Uncertainty in availability generated by inventory management controls in a generic repairable item sustainment system

Abstract

For defence logistics, strategic planning is typically based on mean values. Supply flows are estimated from average throughputs, and supply chain resources are allocated to meet average demands. Operations management is also based on mean values. Mean-value based inventory management techniques are the preferred way to maintain the availability of spare parts. Recent research suggests that defence maintenance systems using such inventory management techniques are sensitive to stochastic variability in stock demand. We illustrate that these deliberate planning actions can lead to increased uncertainty in the prediction of output measures such as operational availability. We use Discrete Event Simulation as well as Design of Experiments methods to model a maintenance system for a single type of repairable item. We demonstrate that the inclusion of inventory management leads to increased average availability of spare parts for a vehicle fleet. However, in some cases the variation in availability decreases the system's apparent reliability. © Austral. Mathematical Soc. 2012.