Method for investigating repair/refurbishment effectiveness

Aerospace systems that fail in service are often repaired or refurbished and returned to service. 1 2 3 Repair/refurbishment may return the system to the equivalent of new condition, to some state less than new condition, or perhaps even to a better than new condition. Respectively, repair/refurbishment may have no effect on future reliability, degrade future reliability, or improve it. Depending on which reliability state the post-failure repair/refurbishment produces for the system, preventative maintenance schemes can differ dramatically. For example, should the repair/refurbishment return the system to a less than new condition with each subsequent failure, shorter preventative maintenance intervals as a function of number of the maintenance cycles increase overall availability and cost effectiveness. Should the repair/refurbishment return the system to a better than new condition, longer preventative maintenance intervals as a function of number of maintenance cycles increase overall availability and cost effectiveness.