The subject of aircraft production is obviously a very wide one—books have already been written on it—books which have been consulted when preparing this lecture. It is proposed to sketch in broad outline the various methods generally known for the manufacture of aircraft, dwelling perhaps more particularly on some with which I am more familiar and which have recently been used very successfully in French factories. Familiar processes which have been in use from the earliest stages of aviation development up to recent years will not be discussed, but an attempt will be made to bring out the salient particular features of the new processes and the new production methods which seem to offer interest not only from the historical, but also from the technical, aspect at the same time indicating the extent to which aircraft engineers have had to exercise their ingenuity in order to build and mass produce aircraft which are being constantly developed and improved by the Design Offices in different countries.

The one-thousandth-and-fourth Lecture to be given before the Society, " London Airport," by Air Marshal Sir John D'Albiac, K.B.E., C.B., D.S.O., was given on 6th November 1956 at the Institution of Mechanical Engineers, London, S.W.I. Mr. E. T. Jones, C.B., O.B.E., F.R.Ae.S.. President of the Society, presided. Introducing the Lecturer, Mr. Jones said that they were to hear from the most competent man in England to give it, a talk on what he would say was the finest airport in the world. He did not think they had had a lecture on a modern airport before and it was worth while reflecting on previous means of transportation. Every previous vehicle of transport before the aeroplane had had to have tracks made for it to take it from one place to another, as well as terminal stations built for it on long distance journeys. Soma people commented on the costs of airports, the amount of concrete, etc., but when one realised that the air was provided free of charge and itself provided the means for the aircraft to go from one concrete patch to another, one appreciated that the airport was cheap compared with previous forms of transport. Air Marshal Sir John D'Albiac had, he thought, possibly one of the most interesting jobs in London; he met all the personalities, film stars, and so on. He had been there since 1946 when London Airport was converted from a small airfield. He therefore knew every little bit about it, control, runways, buildings and everything. Sir John started his career in the Army. He found that a little too slow for him and so he transferred to the Royal Naval Air Service. Whether he found that still not quite fast enough he did not know, but he later transferred to the Royal Air Force and he remained in that Service until about 1946 when he retired with the rank of Air Marshal.

The general requirements for the complete air conditioning of aircraft are discussed in the light of the complete system concept. The author takes into consideration safety, differential pressure, weight saving, power and air supply, passenger comfort, cooling and humidity. Particular systems are then described and there is a section on the test equipment required for the laboratory testing of air conditioning equipment. Cooling systems are taken first and divided into the air cycle system embodying bootstrap, turbine fan, and regenerative applications of cold air units–the vapour cycle system employing a boiling tank and that using proprietary refrigerants; properties of liquid refrigerants are discussed. Regulation of cabin temperature, air flow, humidity, pressure and oxygen is done by control systems and the equipment used is described. Four appendices give (1) suggested detailed requirements for air conditioning equipment and user requirements, (2) sample data and calculations for air conditioning a 100-seater civil transport, (3) some notes on the definition of refrigeration terms and (4) data on pressure losses in aircraft ducts.

As individuals, those who have been born and bred and nurtured in the long, unique and formative tradition of the British people may justly claim a pride in their scientific and technical achievements over the years which cannot be claimed in such measure by any other nation. It is a claim they can make as proudly this very day as they could have done over the past three hundred years.

In the main, this paper is concerned with but a small, although not unimportant, part of the scientific achievement of the Seventeenth, Eighteenth and Nineteenth centuries. It was a period, in Great Britain, of such giants as Isaac Newton, James Watt, John Dalton, Robert Boyle, Henry Cavendish, Michael Faraday, Charles Darwin, Clerk Maxwell, W. J. M. Rankine, Lord Kelvin, Lord Rayleigh, Sir Charles Parsons, Prescott Joule, C. G. Stokes, Osborne Reynolds, Sir J. J. Thomson, C. Babbage, F. W. Lanchester, and so many others whose ideas and achievements have changed the face of the world in this Twentieth century of application.

A considerable research effort is now directed at the problem of vibrations excited in aircraft structures by airborne sound from the power plants. Both jet and propeller aircraft are involved, although perhaps for different reasons. With jet aircraft the problem is to make the structure strong enough to withstand the vibrations and the accompanying stress fluctuations; with propeller aircraft the problem is usually to prevent the transmission of sound through the structure into the passenger cabin.

