From time to time w.e hear of mysterious engine failures, sometimes resulting in forced landings, in which the engine is reported to have gradually lost power until it was ticking over or had cut out completely. This may have been accompanied by sticking of the throttle, so that the pilot was unable to control his engine, and by rough running. Full power is usually recovered at lower altitudes or after landing, and when the engine is run up no defects can be discovered. At certain times of the year similar symptoms have been observed in the case of engines running on the test bed.

The liquid-cooled engine is generally associated with high speed aircraft, and as I have had some experience in connection with the development of racing engines, when I received the honour of an invitation to read a paper for the Royal Aeronautical Society, I chose this title because it gave me a chance to further the cause of the liquid-cooled engine and to interest you in possible developments of engines suitable for high speed and other types of aircraft.

In attempting to forecast possible developments, I am taking a grave risk, as anything connected with aeronautical engineering is doubtful owing to the rapid changes which take place in a short time, and I can only indicate where I think improvements can take place, based on present progress, and can only hope that my remarks will invite criticism and discussion.

During the paper the “ hardy annual ” ‘ frontal area ’ will be raised; a slide will be shown of a liquid-cooled engine superimposed over an air-cooled radialof the same b.h.p.

Almost a decade ago, with the rapid world-wide development of air transportation, came the demand for new types of aircraft. It became evident that a plane capable of operating from land or water was the logical step needed to open up larger areas for air transportation. The proximity of water compared with the remoteness of available landing fields to the centres of population was the deciding factor in amphibian development.

While the advantages of the amphibian are obvious, the limitations and; difficulties of creating an efficient plane of this type are also evident. Compared to the seaplane or landplane, the amphibian must take care of the extra weight and parasitic resistance, as well as solve various other problems connected with combining the characteristics of the land and seaplane in one aeroplane.

It is my privilege to present to the Royal Aeronautical Society a brief summary of the work done and the results achieved in developing the autogiro in the last few years. Many fundamental improvements have been the product of that work, but of still greater importance is the considerable progress in the knowledge of the aerodynamics, dynamics and engineering requirements of the new aircraft. The improvements in the formula have been made possible or practical only because of the painfully acquired technique, which, as is the case in all new arts, is a compound of theoretical developments and empiricism.

It has long been recognised that landing and taking—off are the most hazardous periods of the average flight. In this respect an aeroplane is similar to a boat being launched or beached at high speed; the change from one medium of support to another is bound to involve possible damage especially if speeds are high.

So far as risk of mechanical damage, due to uneven aerodrome surface (or swell in the case of a seaplane), is concerned, the speed of landing should be the minimum practicable. Very low landing speeds have a possible disadvantage in that one may not have sufficient aerodynamic control to compete with gusts, etc., but there are few aeroplanes of to-day which have landing speeds so low that this objection can be raised.

The trend of design in recent years has been to increase aerodynamic efficiency by streamlining and to increase the wing loading.

It is unnecessary to enlarge on the importance of the fuels used in aviation in a paper before this Society. Not only is fuel quality the most important individual factor to be considered in the economics of civil aviation, but engine development, aircraft design and performance depend upon it.

An apology is offered, in view of the title of the paper, that as it is barely possible in the confines of a single paper to deal adequately with the volatile fuels (known as petrols and gasolines) used in the normal carburettor or homogeneous charge engines, other types of fuels have necessarily been omitted.

The Compressed Air Wind Tunnel has now been in more or less regular use fpr a little over a year, during which time some interesting results have been accumulated. While these results are not yet by any means complete enough to enable an exhaustive study of scale effect to be made, they are nevertheless of sufficient extent to throw light on several points in respect to scale effect which have hitherto been somewhat obscure, and in particular to show more clearly the relative effects of scale and turbulence on the important phenomenon of the maximum lift of aerofoils.

It may be well to review briefly the history of the development of the Compressed Air Tunnel and to give a very short account of the construction of the tunnel at the N.P.L. and of the preliminary work associated with its special measuring apparatus, as no mention of these matters has yet been made in the Society's publications

It is a great honour for me to address the members of the oldest learned society devoted to aeronautics, the Royal Aeronautical Society, which was founded in 1866—six years before the Société Francaise de Navigation Aérienne of France was founded for the same purpose.

The choice of a subject nowadays is a difficult matter; great progress has been made in aeronautical science—numerous research workers all over the world are endeavouring to solve the outstanding problems—and the reason I decided to take for my lecture the subject of the maximum speeds of commercial aeroplanes was that it appears to me to be a matter of the utmost importance for the future of commercial aeronautics and for linking up the different peoples of the globe.

Turbulent motion in open air must be studied in a way differing from that followed in laboratory experiments. We cannot choose or arrange for the most suitable conditions; we have to make the best of what nature offers; it is nearly impossible to stain air masses sufficiently so that they show streamlines-we have to judge their possible form from complicated effects. The results arrived at will depend upon the means at one's disposal and the way pursued.

