May I say that I consider it a great privilege to be asked to give this lecture to honour the memory of such a distinguished leader in the Aviation Industry.

Of the principles of war defined by Clausewitz the element of surprise has probably made the greatest contribution to success. In the military context therefore denial of surprise to a potential aggressor is paramount. Equally, the acquisition of intelligence to ensure surprise is a vital factor in any operational venture. As General Lemnitzer said in 1963, when Supreme Allied Commander Europe, ‘Aerial reconnaissance permits the effective use of valuable resources and forces and can easily spell the difference between the success and failure of any military operation’. These words underline the importance of reconnaissance to the successful conduct of war. This has been true throughout the history of warfare and perhaps never more so than during the Arab/Israeli wars of 1967 and 1973.

An extension is made to previous work on spheres in thin jets to cover the cases of high stream turbulence and sphere surface roughness. Limited results for the latter agree with past work by Achenbach. Results for cases of increasing stream turbulence line up not only with other high turbulence data but also with Dryden's long-established results for turbulence levels up to a few percent and thereby present some problems, both in the interpretation of the physical flow processes and in nomenclature for the criticality conditions involved.

The effect of backlash and trailing-edge strips on the flutter speed of a two-dimensional model of a tailplane with tab has been investigated in a series of wind tunnel tests. When backlash is present, a change in preload, which is achieved by varying the incidence of the tab, can dramatically alter the flutter speed. The addition of trailing-edge strips to the tab lowered the flutter speed.

The requirements of the first engine controllers were primarily to satisfy the needs of the engine and, almost as an afterthought, to consider interface with the aircraft and the pilot.

The latter resulted in the overwhelming plethora of ‘essential’ ground test-sets and cockpit instruments that we see today. In a performance and integrity conscious world, beset with ever increasing costs and sometimes decreasing maintenance personnel skills, the engine controller can no longer be considered in isolation from the rest of the system that it serves. The obvious ability of a digital system to self-check and diagnose itself, its interface with the real world, and to make intelligent decisions based on those tests, has enhanced the case for digital engine control.

A vibration analysis of waffle cylinders with various stiffener configurations is made using the energy method. The frequency factors of the stiffened cylinders are obtained in terms of various non-dimensional parameters. To make a comparative study, the frequency factors are maximised for a fixed cylinder mass and stiffener eccentricity ratio. It is observed that spiral and circumferential configurations are efficient whereas axial stiffening is detrimental.