It is important not to automatically apply a newer revision of a material standard to an older design, without understanding the essence of the revisions. Where possible, all revisions and obsolete versions are listed, identified by year of publication. An original standard does much to explain what the original equipment manufacturer was thinking, at the time an aircraft was made. Often designs are a product of constraints of the time, particularly in the evolving field of metallurgy.

Some revisions may be straightforward, eg only the addition of metric measurements to an imperial standard. Some revisions may reflect profound changes in materials and processes as they evolved, eg the introduction of new alloys or vacuum degassing of molten metals. For materials specified during conflicts, some revisions may reflect specific material shortages, and the re-composition of a particular material with substitutes, eg metal ‘Emergency’ alloys responding to nickel shortages during WW2.

The task of navigating from historical materials to modern substitutions is made more challenging by the use of historical classification systems and nomenclature for materials, that may be an alien language to the material scientist of today. A modern material may be identical to a historical material, but be clothed by an almost forgotten language of classification. After much pondering over this issue, the United States derived SAE system for metals classification provides perhaps the best bridge across this problem. For metals, historical standards will list chemical and mechanical properties that can be matched to SAE standards, to begin the journey. I am unable to provide direct recommendations for substitutions, but would always try to help by directing a genuine enquirer to related standards and information. These records will be updated annually, generally in January, so there may be a year’s worth of material not yet displayed. I apologise if I cannot immediately supply copies of some of this material, as it takes a great deal of time to digitise and format these, in between life’s normal obligations.

As the engineers and maintenance personnel familiar with these historic materials and their confident application fly off into the sunset, it is important, at least, to collate this material for future utility. Historic aircraft were often designed for a limited life, while a modern restoration may seek an indefinite life. The correct selection of materials is fundamental. The compilation of these standards is therefore dedicated to the new and coming custodians of our aviation heritage, grappling with problems both old and new, where there never can be such a thing as a dumb question. I have asked plenty, in my time!