I feel that the title of this lecture needs clarification, because it would appear from it that aircraft reliability is necessary only in the interests of Flight Safety. Although safety is vital, the operational capability of the aircraft must also be considered because, as in a missile system, operational reliability is of paramount importance. An aircraft may be completely reliable from the Flight Safety aspect without necessarily having a reliable weapons system.

In the past few years, of course, much has been said about the need for reliability. Conventions have been held in this country and in other countries and it might be thought that the lesson has been so often and so well propounded that to discuss it again is hardly necessary. However, I hope to show that we still have some way to go before we even begin to approach the ideal.

The Ground Stations to be discussed are the large Radio Stations required for a variety of Astronautical applications. The principle categories are:–

• Radio Astronomy,

• Telemetry and Control,

• Communications,

• Military applications,

R. K. Pierson was a great man, not least physically. I can still see those huge shoulders, the hands thrust into the coat pockets, the magnificent head, and the aggressive chin. It is not for me to deliver a eulogy of R. K. P. and his work at Vickers—that has already been well done. But I must say how honoured I feel at being asked to give, on this occasion, the lecture which you arrange annually in memory of an outstanding designer.

My recollection of him goes back to 1933. In the long vacation of that year, as an undergraduate, I crept into the flight sheds at Weybridge for an eight weeks indoctrination from Industry. Rigging Virginias, Victorias and Vildebeestes was the main occupation, with some analysis of flight tests if you showed willing, and banishment to the main shops across the airfield— knocking rivets into Vildebeeste wireless containers— if you were naughty. I enjoyed it so much that I came back for a similar period in 1934 just after graduating. The family atmosphere and team spirit were very marked —Pierson used to rush into the flight office with his pipe and tear through the test flight reports with Mut. Summers; he was quite willing to deal kindly with some diffident and probably idiotic remark put forward by a vacation apprentice clutching a bundle of grubby graphs prepared for Radcliffe—who in those days was the mainstay of the flight test Department (he was outnumbered by the test pilots—there were two of those).

The operations of Chicago Helicopter Airways represent a portion of the total Federal effort within the United States on behalf of helicopter development. This effort has been an outgrowth of the interest of the Civil Aeronautics Board and the U.S. Post Office Department which has a long tradition of looking for new developments in transport and of experimenting in new ways to move mail. Post Office interest in the aeroplane was the chief stimulus to the early development of U.S. airlines and dates back to the first scheduled air mail route authorised between New York and Washington in August 1918. It was natural, then, that the Post Office Department should have interest in the helicopter as it emerged in usable form for civil use after the Second World War.

This paper describes the plasma jet which has recently been put into operation in tha Department of Aeronautics. A brief outline of the apparatus and its equipment is given, and methods are described for obtaining data from the high temperature gas stream. Finally some results of a recent test programme are outlined.

In Ref. 1, Professor D. W. Holder describes a very interesting experiment pertaining to shock wave position and boundary layer separation in supersonic nozzles at low Mach numbers (M ⩽ 1·4). A closer examination of this experiment indicates that the results may only be applicable in the Mach number range of M < 1·48, not in the range of M> 1·48.

The relative merits and possible applications of liquid and solid propellant rocket motors have long been topics for discussion and controversy. The arguments for and against have been sharpened by the fact that the development of the two types of motor are usually vested in quite different teams of people. At the same time, a fair comparison has often been confused because the ultimate choice has been made for reasons which are really not technical at all, but instead depend on availability and the utilisation of already deployed capital resources.

Nevertheless, the merits and de-merits of the “conventional” (as opposed to the packaged) liquid motor and the solid motor can be simply defined with reasonable accuracy. The liquid motor is complicated, demanding at least some, and often a great deal, of attention before use. At the same time, it has a much greater performance potential, can be used repeatedly and can be designed to give variable thrust. The solid motor is simpler (although is getting less so), is cheaper (although this is getting less true) and demands less preparation. However, it has definite performance limitations, is inflexible in its output, and is often quite sensitive to its environment, whether during storage, carriage, or operation.

Structural failures have been experienced recently in some panels of relatively thin plating, dished to about twice the plating thickness, and failure has been attributed to snap-through buckling.

Snap-through buckling may be defined as the lateral instability of a dished panel when loaded on the convex side. (Such an effect js frequently observed in the lids of biscuit tins.)

I am taking as a starting point the basic assumption that the most immediate and feasible use for an earth satellite from an economic and commercial point of view is as a link in the existing world telecommunication system. This is a small part of the field of U.S. space programmes, but is the first application of satellite systems to be commercially viable. It is now uppermost in our minds and the tests to be made during this summer give immediate reality to the project.

Two-dimensional photoelastic tests have been carried out on uni-axially loaded flat-plate specimens with two collinear edge slits, to investigate the effect of finite plate width on the elastic stress distribution. It was found that the effect of slitlength/ plate-width ratio on the elastic stress concentration at the end of the edge slit of length l was virtually the same as that for a central slit of length 2l in a plate of the same width, and could be adequately expressed by existing theories.

In 1961 I assisted Mr. G. M. Lilley in writing a survey of the design and performance of man powered aircraft. Our conclusions were that man powered flight is just possible if the aircraft is carefully designed to give excellent aerodynamic characteristics, with a stiff, light structure and flown by a pilot whose power output is comparable with that of a National Amateur Cycling Champion. Such a machine would not fly more than fifteen to twenty feet above the ground and could operate only in still air conditions. The type of aircraft which emerged from the calculations was similar in general principles to those being developed currently at Hatfield and Southampton.

