AD 2021-06-02 Prompted By The Failure Of A Second Stage Planet Gear Installed In The MGB

The FAA is adopting a new airworthiness directive (AD) for all Airbus Helicopters Model AS332L, AS332L1, AS332C, and AS332C1 helicopters. This AD was prompted by the failure of a second stage planet gear installed in the main gearbox (MGB).

This AD requires identifying the part number of each second stage planet gear assembly installed in the MGB, replacing an MGB having certain second stage planet gear assembly part numbers with a serviceable MGB, modifying the helicopter by installing a full flow magnetic plug (FFMP), repetitively inspecting the FFMP and the MGB bottom housing and conical housing for metal particles, analyzing any metal particles that are found, and applying corrective actions if necessary, as specified in European Union Aviation Safety Agency (EASA) ADs, which are incorporated by reference. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective April 30, 2021.

Supplementary Information: The EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2020-0022R2, dated December 23, 2020 (EASA AD 2020-0022R2) (also referred to as the Mandatory Continuing Airworthiness Information, or the MCAI), to correct an unsafe condition for all Airbus Helicopters Model AS332L, AS332L1, AS332C, and AS332C1 helicopters.

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Airbus Helicopters Model AS332L, AS332L1, AS332C, and AS332C1 helicopters. The NPRM published in the Federal Register on December 21, 2020 (85 FR 82977). The NPRM was prompted by the failure of a second stage planet gear installed in the MGB of an Airbus Helicopters Model EC225LP helicopter. Airbus Helicopters Model AS332L, AS332L1, AS332C, and AS332C1 helicopters have a similar design to the affected Model EC225LP helicopter, therefore, these models may be subject to the unsafe condition revealed on the Model EC225LP helicopter. The NPRM proposed to require identifying the part number of each second stage planet gear assembly installed in the MGB, replacing an MGB having certain second stage planet gear assembly part numbers with a serviceable MGB, modifying the helicopter by installing an FFMP, repetitively inspecting the FFMP and the MGB bottom housing and conical housing for metal particles, analyzing any metal particles that are found, and applying corrective actions if necessary as specified in an EASA AD.

The FAA is issuing this AD to address failure of a second stage planet gear installed in the MGB, which could result in failure of the MGB and subsequent loss of control of the helicopter. See the MCAI for additional background information.

FMI: www.regulations.gov