This paper presents a rational method of stressing single or many cell tubes particularly of the type encountered in wing structures. The theory has been developed for conical or cylindrical tubes of arbitrary cross-section the shape of which is maintained by a closely spaced system of diaphragms rigid in their own planes and parallel to the root section. Within the limits of the assumptions the theory is exact for right cylindrical tubes, and is applicable with adequate accuracy to cylindrical or conical tubes in which the inclination of any generator to the normal to the root plane does not exceed 10°.

The analysis given unifies the theories of bending and torsion and shows that the commonly used method of separating the bending and torsion loads by means of a shear centre is in general incorrect.

The formulae have been developed in such forms that attention is concentrated on the necessary corrections to the stresses as indicated by the ordinary engineers' theory. These correction terms include all effects of shear lag, diffusion, and end effects hitherto taken into account only in some very special cases.

Particularly important for practical applications is the structure consisting of a number of direct stress carrying members (booms) connected by walls effective only in shear. The simplest structure of the latter type is the four-boom tube with or without nose and trailing cells, and in this case explicit formulae are given which are immediately applicable to practical calculations. Formulae are also given for the more complex case of a six-boom tube in which the two extra booms are introduced to represent more accurately the direct stress carrying capacity of the top and bottom panels between the two spars.

A simple formula is presented for the safe life of an aircraft under reasonably good operating conditions from the standpoint of wing fatigue. Gusts are treated as the main factor in determination of fatigue life, though other factors are allowed for as being secondary. Before the formula can be used a simple fatigue test is required on critical components, and is repeated several times to establish variation of nominally identical specimens. The loading cycle for this test corresponds to a sequence of up and down gusts of 8 ft./sec. equivalent velocity. The life obtained is termed the “Standard Life” and corresponds to normal operating conditions on European air lines. Reservations in the use of the formula and correction for other operating conditions are discussed in general terms.

The Air Mail route from Cairo to Baghdad is now securely established. Seven years ago the major portion of it, from Transjordan to Iraq, was no more than a project in certain far-seeing minds. The maps of this region between Amman in Transjordan and Ramadi, a little market town on the Euphrates, 65 miles west of Baghdad, were until 1921 painfully reticent. The countries of Egypt, Palestine, and to some extent Transjordan, had been fairly accurately mapped for some time, and were flown over extensively during the war by ourselves and the Germans. The landmarks are generally speaking abundant, and from the navigational point of view they therefore present no outstanding difficulties.

My purpose is to try to place before you three broad main problems which cover numbers of subsidiary matters of great significance. Taking safety as read (and safety itself is not a problem but a necessity, begetting various problems in varying circumstances), my divisions of the subject are: —

1. 1. Reliability including regularity.

2. 2. Safety in the context of economy.

3. 3. Economy of operation.

It is with considerable diffidence that I find myself about to address you to-night upon the subject of the Paper, which is “The Training of Aircraft Apprentices.” I say with considerable diffidence, firstly; because I realise how very important to the future of aeronautical practice is this question of the preliminary training of mechanics, and secondly, because my own practical experience of this subject is limited to a few years.

I hope that some of those who will take part in the discussion, after the reading of the Paper, will correct any mis-statements I may make in connection with civilian apprentices and will be able to put before you such problems as, are peculiar to that side.

This paper is concerned with a method of improving the utilisation of metal cutting machine tools and thus deals with that part of production covered by machining. It is particularly applicable to the Aircraft Industry, where the production of military aeroplanes must be as rapid as possible and the costs of civil aircraft in a competitive market must be kept to the minimum. As it is designed to be used in conjunction with small quantity manufacture it can be of great assistance in development work.

The limitation to the rate at which machining of any part can take place is generally dictated by the rate at which information can be transferred to a machine tool and converted into appropriate slide movements. In large scale manufacture where batch sizes are high, this transfer of information is normally effected by elaborate pre-set tooling arrangements and the cost and time required to prepare this information is acceptable only as the cost per part becomes very small.

The stresses in annular frames of constant flexural stiffness, as they occur in thin-walled shells are determined, assuming a finite depth of frame cross-section. The calculations are carried out for the fundamental load cases and the results presented in the form of diagrams.

When the Council of the Society did me the honour to invite me to deliver the Wilbur Wright Lecture I found myself in a dilemma. Many of those whose lives are concerned with engineering or with scientific research must feel, as I do, that after a certain stage they cease to be quite the real thing. The realities of the workshop give place to a daily round of files, reports and estimates, and the laboratory knows one only as a visitor.

When a man has entered upon this ink-stained path and is invited to give a public lecture, there are only two things he can do, except refuse. He must either plagiarise or generalise. Of the two, on grounds of morality, I prefer the latter; but it has the disadvantage common to most moral alternatives, it is much the more difficult. For myself, too, there is a further complication, because the field in which I might feel qualified to generalise would be on some subject relating to engines and their development.