The following papers describe developments which are projected in the various areas of the aero-engine scene. I do not wish to pre-empt or overlap these papers but instead propose to attempt to paint a general strategic picture.

Both commercial and military aviation have been transformed by the emergence of the jet engine in the early 1940s. On the civil side, aircraft have become larger, more economical, faster, more comfortable, more reliable and safer. On the military side, the jet engine has made supersonic operation possible and has enabled aircraft size to be reduced even with enhanced mission capability. Also, the small turboshaft engine has enabled the helicopter to be developed to be an integral part of any defence system.

Until the mid-1960s, the civil engines were determined by a need to progressively improve SFC, reduce noise, increase reliability and, at the same time, increase thrust (Fig. 1). We saw only minor changes in cycle and configuration up to the low bypass ratios of JT3D, JT8, Conway and Spey. In more recent times, the large fan engines, JT9, CF6 and RB 211, led to a step-change in both SFC and noise level and the subsequent 10-15 years has yielded progressive refinements of these engines.