We have published elsewhere a considerable amount of work on the development of the cathode ray engine indicator and, while most of the pressure elements and circuits which have been developed are perfectly satisfactory on normal petrol and Diesel engines, it has been impossible up to the present time to obtain a really satisfactory pressure-time card on the high duty boosted aircraft engine, the main difficulty being due to the super position of mechanical vibration on the pressure-time diagram. A satisfactory knock indicator has, however, been produced and a few of the results are here discussed, in the hope that they may be of general interest.

In these days of long distance flights across large stretches of ocean aeroplanes will make considerable use of radio direction-finding apparatus, enabling them to keep their course on to a transmitting station at their goal. Over the Atlantic, for example, a series of beacons all the way across would be quite impracticable. The following is an analysis of the course flown by an aeroplane under these circumstances, showing also the increase in flying time over that on a compass course, and also the maximum deviation from the compass course.

I ought first of all to define what a gyroplane is.

A gyroplane belongs to the helicopter family, aircraft which, as their name indicates, have wings in the form of airscrews.

In effect a helicopter consists of large airscrews, with axes nearly vertical and set in rotation by the action of a motor; the reaction of the air on the blades provides the necessary lift to enable the machine to rise vertically, without forward speed.

I will recall that in order to obtain sustentation without forward speed many suggestions have been made for giving to wings a movement which would produce lift.

In conjunction with H. Fingado, the author has described a graphical method for the rapid determination of the critical velocity of a two-dimensional wing without damping (see L.F.F., Vol. 13, No. 11 (20/11/36), pp. 374-387). The present paper presents a continuation of this work taking into account internal damping of the wing.

The main reasons why trouble due to ice formation on aircraft was not experienced so much in the earlier days of flying as now were two-fold, (a) The greatly restricted amount of flying done during the winter and (b) the absence of means whereby flight in cloud for any considerable length of time was possible.

The degree to which ice forms, however, differs widely. Since much depends on the relative speed of the aircraft, free balloons are practically excluded. In the worst case ice cannot form on such aircraft to the extent to which heavy glazed frost is observed on the ground, unless the balloon pilot is a very bad navigator and remains in the danger zone longer than would be required for the ground surface to be coated with glazed frost.

The general idea of making aircraft of single-shell or monocoque construction is not new. In the middle ages, the great English philosopher and man of science, Roger Bacon, “conceived of a large hollow globe made of very thin metal and filled with ethereal air or liquid fire, which would float on the atmosphere like a ship on water,” and ever since the inception of the aeroplane, suggestions have been made to construct aircraft wings and fuselages in the form of shells like those of crabs, lobsters or other popular crustacea.

There is at present, a marked trend in aeroplane construction towards the increasing use of metal covering both for wings and fuselages. The water loads on the hulls and floats of various aircraft have always necessitated the use of a robust skin, and although at first wood was commonly used, this was at an early stage of development, replaced by metal.

The fact that attention must be given to stiffness as well as strength in aeroplane design is now generally recognised. The provision of adequate strength alone is not sufficient to ensure that an aeroplane is immune from such troubles as flutter, loss of lateral control due to twisting of the wing and wing divergence. This is illustrated by the case of the Puss Moth. As shown in R. and M. 1645 this machine was examined in detail by the Aeronautical Research Committee and found to be completely satisfactory as far as the existing official airworthiness requirements were concerned, and yet it experienced failures which were attributed to flutter, an instability involving the stiffness of the wings and tail.

In the earlier stages of the investigations into these stiffness problems it appeared to many practical people that the work. was of academic interest only. As a matter of fact it was of subsidiary importance while operational speeds of aeroplanes were relatively low, but the higher speeds of the modern aeroplane make such problems of direct practical interest.

When I received the invitation to deliver this Memorial Lecture, and “Turbulence” was chosen as the subject, I remembered that my good friend, G. I. Taylor, gave a very stimulating talk on the same subject ten years ago. It was his G. I. Symons Memorial Lecture before the Royal Meteorological Society. He succeeded in fulfilling his job without using one mathematical symbol, the President of the Society, Sir Gilbert Walker, insisting very definitely that “turbulence without tears” was what he wanted. I do not think that I can duplicate Taylor's achievement completely; however, I shall try to reduce the mathematics to a minimum.

The design of an aeroplane to achieve the greatest possible altitude is, from one aspect at least, a simple matter, because it is a case free largely from the compromises usually necessitated in the endeavour to meet best the operational requirements of a specification.

The starting off point must be the engine. I do not propose to touch the engine side of the problem, other than to regard the engine as an “ embodiment loan ” which has been made to the aeroplane designer and for which he has then to design an. aeroplane which shall achieve the greatest possible altitude when powered by this engine. Obviously, the main requirement from the engine is that it shall give the greatest possible b.h.p. per pound of its weight at very high altitudes. This means, of course, the highest possible supercharging and rather indicates the air-cooled radial engine because of the inherent low weight per b.h.p. of this type.

Before the publication of the results of my original work connected with experimental researches in the Laboratory of the Polytechnical Institute of Warsaw (where I had the help of Prof. Huber and the collaboration of Mr. Kurowski and Mr. Maksymowicz), I want to give here some reproduction of the paper of Mr. W. F. Kisielew in “ Technica Vozdushnogo Flota,” No. 1, 1936, on the design of multispar wings. The results obtained here are very different from those obtained in the above article.

The methods of calculation of the stresses are well-known for monospar and two-spar cantilever wings (compare series of articles in the Reports of I.B.T.L.— Institute of Research for Aeronautics in Warsaw), but present-day methods of construction require more and more attention to be paid to multispar wings as described in this paper.

In the present paper it is demonstrated that variations in the Reynolds number as due to altitude are unimportant, provided that NR at sea level is in the region of 107.

That under these conditions the law of velocity in relation to altitude, is implicitly contained in the expression W= KLρV2 x area, in which ρ and V only are variables; i.e., the velocity of flight must vary in the inverse ratio of .

That the velocity limit due to the elasticity of air is lower at high altitude, for the velocity of sound is lower, the optimum flight velocity is higher. The facts concerning this are set forth.

The object of this note is to draw attention to a few facts which, taken together, suggest that, from a purely aerodynamic point of view, the difficulties involved in flight by human power may not be as great as is generally supposed.

Some years ago, in a lecture delivered to the Royal Aeronautical Society, the German soaring pilot, Lippisch, referred to an account of dynamic soaring given by Lanchester in his “ Aerodonetics ” and to some wind tunnel experiments made in Vienna.