New AD Would Supersede 2007 Directive For Popular Widebody Engine

The FAA is set to supersede an existing airworthiness directive (AD) that applies to all GE CF6-80C2B series turbofan engines. The existing AD currently requires installing software version 8.2.Q1 to the engine electronic control unit (ECU), which increases the engine's margin to flameout. Since that AD was issued, the FAA has received reports of additional engine events.

The proposed AD, expected to be published Monday, would require the removal of the affected ECUs from service. The AD is being proposed to prevent engine flameout or un-commanded engine in-flight shutdown (IFSD) of one or more engines, leading to an emergency or forced landing of the airplane.

On May 30, 2007, AD 2007-12-07, Amendment 39-15085 was issued, for all GE CF6-80C2B series turbofan engines. Since that AD was issued, the FAA has received two reports of ice crystal condition flameouts on engines equipped with the upgraded ECU software. Prompted by these reports, GE developed ECU software version 8.2.R with improved inclement weather capability, and enhanced fuel metering valve (FMV) fault handling logic to reduce the risk of engine IFSD caused by intermittent FMV feedback signals.

Subsequently, the FAA received reports of eight engine IFSD events and four engine flameout ground events. These events were caused by ignition system induced noise creating dual-channel faults in the CPU. The event engines were operating with 8.2.Q1 and 8.2.R versions of ECU software and equipped with the new generation of front panel assembly (FPA) and pressure subsystem (PSS) circuit boards. Prompted by these reports, GE developed an ECU hardware fix to eliminate the potential for dual-channel CPU faults due to ignition system-induced noise. The proposed AD removes the affected ECUs from the fleet.

The FAA estimates that the total cost of the AD to U.S. operators to be $3.4 million. The AD would be open for comments until January 13, 2012.

FMI: Federal Register