*3.1. Approach and Design Goals*

Before presenting the case study and proceeding to the description of the simulation models prepared for the project, it is necessary to detail the scope, objective, and limitations of the research activities. The main research goals pursued with the definition of the PHM system was to provide a proof of concept of a prognostic framework, demonstrating its feasibility within the constraints of a civil aviation application in terms of signals management and computational constraints, while assessing the maturity level of the algorithms available in the literature. As such, it is underlined that the objective of the research activities was not to provide a high-TRL solution, such as a PHM framework ready to be deployed in the operational scenario. In particular, the experimental activities supporting the definition of the high-fidelity models and the real-time models did not involve the study of real actuators under degraded health conditions. Such constraints could be justified considering that the actuators mounted on the iron bird were prototypes produced in very limited numbers, meaning that no spare actuators could be brought to failure during the experimental activities. Faulty conditions were studied through simulations only, through the degradation models available in the literature. It is worth mentioning that even if mutual interaction between different degradations is potentially available, in the context of the present work, only 1 fault at a time was considered for the definition of the PHM framework. Although the results obtained through this approach are expected to be realistic, it is worth noting that the complete validation of the PHM system falls outside the perimeter of the project.
