The flight of heavier-than-air craft has marked as it were the triumph of man over gravity; while, “the struggle of power versus weight” constitutes an outstanding feature of technical development. Aviation was effectively born on that day when the mechanical engineer was able to design a sufficiently light engine: in France, Ader who conceived and made use of a steam engine weighing only 6.5 lb./B.H.P. (3 kg./C.V.) is credited with the first flight, in October 1897, of a piloted aircraft. A few years later, the Wright Brothers bettered the exploit, thanks to a sufficiently light engine, this time a petrol engine.

The aeroplane in which Louis Blériot flew across the Channel is worthy of attention today, because it is typical of the 1909–1910 type of aeroplane.

In this paper an attempt is made to review present knowledge of the subject of boundary layers at high speeds, without delving too deeply into the theory, and to draw attention to the results of practical interest. The introductory remarks describe broadly the special features of boundary layers in compressible flow, namely the existence of both thermal and velocity layers and their interdependence, the sensitivity of the external flow to the layers, and their inter-action with shock waves. The results of importance arising from the theory of the laminar boundary layer and of its stability to small disturbances are then discussed, followed by a summary of the present inadequate state of knowledge of turbulent boundary layer characteristics. It is noted that progress in the latter must await the production of more experimental data. The paper concludes with a discussion of scale effects and the allied problem of boundary layer—shock wave inter-action.

Much has been written about planning and progressing as applied to manufacture, but there is a noticeable lack of information on its application to the design work which must precede construction.

It is in order to help fill this gap that the present paper has been written.

The paper deals with planning applied to the development of prototype aircraft from the time of submitting a tender up to the first flight of the first prototype.

It discusses the methods of estimating the lapsed time up to first flight, the design man-weeks likely to be expended, methods of measuring design progress and the cost of design changes.