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THE simplest type of aircraft power control is probably that shown in FIG. 1. The dynamics of this type of servo have been discussed in papers by Harpur and others, and it is shown that if the valve has cither zero or positive overlap the servo will be unstable with inertia loading. Harpur suggested the following methods of stabilizing the servo:

Academician A. N. Tupoley, designer of the Tu‐144 supersonic transport, has been awarded an Honorary Fellowship of the Royal Aeronautical Society. Honorary Fellowships have also been awarded to Sir Robert Cockburn, Fellow Commoner, Churchill College, Cambridge, and to Dr C. S. Draper, Professor Emeritus, Massachusetts Institute of Technology. Honorary Companionship has been awarded to Sir Anthony Milward, ex‐Chairman of B.E.A. The Society's Gold Medal is awarded to Mr Walter Tye, Chief Executive of the Air Registration Board, and the Society's Silver Medal to Mr E. E. Marshall, Technical Director, B.A.C., Weybridge. Mr N. F. Harpur, Chief Technician at British Aircraft Corporation, Filton was awarded the Society's Bronze Medal, and the Wakefield Gold Medal went to Mr J. H. Briggs, Director/Electronics, Research and Development (Civil Aviation), Ministry of Aviation and Supply. The British Gold Medal for Aeronautics for 1970 has been awarded to Mr P. A. Hufton, Deputy Director of the Royal Aircraft Establishment and the British Silver Medal for Aeronautics for 1970 goes to Mr M. J. Brennan, Executive Director Special Projects, Hawker Siddeley Aviation Ltd.

DEVELOPMENT of the supersonic transport is involving a wide variety of activities in all fields of aeronautics. This paper describes the work which has taken place, or is planned, in the field of structures. Although Concorde is designed for Much 2, a speed at which aluminium alloys can continue to be used as the primary structural materials, evaluation of the particular alloys chosen and study of their behaviour under complex temperature‐stress histories involves considerable laboratory effort. While many aircraft have already operated under these conditions none has previously had to last for at least 45,000 hours in service. This gives rise to the two most significant new design considerations, viz. creep and thermal fatigue. Creep affects the choice of basic material, the design of joints and the design of structures through its interaction with fatigue life. Thermal stresses, arising from differential expansions within the structure and superimposed upon the normal flight stresses, have a more important effect on fatigue design than on static strength. While the experimental techniques involved are novel, practical methods of accelerated thermal testing using convective heating and cooling are described.

It is a great privilege and honour to be asked to deliver the annual Chester Beatty Lecture, particularly in the presence of Mr Chester Beatty himself. The theme of these Lectures is “metals in the service of mankind” and, in this respect, the material which I will be covering in this lecture has been serving mankind for a relatively short time compared with other metals such as copper, zinc, iron, etc. Titanium is a metal which has only achieved direct engineering usage, as distinct from some minor applications as a strengthening alloy in other metals, since the Second World War. Its rise in importance for structural purposes has been very rapid and the purpose of this paper is to outline its history, to indicate the reasons why designers are so impressed by its potential, and to give some examples of present and future applications.

Clad 2024‐T3 and 7075‐T6 sheet specimens were loaded at three different load amplitudes and three different mean loads. It turned out that the mean stress had an important influence on the crack propagation rate. The crack growth rate in the 7075 specimens was three to four times as large as in the 2024 specimens.

THE method used at present in fatigue testing aircraft joints and components by applying cycles of constant stress amplitude of a magnitude considered to be the most damaging is based on the assumption that Miner's cumulative damage rule, Σ(n/N)&equals l, holds good. This rule is known to be true only under certain conditions which may not apply to those under which fatigue damage is accumulated in aircraft.

In order to provide information for flutter and dynamic stress calculations on an aircraft a knowledge of the normal modes of vibration is required. In the following paper a matrix method, due to Dr Traill‐Nash, is extended and used to obtain a general expression for the complete aircraft normal modes, and is applicable to most aircraft configurations. The method is considered to be eminently suitable for use with modern digital electronic computational equipment. Methods arc discussed vthcrcby the degrees of freedom may be economized without significant loss of accuracy. By restriction of the degrees of freedom allowed, important subsidiary cases arc drawn from the general expressions, allowing standard matrix solutions suitable for normal oflicc routine.

ONE hundred and seventy‐five delegates from Italy, France, West Germany, The Netherlands, Sweden, the United States and the United Kingdom met in London on November 3 and 4, to participate in an Aircraft Transparencies Symposium organized by the Society of British Aerospace Companies. This Symposium, the first of its kind to be arranged by the S.B.A.C., concerning a facet of aerospace engineering which has hitherto received rather less than its fair share of attention in the world's technical forums, took the form of nine papers read by leading authorities in this field, discussion following each individual paper, and an exhibition of windscreens, canopies and windows produced by leading transparency manufacturers in this country and North America. The full proceedings of the Symposium are thesubject of detailed coverage in this issue of AIRCRAFT ENGINEERING.

THE development of synthetic resin adhesives has proceeded very fast since about 1937 when the first urea formaldehyde wood glues were being produced on a pilot scale. The excellent resistance of these materials to weathering conditions has enabled very considerable advances in structural design both in wooden structures and rather more recently in metal aircraft. These synthetic resin adhesives are basically ‘thermosetting’, that is to say, they harden by the addition of catalysts or by the application of heat, the chemical process which takes place being irreversible and not dependent upon the evaporation of solvents. This concept leads not only to good weather resistance, but also to the practicality of sticking together non‐porous materials such as metal. The first use of bonding of mstal in aircraft structures was in the de Havilland Hornet in 1943,1 and since then bonding has proved its advantages over other methods of joining for both primary and secondary structures. Other new methods of fabrication have appeared since that time and the requirements for structures in terms of loading and environment have changed considerably; but both mctal‐to‐metal bonding and its newer partner honeycomb sandwich show signs of much more extensive use in the future. These two most important applications of synthetic resin adhesives in modern aircraft will now be considered.

The Thirteenth Wright Brothers Lecture delivered by Mr A. E. Russell of The Bristol Aeroplane Co. Ltd. before the Institute of the Aeronautical Sciences in New York on December 17, 1949. The problem of flutter is one of the earliest associated with flying but has, until comparatively recent times, been solved merely by solving the problem of strength coupled with the tactical distribution of lead weights. We are now becoming quite proficient at solving the problem of strength and are disturbed if our test structures do not fall within 1 or 2 per cent of the design loads (however arbitrary these loads may be). At the same time this steady refinement of design has resulted in a reduction of structure weight for given design loads. Refinement of structural design has reduced the stiffness of the structure and this, coupled with a steady increase of cruising speeds, has brought the flutter problem into its present prominence.