In the first Henry Tizard Memorial Lecture presentee here at Boscombe Down on the 28th October 1964, Professor R. V. Jones gave a masterly survey of the life and times of Sir Henry, as one who knew him well and it will be no part of my plan to retrace the story of this great man tonight.

While re-reading Jones’ paper I was reminded of the men of stature who were around in the aviation business in the years immediately before the Second World War. It was one of Henry Tizard's great tasks to harness these giants at a time when this country led the world in scientific research.

I, personally, had little to do with Tizard as in those days my job was to carry the bags for those who had the message to convey. This in no way detracts from my admiration of him as a quite outstanding person and a rare example of a real scientist who understood the practical problems associated with the interpretation of new ideas.

It is a great honour for me to be asked to give this, the Sixth Henry Tizard Memorial Lecture.

When one attempts to define “advances in helicopter avionics” it is possible to do one of two things:

• (a) either describe in some depth the development of one particular aspect of helicopter avionics, or

• (b) illustrate the broader impact of avionics on the increased use of helicopters in general.

In the present context the latter appears to be the more important because otherwise it is possible to give the misleading impression that helicopter avionics is a limited or narrow field, as it was in the past, whereas it is very wide and covers the whole spectrum of helicopter operations. The importance of avionics can hardly be over emphasised because in many ways avionics transforms the basic helicopter attributes of vertical flight and flexibility, and the continued development of helicopter avionics will be inevitable. It will also be inevitable because, in order to survive, our forces must continually improve their operational capabilities and avionics developments can allow them to do so. Now the most rapid advances in helicopter avionics may be achieved by adapting fixedwing aircraft technology although there are situations where entirely new techniques are called for. In any event the primary task is one of defining and tailoring equipment to the helicopter and its environment.

Given the situation that there is at present something of a resurgence of interest in airships as practical vehicles, and that most people in aeronautics today are not very familiar with lighter-than-air flight, particularly in its technical aspects, it seems worth setting down a brief survey of the special characteristics of airships, as a contribution to the general understanding.

The present article was written with this aim in mind. It refers mainly to non-rigid or pressure airships, reflecting the fact that in most applications these appear to be simpler and cheaper than rigid airships, even for very high volume. However, much of the text applies equally well to rigid ships, and it must be accepted that adopting the “rigid” approach can give a useful extra measure of design flexibility (e.g. for internal cargo stowage).

The advent of SI units makes it necessary to revise many standard constants and numerical values which are familiar to a generation of aeronautical engineers whose education and practical experience have been solely with the British system of units.

Most affected by these changes are not so much those who spend all their time carrying out (computer-aided) calculations, but those who direct such work and whose personal calculations are limited to the backs of envelopes. The task, for the latter, of assessing and communicating data presented in unfamiliar units is very daunting, and the possibility, for them, of ever being able to think in the new units may seem remote.

Shock expansion theory was first used by Epstein to calculate the characteristics of aerofoils with sharp leading edges and attached shock waves. In this case the aerofoil characteristics were found by assuming that the flow downstream of the leading edge shock was the same as in a Prandtl-Meyer expansion with all reflected waves neglected. In 1955 Eggers and Savin considered the extension of the method to three-dimensional hypersonic flows, with particular reference to bodies of revolution at incidence. Eggers and Savin point out that the most important factor influencing the method is the accuracy of the basic conical solution at the apex, since inaccuracies at the apex are reflected strongly in the pressures downstream. For this reason most applications of the method have been restricted to inclined bodies of revolution with pointed noses, since solutions for yawed cones can be used to start the solutions. Recently it has been shown that thin-shock-layer theory as originally developed by Messiter can give accurate solutions for the shock shapes and pressure distributions on the lower surfaces of conical bodies with a wide variety of cross-section shapes and for a wide range of hypersonic flight conditions.

The operating characteristics of certain types of fluidic element and fluid control valves are largely determined by the pattern of reattaching flow downstream of a nozzle or an orifice. In the simpler configurations, where a twodimensional (2-D) pattern can be assumed, the flow is similar to that studied by Bourque and Newman and by Sawyer, following on the earlier work of Dodds. These studies were concerned with the reattachment of a 2-D jet emerging from a parallel sided nozzle to an adjacent flat plate, and took into account the effect of turbulent entrainment on the lateral spread of the jet and of pressure difference across the jet on its curvature.

Rolls-Royce aero engines are used by 200 airlines, 300 corporate customers and 77 armed forces. To date 34 000 aeroplane engines have been built and, in the time that it has taken you to read this far, 10 aircraft propelled by Rolls-Royce engines have taken off.

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