Commercial aircraft, in common with all public transport, must be subjected to routine inspections and regularly overhauled in the interest of both safety and economy.

Aircraft maintenance and overhaul are not just the domestic concern of the organisation doing the work. There must be adherence to Standards approved by the Air Registration Board on behalf of the Ministry of Civil Aviation; and these Standards are the national interpretation of some of the directives issued by the International Civil Aviation Organisation as part of the international agreements regulating air safety. The regulations are neither rigid nor detailed, but they exist for the protection of air travellers against the remote chance of an operator failing to maintain airworthiness. In particular, they call for regular maintenance checks and, to procure annual reissue of the Certificate of Airworthiness, an annual overhaul or its equivalent.

The first part of this paper discusses some fundamentals of Air Transport and shows how these affect the organisation of airline operators. Against this background, Part II examines some of the particular problems of the short haul operator—the side of the Industry with which the author has been associated in British European Airways.

Commercial Air Transport has existed for more than thirty years. It has made important progress, but has still a long way to go to fulfil its destiny. Although progress in developing the vehicle since the first aeroplane flew in 1903 has been highly spectacular, Air Transport itself has made a slow start. This is shown by Fig. 1 which compares the increases in passenger traffic that occurred in the first thirty years of British rail and air transport.

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.

Progress of any organisation may be related either to an assumed basis within the organisation itself, or to some other organisations, preferably competitors in the same business. The second method is more realistic and by relating the corresponding data in ratios, it helps to eliminate to a great extent the influence of price changes, which distort yearly comparisons of revenues and expenses.

In the United States the trunk lines represent over 95 per cent. of the total revenue ton-miles flown on the domestic routes and in international aviation, the largest system with the highest quality of service. Therefore, by comparing in Part I the domestic services of Trans-Canada Air Lines (T.C.A.) to corresponding services of the U.S. trunk lines, the most severe criterion was chosen.

Part II contains an investigation of trends of particular expenses in relation to the total expenses for T.C.A's North American Services.

The 846th Lecture to be given before the Royal Aeronautical Society was read under the auspices of the Brough Branch by Mr. K. G. Hancock, B.Sc, A.F.R.Ae.S., and Mr. P. Person, M.A., A.F.R.Ae.S., on “ Power Steering for Aircraft,” on the 21st February 1952, at the Electricity Showrooms, Hull.

There has been little practical experience in the United Kingdom on the operation and use of bogie undercarriages, although the de Havilland Comet, the production version of which is fitted with four-wheel bogie main undercarriages, has done enough flying now to give some idea of the snags likely to be encountered.

These remarks are confined mainly to the theoretical and practical advantages and disadvantages of bogie undercarriages in general, with brief descriptions of some of the various types.