My original title for this lecture was “Aspects of Accessibility.” Then I discovered that people assumed it concerned accessibility in connection with aircraft maintenance. That assumption implied that an engineer is expected to stick to engineering. Having written what is to follow, I wonder whether that implication might well be right, and that all I have to say could be entitled:

On the other hand G. K. Chesterton clearly demonstrated that when the obvious is stressed, it often turns out to have unexpected aspects.

I would like to begin by expressing my appreciation to the Society, especially the Test Pilots’ Group, and specifically to Bill Bedford for the invitation. It is a distinct pleasure and certainly an honour for me to be here. My discussion will centre on the X-15 research aeroplane, some of the essential items that we uncovered in our development flying programme and some characteristics of the aeroplane. I would hope I could go into this in sufficient detail. Being away from the programme for some time now, I have lost some of the intimacy that I had in the past but I think not completely so. At least, not enough so it will deny me the opportunity to present you with some information.

The previous paper in this series described what operational research is and illustrated some of its methods. The succeeding articles are concerned with considering some of the problems in the different branches of the aviation industry and showing how OR may be profitably applied to them.

This paper and the next form a continuous narrative. They differ in that the first concentrates on capital investment programmes and the procurement of aircraft, while the programmes and the procurement of running an airline. In the first, a discussion of cost structure leads on to some detailed models. A further series of models forms the basis of the second.

I took the unusual course of suggesting this lecture because I have something to say. I should have done this ten years ago. Better late than never. The position is that after £20 000 million spent on defence in the past 12 years, of which the air industry has had more than its full share, there is a culmination of industrial mismanagement, a crisis of confidence, a prevailing sense of bewilderment, an air of frustration and, therefore, a craving for new leadership in industry to make a true and worthy partnership of heart and mind with the active new leadership in Government. I sense moreover that behind the shadow boxing lies at this moment a more bi-partisan approach to meeting the future than immediately meets the eye. So this is not an exhortation but a demand to adopt new habits of thought that will lead to evolution of equipment calculated to sell well as a general rule instead of it being more the exception. And this is not a plea, but a demand, for a new resolve and leadership in industry coupled with a determination to make a better export showing in the 1970s on a smaller Government investment. The present Government's actions to promote research mergers and industrial co-operation with other countries seem a logical turning point for a re-start. So why not let us make resurgence date from now ?

It has been shown both experimentally and theoretically that the Mach number range from 1·0 to 1·5 is very critical for panel flutter. Also, the correlation between experiment and theory in the above range has generally been poor.

Sufficient papers have now been written which are relevant to the title subject that it is possible to make a review of the subject and to make recommendations for further work. These papers are reviewed in approximate chronological order. In all cases the panels referred to are rectangular and unswept with the air flow on one side only, unless otherwise stated.

The author presented in his recent main lecture to the Society, “The Computer Shapes the Theory”, a number of novel developments in the matrix displacement method. Since the publication of the lecture and discussion will inevitably be delayed and cannot but illustrate the application of the new ideas on a series of examples, he has been repeatedly urged to summarise some of the more important theoretical contributions in the form of Technical Notes. The first deals with the elasto-plastic analysis, in the presence of strain hardening, of arbitrary three-dimensional configurations. The reader is assumed to be familiar with the corresponding elastic analysis given in refs. 2 and 3, where the medium is represented by a suitable assembly of tetrahedra under constant stress and strain. The corresponding two-dimensional case is investigated on the basis of triangles. Arbitrary anisotropic behaviour and large displacements were also included in refs. 2 and 3.

Formulae are presented giving the centre of pressure of axi-symmetric bodies at zero incidence having profiles for which the drag is a minimum in Newtonian flow.

Boyd has suggested that a close correlation may exist between such profiles, and profiles derived from exact pressure distributions, in supersonic flow.

Diagonal tension analysis of flat panels in shear is commonplace in aircraft design; such an analysis is presented in detail in the Royal Aeronautical Society Structures D.S., 02.03 series. In their present form, although well presented, they are time consuming and laborious to the engineer. It is therefore desirable to transform these data sheets into a form which can be easily programmed for solution by computers. The aim of this paper is to present such a format. The method is adequately covered in the data sheets, but important points are listed here. A step by step procedure for the analysis is given with a suggested programme input sheet and output format. An example is given with corresponding output data to be used for programme check-out purposes.