AD FAA-2012-0448

We are adopting a new airworthiness directive (AD) for Agusta S.p.A. (Agusta) Model A109S helicopters to require modifying the electrical power distribution system to carry a higher electrical load. This AD was prompted by an electrical failure on an Agusta Model A109E helicopter that resulted from "inadequate functioning of the 35 amperes (amps) BATT BUS circuit breaker." The actions of this AD are intended to require modifying the electrical power distribution system to prevent failure of the circuit breaker, loss of electrical power to instruments powered by the "BATT BUS" system, and subsequent loss of control of the helicopter.