In reviewing the various papers on power controls which have been read before the Society in the past few years, it soon became apparent that, considering the broad issues involved, there is little to add to what has already been said.

D. J. Lyons admitted, somewhat reluctantly, that power controls might become a necessity on aircraft designed to fly for extended periods in the transonic region.

The emphasis in this paper is on design because the author is engaged on design work and, therefore, is more competent to deal with design than with manufacture. In any discourse on design, however, consideration must be given to the available capacity for manufacture, as this has a considerable bearing on the subject.

The application of aircraft to agriculture began in the 1920's; experiments in insecticide dispersal were made in Ohio in 1921 and a bulletin was issued by the U.S. Department of Agriculture on dusting cotton crops by means of Curtiss JN6H aeroplanes in 1924. Since then the idea has been developed, notably in countries of large area. In 1928, for example, crop dusting experiments were made in the United Kingdom but the results were not very encouraging because of the drift problem with comparatively small fields.

The object of this paper is to indicate briefly the suitability of plastic materials to aircraft construction and design. Attention is focused on the mechanical properties of the materials, and the types of design. At the same time, the general engineering worth of the materials under service conditions is indicated.