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 intention in presenting this paper is to outline the main trends in recent alloy development and to indicate the current state of the art as far as the user is concerned, particularly on the behaviour of the new products in the problem areas so designated by the engineering metallurgists and materials specialists in the industry.

In reviewing recent alloy development it is convenient to identify two main lines in terms of the metallurgical structures involved, since these tend to define the more appropriate areas for design interest.

Willy Messerschmitt’s most notable impact on aviation history occurred during the wartime period 50 years ago. While there is a general belief that the business approach under the extraordinary circumstances of this period is in no way relevant to today’s business environment, this paper will, nevertheless, attempt to illustrate that some elements of Messerschmitt’s approach may still be worthy of consideration.

Messerschmitt’s approach had not been that of “big business” but rather comparable to that of an artist-craftsman. Since the approach of an artist is best reflected by reviewing his “oeuvre”, this paper will be proceeding accordingly. Figure 1 shows Messerschmitt in 1935.

A simple theoretical analysis is given of the quantities affecting the sensitivity and range of a schlieren apparatus. In regions of large density gradient the deflections of the light rays may lie outside the normal working range. When this occurs, dark regions may appear in parts of the photograph that would normally be light. Examples of this effect are given, and it is shown that confusion can be avoided by taking photographs in pairs, with the knife edges or slits arranged to give sensitivities of opposite sign.

The deflections of light rays in various typical disturbances in a supersonic air stream are calculated, using geometrical optics. Prandtl-Meyer expansions, boundary layers, and plane and curved shock waves are considered. From these calculated deflections it is shown that some of the anomalous effects commonly observed in schlieren photographs can be explained.

The aviation industry has not yet given much attention to the development of rotary winged machines as specialist agricultural tools which would help to make farming easier, more efficient and more productive. The emphasis is, and naturally has been, on the development of the immediately bigger markets for military aircraft. It is understandable, if unfortunate, that the farmer has to wait his turn well down in the queue of various armed forces specialists. He is waiting for aviation to turn the focus, some day, of its technical knowledge and research resources onto the way that the versatility, manoeuvrability and usefulness of the helicopter can be used to grow more food, timber, wool and other natural products.

It is possible, and even probable, that the next generation of defensive missiles will use modern methods of optimal control of the interception trajectory. Miniaturised computing is becoming so readily available that it becomes feasible to compute the optimal trajectory to the interception point.

Consider a ground site, defended by a surface-to-air missile, which is being attacked by a low-level intruder aircraft. As soon as the intruder is attacked, by launching the defensive missile, the intruder attempts to avoid interception by using evasive tactics; the intruder becomes the evader and the defensive missile the pursuer. When both the pursuer and evader use optimal tactics, the one to achieve interception and the other to avoid it, the result becomes the outcome of a game of pursuit and evasion, as described by Isaacs in Reference 1.

During the last twenty years a revival of interest in the subject of map projections has taken the form of a renewed attack upon certain basic limitations which face the cartographer. A necessary stimulus has been provided by the growth of a technique of air navigation, which in many ways has departed from the traditional practice of the marine navigator. From this and other directions emphasis has been laid on the need for precise cartographic representation of distance, direction and position on the earth. But although certain problems may be treated by devising new projections to meet special needs, it is obvious that there is a limit to any purely cartographic approach.

The requirements of the new navigation are, briefly, that its methods should be rapid, convenient to use, and of an accuracy consistent with the limitations imposed. The traditional solution by means of spherical trigonometry is thus ruled out on at least two of these counts. In its place, there are now available a number of graphical, mechanical and simplified tabular methods, many of which have no cartographic basis. Since a map projection is an obvious medium for the measurement of spherical relations, the needs of long-distance air navigation have encouraged the adaptation of certain projections in the form of special instruments and devices.

A convenient method is pointed out for calculating the response of a damped linear system with one degree of freedom to harmonic excitation. Results of such calculations are usually represented by the familiar “ resonance curves ”—one curve being plotted for each intensity of damping. These curves are not particularly convenient to use and Yates has overcome several of their defects by throwing them into a nomographic form. Yates' nomogram is based upon the concept of viscous damping and it does not give the information of a conventional set of resonance curves in that it relates to the velocity of vibration. By changing over to hysteretic damping, a nomogram of somewhat similar form may be constructed such that it gives amplitudes and phase angles of displacements while retaining the advantages, over resonance curves, of this form of representation.

For the definition of the acccuracy of an internal strain gauge balance no general agreement exists. So it is difficult or even impossible, to compare balances from different manufacturers or balances used at different places.

Since most wind tunnel tests at least in the aeronautical field are done on a reference basis i.e. the results are compared with earlier results achieved with a more or less different configuration, repeatability is at least as important as absolute accuracy or even more important. So also repeatability, which in a physical sense is quite different from accuracy, must be defined and proven for each balance.

With the examples of several balances manufactured for the DNW (Deutsch-Niederländischer Windkanal) and ETW (European transonic tunnel) accuracy and repeatability definitions are discussed.

A proposal for a generally binding definition of accuracy and repeatability is given.

A theoretical analysis is presented for a two-dimensional air strut with walls consisting of thin membranes which are joined by many inextensible strings. The strut is deflected through large angles so than an appreciable portion of each membrane is buckled and lies along the solid plates which form the ends of the strut. Numerical solutions are obtained for two cases and, in particular, the resultant force on each end plate is determined.

This lecture is an attempt to provide a general view of soaring, including the views of the pilot, the meteorologist, the engineer, and the club. If this can be done, it will be easier for each specialist to recognise how he can best contribute to the advance of the pastime.

I think that the technique to build a glider has been available for several hundred years, but the knowledge and desire have only recently grown. The present state of gliding is due to advance in two ways, in art and practice, and in organisation. Perhaps I should not leave out science which is the record of the practice and of the experiments which have been made to improve the practice.

Although I deem it a great honour to have been asked to give this lecture I will be perfectly honest and tell you that for a long time I resisted. 1964 is an important landmark in the Hatfield Branch history. It has been in existence for a quarter of a century and the developments which have taken place during this period in the Aeronautical World have been remarkable. The lecture also ranks as a Halford Memorial Lecture and so I felt that someone far better qualified than myself was needed in order to do justice to the joint occasion. However, I finally agreed and I would like you to know that this was not because some sudden inspiration gave me confidence that I was the man for the job, but rather because I felt that as the Hatfield Branch had done so much for me I should try and do something in return.

We have published elsewhere a considerable amount of work on the development of the cathode ray engine indicator and, while most of the pressure elements and circuits which have been developed are perfectly satisfactory on normal petrol and Diesel engines, it has been impossible up to the present time to obtain a really satisfactory pressure-time card on the high duty boosted aircraft engine, the main difficulty being due to the super position of mechanical vibration on the pressure-time diagram. A satisfactory knock indicator has, however, been produced and a few of the results are here discussed, in the hope that they may be of general interest.