The preparatory work of the preceding technical note is followed up by deriving the elastic stiffness and the initial load vector of an arbitrary TRIAX 6 element subject to an axisymmetric state of stress or strain.

The operational sortie of some military aircraft involves a patrol phase. Typical of these aircraft are Airborne Early Warning (AEW) aircraft, or interceptors operated in a “combat air patrol” mode. For this type of operation, the available endurance on patrol is obviously an important attribute, and in presenting the performance of an aircraft the maximum patrol time as limited by the fuel capacity of the aircraft is usually computed and quoted.

However, the overall reliability of a complex modern weapon system is such that the “mean time between failures” (MTBF) is usually not large in comparison with the fuel limited flight time. A significant proportion of flights will therefore be curtailed by failures, which necessitate a premature return to base, rather than the flight continuing to the maximum flight time.

A Definitive history of materials in aviation has not yet been written, and the present contribution makes no claim to fill the gap. It presents a mainly individual impression of significant stages in the development of the materials which have been used for the structures of aircraft from the beginning of practical aviation to the present time. The subject is limited to heavier-than-air machines.

The basic requirement for the structural material of an aircraft is strength with lightness. A host of other properties is significant, and in some circumstances is of critical importance.

It was wise of Duff Cooper to remind us that “old men forget”, and I fully agree with him. But, like so many others, I find myself remembering more about the events of fifty years ago than I do about those of yesterday.

My entry into the world of aeronautics was brought about by R. V. Southwell (now Sir Richard), who asked if I would take a metallurgical post in the RNVR at Kingsnorth. I was, however, placed in the Materials Section of the Technical Department of the RNAS.

The head of the Materials Section was Commander Charles Frewen Jenkin.

Between 1910 and 1966 British aircraft design fell into certain distinct periods, each of which, more or less irrespective of the number and arrangement of the power units, may be recognised by its common structural pattern. In each period, as might be expected, there were exceptions to the contemporary common pattern, often only experimental, or built in srrall numbers.

In the first period, which lasted until about 1924, wirebraced wood airframe structures were the common pattern.