Statistics for Maintenance Modelling: Repairable Systems

# Maintainability¤

Maintainability is defined to be the probability that a component or system that has failed will be restored to full working order within a specified period of time, t.

Times are frequently assumed to be exponentially distributed, and therefore the rate of repair is given by the reciprocal of mean time to repair (MTTR) (click here for a summary of the exponential distribution). In this case, the maintainability,
M(t), may be expressed as:

M(t) = Prob (repair completed before t)

= P (X t) (X is exponentially distributed with mean = MTTR)

= 1 -