<p>Harmonic drives are commonly used in systems that demand high positional accuracy within a compact form factor. Despite these advantages, their use in aerospace applications is still relatively limited, primarily due to uncertainties associated with durability and long-term operational reliability. This work presents a preliminary dedicated prognostics and health management (PHM) framework aimed at fault detection and remaining useful life (RUL) oriented indicators estimation for harmonic drives employed in aerospace electromechanical actuators (EMAs), with particular focus on urban air mobility platforms. The proposed framework integrates model-based approaches with data-driven techniques to enhance fault identification, diagnostics, and prognostic capabilities. The research methodology comprises a comprehensive failure modes, effects, and criticality analysis (FMECA), along with the development of high-fidelity models capable of capturing both nominal and degraded system behavior. A wear-induced degradation scenario is selected as a representative case study. To support the analysis, an extensive simulation campaign is carried out to generate a representative dataset, from which meaningful health indicators suitable for both on-ground and in-flight condition monitoring are derived.</p>