This paper is concerned with a method of improving the utilisation of metal cutting machine tools and thus deals with that part of production covered by machining. It is particularly applicable to the Aircraft Industry, where the production of military aeroplanes must be as rapid as possible and the costs of civil aircraft in a competitive market must be kept to the minimum. As it is designed to be used in conjunction with small quantity manufacture it can be of great assistance in development work.

The limitation to the rate at which machining of any part can take place is generally dictated by the rate at which information can be transferred to a machine tool and converted into appropriate slide movements. In large scale manufacture where batch sizes are high, this transfer of information is normally effected by elaborate pre-set tooling arrangements and the cost and time required to prepare this information is acceptable only as the cost per part becomes very small.

Judging by the number of present-day aircraft which have suffered changes of fin shape, it is clear that there is still some difficulty in estimating the size and shape of fin required on a new project. In this paper some of the principles on which fin design is based will be explained, and some of the difficulties involved described.

It is necessary to have some sort of fin to provide weathercock, or directional, stability. This is illustrated in Fig. 1. This shows the balance of yawing moments, due to sideslipping. In general, the side force acting on the fuselage, represented by the black arrow, has its c.p. ahead of the e.g. of the aircraft, and hence it produces a destabilising moment about the e.g. Sufficient fin area must be provided for the yawing moment due to the fin side force, represented by the white arrow, to at least equal the destabilising fuselage moment. Otherwise, when disturbed laterally due to, say, a gust, the aeroplane will tend to swing still further out of wind, making it difficult to fly accurately. The minimum permissible fin area can, in fact, be fixed simply by this requirement for weathercock stability.

The 1,000th Lecture to be given before the Society and the 27th Main Lecture to be held at a Branch of the Society was held under the auspices of the Henlow Branch. The lecture, “Rocket Engines,” was given by Mr. S. Allen, F.R.Ae.S., on 11th October 1956. Professor A. J. Murphy, A.F.R.Ae.S., President of the Henlow Branch, opened the meeting, and Mr. E. T. Jones, C.B., O.B.E., F.R.Ae.S., President of the Society, presided for the rest of the meeting.

Professor A. J. Murphy: Tonight they had the great honour of welcoming to Henlow for the first time the parent body of the Royal Aeronautical Society for a Main Society Lecture. On behalf of the Branch he welcomed the President, Mr. E. T. Jones, several Members of Council and other members of the Royal Aeronautical Society.

He had been asked to introduce Mr. Jones, and of all the redundant things that he had been called upon to do, that was the most unnecessary. All of them were aware of Mr. Jones' distinguished career in aeronautics and would forgive him, as he knew Mr. Jones would, if he did not enlarge on that aspect. However, there were a large number of people both from the Royal Air Force and the Ministry of Supply present and it seemed appropriate to recall that Mr. Jones served as a pilot and flying instructor in the Royal Flying Corps and Royal Air Force until 1919. Thereafter he joined the Aerodynamics Department of the R.A.E. at Farnborough and since then, as they knew well, he had played an increasingly distinguished part in the experimental establishments connected with the Aircraft Industry and the Royal Air Force and in the field of Aircraft Research and Development. This year, in addition to being elected President of the Royal Aeronautical Society, Mr. Jones became the Director-General of Technical Development (Air) in the Ministry of Supply.

Mr. E. T. Jones: This was the first Main Lecture of the Society to be held at the Henlow Branch and in that respect the evening was an historical one.

The practice of holding Main Lectures of the Society at Branches was started in 1948 and the underlying idea was to take the Society to the Branches.

In all, some two dozen Main Lectures had now been given at one or other of the twenty-four Branches of the Society and it gave him much pleasure to see such a large attendance.

This was but the second Main Lecture of the season and curiously enough it was the second to be held at a Branch, This fact caused him to look more closely at the lecture programme and he found that four Main Lectures out of a total of nine this season would be held at the Branches. Thus the Council was doing its best to bring the Society more and more into contact with the Branches and this must surely be a good thing for all those who were interested in aeronautics.

