Is prevention better than cure?

This paper uses a discrete event simulation model to compare a number of different maintenance policies applied to high–value, repairable assets subject to age–related failure modes with particular reference to aero–engines on civil aircraft. The policies considered range from one of allowing components to fail before doing any maintenance through various forms of opportunistic maintenance to full preventative maintenance by setting hard lives to drive assets into maintenance. The conclusions reached are that setting soft lives tends to be more cost effective than hard lives but using target build lives (a method described in more detail within) tends to be even better. Simply waiting for parts to fail is only sensible if the cost of arisings is negligible. For airlines, engine failures are likely to result in diversions, delays and cancellations as well as customer dissatisfaction and potentially litigation, all of which can be extremely expensive.