In this paper an attempt is made to analyse the overall gains that have been obtained in aerodynamic cleanness in the past, to review the overall performance improvement that can be expected in the immediate future from increased cleanness along orthodox lines, and to survey critically certain more advanced concepts aimed at giving still lower drag coefficients and better performance characteristics.

This lecture does not set out any new method or offer any ideas to enable the design office to start cutting down the weights of new projects.

The last lecture dealing with the weight of aircraft was given by Major T. M. Barlow, M.Sc, M.Inst.C.E., M.I.Mech.E., F.R.Ae.S., in 1929.

This paper is concerned with a suggested technique whereby light alloys, already possessing high mechanical properties due to heat-treatment, may have these properties further enhanced by the judicious use of cold-work. It is proposed that in the search for methods of reducing the weight of important aircraft components, the question of mechanical properties in general, and ductility in particular, should be reconsidered from an unorthodox angle.