In the Notice of Proposed Amendment (NPA) for the proposed rule, EASA recognizes that rotorcraft are potentially more vulnerable to catastrophic mechanical failures than fixed-wing aircraft. EASA attributes this to their reliance on the integrity of fatigue loaded, single load path components within the rotor and rotor drive systems. Because of this single load-path-reliance, a single failure of any of these components can result in catastrophic effects on the rotorcraft.
Metallic particle detectors are one important strategy used to indicate if a gearbox is generating metal – this helps to provide advance warning of bearing failures and accelerated wear of other components.
EASA believes that metallic particle detectors alone are not a reliable early warning system for certain failure modes, including fatigue cracking. EASA feels that VHM systems are valuable tools for monitoring the health and integrity of helicopter rotor and rotor drive systems.
The proposed rule would set new Certification Specification (CS 29.1465) and associated AMC (AMC 29.1465) covering the design and certification of VHM systems. It would not mandate VHM; instead it would set minimum design and performance standards where VHM systems are included in a design. Actual compliance with CS 29.1465 would be accomplished:
* on a voluntary basis on the part of the airframe manufacturer (were deemed appropriate for a design), or
* to comply with an operational requirement (no operational requirement is yet being proposed), or
* to mitigate a Hazardous/Catastrophic failure condition identified through a design assessment (one could conceive that might include post-design installation in response to an AD condition).
Comments can be placed online at this URL: hub.easa.europa.eu/crt. Comments should be submitted by January 15, 2011.MARPA members wishing to comment on this proposal should forward copies of their comments to MARPA, as well, in order to be sure that any comments that MARPA may file are consistent with the interests of the members. MARPA asks that members file proposed comments with MARPA by December 15, 2010.
