A meeting of the Society was held in the Great Hall of the Institution of Civil Engineers, Great George Street, Westminster, S.W.1, on Thursday, 31st October, 1946, at which a paper on “Aeroelastic Problems at High Speed,” by Professor A. R. Collar, M.A., D.Sc, F.R.Ae.S., was presented and discussed. In the Chair, Dr. H. Roxbee Cox (Vice-President).

This Paper was originally written at the request of L'Association Francaise des Ingenieurs et Techniciens de L'Aeronautique (AFITA) and was presented at a meeting in Paris on 30th April, 1946. The Service Technique of the French Air Force were also interested.

The Paper reproduced here represents the entire lecture, except for those parts which were concerned purely with the French picture.

During the past few years a new series of low drag aerofoils has been developed which represents a radical departure from earlier practice. The changes envisaged are much greater than those which accompanied the general change-over from the biplane to the monoplane, and give rise to many problems whose solution requires considerable theoretical and experimental work. An important feature of the new sections is the precision in design and manufacture which is essential for their success. This has given renewed interest to the investigation of many of the detailed problems of air flow and calls for parallel improvements in manufacturing technique so as to achieve the high standard of surface finish required.

The purpose of this paper is to give a brief account of the theoretical basis of the design and application of the modified profiles as aircraft wing sections. It deals with the design of aerofoils for the subsonic range only, or, to be more precise, for flight at speeds below the critical Mach Number at which shock waves are first formed. The critical value usually lies in the range 0.6 to 0.8, depending on the wing shape and incidence, as will be described in more detail later.

Some aspects of the determination of the strength of materials formed the subject of two meetings held jointly with the British Rheologists’ Club (President, Prof. E. N. da C. Andrade) and the Royal Aircraft Establishment in the Assembly Hall, Farnborough, on the 16th June, 1945, and with the Royal Aeronautical Society in the library at 4, Hamilton Place, on the 19th February, 1946, under the chairmanship of Sir Ben Lockspeiser.

At the Farnborough meeting three papers were read, namely, “The investigation of failures in wood by microscopical examination” by M. C. Pryor and A. Rayne; “The effect of duration of loading on the strength of brittle materials” by C. Gurney; and “Application of statistical methods to mechanical test results” by B. Chalmers and E. R. W. Jones. At the London meeting Prof. N. F. Mott of Bristol University spoke on the “Griffith theory of cracks in solids and recent developments of this theory, with application to brittle fracture in glass and in metals.”