On 13th November 1945, my distinguished countryman, Sir Hudson Fysh, KBE, DFC, delivered the first British Commonwealth and Empire Lecture inaugurated by the Royal Aeronautical Society. Significantly, in 1957 the title of this lecture series was changed to “The British Commonwealth Lecture”. Sir Hudson chose as his subject “Australia in Empire Air Transport”.

I feel deeply honoured to have this opportunity to contribute to the very considerable accumulation of knowledge which this series of lectures represents. My topic, despite the difference in title, is really a continuation of Sir Hudson's theme, with the advantage of an additional twenty-five years of hindsight.

One of the great challenges of our time lies in the exploration of space. Part of this challenge has already been fulfilled but, up to this date, the transport of men and materials has been accomplished by means of expendable booster systems. In order to meet this challenge effectively, a new, fully reusable transportation system has been conceived which will be dramatically lower in overall cost than present-day launch systems. The proposed space shuttle is a fully reusable spacecraft consisting of a booster and an orbiter. A key factor in the design of the space shuttle is the selection and development of materials. Many current materials which have been widely and successfully used in space vehicles were developed for the most part with only a single short-time use requirement. The reusable, long-life requirements of the shuttle vehicle necessitates re-evaluation of the suitability of existing materials for this distinctly more demanding task for materials.

It is a great privilege for me to give the Twelfth Cierva Memorial Lecture. The title, which was suggested by the Society, might imply a mere recitation of past deeds. This would hardly be a fitting tribute to a great inventor like Cierva. Such men are usually impatient with the past and eager to explore the future. Accordingly I will deal with Bell's history as briefly as possible, and then discuss some aspects of helicopter rotor systems which have recently come to light.

The obtuse corner of the skew plate is a singular point with a stress singularity growing in intensity with an increase in the angle of skew. For regaining the full rate of convergence of the finite element method the mesh around the singular point should be properly refined or the leading singular terms included in the finite element scheme. In any event a large number of unknowns may be required. For obtaining an accuracy of 1% in the 10th Eigenvalue of a clamped square plate discretised with the 16-degrees-of-freedom elements used in the present calculations, about 300 variables are required. For computational convenience calculations were carried out here with a uniform mesh requiring even a larger number of unknowns.

The many methods by which Pontryagin's Maximum Principle is applied in optimal control problems can be divided into two groups, termed direct and indirect. The indirect methods use the conditions required for mathematical optimality as the starting point and attempt to satisfy the boundary conditions. The direct methods on the other hand satisfy the equations of motion and boundary conditions and then attempt to improve the performance index. It has been reported that the direct methods, while normally converging from very bad initial assumptions, have the inherent disadvantage of very slow convergence in the neighbourhood of the optimal solution and, so, complicated second order methods have recently been devised.

In a recent publication, Professor L. Dixon applied to a structural optimisation problem elements of the Pontryagin theory of optimal processes; well known in control systems. The problem considered was that of the minimum deflection of a cantilever beam under its own weight with constraints on the geometry. Digital and hybrid solutions of the two point boundary value problem arising from the optimisation problem were presented. Significant differences in the digital and hybrid solutions by the hill-climbing method were found. The present authors have examined the numerical methods for solving the optimisation equations, have developed a computing method which does not have the inherent convergence problem of the methods of Dixon, have re-examined the governing equation, and have noted a correction to these equations.

When I was invited to address this distinguished gathering on the subject of All-Weather Operations it was with some trepidation that I accepted. It always strikes me that, to an audience the majority of whose members are not directly involved in furthering the cause of bad weather landing, yet another progress report on this topic must sound rather like the Continuing Story of Peyton Place—a complex intrigue of interwoven plots with little defined end result. I personally do not believe that the situation is really as depressing as this, and my task is to try and convince you that this is so, hopefully, by presenting objectives and achievements in simple terms. I will try (not completely successfully I fear) to avoid the plethora of jargon that the international civil aviation fraternity has necessarily had to employ in its complex debate and arguments. If, as a result, I can be accused of oversimplification, I apologise to the experts, and only hope that it is of genuine assistance to the non-experts.

The subject of this discussion is not one which readily lends itself to division into separate compartments but, for the purpose of presenting our respective papers, Mr. White and I have agreed to divide the subject between us on the basis that he will deal with the legal aspects of international co-operation as between the participants in the project and third parties, while I propose to discuss some of the legal aspects arising out of the relationship between the companies engaged in such projects. As I have implied, such a division of the subject must of necessity be an arbitrary one, and it is evident that there will be many areas where the two sides overlap, so that they cannot in practice be treated in isolation, and Mr. White and I have felt free to include in our respective papers, matters arising from our own experiences which in some cases may be more appropriate to the other's half of the programme.

Mr. Jenkins has described to you the matters between the collaborating parties. My task is to describe the problems between them and outsiders.

Because hardly any major European aerospace project lacks some form of collaboration, perhaps I may just make a few points from my own experience of this sort of business.

International collaboration has daunted many people, for rather the same reason that a lawyer like myself feels incapable of imagining how the process of a design office can ever achieve anything!

A lot of what occurs in the design office is summed up in the phrase “know-how”—I have often thought that there is no less a “know-how of collaboration”, particularly international collaboration.