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The Fifth British Commonwealth and Empire Lecture will be held on Thursday, September 15, 1949, at 6 p.m. at the Institution of Civil Engineers, Great George Street, Westminster, S.W.1. The lecture will be given by Mr E. H. Atkin, F.R.Ae.S., Chief Designer, Airframe Division, A. V. Roc (Canada) Ltd., on ‘Inter‐City Transport Development on the Commonwealth Routes’.

THE increasing operational speeds of the modern aeroplane have involved the designer of the aircraft structure in problems which necessitate the experimental determination or calculation, not only of the strength, but also of the stiffnesses of the various major components of the airframe. It has become very apparent that stiffness rather than strength is the determining factor in the design of many aeroplane components.

As a result of the election held in March the Council of the Royal Aeronautical Society for the year 1939–1940 is constituted as follows:

THE tapered beam is of frequent occurrence in various branches ofengineering.

TENSION diagonal fields frequently occur in the webs of beams or the faces of hollow torsion members in association with considerable end loads in the booms at the corners.

THE advent of the metal‐ and ply‐covered plane has caused a number of one‐time academic problems in the theory of torsion to become of practical interest to the aircraft designer. Any satisfactory solution, therefore, of the academic problem implied in the title to this paper will be a step towards the more complete analysis of the stresses in the root portion of the metal‐covered wing.

PART III.—Taper Beams with uniform thin webs and concentrated booms of constant cross‐sectional area. This type of girder is shown in Fig. 1.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics and publications of other similar research bodies as issued

ALTHOUGH, in general, curved members are “anathema” to the designer of structures, there are occasions on which they are desirable. For instance, curved members in the sides or top of a cabin or fuselage very often lead to a great improvement in the appearance and comfort of an aircraft. Again, spars with flanges of varying thickness have an effective camber, while cranked push ‐ and ‐ pull rods are obvious examples of this type of member. On these occasions an easy method of determining the strength of such a member is very desirable.

In this article solutions are set out for various types of external loading of a plate in the shape of an infinite wedge. All the problems considered are two‐dimensional in character and a state of generalized plane stress is assumed throughout. The general approach is that developed by A. C. Stevenson in terms of complex potentials, details of which have been published, but a summary of the results required in this article is included in §1. This method embodies also the use of stress combinations Θ and Φ which together with the complex potentials leads to a compactness of solution which compares very favourably with the Airy stress function method, particularly in respect of boundary conditions. Certain classical problems are presented in this light and used to obtain the approximate stress distribution when the beam is under the action of an elliptically distributed load. The effect of the weight of the beam is also indicated. Although not engaged in work on aircraft design, the writer is encouraged by work previously published on this subject to believe that the solutions contained in this article may have applications in that field.