Airworthiness Directives; Eurocopter Deutschland Model EC135 Helicopters
We are adopting a new airworthiness directive (AD) for Eurocopter Deutschland (ECD) Model EC135 helicopters. This AD results from a mandatory continuing airworthiness information (MCAI) AD issued by the aviation authority of the Federal Republic of Germany, with which we have a bilateral agreement, to identify and correct an unsafe condition. The MCAI AD states that in the past, the FADEC FAIL caution light illuminated on a few EC135 T1 helicopters. It states that this was caused by a discrepancy in the parameters that was generated within the fuel main metering unit and transmitted to the FADEC. This discrepancy led to the display of the FADEC FAIL caution light and ``freezing'' of the fuel main metering valve at its position, resulting in loss of the automatic engine control in the affected system. With the MCAI AD, a synchronization procedure for pilots, which was already used in the past, is being reintroduced, which prevents the parameter discrepancy arising and thus sustains the automatic engine control. The AD actions are intended to prevent failure of the FADEC to automatically meter fuel, indicated by a FADEC FAIL cockpit caution light, and subsequent loss of control of the helicopter.