Airworthiness Directives; Eurocopter France Model EC155B and B1 Helicopters

This amendment adopts a new airworthiness directive (AD) for the specified Eurocopter France (ECF) model helicopters that requires cleaning the auxiliary system unit (ASU) board and modifying the wiring and wiring harness. If a temporary modification is done, the AD requires inserting a placard regarding on- ground operation of the emergency landing gear pump (pump). Also, this AD revises the Limitations section of the Rotorcraft Flight Manual (RFM) to limit the operation of the pump. Permanently modifying the wiring and wiring harness and removing the placard and limitations from the RFM is terminating action for the requirements of this AD. This amendment is prompted by the report of an emergency landing with the landing gear retracted. The landing gear failed to extend in normal and emergency extension modes following failure of the ASU board 10 Alpha 2. The actions specified by this AD are intended to prevent an electrical short circuit, failure of landing gear to extend, and a landing gear-up emergency landing.