It may be said that the title of this paper covers too wide a scope to be dealt with satisfactorily in the time available and that as a consequence the treatment of each section will be of a sketchy nature.

This is undoubtedly a justifiable criticism, particularly from the point of view of a specialist, but the aim has been to present what it is hoped will be helpful information of a practical nature to builders of aircraft rather than aero engines. There is no intention to enter deeply into the technical aspects of the applications of aluminium and its alloys to aircraft, but rather to review some of the many problems and enquiries which have been encountered during several years' contact with the aircraft industry.

When the writer undertook the preparation of this paper, he rapidly discovered that it was not easy to find any branch of the subject which had not already been dealt with exhaustively by far abler pens than his. One or two matters have, however, been chosen about which information is somewhat meagre or scattered, and which may not, perhaps, be familiar to the aircraft engineer.

First a review will be made of the various types of electronic engine indicator which have been developed up to the present time; this instrument is coming into prominence now, and although it has by no means reached a state of perfection, it is a valuable asset in the hands of the research engineer for the study of fuel problems and other minor points.