One of the few privileges the public lecturer has is to divide all mankind into two classes according to his prejudices, and this I intend to do: on the one hand those restless souls who constantly strive for innovation and change; on the other the great mass of humanity who resist and even resent any disturbance of the even tenor of their ways.

The first fish-like beast that crawled out of the primeval swamp on to land must have had something of this spirit of change and adventure. And from the dawn of history the rare men with these characteristics have provided the leadership and sparked the changes that have been at the heart of human progress.

Although the Hatfield tunnel has been doing some useful testing for just over eighteen months, the experience so far obtained is still limited as each new model brings its own special problems. It is perhaps still too early to give an account of the experience obtained, but because of the interest in this tunnel it was thought that an account, even incomplete, would be useful.

Almost every facet of experience so far obtained is related to some of the special design features of the tunnel and I propose to review some of the problems encountered during the design stages of the tunnel dealing with these design features, before reviewing the actual model testing experience.

I had the privilege and pleasure of working directly under Roy Chad wick from 1942 until the time of his death in 1947. I use the word “pleasure” advisedly, for he seemed at that time to be the most unreasonable of men. At one moment he would be full of charm and consideration, and at the next a martinet who drove us well beyond what we mistakenly thought to be the limits of human endurance. I well remember standing in Oldham Street on a cold Manchester war-time morning, having missed all reasonable buses to Chadderton, to be picked up by Chadwick in a shiny Armstrong-Siddeley. All the way out to the factory he talked about the good old days of aviation, and the challenge of my chosen profession. At the front door we were welcomed by the commissionaire, and I went to my desk confident that God was in his Heaven and all right with the world. Within ten minutes the telephone—Miss Jackson summoning me to Mr. Chadwick's presence. As I entered his office he scowled at me and started in—“Lindley —you were late this morning ….”.

The formation of the Steering Committee of the Management Studies Group is not an isolated manifestation of concern on the subject of management in the aircraft industry. During the past five years there have been events such as the loss of technologists to other countries, the massive cancellations of advanced projects, the Plowden Committee and many debates and ex parte statements by both the various Ministers and by industry spokesmen.

In addition to the public debate, there have been less formal meetings and approaches to the Council or the President of the Royal Aeronautical Society which indicate deep concern—almost universal—about “cost effectiveness” or, bluntly, our cost comparisons with competing aircraft industries elsewhere.

A long untapered tie under tension exhibits localised stress concentrations when one end is subjected to a flexural rotation. These stress, concentrations can be avoided by tapering the tie. The optimum tapers for ties of circular and rectangular section are determined in this paper, and the resultant flexural stiffnesses are compared with those of untapered ties. Results are of interest in the design of certain satellite model support systems.

The technical note by Dr. Alexander implies that hovercraft jet performance might be better than simple theory predicts for values of 1/x greater than 4. The experimental points used to compare with theory were obtained at the beginning of hovercraft development, but subsequently a number of British and American reports have been issued whose data can be interpreted to give points for comparison with theory. These results show that the simple theory overestimates the performance of the jet.

It has recently been suggested that the tracked hovercraft is a suitable means of high speed transportation. On some routes it may be necessary for the vehicle to pass through tunnels. The purpose of the present note is to determine the effects of steady tunnel operation, and in particular to find if the “piston effect” is likely to adversely affect the performance of the air cushion.

The rapid growth of interest in fluid logic and control elements has refocused attention on the reattachment of two-dimensional jets to plane surfaces. Of particular interest is the size of the low-pressure bubble enclosed between the jet and the adjacent inclined plane, and the effect on this of fluid velocity and compressibility. Several full studies have been made of such flows, notably by Bourque and Newman, Sawyer and Olson, and the basic characteristics have been well established. Agreement has been reached that bubble length is independent of jet Reynolds number (above 104), but doubts remain as to the best method of measuring the bubble length and also as to the effect of compressibility on this measurement. In order to clear up some of these points for an investigation of compressible flow through control valves, some experimental tests have been carried out on the reattachment of air jets to a plane.

This note describes how a single constant temperature hot wire may be used for measurements of direction, velocity and turbulence in a two-dimensional flow. The wire probe is rotated by a servo motor which automatically sets the wire with its axis either in the stream direction or normal to the flow. The accuracy of setting the wire in the direction of the stream is about , and across the stream is about 1°. If the higher accuracy is demanded the velocity and turbulence measurements require a second setting of the probe, at 90° to the previous one. When less precision is acceptable, the angle, velocity and turbulence measurements may be taken at the single setting, normal to the stream.