AD FAA-2013-0239

We are adopting a new airworthiness directive (AD) for all Eurocopter Deutschland GmbH (ECD) EC 135 P1, P2, P2+, T1, T2, and T2+ helicopters equipped with a certain main transmission housing upper part. This AD requires installing a corrugated washer in the middle of the main transmission filter housing upper part and modifying the main transmission housing upper part. This AD was prompted by an inspection of housing upper parts that revealed the bypass inlet in the oil filter area was not manufactured in accordance with applicable design specifications. The actions of this AD are intended to prevent failure of the main transmission and subsequent loss of control of the helicopter.