The method referred to in Dr. Coleman's notes was developed with the collaboration of my colleague Mr. J. B. Edwards of Handley Page Research Department. The purpose was to obtain a rational estimate of suction quantities and suction distribution, linked up with measurements of boundary layer profiles and suction quantities on wind tunnel models, and also to assess the effect of a certain degree of roughness of the order to be expected on actual wings. Existing theoretical methods ignore roughness which, however, is a most important parameter not only in wind tunnel tests, but also in flight at higher values of the unit Reynolds number; surface roughness obviously limits the intensity of suction which can be applied at a spanwise suction strip.

It was intuitively assumed that the removal of fluid by suction was equivalent to cutting off the lower portion of the boundary layer profile at the upstream edge of the suction strip and that a rapid re-adjustment of the boundary layer profile within a short distance took place.

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.

A simple and convenient “ endurance chart” for the presentation of basic fatigue data is described, where static failure is regarded as simply fatigue failure in one cycle of loading.

This chart shows the effects of mean stress, residual stress and pre-tension, and displays several interesting features of fatigue data. It is easily constructed directly from fatigue test results, and is very well suited to the calculation of stress concentration effects, including “ plastic relief ” effects.

With the aid of such charts the relative fatigue strengths and structural efficiencies of different materials may be readily compared, and it is clearly shown that in certain circumstances a “ high-strength” alloy may in fact have considerably less fatigue strength than a “ medium-strength ” alloy at a given life, or conversely a lower life at a given stress level.

It is demonstrated that the fatigue life of a component subjected to combined mean stress and alternating stress may be found only with a knowledge of the complete fatigue characteristics of the material (such as are presented in the endurance chart); and that attempts to estimate fatigue life from spot-value comparisons, such as the fatigue strength at an arbitrary given endurance, can be dangerously inaccurate. A chart of the form described thus forms a valuable step towards the accurate calculation of fatigue life.

The method is illustrated by the provision of endurance charts for 14S-T (L.65), 75S-T, and D.T.D.683; and with experimental results for notched components of L.65 and D.T.D.683.

An example illustrates the application of the chart to the calculation of the fatigue life for the case of two independent systems of loading acting on a pressure cabin with circular window cut-outs.

When, in the course of his visit to Paris in May 1948, Dr. Roxbee Cox invited me to lecture to the Royal Aeronautical Society on our work in the field of turbopropeller and turbo-reaction engines, I was torn between two sentiments; the great honour which was done to me, and the seeming temerity for a French engineer to discourse on aircraft turbines before some of the people who had been responsible for the W2 700, the Nene, Ghost, F2, Theseus, Mamba, and other engines. The first of these sentiments however carried the day, as it could hardly fail to do in view of Dr. Roxbee Cox's extreme kindness.

Therefore I ask for the indulgence of my audience in listening to this, the first account to be given of the modest work done since 1941 by a team of French technicians, who were specialists in steam and industrial gas turbines, who had foreseen the possible development of the latter for aircraft, and who, completely cut off from the engineering world during the Occupation, at first worked literally in complete isolation, unaware even of the existence of the British and German achievements.

No one denies that speed is an essential to air travel. It seemed curious to me that air liners were operating at speeds varying from 100 to 150 miles an hour, and some months ago I set out to find a logical basis for determining the most economical speed of flight. I did not expect to arrive at an exact solution; but, rather to my surprise, I satisfied myself that I could give a general answer to most of the problems that interested me. I ventured to submit my calculations in a short memorandum to the Aeronautical Research Committee, and I had the privilege of meeting a sub-committee with whom I discussed my ideas. It was suggested that some further calculations on the same lines would be of interest, and it was proposed by Mr. Tizard, the Chairman of the main committee, that I should send a communication on the subject to the Aeronautical Society. The paper that I am reading to-night is the result of this suggestion.

The purpose of this note is to point out that in certain simple cases an immediate solution of the problem of finding- an initial stress is provided by an inverse application of the functions tabulated by A. Berry in his work on the generalised theorem of three moments.

Three years ago I had the pleasure of speaking before the Royal Aeronautical Society, and I feel highly honoured that I have again been requested to say a few words about the German commercial air services. From this request I draw the conclusion that Great Britain is as much as ever interested in the progress of German commercial flying. The essential basis of good relationship between the nations, namely, that in order to understand each other they must know each other, applies also to the realm of commercial aviation. The present developments in commercial flying demand that the nations interested shall work with one another and not against one another. This, however, will only be possible if there is a mutual understanding and knowledge of air activities on both sides.