As the result of over a decade of intensive Anglo-French effort on both the airframe and the powerplant, the Concorde supersonic transport has completed its development and has convincingly demonstrated its ability to cross the Atlantic non-stop at Mach 2·0 with a full payload.

This represents a major milestone in the evolution of aviation where increases in speed and reduction of journey times have always attracted traffic. It also represents a major break-through in reducing passenger travel fatigue as has been demonstrated to a large number of people during the recent route-proving trials.

This paper is on the practical experience in British Airways on civil helicopters during the past 29 years, and my recommendation for the continued expansion and success in the vertical flight field of which the present day helicopter is the first example.

I still believe that open rotors, because of their low noise and low speed control aspects, will certainly have a future as far as we can see on short stage lengths up to the end of the century; and by short stage lengths I mean up to 4/500 miles.

My experience qualifies me only to discuss maintenance aspects of our operation, and I feel very strongly that we in British Airways Helicopters have been forced into developing major design modifications in the past and that insufficient time and experience has been left over to devote to improving our maintenance philosophies and systems.

This was inevitable in the early days, but I now wish to make our position perfectly clear. We, in engineering, are predominantly in the maintenance business and our development and research time will become more and more biased towards maintenance problems.

In the theoretical and experimental work on the buckling of sandwich panels with laminated faces reported in Refs. 1 and 2, panels which had certain coupling terms present in the constitutive equations for the faces were solved in an approximate manner. The previous theoretical solution for angle-ply lay-ups assumed that there were sufficient layers present to treat the faces as orthotropic, with the Bij coupling terms in the constitutive equations put equal to zero. Further simplifying assumptions were made when comparing theoretical and experimental results in Ref. 2 where tests were carried out on three different types of carbon fibre faces; orthotropic, balanced angle-ply and unbalanced cross-ply. It was only in the first case that an exact theoretical analysis was carried out, and the second case was again treated as an orthotropic panel neglecting coupling between direct and shear deformations and bending and twisting curvatures. The unbalanced cross-ply lay-up, which consisted of two fibre reinforced plastic orthotropic layers, one at 0° to the plate axis and one at 90°, gave rise to large B11 and B22 coupling terms which were taken into account approximately using “reduced stiffness” terms with the orthotropic equations. However, the disparity between theory and experiment was greatest in this case, particularly as far as wrinkling was concerned, where the experimental failure load was 78% higher than the theoretical wrinkling load. This type of cross-ply layup is important since it is used when making carbon fibre sandwich floor panels; it being chosen from the point of view of manufacturing convenience rather than from considerations of strength and stiffness. Furthermore, the bending stresses in the faces, which result from the normal loads, predominate in one direction so that one face is subjected to essentially a uniaxial compressive stress which might cause the faces to wrinkle. In order to study this problem in greater depth, it was decided to carry out further theoretical and experimental work on the simpler problem of the wrinkling of sandwich columns with carbon fibre cross-ply faces.