West Africa, particularly British West Africa, has been one of the last areas to be opened up to Air Transport and because of physical and financial difficulties, progress has been slower than in most other parts of the Empire.

As West Africa, even today, is not very well known in other parts of the Empire, it will be useful to give a brief description of the territory and the early history of aviation there before dealing with the special problems encountered in the development of air transport. While the particular territories dealt with in this lecture are the four British West African Colonies and Protectorates of the Gambia, Sierra Leone, the Gold Coast and Nigeria, it will be necessary, from time to time, to make passing reference to the adjacent French territories and even to the Anglo–Egyptian Sudan. The four British territories, unlike those in East Africa, are not contiguous but each is surrounded on the land side by the intervening French territories of Senegal, Guinea, Ivory Coast, Dahomey, Volta, Niger, Chad and the Cameroons.

Because of the limited nature of its application the wind tunnel balance has never been the subject of steady development along well defined lines such as are discernible in the development of most other mechanisms of comparable size and complexity.

The diversity of types and forms of balance which have been constructed in the past, reflect the wide range of tunnel sizes, financial resources, and personal preferences which are characteristic of some laboratory equipment.

The design and construction of a balance suitable for use in a medium–to–large industrial wind tunnel is a relatively costly undertaking, and the problem of providing such equipment is made more difficult by the paucity of published information, of a sufficiently detailed nature to be of assistance in making a decision on either a suitable specification for this class of machine, or the practical means by which a specification can best be met.

As part of the modernisation of the Blackburn and General Aircraft Aerodynamics Laboratory at Brough, a new six–component balance was installed, some few years ago, in a 7 ft. x 5 ft. wind tunnel having a maximum speed of 300 ft./sec. A detailed description of this balance is given.

This note considers two cases of bending beyond the limit of proportionality which have not received a great measure of attention in the past. These are Case (i). A beam subjected to a pure bending moment acting in a plane other than one of symmetry. Case (ii). A beam subjected to a bending moment and an axial load.

A mathematical form is used for the stress–strain curve in order that the results shall be applicable to a large number of materials and to avoid the tedious arithmetical summations which would be necessary if actual stress-strain curves were used. All the results are presented in terms of form factors since this notation is convenient for design purposes and is consistent with current British practice. Although the method adopted in the analysis is applicable to a number of different types of beam cross section, only rectangular cross sections are considered in detail at the present time.

Curves are presented showing the variation of the form factor with respect to the angle of the plane of loading, for Case (i), and with respect to the ratio of bending moment to axial load for Case (ii). These curves are based upon a standardised form of the stress–strain curve which may be taken as representative of a range of aircraft materials. Consideration is given to the automatic satisfaction of present military proof loading requirements when these form factors are used for the estimation of maximum permissible bending moments and axial loads under ultimate loading conditions.

The recommendations of F. P. Cozzone, for dealing with these two problems are examined and comparison is made between the theoretical work of this note and a limited number of test results available for Case (i).

There have been many proposed, but few practical, methods of refuelling in flight since the first early experiments in 1923, and until some three years ago the only tried and accepted method was the “ looped hose ” system developed since 1934 by Flight Refuelling Limited, and still in use (with British equipment) by the United States Air Force.

This system consisted, briefly, in carrying a hose unit with a capacity of some 230 ft. of hose in the tanker aircraft, and a hauling line and windlass in the receiver aircraft. Operators were employed for both tanker and receiver aircraft.

To make contact between the aircraft, the receiver operator first trailed his hauling line, with a “ sinker ” weight on the end of it, so that the line curved downwards. The tanker aircraft then flew alongside and a projectile, attached to a “contact line,” was fired from a line–throwing gun, so as to pass the contact line under the hauling line.

The Conventional method of assessing the direct costs or the aircraft type costs on a passenger mile or ton mile basis does not necessarily give a sufficient indication of the economic merit of a particular type of transport aircraft. It can be misleading when comparing aircraft of widely different design, and it does not indicate the best routes for effective airline exploitation.

The profit margin in relation to the fundamental cost or investment unit of the individual airline must be the ultimate yardstick of transport aircraft selection and this is here analysed with a view to providing further insight into the optimum conditions for potential profits. This study of the subject draws attention to the primary factors involved and suggests a criterion which can be simplified into a form valid for most airline economies.

The normal functions of beam vibration may be used in series to solve statical problems of beam flexure and the recent appearance of tables of these functions has rendered this method practicable. An outline is given of the procedure.

The simple equation of free flexural vibration of beams is

1

where v is the displacement, EI the flexural rigidity andAp the mass per unit length. The separation of variables and the application of appropriate boundary conditions at the ends x = 0 and x = l, gives the following normal functions ϕ(x).