Major T. M. Barlow : All historical records of aviation from the earliest attempts at flight to our present-day Schneider Trophy and other record flights, show that in common with those nineteenth century experimenters our modern engine and aircraft designers are in one continuous struggle with the physical laws of weight. It is true that the early pioneers were faced with the problem of flying as such to the extent of carrying one man by a heavier than air machine a few hundred yards, but once this was achieved development quickly enlarged, the problem, and weight, with its relationship to power, lifting surface, safety factors, performance, range, and later—with the coming of civil transport—financial weight in the form of pay load, have become the all important item with the aeronautical engineer and constructor.

It is now rather more than three years since I last had the honour of presenting a paper before this Society dealing with air-cooled aero engines. At that time the air-cooled engine had not fully won a place “in the sun,” which may be fairly stated to be the case to-day.

For some years after the war there was a considerable aversion towards the air-cooled aero engine owing to certain types which had been developed during the war which were supposedly air-cooled, but in reality obtained the greater portion of their cooling by means of exorbitant fuel and oil consumption. As lately as four years ago the practical advantages of the air-cooled engine were only tentatively appreciated by the aircraft constructor, and naturally, owing to his somewhat painful experiences in the past in respect of unreliability and high fuel consumption; it required some missionary work and proof in order to persuade him that the new family of air-cooled engines would really perform in the way their designers claimed for them.

The science of aerodynamics consists in the study of the phenomenon following upon the motion of a body through air, the object being to investigate the nature of the forces brought into action and to discover the reasons for these forces. We know from experience, for instance, that under certain conditions an aeroplane wing fails to exert sufficient lifting force to keep the aircraft in steady flight. From experiment it has been found that these conditions correspond to a breakdown in the flow of air over the upper surface of the wing,, and if we can discover some means of preventing this change we have, at least, served some useful purpose.