Optimal policies for aircraft fleet management in the presence of unscheduled maintenance

Abstract

This paper presents a fleet management model for military aircraft that generates daily flying and maintenance allocations. This model has two novel features that distinguish it from previous models of fleet management in the literature. Most notably, random unscheduled maintenance is integrated with an optimisation approach. This is important, as unscheduled maintenance is a regular occurrence in day-today military aircraft fleet management, thus limiting the ability of deterministic models to provide useful guidance. Furthermore, the model is designed to discover policies that dynamically adapt to random events to deliver optimal fleet serviceability. Other features of the model include flying-hour based phased maintenance with variable induction (day when maintenance begins), day-based regular inspections, and separate phased and flight-line maintenance facilities with both manpower and line capacity constraints. In the model, serviceable aircraft fly up to a specified number of hours per day. Once a certain number of flying hours has been achieved, those aircraft must begin phased maintenance within an allowable induction range. Regular inspections are an additional type of scheduled maintenance based on elapsed time. Phased maintenance typically takes a few hundred maintenance man hours, whereas regular inspections take tens of man hours. Two types of maintenance facilities are included. Phased maintenance can only be undertaken on the phased maintenance line, and regular inspections are typically undertaken on the flight line. If a regular inspection is due at the same time as a phased service, these can be performed concurrently. Unscheduled maintenance is undertaken in flight line maintenance if incurred on serviceable aircraft, or in either facility if discovered during the course of scheduled maintenance.