NPA 2022-03

Reduction in accidents caused by failures of critical rotor and rotor drive components through improved vibration health monitoring systems

The use of vibration health monitoring (VHM) systems to monitor the condition of critical rotor and rotor drive components has been demonstrated to improve incipient fault detection capabilities by complementing those provided by traditional inspection techniques. However, the current acceptable means of compliance are not sufficient to ensure that these systems can be used to optimise maintenance interventions for certain rotorcraft systems. 

This Notice of Proposed Amendment (NPA) proposes to enable VHM systems to be a more integral part of the continued airworthiness regime of the rotorcraft and to ensure that better and updated guidance is provided for the design as well as the routine and effective in-service use of these systems. This will allow VHM systems to support the optimisation of maintenance of the rotor and rotor drive system and, thus, reduce the risk of maintenance errors.

An amendment of the associated acceptable means of compliance for large rotorcraft is proposed to clarify the means for establishing compliance with CS 29.1465 where VHM applications are used as a compensating provision for the continuing airworthiness of the rotor and rotor-drive system. In addition, guidance is provided to support the certification of VHM applications for on-condition maintenance of critical components. This should help to promote the development of VHM systems with improved fidelity and reliability. 

With this proposal, the European Union Aviation Safety Agency (EASA) addresses the safety recommendation received by EASA (UNKG-2018-007) related to an accident that occurred on 28 December 2016 at the West Franklin wellhead platform, North Sea, UK involving a Sikorsky S-92A helicopter (registered G-WNSR). The proposal also reflects the state of the art of rotorcraft certification.