The effectiveness of any braking system is ultimately limited by the point at which the wheels lock and slide over the surface on which the stop is being made. When surfaces are clean and dry the adhesion with a rubber tyre is high enough to meet most requirements of braking without risk of skidding. In wet, or in icy conditions, however, adhesion may be reduced to such an extent that, even with efficient brakes, stopping distances are greatly increased and dangerous conditions can arise. Under wet conditions there are special difficulties. Different surfaces may have very different skid-resisting properties and, in addition, when surfaces are wet, the adhesion with a tyre depends on speed, generally diminishing as speed is raised.

I have chosen for my address the subject of Co-ordination of Aeronautical Research in the British Commonwealth, not only because this is a very important and vital matter, but because at this time there are being held in Melbourne meetings between aeronautical research workers from Australia, New Zealand, South Africa and the United Kingdom in certain fields of research. Simultaneously, in Canada similar meetings are being held between aeronautical research workers from Canada, United Kingdom and Australia.

Aeronautical research, like human flight, is of comparatively recent origin as far as serious work is concerned. In Australia we can be proud to have had one of the pioneers—Lawrence Hargreaves—while the Wright Brothers based the design of their aircraft on experiments with aerofoils carried out in a wind tunnel of their own design.

The range of frequency for which aerial systems for aircraft are required is immense: the highest used frequency is over one hundred thousand times the lowest. Very differing techniques are required throughout this range and this lecture will be chiefly concerned with the principles on which these techniques are based, rather than on individual aerial systems.

One method of classification of aerials is by their operating frequency or wavelength range.

More than two years ago Pollard in a paper given to the Society made out the case for the use of fibre-reinforced plastics in the structural field. He and others have shown that materials based on strong, inert fibres, such as glass or asbestos, have mechanical properties which, when stabilised by suitable resins, permit them to function with a high degree of efficiency within certain well defined parameters of loading.

Four distinct groups of resin are used in combination with such fibres, phenolic, polyester, epoxide and silicone. With the present exception of silicone resins, each can be used at low or even contact pressures during moulding and thus do not impose serious processing limitation upon the size, quantity or complexity of the structures which can be contemplated.

The introduction of rational performance requirements governing the operation of civil transport aircraft has given rise to a need for accurate and detailed information on obstructions in the vicinity of aerodromes. This paper states the origin and nature of the requirement and describes a survey technique, a particular application of terrestrial photogrammetry, which was used to meet it.

In the United Kingdom and in other member countries of the International Civil Aviation Organisation considerable progress has been made towards the rationalisation of performance requirements governing the operation of civil transport aircraft.

A method is given for finding the reciprocal of a matrix which is triply partitioned horizontally and vertically in such a manner that the sub-matrices in the principal diagonal are square, but these matrices need not be of the same order. A preliminary rearrangement of the matrix may be helpful.

In theoretical work it is sometimes required to find the reciprocal of a matrix which can be so partitioned that some of the sub-matrices are of simple types, e.g. triangular or nul matrices, and the calculation of the reciprocal may then be facilitated by using formulae for the inversion of partitioned matrices. The same method will be often advantageous in numerical work also. In an earlier paper the reciprocation of doubly-partitioned matrices was treated in a general way and a method was given for triply-partitioned matrices subject to the restriction that the sub-matrices in the principal diagonal are square and of the same order.

Unshrouded impellers of centrifugal compressors and centripetal turbines manifest an increase of the flow losses in comparison with the shrouded ones. Assuming that the controlling factor in such increase of loss is the leakage through the gap between wheel and casing, the author develops a simple theory leading to a formula for the volumetric efficiency. Only one experimental quantity is required for applying the formula; and tentative values, based on some experimental evidence, are presented.

In a previous note the authors gave a method of solution for the problem of a finite rectangular plate under constant skew and inclined loadings, two of the edges being rigidly held and the other two simply-supported. In this note the same problem is considered for a plate in the shape of a parallelogram.

This note shows how a pure resistance analogue can be used to find the lift on low aspect ratio wings travelling, with small incidence, at speeds close to the sonic velocity.

The method is applicable to flat, twisted or cambered wings and is simple in operation; the results obtained being in close agreement with those obtained by calculations based on the same theory.

The solutions given in this note are essentially those corresponding to the Jones theory, which is applicable to low aspect ratio wings at small incidence, travelling with velocity close to the sonic value. Under these conditions it has been shown that the three-dimensional problem reduces to a series of two-dimensional problems in planes perpendicular to the direction of motion. Thus the wing can be considered as a series of spanwise sections, the solution for each section, in terms of the velocity potential, being considered in turn.

The advent of the jet transport age both for commercial and military aircraft will require conversion to jet training for pilots of all types of transport aircraft. This is the time therefore when consideration ought to be given to some comprehensive scheme on an Empire-wide basis for future recruitment and training of Pilots to a common standard.

It is not enough to assume that the needs of commercial aviation will be supplied by the Royal Air Force. There are two sound reasons why reliance on such a flow will prove erroneous. Firstly the training of the R.A.F. Transport and Bomber pilot is much akin to the requirement for the commercial airline, and once Air Forces have trained their long distance pilots they will make a career sufficiently attractive to induce the pilot to stay. Transport Command of the R.A.F. has already inaugurated such a scheme.