He hoped, too. that it would encourage more of the aeronautically minded to attend those of the Main Lectures which were to be held in London.

Now it was his pleasant duty to introduce the lecturer.

Mr. Sidney Allen was a Fellow of the Society and had had thirty years' continuous experience in the design, research and development of all forms of internal combustion engines for aircraft. For twenty years he had been with Armstrong Siddeley Motors and over the past seven years he had been Chief Engineer of their Rocket Engine Division.

He thought he would be right in saying that few people could have more experience in the United Kingdom of rocket engines and he had much pleasure in calling on Mr. Sidney Allen to give his paper.

When Viscount 720 aircraft were delivered to Trans-Australia Airlines it became clear that increased attention would have to be given to performance analysis and the preparation of flight planning data.

Previous operational experience had been restricted to piston-engined aircraft which, for flight planning purposes, could be regarded as cruising at a certain air speed and burning fuel at a certain rate. Temperature effects were negligible because it was the accepted practice to restore power on hot days by slightly increasing boost settings. Altitude effects, although not truly negligible, were certainly small and could be covered by using flight planning figures from the conservative side of the range. With the Viscount, however, the specific range at cruising altitude was found to be almost twice its sea level value and a 10°C. rise in temperature was capable of reducing true air speed by 20 knots.

Some experiments concerned with the wake flows of a number of flat plates of low aspect ratio (Fail, Owen and Eyre) have suggested that for large angles of inclination to the undisturbed stream the wake includes a region of recirculation. The present observations include a detailed study of this region, with particular reference to the wake produced by an equilateral triangular plate, and an attempt is made to explain why the recirculatory flow is found only at angles of incidence greater than 35°. The data includes some wind tunnel measurements of force coefficients, static pressure and mean velocity, and observations of the wake flow made in a smoke tunnel and in a water tunnel.

So much has been said in the past four or five years of the need for Great Britain to increase the numbers of her trained scientists and engineers, and so much emphasis has been put on training by industry, that the country as a whole is aware, if somewhat vaguely, of the urgency of the present national need. Whether there is a real awareness of the continuing nature of the need, is, however, far less certain; and I make this my apologia for attempting some further discussion of a position which, to engineers at least, is at present patently and painfully obvious. It must be remembered that only a few short years ago, engineering skill was at a discount and the engineer something of a social pariah; moreover, the higher his academic training, the further he was beyond the pale.

It is well known that the performance at high subsonic and transonic speeds of a swept-back wing-body combination in which the wing is untwisted and has the same section at all stations along the span and in which the body is not specially shaped to allow for the presence of the wing, falls far short of what would be predicted for the corresponding infinite sheared wing. For example, with a sweep of 45° and a thickness/chord ratio of 6 per cent it has been found experimentally that a rapid shock-induced increase in drag occurs above a Mach number of about 0·95 and a peak value of CD is obtained at Mach numbers slightly in excess of 1·0, whereas it can be estimated that for the corresponding infinite sheared wing, sonic speed in a direction perpendicular to the isobars (the lines joining points where the pressure is equal) would not be obtained until a Mach number of 1·18 was reached. The poorer performance of the finite swept-back wing results principally from the fact that the pressure distributions for sections near the root and tip are distorted in shape from what would be obtained on an infinite sheared wing and, as a result, the isobars tend to lose some or all of their sweep. With a moderate aspect ratio such as 3, such effects extend over most of the span at high subsonic speeds.

Under the heading “C. of A. Flight Testing” many different subjects could be discussed; most of them, however, and particularly those concerning procedures and basic philosophies, are well understood and need little elaboration: the interest really lies in those items which regularly give trouble and, if I may borrow the current American expression, these “ problem areas ” form the basis of this paper.

In the time available I cannot hope to cover the whole picture and must limit myself generally to the large transport aircraft and, apart from one or two divergencies, to qualitative handling. The paper is my own and I take responsibility for the opinions expressed in it.

