Material specifications and associated statistical design allowables for many of the "workhorse" metallic materials for aerospace were developed many years ago. In most cases, the minimum mechanical properties in the AMS or MIL specs and the allowables in MIL-HDBK-5 (now MMPDS) have remained unchanged since that time. However, in the passing years, material suppliers have come and gone, processing and purity have been improved and the push for lower costs has led to changes in production methods.

The net result of these changes is that the applicability of published mechanical properties for currently produced material is not always known. Examples will be presented to illustrate this potential impacts (positive or negative) for structural design and analysis engineers and those responsible for aircraft certification.