Nearly twenty years have passed since the author had the pleasure of giving a paper on the same subject to this Society. Progress in the meantime as regards the means and art of flying has been not only sustained, but rapid, as is brought out by the simple facts contained in Table I. The amazing technology is well represented by the De Havilland Comet, which has just flown tc Australia and back in thirteen and a quarter days, developing 460 h.p. with a weight ratio of i2lbs. per h.p. It therefore becomes interesting and perhaps useful to determine the extent to which metallurgy has contributed and is contributing.

It is proposed to confine this paper to Ferrous Metallurgy, since that is the field with which firstly the author feels most qualified to deal, and secondly, because steel, in a manner unparalleled amongst available metals, can be so profoundly modified in properties by changes in composition and heat treatment.

It is with some misgiving that I come here this evening to lecture to this Society on the training of an aeronautical engineer. The subject is not one which I chose myself; indeed, I think that it is probably the very last which I should have selected to talk about, but the Council of the Society, for some reason which I have not yet been able to understand, invited me to deal with it. I rashly promised to do it, but now that the time has come to redeem that promise I feel that I ought to have refused and chosen a subject on which perhaps I could speak with a little more authority. I suspect, however, that the Council was anxious to obtain a discussion on a topic which to any Society is a very important matter and that I have been put up to serve as a target for your criticism in the hope that something useful may emerge from your comments rather than from my paper.

In section 8 the author's apparatus for the study of skin friction, based on direct application of the momentum theorem, has been described (Fig. 99). In a paper published in 1914, this idea was further developed and it was shown that it is possible to calculate approximately in this way the skin friction and the distribution of air velocities in different régime.

The problem of the maximum lift of airfoils has concerned the authors greatly since there were first discovered in the spring of 1932 serious discrepancies in this characteristic between results obtained in the wind tunnel of the Guggenheim Aeronautics Laboratory at the California Institute of Technology (GALCIT) and those reported from certain other wind tunnels. An elaborate experimental investigation by the junior author and A. L. Klein indicated that the value of CLmax for a given airfoil was strongly affected both by Reynolds number and by the degree of turbulence in the tunnel wind stream.

The present stage in the evolution of commercial aeroplanes brings questions of speed and load into prominence, and it is hoped that an attempt to look at these things from a designer's point of view may be justified.

An aeroplane at first glance might appear to be an uneconomical vehicle. It may have over 100 h.p. installed per passenger, and this gives an expensive impression. The other side of the picture is that aeroplanes can achieve over 60 passenger miles per gallon of petrol at a higher speed than any other form of transport.

In the spring of 1904, when echoes of the Brothers Wright first flights began to be known in Europe, the author founded at Koutchino, near Moscow, on his family estate, the Aerodynamic Institute of Koutchino.

Air is the fluid meant by the term “aerodynamic” and artificial flight was the most important of the applications included in the programme of the Institute; foreseeing, however, the importance of comparative researches in air and water, the author chose intentionally a location particularly suitable for hydraulic experiments. A small river, dammed so as to form a pond, afforded the possibility of regulating the speed of the current at will, and since 1905 parallel researches were carried on in the wind tunnel and in the stream of water.

The idea of such an institute was very favourably received in the Russian scientific circles. When the author asked N. E. Joukovsky, V . V . Kouznetzoff and S. S. Nejdanovsky to participate in the organisation of this institution, they willingly gave their assent.

Tetraethyl lead is a constituent of most fuels of high anti-knock value, but such fuels cause serious corrosion of magnesium-base alloy tanks and may completely penetrate them in a few months. No work on the mechanism of this attack has been published and no satisfactory method for protection exists, so that magnesium-base alloy tanks cannot be used for leaded fuels. Since tanks constructed from an ultra-light alloy would be of advantage for aircraft, experiments have now been carried out to elucidate the mechanism of their corrosion, this work representing the first stage of an attack on the problem of providing protection against such corrosion.

The subject which I have chosen for my lecture this evening must be one of profound interest to all engaged in the design of aircraft to meet military requirements.

This country, with its great Empire sprawling over some three-quarters of the habitable globe and in many parts sparsely inhabited, must form an object of envy to nations cooped up within narrow confines with teeming and everincreasing populations. We therefore cannot shut our eyes to the possibility of attacks being made upon us which we shall have no alternative but to defend ourselves against, if we are going to exist and hold the Empire which our forefathers have bequeathed to us.

The next consideration which we do not require professional training in military or naval tactics to appreciate, is that the predominant and indeed possibly almost solitary duty will fall upon the aviation arm of our military forces to resist attack and carry on a war.

Four essential features are generally required of any form of transportation : Speed, safety, comfort and economy. The airplane must compete with other forms of transportation and with other airplanes. The greater speed of aircraft travel justifies a certain increase in cost. The newer transport airplanes are comparable with, if not superior to, other means of transportation. Safety is of special importance, and improvement in this direction demands the airplane designer's best efforts.