In trying to assess the effect of a new material on design there is little past experience on which to draw: the only time when a really new material was introduced was when light alloy began to replace wood as a major structural material. Nevertheless, a few general conclusions can be drawn from this period. Although in the long term considerable changes in structural form may be anticipated, there is unlikely to be any sudden dramatic change in design thinking, rather, such changes will be introduced as a result of continuing development soundly based on previous experience. Improvements in design and analytical techniques will play their part, but the dominant influence will be an increasing awareness and appreciation of the material characteristics; the best ways to use the properties of the material and the manufacturing techniques to which it lends itself.

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.

After an initial evaluation of the carbon fibres and matrix resins available at the time (1968) Hawker Siddeley Aviation embarked, under the sponsorship of the then Ministry of Technology, on the design and development of a number of representative aircraft structural components in order to gain experience of the overall problems involved and to give a lead in determining the direction of the necessary materials and process development programmes. An essential feature of this work was that the components produced should be cleared for extended flight trials so that not only would a good deal of useful service experience be gained but also many principles of quality and process control would be established and a platform for discussions with the various official bodies would be provided. In addition, by using the normal shop facilities for the manufacture of the components, it was hoped to introduce as many company personnel as possible to the new material.

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.