The seven year life of the Ministry of Aviation was a time of dramatic change, not only in engine technology, but also in defence and procurement policy, in industrial organisation and in the public image of the aircraft industry. The rapid increase in the cost of developing and producing new aircraft and weapon systems made development management and cost control issues of the greatest importance and much effort was devoted to devising improved management procedures. In summarising the technological achievements of the period, attention is particularly drawn to changes in engine noise characteristics, in selling price and in the growth of overhaul life and reliability. The nature of engine development is examined in some detail and it is pointed out that the development content of engine programmes is normally much greater than that of airframe programmes. The high development effort and expenditure demanded by aero engines is explained and justified. Attention is drawn to the relationship between development cost and (a) manufacturing cost, (b) the magnitude of technical advance.

Some of the problems encountered in the search for an effective system of cost estimation and control are indicated.