Speed in Aviation

Abstract

IN his Friday evening discourse delivered at the Royal Institution on Friday, March 22, Prof. B. Melvill Jones discussed the problems of speed. The speed of aerial transport is limited solely by the power which can be provided to drag the aeroplane through the air, without reference to its support; the power required increases very rapidly with speed, but can be much reduced by good stream-lining. The recent increases in speed of civil air transport are due mainly to improved stream-lining. With well stream-lined aeroplanes the power is expended mainly in overcoming skin friction, so that the detailed study of the skin friction on the curved surfaces of the wings and body merits, and is receiving, great attention by research workers. The magnitude of the skin friction force is delicately dependent on surface smoothness and on the smoothness or otherwise of the flow very close to the surface of the wings and body. After perfect stream-lining, in the ordinary sense, has been achieved, still further important increases in speed would follow from any considerable extension of the area over which the flow remains smooth very near to the surfaces of the wings and body; but to obtain this smooth flow over large surfaces moving at high speeds may be very difficult, and it is still a matter for conjecture how much of the great increase of speed which might conceivably be obtained in this way will ever be realised in practice.