It is a very great honour to be the 41st person elected as President of the oldest aeronautical society in the world. I am very grateful to those who have thus shown their confidence in me for this elevated position and to my company, Westland Aircraft Ltd, for its full support in so many ways to the Society, and in particular to me during this Presidential year.

Our Society's view of Presidential Addresses is a thoroughly democratic one in that they are not a fixed custom, as in many other professional institutions in the UK. Whether to have one or not is entirely up to the President of the day.

“The true inventor of the aeroplane and one of the most powerful geniuses in the history of aviation” are the words used by a modern French authority, Charles Dollfus, to describe Sir George Cayley (1773-1857), a scholarly Yorkshire baronet who until fairly recently was unknown to many historians of applied science. This curious state of affairs has been righted by the researches of the late J. E. Hodgson, of Dollfus, of the late Captain J. L. Pritchard, and of the present speaker, who have now secured universal agreement in regarding Cayley as the true inventor, or perhaps originator, of the modern aeroplane, and the originator of the science of aerodynamics as applied to aircraft. And, in 1962, the Royal Society itself admitted that “the absence of the name of Sir George Cayley from the Roll of Fellows is one of the most notable omissions”.

The need to provide members of a population with acceptable standards was clearly recognised by Juan de la Cierva. In a paper published in the Cambridge University Engineering and Aeronautical Society's Journal of 1934 under the title “Rotary Wing Aircraft”, he discusses the relative merits of autogyros, helicopters and fixed wing aircraft. It is interesting to note that his section headings include efficiency, utilisation, piloting, safety, simplicity and comfort, which show that he was well aware of the human and economic factors as well as the aerodynamic and structural developments for which he is rightly remembered. I have little doubt that if Cierva were to lecture today on choice, he would review not only the topics listed above for the occupants of the rotary winged aircraft but also he would examine the environmental advantages and possible difficulties which the use of such aircraft can confer today and in the immediate future. This lecture, which it is an honour to be invited to give, is an attempt to perform such an exercise.

When Louis Bleriot crossed the Channel for the first time on the 25th July 1909, he certainly did not realise that he was sowing the seeds of a very fruitful co-operation between our two countries in the aeronautical field.

The heaviest inter-city air traffic in Europe is between London and Paris, Bleriot took 37 minutes to cross the Channel but today it takes about three hours to travel from the middle of Paris to the middle of London.

The basic building block of a filamentary-composite laminate is a ply or a lamina consisting of a larger number of stiff filaments (e.g. glass) embedded in a compatible material (e.g. epoxy). The laminate or multi-directional composite is considered to comprise a number of perfectly bonded laminas with different fibre orientations. The deformation response of a laminate to an applied force is calculated by means of its material constants. One of the common methods of determining these constants is by means of a micro-macro mechanical analysis in which the characteristics of the composite are found in terms of the constituent material properties, geometry, and volume percentage of fibre content. Numerous papers have been published to investigate the micro-macro mechanical approach. Some of these works are based on the mechanics of materials approach and on the variational principle of minimum potential energy, as well as on the classical theory of elasticity.

Increasingly stringent attitude stabilisation requirements are the current trend in both experimental and commercial satellites as is seen in the current Intelsat, ESRO and UK communication studies. These craft must be lightweight, compact and rugged during the launch phase but after mission capture such requirements no longer apply. The increasingly high power requirements of such craft are met by the use of large flexible solar arrays which are packed away during launch and unfurl when the craft becomes operational. For the three-axis stabilised craft being studied reaction jets are used to achieve the high pointing accuracy required. Such actuators may be hot or cold gas systems or in the future may be electric engines’. The broad spectral content of these actuators will inevitably excite modes of vibration in a wide range of frequencies. The influence of these highly resonant modes on the performance of on-board controllers, needing a relatively high bandwidth of 0-10 Hz, to achieve high pointing accuracy of up to a few seconds of arc may lead to design difficulties.

I must begin with a confession which, but for the current high price of eggs and tomatoes, would probably have involved me in a bombardment of those agreeable, if messy, missiles. I approach this topic very much from the standpoint of one who served for two substantial terms at the Treasury.

I will put forward what I hope are reasonable explanations of why some of the more important features of the aircraft cockpit and the way in which an aircraft is controlled have been related to a particular side or direction of turning and circling; including the much debated origin of the left-hand circuit.

The ergonomists and the human factors researchers talk of the man/machine relationship and before getting down to detail cases we need to look closely at the human component of the man/machine interface in aviation. Relevant to the subject are the hand and side preferences of the human component, the pilot.

In 1929 when I was a young schoolboy in York, I was fortunate to become one of a small band of nomadic gliding enthusiasts centred around a most enterprising chap called Percy Watson, who had built himself a German Zoegling training glider above his chemist's shop in Micklegate. Each weekend we flew this machine — on which one sat in the open with an awe-inspiring view of the ground—from a wide variety of hills and precipices in the country to the east of York in the direction of Scarborough and Whitby.

