly of interacting sub-systems, and rarely fits into a neat mathematical framework; but the need for a sound theoretical background is perhaps even more acute in this than in other fields, because of the almost prohibitive cost of protracted experimentation and cut-and-try methods. A theoretical model—even an approximate one—can greatly reduce the amount of experimental work necessary to prove a system, since the less efficient arrangements can be eliminated without a shot being fired. The use of simulators and computers, although indispensable, is in no way a substitute for this theoretical understanding: for the computer solutions can be obtained only for specific cases, and are of limited use unless they can be generalised to apply to other situations.

Of all those forms of corrosion with which the engineer must deal, such as atmospheric corrosion, galvanic and fretting, stress corrosion is perhaps the most difficult to understand, to predict and to prevent.

Unlike that other troublesome characteristic of metals, namely fatigue, which also defies exact analysis, it is caused by static tensile stress acting in a corrosive environment (in many cases, the atmosphere). This may be due to internal residual stress or externally applied assembly stress and under such circumstances the possibility of stress corrosion occurring is ever present and is not necessarily removed by the cessation of the working loads.

Most alloys are susceptible to some degree ranging from those which suffer in practice to those which only exhibit the phenomena under exaggerated laboratory conditions. Some examples are railway locomotive boilers, stainless steel construction, commercial spot-welded construction and, of course, aeroplane structures in light alloy.

I would thank you for the honour you have done me by the invitation to give this lecture.

The admiration I have always had for the engineer founder of this famous Derby firm, and the affection for the firm itself from many contacts over the years, both as an itinerant fuel development engineer and, later, as an official in a Government Department, makes this a very pleasant occasion for me.