From a general consideration of the available data on the flutter of wings with localised masses certain deductions are made as to the possible types of flutter that can occur. On the basis of these deductions it is shown that there is an optimum choice of modes for use in flutter calculations for wings with localised masses. These modes are obtained with artificial constraints imposed on the wing at the localised mass section fixing the wing at this section in translation and/or pitch. It is deduced that for certain mass locations types of flutter are obtained that are insensitive to increase of localised mass, beyond a certain value, with flutter speeds considerably greater than that of the fixed root bare wing. It is also deduced that for the majority of aircraft configurations the maximum flutter speeds for these types of flutter will be realised when the localised mass is in the region of two-thirds semi-span from the root. A limited theoretical investigation is made for a rectangular unswept uniform wing with symmetric and antisymmetric body freedoms, to illustrate and confirm the conclusions derived from general considerations. At the same time the investigation shows that an ill placed localised mass can reduce the wing flutter speed to a very low value.

The purpose of this paper is to review briefly some means of reducing the normal-pressure drag at transonic speeds of wings and wing-body combinations without lift. By transonic speeds is meant here not only the range of main stream Mach numbers around unity but, more generally, that speed range where a transonic type of flow around the body may exist. Thick non-lifting bodies as are considered here cause a displacement flow and it may be recalled that at least three different types of flow are involved: a subsonic, a transonic, and a supersonic type of flow, all of which are here assumed to have one attachment line along the leading edge and one separation line along the trailing edge. This excludes types of flow where separations occur elsewhere, such as shock-induced separations along some line within the wing chord.

High temperatures affect buckling because the properties of the materials change and because thermal stresses and creep develop. A survey is given of the known solutions of problems arising in consequence of these phenomena and new theories of the creep buckling of columns and of thin circular cylindrical shells are presented.

A new concept is put forward which should help materially in the design of engine test cells and ground mufflers. It is suggested that a relatively small spreader can be added behind a jet nozzle which changes, the shape of the jet from circular to a long annular slot. The frequency rise which may be obtained in this way is used to reduce low frequency noise, possibly at the expense of more easily attenuated high frequency noise. As a modest example, tests are described on one particular version which gives an attenuation in the most important low frequency range of nearly 20 decibels. It is shown that the back pressure on the engine is negligible even with a cooling flow equal to the engine mass flow. Other applications are discussed and tested, while suggestions for full scale installations are made.

A simple exposition, using d'Alembert's principle and methods of virtual work, is given of the properties and applications of the normal modes of vibration of a linear elastic system. The use of the normal modes in problems of free and forced vibration and dynamic loading is discussed with the aid of simple examples, and it is shown that by these methods dynamical problems for any linear system may be solved without the use of the fundamental equations of motion, provided the natural frequencies and modes of the system are known. In most problems the solutions converge rapidly, so that only the first few modes of vibration need be considered, and in these cases the solution may be modified to give further improvement in convergence. Unsatisfactory convergence may be obtained, however, in problems where there is an exciting force of very high frequency, or an impact of short duration. An approximate allowance may be made for damping, provided this is small.

The reduction of the vibration amplitudes of a system subjected to external exciting forces can often be achieved by a suitable alteration in the mass or stiffness of the system. The natural frequencies of the system are thereby changed and are no longer in the neighbourhood of the peak harmonic components of the exciting force. This procedure can be shown to have little effect on the problem of jet efflux excitation (unless a really radical change of stiffness is made, such as could only be obtained by a complete change in the type of construction). This is due to the jet efflux pressure field having a fairly flat pressure spectrum and therefore containing harmonic components of all frequencies (over its range of flatness) which are more or less equal in magnitude. However, despite this flatness the spectrum of the generalised force exciting a particular mode has a large peak at the frequency where the sound wave of that frequency has the same wavelength as the structural mode (the coincidence effect).

A problem which occurs frequently is that of choosing a suitable shape for a duct, such as a wind tunnel contraction or an air intake. Basically similar problems, involving potential flow fields, occur in other branches of engineering, particularly in electrical engineering, and the electrolytic tank is now established as a tool which may usefully be employed in their investigation. The use of the simple shallow tank is limited to those fields which can be treated as two-dimensional or axisymmetric, but many problems fall within these categories.

In forming a duct model for the electrolytic tank the walls of the duct are represented by insulating surfaces, and electrodes are positioned to represent two suitable velocity potential surfaces up- and down-stream of the duct. To represent a sector of an axi-symmetric duct the base of the tank must be inclined at 3°-5° to the horizontal and the water line on the tank base then represents the axis of symmetry.