Implementing PHM for Legacy Flight Control Actuators Through Operational Aircraft Data: Approach and Lessons Learned

The prospect of optimizing fleet operations and streamlining maintenance processes has made Prognostic and Health Management (PHM) strategies valued in many engineering applications. However, implementing PHM for legacy equipment presents significant challenges, especially when existing monitoring frameworks were not designed for PHM. This paper presents a case study in which a data-driven PHM framework was developed for an Advanced Jet Trainer's flight control Electro-Hydraulic Actuator (EHA), relying solely on aircraft-level information. Rather than introducing new algorithms, this work documents the process, compromises, and adaptations necessary to extract actionable health and usage insights when ideal data conditions are not available. While PHM typically relies on monitoring equipment status signals to identify precursors of degradation, this approach is often impractical due to the absence or inadequacy of equipment-level data. The architecture described here was specifically designed to operate within these constraints, demonstrating how established PHM concepts can be tailored to real operational environments. The gained experience highlights both the opportunities and limitations of PHM in practice, offering practical guidance for similar efforts in aerospace and other domains where data quality and availability are major concerns. Through this study, we aim to provide a transparent account of the challenges faced, the solutions adopted, and the lessons learned, contributing to the broader understanding of PHM implementation in complex, data-limited settings.