The maintenance conversion scheduling problem: Models and insights

Abstract

The maintenance conversion scheduling problem (MCSP) is faced by organizations such as those in the airline, defense, heavy equipment, and transportation industries switching from an asset maintenance program with longer, less‐frequent service visits to one with shorter, more frequent visits. One example is the United States Air Force (USAF) High Velocity Maintenance program piloted at the Warner Robbins Air Logistics Center on the C‐130 aircraft line. The USAF MCSP is complex, as planners must schedule significantly more aircraft depot maintenance visits during the conversion period and must determine the timing and specific order in which each aircraft completes a repetitive sequence of maintenance visits. The conversion is expected to yield a stable long‐term maintenance schedule, while balancing annual depot workload and operating within reasonable flow times and work‐in‐process levels. While practically important, this problem has received little to no attention in the literature. Therefore, this research formalizes the general MCSP within an optimization framework, shows the MCSP is NP‐complete, proposes a computationally effective solution approach, and shows that a balanced long‐term schedule depends critically on the conversion period schedule. Our solutions are markedly better than USAF proposed schedules and underscore the value of leveraging synergies between asset availability and maintenance efficiency. Our approach moves the focus away from batch scheduling toward a smoother, more uniform, mixed‐model type schedule that yields more stable maintenance operations and a more consistent, predictable level of aircraft readiness. The manuscript concludes with a discussion of the main theoretical and practical implications of our work.