Before passing to the subject of the paper may I ask your indulgence for my limited knowledge of English, which prevents my giving a free discourse, and constrains me to a set lecture. This I view with regret since it makes it difficult to impart to my words the lively and vivid feeling which a more formal picture of the importance and attractiveness of gliding flight may not give.

We are looking back on ten years of development and on an unbroken series of ten gliding competitions held at the Wasserkuppe in the Rhön, since 1920.

Range in any given vehicle of transport is generally understood to be the distance that it could travel without requiring to stop for any supplies necessary to maintain its normal performance.

It is, moreover, at least one quality in the aeroplane to which the designer may set a limit to his ambitions. With regard to speed, load carried, and so forth, he faces an endless task, but when range has reached a distance of just over 12,000 miles, equivalent to the greatest distance between any two points on the planet, his task in this respect is presumably at an end and in practice probably much earlier as the distance between which aeroplanes will need to operate will certainly be less than this.

Much has been learnt, in many branches of science and engineering, from the use of small scale models. The earliest successful experiments in humanly contrived flight with heavier-than-air craft, were made with small scale prototypes of the man-carrying machine of a later day : experiments with man-carrying craft, kite, glider and power-driven, followed.

I realise that many readers of this paper know more about private flying than I do; on the other hand, many may not be so experienced or have even flown. I have tried to put in things of interest to both and hope I shall be forgiven if I have put in too much elementary detail, or that my simple suggestions appear childish. I find that often it is the small and simple things which go to make for safety, comfort, and efficiency. I have no technical knowledge other than that gained by sitting behind internal combustion engines, which I have done during a great part of the last twenty years.

The invitation which you, Mr. President, were good enough to issue to me some months ago really amounted, I am afraid, to a request that I should come here to prophesy. My reply was that it was not possible, or at any rate, I did not propose to undertake it. All one could do was to follow the recent development of materials for aircraft purposes as well as possible in order to see the general tendencies of that development and those which seemed likely to be followed in the near future. But even with regard to that limited degree of forecasting, I must warn you that it is undertaken with every possible reservation, and for this reason, that while one may be able to foresee to a certain extent a number of feasible lines of advance, there have always been in the past history of all branches of technology unexpected developments which no man could foresee, and which I personally make no pretence of being able to visualise. Therefore I would ask you to look with more confidence on what I have to say about what has been and what is, than about what may be.

The object of the present paper is to place before the Society certain general considerations regarding the effect of airworthiness regulations on the design of civil aircraft.

I should like first to thank the Air Ministry Authorities for permitting me to read this paper, and to explain that any opinions expressed are entirely my own.

The Air Navigation Regulations, which set up organised Government control of civil aviation in this country, came into effect on the 1st May, 1919, so that the influence of Government supervision has been present during the whole period of post-war development of civil aviation.

An internal combustion engine divides the heat energy obtained from its fuel into three fairly equal parts. About one-third of the energy becomes useful work; rather more than one-third escapes into the atmosphere in the exhaust gases : and rather less than one-third gives its heat to the cylinders and pistons. As its name implies, an air-cooled engine is one in which the cylinders are cooled directly by air. While the engin.e can and does part with a small amount of its heat by radiation, the bulk of the heat is carried away by air moving more or less rapidly over the surface of the cylinders and cylinder head, which are provided with fins in order to increase the surface in contact with the air. As the loss of heat is nearly proportional to the velocity of the cooling air the faster the aeroplane goes the better will a given engine be cooled; consequently, on a high-speed aeroplane it would be permissible to reduce the area of the cylinders in contact with the air; that is to say, we might save weight by reducing the size and number of fins or, alternatively, the velocity of air over the cylinders need not be equal to the speed of the aeroplane.

Since this paper is prepared at the request of the Council of the Royal Aeronautical Society–a body which represents in the main the scientific aspect of aviation–I have endeavoured in preparing it to remember that I must infuse into its composition something of worth to the technician as well as to the pilot. If I manage to convey to the former some of the problems which confront the latter and which are not quite the same as those with which he is himself faced, I may have rendered some small service in response to the honour which the Council of the Society has done me in asking me to undertake this duty.

The possibility of sustained flight by heavier-than-air-machiaes was fully recognised during the last century by those who had studied the aerodynamic problems involved and it was realised that its accomplishment awaited only the development of a prime mover of sufficiently light weight.

Of all the known forms of prime mover, the internal combustion engine alone held out any promise of fulfilling the conditions necessary .for sustained flight, namely, light weight not only of the engine itself but also of the fuel it consumes. Early attempts had, however, been made to fly with steam, propulsion and it is of interest to note that the very remarkable and cleverly-designed steam plant employed by Sir Hiram Maxim in 1894 was actually very considerably lighter per h.p., even including the boiler and condenser, than the petrol engine used successfully some nine years later by the Wright Brothers.

The present-day tendency of automobile design is to increase the power/weight ratio of the engine, while at the same time retaining or improving the efficiency, and to reduce the weight of the chassis generally for a given power. The drawing office creates the efficient engine, and the inspection department enables the design to be put into and maintained in effective production. Now, the modern high-efficiency machine is due, amongst other things, to a more accurate knowledge of stress distribution, and consequently the factor of safety, or the factor of ignorance as it sometimes used to be named, may approach unity—provided that the materials used are consistent.

The work which forms the subject matter of this paper relates to a device for reducing the air resistance of an air-cooled radial engine. It can be added to the engine without completely enclosing the cylinders, either singly or collectively, in streamline casings of the conventional type, which usually render the engine inaccessible.

Six years ago the present authors read a paper on “Aviation Spirit, Past, Present and Future.”

At that time the subject of special interest was the possibility of finding substitutes for petroleum spirit and a variety of alternative volatile combustibles was described.

Six years ago there happened one of the periodical scares regarding a possible world-famine in petroleum and naturally the chemist at that time was anxious, to find substitute fuels.

The recent revival of interest in gliding in this country is my excuse for drawing attention to a feature in the wings of birds whose gliding depends primarily on ascending currents, mainly raptores (eagles, vultures, hawks, kites, etc.), especially in the tropics.

After some thought I have chosen the subject of this paper to enable me to include information gleaned in the last six years of intensive development work at the firm where I am employed, and I think that by this choice I shall be making the most useful contribution towards the production of the ideal engine, safe and efficient, which we all desire.

This paper aims at giving the most important results of modern German research upon the motion of incompressible fluids. Before dealing with the latest developments, I have thought it advisable to give a short account of the older researches upon which the present work is based. It is hoped that this résumé will give a fairly complete survey of the methods that have led to the present insight into the hydrodynamical mechanism.

Many books on aerodynamics are prefaced by a short historical introduction, in which, after having quoted Aristotle for his ideas on the motion of bodies through the air, and Newton, from whom aerodynamics is admitted to start, the name of Leonardo da Vinci is recorded, pointing out that he was the first to attribute to the resistance of the air the cause of the lift and flight of birds, recognising in the same resistance the possibility of solving the problem of flight.

Before opening my subject let me explicitly impress upon you that any opinions I may be found to have expressed in these notes are purely my own, and not necessarily shared by the Service to which I have the honour to belong, much as I owe them to its inspiration.