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THE assumption of a pin‐jointed end condition will give optimistic results when the stress condition near the ends of a strut in a rigid‐jointed frame are of importance. The method given in this note suggests a means of determining the stress distribution in such cases.

NUMEROUS difficulties are encountered in any attempt to ascertain the loads which come into action on a gyroplane rotor blade, and the stresses which these loads impose on the blade. The loads are not steady but variable, complicated and subject to intractable fluctuations. In consequence the blades are in a continual state of agitation. Even when various simplifying assumptions are made the resulting differential equations of motion do not readily yield to conventional methods of treatment. So far as the modes of free vibration are concerned the analysis is relatively simple, but so far as the stresses in forced vibration are concerned the difficulties are formidable. In this paper it will be assumed that the loading over the blade is steady at any instant of a given flight condition. Subject to this restriction, the stresses in the blade may be found to any required degree of approximation by the generalised theorem of three moments suitably modified. In addition the gyroscopic moments of a blade and its frequency of “Happing” vibration will be found on the assumption that the blade is rigid and regard being had to imposed rotation.

THE method given in “The Stressing of Rigid‐Jointed Frames” published in the Journal of the Royal Aeronautical Society for June, 1936, may be applied to the case of frames embodying initially curved members, as for example, monocoque rings.

THE importance of achieving a low structural weight is illustrated by simple estimates of the large decreases in aircraft gross weight and size made possible by conscientious weight saving in structural design. A brief review is then made of the many variables in aircraft design which affect the weight of the structure. The review is made chiefly to emphasize the close interplay in project work between the structural and aerodynamic effects of changes of layout. Finally some remarks are made about comparative structural design efficiency. It is concluded that good weight prediction formulae are at present the best means by which the structural design efficiencies of different aircraft may be readily compared.

THE greater part of the development of the components of a complicated mechanism, such as an aircraft engine, can with advantage be done apart from the mechanism as a whole. The study of any part can be more complete and improvements in operation effected more readily when it is not necessary to keep the whole working. A carburettor is in many respects a complete unit whose action may be studied with advantage apart from the engine with which it will be used. While the ultimate criterion of the performance of a carburettor is its behaviour on an engine, a great deal can be learned from suitable bench tests in which the engine is replaced by a suction plant; more use could be made of such testing methods than is done at present.

THE method used at present in fatigue testing aircraft joints and components by applying cycles of constant stress amplitude of a magnitude considered to be the most damaging is based on the assumption that Miner's cumulative damage rule, Σ(n/N)&equals l, holds good. This rule is known to be true only under certain conditions which may not apply to those under which fatigue damage is accumulated in aircraft.