AD FAA-2020-1123

The FAA is superseding Airworthiness Directive (AD) 2016-23- 05, which applied to certain Airbus Helicopters Model SA-365N1, AS- 365N2, AS 365 N3, SA-366G1, EC 155B, and EC155B1 helicopters. AD 2016- 23-05 required repetitive checks of the oil level of the tail rotor gearbox and, if necessary, filling the oil to the maximum level; and replacement of a certain control rod double bearing (bearing) with a new bearing. This AD retains the requirements of AD 2016-23-05 and also requires modifying the helicopter by replacing the tail gearbox (TGB) control shaft guide bushes; repetitive inspections of the TGB magnetic plug and corrective actions if necessary; repetitive replacements of the bearing; and modifying the helicopter by replacing the TGB; as specified in a European Aviation Safety Agency (now European Union Aviation Safety Agency) (EASA) AD, which is incorporated by reference. This AD also adds helicopters to the applicability. This AD was prompted by reports of occurrences of loss of yaw control due to failure of the TGB bearing. The FAA is issuing this AD to address the unsafe condition on these products.