Rotor System Diagnostics and HUMS Extensions for Affordable CBM

Whilst drive-train health monitoring is a mature technology and should form an integral part of any helicopter Health and Usage Monitoring System (HUMS), the same cannot be said for rotor system health monitoring, despite the fact that the numbers of helicopter accidents caused by rotor failures are comparable with drive-train failures. This paper summarises research efforts funded by the UK Civil Aviation Authority (CAA) and the UK Ministry of Defence (MOD) that have been targeted at identifying strategies for a next generation HUMS that could diagnose rotor system faults and be used to realise Condition Based Maintenance (CBM). These efforts have focused on helicopter simulations including dynamic/aerodynamic models, finite element representations and a suite of fault simulations. The simulations combined with in-service data have been used to establish relationships between faults, vibration, loads and damage. Thorough investigations of these relationships have been used to establish the requirements for an advanced HUMS; it was concluded that drive-train and Rotor Track and Balance (RTB) diagnostics should be combined with advanced rotor system diagnostics and usage models (e.g., flight condition recognition approaches) to deliver CBM. This paper describes the helicopter simulations, in-service data, rotor system diagnostic strategies and usage models, and presents the main conclusions of the research efforts.