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.

The recognition of the political importance of energy supply, inefficient energy usage and its adverse ecological impact combined to produce rapidly inflating energy prices which in turn contributed to an industrial slump. With this platform of a decade of uncertainty, predicting future requirements is, to say the least, somewhat problematical. One thing, however, that seems certain is that the future will offer more free time for the population generally which, together with a continuously improving standard of living, will promote cost effective travel as an essential ingredient to satisfying leisure demand. The most cost effective and energy efficient means of travel over significant distances, and certainly over water, is the 0·70/0·85 Mach No subsonic aircraft. We have, therefore, to speculate about the relative operational priorities of the powerplant to be utilised.

In 1945, the world's first turboprop-powered aircraft took off. It was a converted Gloster Meteor fighter aircraft, powered by two turbopropeller derivative engines based upon the Derwent 2 jet engine (Figs. 1 and 2).

By 1953 the world's first turbopropeller-powered airliner entered service. It was the Vickers Viscount powered by four Rolls-Royce Dart engines (Figs. 3 and 4).

To date, 7125 Darts have been sold and by the end of 1982 they had accumulated more than 100 million hours in service. The case for the turboprop as a powerplant for the commuter aircraft continues as strong as ever it was, but the Dart must be replaced by a low cost more fuel-efficient engine. Rolls-Royce plans for this are outlined.

With the present emphasis on fuel efficiency, a case is emerging for a 90-100-seat twin turboprop-powered super commuter — a market which Rolls-Royce intends to enter. Current estimates for a service date for such an aircraft place it in the region of 1992 to 1995.

The flow from a high aspect ratio rectangular nozzle has been studied, so as to provide data to aid prediction of the effectiveness of this type of jet flow for acoustic shielding. Flow parameters investigated in both stationary and parallel, coflowing, airstreams, include axial centre-line velocity decay, jet width growth and velocity profile similarity. The existence of significant velocity peaks towards the edge of the jet in the plane of the major axis was observed, together with an unexpected interaction on this jet flow by an adjacent circular and subsonic jet.

A method for determining stress intensity factors for cracked plates is proposed. The method uses a generalisation of Westergaard's stress functions to describe the stress intensity at the crack. Eigenfunctions of angular regions are used to satisfy the boundary conditions.