Increasing mechanisation and population densities in our society, coupled with higher standards of living and education, have in recent years resulted in a growing concern about pollution and its effects on the environment. The era of sporadic individual complaints to government is being rapidly superseded by one where strategic concerted action by irate citizens’ interest groups is becoming commonplace. As a result, governments are becoming increasingly involved with the problem of environmental pollution; in Canada, for example, the Environmental Protection Service of the Department of Fisheries and the Environment for fiscal year 1976–77 had a staff of approximately 800 and a total budget of $22 million.

It is to me a signal honour to be invited to give the 33rd British Commonwealth Lecture of this august Society on the subject of the Commonwealth Advisory Aeronautical Research Council. It has fallen to my lot to serve this Commonwealth body from its inception until my retirement a few days ago and, although during most of this period my work for the CAARC has represented only a part of my professional duties, it is a part which has lain very close to my heart.

Many factors influence the choice of the electrical power generation system and the design of the associated busbar distribution network in an aircraft. Beyond the usual factors of safety, initial cost, weight, maintenance cost and the actual rating, the characteristics of the electrical power demanded by the utilisation system, and in particular the avionics equipment, are becoming a factor of increasing importance. The influence of such systems will, of course, vary with the aircraft size, its role, and its overall complexity. Perhaps it is as well also, to point out that the purpose of any system is to enable the aircraft to fulfil its role in the most cost effective manner. This may be a novel approach to the systems engineer whose enthusiasm leads him to believe that the aircraft's sole purpose is to carry around his pet system.