Improving operational flexibility and managing inventory in an aero engine repair shop environment: a simulation-based approach

This study addresses the persistent issues of excessive work-in-process (WIP) inventory and poor service levels in an aero-engine component repair shop operating under a Material Requirements Planning (MRP)-based shop floor control (SFC) system. The research aims to evaluate and identify a more responsive, low-investment control strategy that can improve turnaround performance without compromising operational simplicity. Four established SFC mechanisms-MRP (push), KANBAN (pull), Hybrid Theory of Constraints (TOC), and Constant Work-in-Process (CONWIP)-were comparatively assessed through an ARENA-based discrete-event simulation model that replicated actual repair operations. Quantitative evaluation across key indicators-service level, flow time, repair lead time, and total WIP-showed that CONWIP outperformed both MRP and current practice, achieving the shortest average repair lead time of 9.33 days and the lowest total WIP of 39.22 units under normal conditions. Under lumpy demand, CONWIP sustained 7–8% higher service levels while limiting lead time variability, although a wider spread (standard deviation of 20.68 days) was observed. A FIFO scheduling scheme further improved CONWIP’s lead time and inventory performance, confirming the sensitivity of pull systems to queue discipline. Overall, the findings establish CONWIP as a robust and intuitive SFC alternative for repair shop environments, enabling a reduction in lead time of up to 40% and significant inventory optimization without incurring additional capital or training burdens. The study advances the objectives of UNSDG 9 (Industry, Innovation and Infrastructure) and UNSDG 12 (Responsible Consumption and Production) by promoting adaptive, resource-efficient production control in maintenance, repair, and overhaul (MRO) industries.