Airworthiness Directives; General Electric Company CF34-8C1 Series and CF34-8C5 Series Turbofan Engines

The FAA is superseding an existing airworthiness directive (AD) for General Electric Company (GE) CF34-8C1 series and CF34-8C5 series turbofan engines, with certain serial number (SN) master variable geometry (VG) actuators installed. That AD currently requires initial and repetitive reviews of the airplane Maintenance Data Computer (MDC) for master VG actuator fault messages, and if the MDC is inoperative, reviews of the Engine Indication and Crew Alerting System (EICAS) for fault messages. That AD also requires replacing actuators reported faulty by the Full Authority Digital Engine Control (FADEC). This ad requires those same actions, and expands the applicability to additional actuators by part number (P/N) and SN. This AD also prohibits installation of affected master VG actuators onto any CF34- 8C1 and CF34-8C5 engine after the effective date of this AD. This AD results from the need to add to the list of affected parts, master VG actuators made by parts manufacturer approval (PMA). We are issuing this AD to prevent dual-channel electrical signal faults in the VG master actuator, which will cause an uncommanded reduction of thrust to idle with a subsequent loss of the ability to advance thrust above idle, and which will result in a multiengine loss of thrust if dual- channel faults occur on more than one engine simultaneously.