As stated in the introduction to Section 6.5 the practically important case of an open section tube with no St. Venant torsional stiffness (see Fig. 38) will be treated as the limiting case of the open tube with J as J→0.It will be shown that the stress system g 1 h 1over the open tube degenerates into a stress system gгhг which is statically equivalent to the torque TBS about the shear centre. This stress system is for a uniform cylindrical tube with no J identical to the Wagner-Kappus torsion-bending stress system in open tubes.

This paper contains a report on the principal aeronautical research work carried out by the Aeronautical Committee of the Royal Swedish Institute for Scientific Industrial Research.

The Royal Swedish Institute for Scientific Industrial Research in 1925 appointed an Aeronautical Committee with the object of promoting–scientific technical research work and general development work in the field of aeronautics. In the first place work has been concentrated on such problems in aeronautics which are of particular importance with regard to special Swedish conditions.

The Aeronautical Committee has been concerned in establishing an aeronautical chair, combined with an aeronautical laboratory, at the Royal Technical University in Stockholm. The aeronautical professorship is now established by Parliament, and a professor will shortly be appointed. The establishment of the aeronautical laboratory has been postponed for the present, but there is hardly any doubt that the laboratory will be in being within the next few years.

The idea of using the reaction of a jet of water pumped sternwards from a ship is endowed with a respectable antiquity, but tests on the efficiency of such propellers, whether model or full-scale, have not been extensive. Perhaps the most thorough tests were those of S. W. Barnaby (Thornycroft and Co.) in 1880, described by him in the Proceedings of the Institute of Civil Engineers, Vol. LXXVII, page 1, 1883. This investigator measured the reaction on a nozzle delivering water under pressure into still water by a force balance connected to the nozzle itself. As a result, the “ Waterwitch,” a vessel of 1,160 tons, was constructed to work on this principle, the jet being supplied by a centrifugal pump which took water from a scoop amidships. The efficiency of the jet itself worked out at .71, but with the pump the combined efficiency was only .38.

The theory of the aerofoil has now been studied to such an extent that, from this province, it is hardly possible to expect further material improvement in its aerodynamical qualities : profiles differing but little from an inverse of a parabola (Joukovski profile) would appear to be the theoretical ideal. Subsequent important progress in that respect may be sought only in another direction, viz., in the application of a series of supplementary contrivances having a marked influence on the properties of the flow around the aerofoil. Here we are referring to such devices as the sucking away of the boundary layer (Absaugeflügel), or the insertion of appliances on the aerofoil itself. Nevertheless, up to the present, only one of the very earliest attempts in this direction, namely, the slotted wing, has developed sufficiently to be in any way widely adopted in contemporary aircraft construction.

Before beginning this lecture I have first of all to thank the Air Ministry for permission to give it and to explain that any opinions expressed are my own and do not necessarily reflect the opinion of the Air Ministry.

Secondly I must express my appreciation of the honour conferred on me by the Society in asking me to deliver a lecture before them; though I wish they had chosen a less difficult subject.

As regards the title of this lecture it sounds very circumscribed, but you can't test anything without having a fair idea of what its complete function is or without some standard of reference; and in trying to discuss these parts of the problem I am afraid you will find that I have been, if anything, too. general.

It is many years since aircraft were first A operated under extreme low temperature conditions, mainly by bush pilots pioneering the northern latitudes of Canada.The aircraft used were of the light and semi—medium type fitted with simple, low—powered engines. Consequently, crude methods could be adopted to keep them operating.

With the advent of high—powered boosted—engined aircraft, with their complexity and numerous complicated installations, together with other associated equipments, the difficulties became manifold and the earlier methods used were either impracticable or inadequate.

For this reason, some intensive testing and research has been done on the latest type of aircraft, engines and equipment, in an endeavour to solve the problems and, if not entirely successful, find what medium of success can be achieved with the least amount of subsidiary aid.

A convenient method is pointed out for calculating the response of a damped linear system with one degree of freedom to harmonic excitation. Results of such calculations are usually represented by the familiar “ resonance curves ”—one curve being plotted for each intensity of damping. These curves are not particularly convenient to use and Yates has overcome several of their defects by throwing them into a nomographic form. Yates' nomogram is based upon the concept of viscous damping and it does not give the information of a conventional set of resonance curves in that it relates to the velocity of vibration. By changing over to hysteretic damping, a nomogram of somewhat similar form may be constructed such that it gives amplitudes and phase angles of displacements while retaining the advantages, over resonance curves, of this form of representation.