A new methodological approach to dispatch reliability in spare parts inventory management for airlines

Abstract

The performance of aviation spare parts inventory management for commercial airlines depends on the timely availability of the required parts for maintenance. Inventory performance is often evaluated using the fill rate, which is defined as the proportion of part requests that are fulfilled within the specified lead time. Although the fill rate is easy to calculate, it does not explain how inventory shortages lead to flight operations. The present paper proposes a new inventory performance measurement: dispatch reliability. Dispatch reliability represents the probability that parts critical to the departure of incoming flights are available at the moment of failure. Dispatch reliability is comprised of two observables: the Poisson-based fill rate for each part and the historical failure risk for each part on incoming flight. The subsequent case study evaluates ten critical repairable parts for departure in the Boeing 757 fleet, including their removal records and the corresponding recommended spare parts list. The study then generates several inventory level combination scenarios using Latin hypercube sampling. A comprehensive analysis was conducted to calculate the overall fill rate, overall dispatch reliability, and the total inventory cost for each scenario. The results demonstrate that, when grouped by nearly the same fill rate, scenarios that are oriented towards dispatch reliability can significantly improve the performance of inventory management without substantially increasing total inventory cost (or even reducing it in some scenarios). The results also demonstrate that fill rate alone may obscure opportunities for cost-neutral inventory management. By combining fill rate with the proposed dispatch reliability, airlines can identify inventory plans that provide higher operational flexibility at the same or lower cost.