In 1936, as a result of this exciting and sometimes quite terrifying activity, I joined Slingsby Sailplanes at Kirbymoorside, where I became happily involved in the design and development of Kirby Cadets and Tutors and the like. It was a most satisfactory occupation for a young chap dedicated to gliding and in consequence I developed a love of the wolds and moors of East Yorkshire from Sutton Bank to the sea, which continues to this day.

Man-powered aircraft have been built in which a man generating between 0·5 and 0·6 horse-power has remained airborne in straight flight for upwards of 3 minutes. Noone has yet succeeded in demonstrating sustained turning flight nor can sufficient endurance be expected in order to achieve the difficult Kremer prize course.

It seems probable that refining the current design of aircraft is unlikely to bring the required horse-power down by a factor approaching two and therefore a radically new approach is required if the Kremer course is to be successfully completed.

The first tandem-wing aircraft I saw appeared in an early 1960s edition of the boys comic—Lion. I dismissed it as a figment of the artist's imagination, but later came across the self-same aircraft in War Planes of World War 2—Fighters—Volume 2 by W. Green. From then on I have been collecting information on tandem-wing aircraft. Some eight years later what started as an interest in aircraft took an academic turn when I did a design study of a tandem-wing aircraft as part of an MSc.

It is a great honour for me to speak to such a distinguished and competent audience. Needless to say, I was pleased to receive the invitation from the Royal Aeronautical Society but was also concerned with the responsibility of treating a subject involving dramatic aspects, which require understanding, and the selection of a certain number of events for presenting a reasonably effective picture of the subject.

I know that it will be impossible for me—for lack of ability and also time—to give a full story of these adventures and ventures and 1 apologise for the omissions. In fact I will only briefly mention some of the facts which have more deeply impressed me or in which I have been directly concerned.

In determining the airworthiness of a helicopter to fly in all weather conditions it is necessary to examine all the effects of such flying on the safety of the passengers, flight crew and third parties involved in such flying. Rule 24 of the Rules of the Air defines that “for VFR outside controlled airspace that an aircraft shall fly at least one nautical mile horizontally and 1000 ft vertically away from a cloud with a visibility range of five nautical miles, except that below 3000 ft the aircraft must be flown clear of cloud and in sight of the surface”. Inside controlled airspace the same rule applies except that the aircraft on Special VFR shall be flown in accordance with the specific instructions given by ATC.

Despite the wide use of Alclad aluminium alloy sheets in the aircraft industry, information on the effect of cladding on the mechanical strength of the strong alloy core is mainly limited to comparative fatigue testing of clad and unclad sheets, tested as plain specimens and subjected to constant-amplitude loadings. S/N curves obtained under such conditions were published by Smith, Brueggeman and Harwell for 24S-T3 material and by Shabalin for the D16T alloy (Russian specification). Both sets of data show that the soft cladding had a detrimental effect upon the fatigue strength of the strong alloy. Forrest has presented several comparative S/N curves which also show a reduction in the fatigue strength of the Alclad unnotched specimens compared with the bare alloy. Karlashov and Batov investigated the behaviour of cyclically-strained D16AT alloy (Russian specification), with particular reference to the nature of the mechanism of protection offered by pure aluminium. Although the core was electrochemi-cally protected against corrosion, intense damage occurred in the cladding layer.

Several recent theoretical advances have been incorporated in computer programs which find the initial buckling loads of prismatic assemblies of thin plates “exactly”. Any such assembly of plates which are connected together and/or supported along their longitudinal edges, while being simply supported at their ends, can be analysed. Furthermore, curved plates and anistropic materials are allowed. Thus plate assemblies with many practically important types of cross-section can be analysed. Consequently, published results mainly relate to a few crosssections of each of several possible types. However, the designer needs comprehensive design curves, like those in the Structures Data Sheets of the Royal Aeronautical Society, for as many common cross-section types as possible. Unfortunately, production of such curves using the programs mentioned is unlikely to be achieved for all desired types of cross-section, at least for some time, because each type involves plotting curves as several parameters are varied. Nevertheless, a range of results for one type of cross-section is obviously valuable. Thus the lipped channel strut made from isotropic material is considered in this Note (see Fig. 1).

Three theories of bending are available to the designer for the determination of bending stresses in curved beams. (1) The Euler-Bernoulli hypothesis (often referred to as the simple theory of bending), which assumes a linear distribution of bending stress, having a zero stress value at the mid-plane, i.e. the centroidal and neutral axes are coincident. (2) The Winkler theory, which predicts a depression of the neutral axis away from the centroidal axis and towards the centre of curvature. This theory produces a hyperbolic distribution of bending stress across the section, having a maximum amplitude at the fibre nearest the centre of curvature. (3) The Golovin theory, which is exact.