Sat, Nov 12, 2011
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.
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