AD FAA-2013-0554

We are adopting a new airworthiness directive (AD) for Eurocopter Deutschland GmbH (Eurocopter) Model EC135P1, EC135P2, EC135P2+, EC135T1, EC135T2, and EC135T2+ helicopters. This AD requires analyzing the main gearbox (MGB) oil for indications of metal chips or pieces, reviewing the MGB log or equivalent record, and inspecting certain teeth in the MGB after two chip indications. This AD was prompted by a partial tooth rupture found in an MGB that was returned to the manufacturer for repairs. The actions of this AD are intended to detect wear in the MGB that could lead to a gear tooth rupture, failure of the MGB, loss of power to the main rotor, and subsequent loss of control of the helicopter.