Mathematical Modeling, Optimization and Scheduling of Aircraft's Components Maintenance and of the Maintenance Workshop

Licentiate thesis, 2021

This research concerns the simultaneous scheduling of preventive maintenance for a fleet of aircraft and their common components along with the maintenance workshop, to which the components are sent for repair. The problem arises from an industrial project with the Swedish aerospace and defence company Saab.

While an aircraft operates, its components deteriorate and in order for it to remain operational, maintenance of its components is required. Components that are to be maintained are sent to the maintenance workshop, which schedules and performs all maintenance activities. Our modelling is based on a mixed-binary linear optimization model of a preventive maintenance scheduling problem with so-called interval costs over a finite and discretized time horizon. We extend this scheduling model with the flow of components through the repair workshop, including stocks of spare components as well as of damaged components to be repaired. Along with the scheduling problem, we address and analyze two different contracting forms between the two stakeholders: aircraft operator and maintenance workshop. Namely, an availability of repaired components contract and a repair turn-around-time contract of components sent to the maintenance workshop. We present both an individual and a type-based component flow modeling. Our model is able to capture important properties of the results from the contracting forms and it can be utilized for obtaining a lower limit on the optimal performance of a contracted collaboration between the stakeholders.