AD 2022-03-17 Prompted By A Report Of Loss Of Tightening Torque...

The FAA is adopting a new airworthiness directive (AD) for all Airbus Helicopters Model AS332L2 and EC225LP helicopters.

This AD was prompted by a report of loss of tightening torque on the nut that attaches the tail gear box (TGB) bevel wheel. This AD requires repetitive inspections (measurements) of the angular clearances of the TGB, and, depending on the findings, replacement of the TGB with a serviceable TGB, as specified in a European Union Aviation Safety Agency (EASA) AD, which is incorporated by reference. This AD also provides terminating action for certain repetitive inspections. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective March 22, 2022.

Supplementary Information: EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2021-0184R1, dated October 8, 2021 (EASA AD 2021-0184R1), to correct an unsafe condition for Airbus Helicopters, formerly Eurocopter, Eurocopter France, Aerospatiale, Model AS 332 L2 and EC 225 LP helicopters, all serial numbers.

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 AS332L2 and EC225LP helicopters. The NPRM published in the Federal Register on December 1, 2021 (86 FR 68166). The NPRM was prompted by a report of loss of tightening torque on the nut that attaches the TGB bevel wheel.

Additionally, the subsequent investigation highlighted that loss of the tightening torque might lead to degradation of the splines between the tail rotor shaft and the TGB bevel wheel. The investigation is still on-going to identify the root cause of the tightening torque loss. The NPRM proposed to require repetitive inspections (measurements) of the angular clearances of the TGB, and, depending on the findings, replacement of the TGB with a serviceable TGB, as specified in EASA AD 2021-0184R1.

After the FAA issued the NPRM, EASA issued EASA AD 2021-0184R2, dated January 12, 2022 (EASA AD 2021-0184R2), which revises EASA AD 2021-0184R1 to correct the allowable angular clearance range. EASA specifies that the angular clearance range specified in EASA AD 2021-0184R1 was defined stricter than the one defined in the service information. Therefore, EASA issued EASA AD 2021-0184R2 to correct the allowable clearance range accordingly. The FAA is issuing this AD to address loss of tightening torque on the nut that attaches the TGB bevel wheel, which, if not corrected, could lead to structural failure of the TGB drive, resulting in reduced, or loss of, control of the helicopter. See EASA AD 2021-0184R2 for additional background information.

FMI: www.regulations.gov