AD 2014-0040 AB412 and AB412 EP
AB412 and AB412 EP helicopters : Tail rotor Drive - Flanged Adapter - Inspection / Replacement.
A crack has been found during a scheduled inspection of a flanged adapter, Part Number (P/N) 412-040-622-101, installed on the tail rotor drive shaft P/N 412-040-621-107 of an AB412EP helicopter.
This condition, if not detected and corrected, could lead to tail rotor drive shaft failure, possibly resulting in reduced control of the helicopter.
To address this potential unsafe condition, AgustaWestland issued the Bollettino Tecnico (BT) 412-139, providing instructions to inspect the affected parts. However, the investigation to determine the root cause of the crack on the flanged adapter is in progress and the instructions of BT 412-139 will be updated according to the investigations results.
For the reasons described above, this AD requires repetitive inspections of the flanged adapters, P/N 412-040-622-101 and P/N 412-040-623-101, installed on the tail rotor drive shaft and, in case cracks are found, replacement of the cracked part with a serviceable one.