Research into Materials Aspects of Aircraft Maintenance and Life Extension — Part 1

OVER several decades the Defence Science and Technology Organisation's Aeronautical Research Laboratory (ARL) has undertaken materials research focussed on support for maintenance and life extension of military aircraft. The reason for selecting this research focus — rather than development of new materials — derives from the fact that approximately half of the through‐life cost of a military aircraft is spent on maintenance. The cost‐effectiveness of research which reduces maintenance costs can therefore be substantial. Similarly, research activities which prolong the service life of an aircraft can provide large benefits by delaying purchase of a replacement fleet; acquisition costs are also large, at approximately one‐third of the through‐life cost of an aircraft fleet. A recent Australian evaluation of the cost‐effectiveness of materials‐related research aimed at reducing cost‐of ownership reported a benefit: cost ratio of the order of 25:1. One example is the Mirage IIIO whose initial design safe life of 24000 flying hours was extended to 4,000 flying hours as a result of research and development carried out at ARL; the aircraft was flown for six years more than initially planned, effectively delaying the need to replace the fleet. This type of life extension R&D requires a range of scientific and engineering approaches, focussed on evaluation of potential problems, and the development of technologically feasible life‐extension measures. Many of the maintenance‐reducing and life‐extension developments for military aircraft are readily applicable to aging civil aircraft. This paper highlights some of the materials research — specifically improved corrosion protection, evaluation of defects using non‐destructive inspection and repair of damage — which is now proving to be applicable to aging aircraft.