In this lecture I propose to investigate some of the basic relationships which are involved in the hope that possible ways of obtaining further improvements may emerge. Since the conclusion of our survey was that flight was marginally possible, slight improvements might well go a long way towards making man powered flight possible.

Since the first decade of this century aircraft have been equipped with instrumentation to show attitude and direction and to assist navigation and to monitor the performance of the prime mover, if any. Their sophistication has grown with the aircraft but while aerodynamic shapes have apparently simplified over the years, instrument configuration has tended towards complex arrays of electro-mechanical analogues.

Fundamentally, instruments are means of data communication between the systems of the aircraft and the human crew, the latter functioning either as part of a closed loop or, alternatively as the monitor of an automatic control. When functioning as a monitor it must always be considered that the human operator may have to revert with minimum delay and disturbance to the first role, namely that of an active part of the control system. In extreme cases of multiplex automatic systems, such as those intended for Auto-land, there may be a case for denying revertion on the grounds that channel redundancy will reduce the failure rate to an acceptable value, added to the fact that the pilot might in fact be incapable of improving the situation after a certain point in time and space had been reached.

After many years of helicopter design, development, and operations, a practical flying crane helicopter is under construction whose particular features promise an unprecedented utility. The steps leading to this new helicopter configuration were evolutionary in nature dating back as far as 1922 when the deBothezat quadrotor machine hovered for one minute and forty-two seconds.

Early military interests in improved mobility of the armed forces and the experiences gained with helicopters in the Korean War gave impetus to the development of vertical lift capability. In addition to the basic helicopter developments specific crane flying test beds and parametric studies were sponsored by the military. These projects included the Hughes XH-17 flying crane, the McDonnell XHCH-1 rotor test programme and the Sikorsky HR2S-1 (H-37) helicopters. In addition design study contracts were sponsored which determined the feasibility of constructing crane-type helicopters of 8 to 16 ton payload capability.

The following is a report of preliminary tests to determine the effect of vortex generators on the drag of a circular cylinder. It was thought that with suitable placement of the vortex generators on the cylinder, the laminar separation of the boundary layer at subcritical Reynolds numbers might be delayed, and a reduction in drag coefficient obtained.

Provided the relationship between the form-parameters H32 and H12is known, the two-dimensional turbulent boundary layer may be calculated by means of the approximate theories of Walz and Truckenbrodt without the necessity for an explicit law for the velocity profile. This relationship H32=f(H12) introduces the influence of the velocity profiles into the calculation. It is the third empirical relationship—beside those for skin friction and dissipation— which is needed to solve the momentum and energy integral equations. The formulae or curves for H32=f(H12) which are given in published papers show considerable deviations from each other so that it was felt necessary to investigate this relationship again. Fig. 1 shows the different curves.

The art and science of re-entering a vehicle into a planetary atmosphere poses many problems, which are today on the edge of man’s mental and industrial capabilities. Re-entering a vehicle into the earth’s atmosphere incurs the following major problems: —

• (a) Kinetic heating as it passes through the denser regions of the atmosphere. Materials have to be found which can deal with the enormous amounts of heating experienced by the vehicle.

• (b) Design of a vehicle to withstand large thermal and mechanical shock.

• (c) Dynamic stability at hypersonic velocities.

• (d) Accuracy of direction of entry into the atmosphere.

• (e) Recovery of the capsule after impact, wherever it landed.

This paper deals with the kinetic heating aspect of re-entry and shows how present day materials are utilised in restricting the inside temperature of re-entry vehicles to within reasonable limits. Unmanned re-entry is specified because to re-enter a manned capsule puts large restrictions on deceleration and inside temperature limits and hence produces some unique problems which are not covered in this paper.

The fundamental advantage of two-dimensional photoelasticity is its great simplicity. Neither the frozen-stress three-dimensional method nor the photoelastic layer technique share this simplicity as yet. Whereas the frozen-stress and layer techniques are most suitable for final investigation into the strength of a finished design, the simple plane photoelasticity can be used as a tool by the designer at every stage of his design, as a specialised slide rule, so to say, that gives sometimes faster and frequently more accurate answers than complicated stress calculations. The consequences of given changes in the outlines of a component can often be studied more conveniently and cheaply by this method than by almost any other.

For many years certain similarities between the mechanics of the sailing yacht and of the slow speed aeroplane have been recognised and the wealth of knowledge in the science of “Aerodynamics” has undoubtedly led, by the slow process of evolution, to increased ability of the yacht in skilful hands to beat to windward. Interesting comparisons in this respect have been made by Davidson. But there are essential differences between the yacht and the fixed-wing aircraft, apart from the more obvious ones, which are so profound that a study of yacht dynamics would appear to be worthy of more attention than it has yet been given.

Brearey was a most energetic Honorary Secretary. His belief in the ultimate success of the cause which he had taken up in the fiftieth year of his life with such enthusiasm was practically demonstrated by the many aircraft models with which he experimented and the lectures he gave. As has already been noted, he was not content with encouraging an interest in Aerial Navigation by means of the Aeronautical Society, but he founded the Aeronautical Club, where the more enthusiastic members could meet on the third Tuesday in each month and discuss their ideas in private. It was owing to the meetings of this Club that public lectures were arranged and demonstration given at the Annual Meetings of the Society.

Recently Cox and Boxer determined natural frequencies and mode shapes of flexural vibration of uniform rectangular isotropic plates, that have free edges and pinpoint supports at the four corners. In their analysis, they obtain approximate solutions of the differential equation through the use of finite difference expressions and an electronic digital computer. In the present note, the frequency expression and mode shape for a square plate, vibrating at the lowest natural frequency, are determined by considerations of energy. The values obtained are compared with those given in reference.