It is a great pleasure and honour to accept the Royal Aeronautical Society's invitation to deliver the Eleventh Cierva Memorial Lecture. I remember Cierva from a number of meetings and conversations. He was one of the great pioneers without whose work the autogyro would have been developed only far later, or possibly not at all. His significant contributions included the following:

He created a completely new concept, the autogyro.
He perfected the flexible, rotating-wing which was later used by the helicopter.
He demonstrated autorotation. Before Cierva many doubted that autorotation was possible in case of engine failure.

If R. J. Mitchell were still alive, then it is very probable that this creator of the Spitfire, the Schneider Trophy seaplanes, and other classic aircraft would be attracted by the challenge of space flight. This is more than ever likely at this precise point in time, when the technology of the aeroplane is being joined with that of the ballistic rocket, in readiness to take the next great step forward in astronautics with the new vehicles which have come to be called “space shuttles”.

It was with these thoughts in mind that I chose the subject matter of this Memorial Lecture, when the Southampton Branch honoured me with the invitation to deliver it.

On reflection, the development of the Royal Australian Air Force over the past 50 years may be considered to have taken place in three phases—the creation and slow growth of an air force as a distinct entity in the 1920s and 1930s, fostered in part by a series of daring transoceanic flights by both military and civilian aviators; the great expansion of the force during the Second World War which, in half a decade, transformed the RAAF from the biplane era to the jet age; and, finally, the restructuring and development of the force in the so-called post-war era but one, in fact, in which the RAAF has been required to participate in such military operations as confrontation with Indonesia, the anti-terrorist campaign in Malaya, limited war in Korea and the current pacification of South Vietnam.

The five hours flying training obtained under the above Royal Aeronautical Society Award was given at Bristow Helicopter Flying Training School, Army Air Corps Centre, Middle Wallop. In this instance the training consisted of seven approximately equal duration flights in a Westland built Bell 47G-4 helicopter.

My flying experience prior to this award consisted of two short helicopter flights as a passenger apart from scheduled airline flights. I therefore found the flying a thoroughly enjoyable personal experience, and think the flying training will be of some professional value to my career as a helicopter engineer. It is difficult, however, to qualify this training in terms of benefit to my future work since the experience has primarily led to an environmental appreciation of the helicopter in flight.

There are several situations of practical importance where it is essential to maintain a satellite in a fixed orientation relative to the earth. Of the numerous methods proposed for such station keeping, gravity gradient stabilisation has gained considerable attention primarily due to the passive nature of the system. The pioneering work for pure gravity orientated satellites was carried out by Klemperer who obtained the exact solution for planar librations of a dumbbell satellite in circular orbit, and by Baker who found periodic solutions of the problem for small orbit eccentricity. Schechter attempted, with limited success, to extend Klemperer's solution to non-circular orbital motion by perturbation methods. Zlatousov et al and, more recently, Brereton and Modi successfully employed numerical methods, involving the use of the stroboscopic phase plane, to analyse motion in the large for orbits of arbitrary eccentricity.

In a recent note, Allen has investigated the use of Preston tubes and Clauser charts for determining the skin friction in supersonic, boundary-layer flows. He concluded that the Preston tube was best used in conjunction with the law of the wall of Fenter and Stalmach but that the Baronti and Libby wall law was most suitable for determining local skin friction from velocity profiles; both methods are complex and do not permit the direct use of Clauser charts. The present note presents a simple transformation which permits incompressible Clauser charts to be used for the evaluation of skin friction in supersonic flows; the method is applicable to both adiabatic and nonadiabatic situations. Some conclusions, based on experimental experience, are drawn regarding the determination of skin friction by sub-layer methods.

This paper first considers briefly the properties of titanium alloys in relation to other airframe materials, and describes some applications in the Concorde airframe. Finally there is some discussion of developments which indicate opportunities for extending their application.

Developments in the technology have caused a steady decrease in the cost of introducing titanium into aircraft structures. This encouraging state of affairs has resulted in an increased use of titanium alloys, especially in the USA, where the development of supersonic aircraft has provided a prima facie case for their introduction.

In the UK the technology has not developed so rapidly, although both civil and military aircraft have gradually introduced more and more titanium components, principally forgings (see Fig. 1). Some years ago, however, it became apparent that the British aerospace industry could not afford either the time or the money involved in developing the technology for a specific new project. On the other hand, a new project without a substantial percentage of titanium in its structure could well be less efficient than a competitor featuring a large number of titanium components.

While in the design of aircraft hydraulic equipment and landing gear, the final choice of materials used is obviously influenced by a large number of factors including space, wear corrosion resistance, fatigue and, the achievement of minimum weight at an economic cost is usually a primary consideration, the acceptable premium for each kg of weight saved varying from under £5 to over £200 depending on the aircraft type.

The range of materials available to the equipment designer is wide and it is therefore desirable to formulate some guide lines to assist the designer in making the most appropriate material selection for the type of equipment being considered.

In the paper by Messrs. Wood and Hammond it has been shown that titanium is likely to save weight compared with steel, where complexity together with the cost of manufacture make it necessary to have some material which is “structurally inert”. The presentation also showed that at high complexity factors, changing from aluminium to titanium would add weight. If the presentation could have included the effect of increasing the operating temperature it would have shown a narrowing gap until at temperatures above about 250 °C, aluminium is no longer viable.