| When two machines are inoperative because of a different failed part in each, a common maintenance practice is to "cannibalize" the required part from one machine to restore the other. Cannibalization actions produce an immediate benefit by increasing the number of operable machines, but at the cost of expending resources (particularly maintenance man-hours) that could be used for other purposes, including repair of the parts that were originally needed. Because cannibalization decisions are an important part of maintenance systems in which the machines are aircraft, this investigation is focused on the decisions of if and when to cannibalize in aircraft maintenance systems, although the results are more widely applicable.;Both mathematical and simulation models are used to test the performance of several cannibalization policies where each policy represents some restriction on the circumstances under which cannibalization is done. The average number of inoperable aircraft (commonly referred to as "backorders") is the primary performance measure, but the frequency of cannibalization, length of backorders, distribution of backorder level, server utilization, fill rate, and proportion of man-hours used for cannibalization are also reported.;The cannibalization policies tested range from no cannibalization to unlimited cannibalization and are based on manpower availability, number of inoperative aircraft, and cannibalization and repair time requirements. The best policies found are those that allow cannibalization only when it can either be done very quickly or when it does not interfere with repair. Complete cannibalization (the policy of always cannibalizing when it is possible) is found to be attractive only when either average server utilization is very low or when average cannibalization times are very short compared to average repair times. |
