As Much As 70 Percent Reduction In Timeframe For CF6s
A June incident
involving an American Airlines 767-200 parked at Los Angeles
International has resulted in a long-term ripple effect for several
widebody operators, with the FAA mandating a much tighter
maintenance schedule for aircraft equipped with General Electric's
popular CF6-80 turbofan.
The LA Times reports the order will affect as many as 800
engines, and follows an independent investigation of the
catastrophic engine failure that occurred June 2 during a ground
run-up at LAX.
As Aero-News reported, the
airliner's number one CF6-80 engine caught fire during the
maintenance check, hurtling debris across several taxiways, through
the plane's fuselage and number two engine -- and led to the
closure of Runway 25R for about two hours.
Under the new directive, the existing inspection and repair
intervals on the oldest CF6-80s in service will be cut by as much
as 70 percent -- with newer engines requiring a 40 percent shorter
interval time.
Regardless of usage, the first checks must be completed by
December 2008.
The National Transportation Safety Board found
disturbing similarities with the LAX incident and two
other CF6 failures over the past six years. All three incidents
involved structural failure of the high-pressure turbine stage one
disk -- a problem the board thought had been solved in 2003.
Approximately 1,155 CF6s are currently in service in the US --
in aircraft such as the Boeing 747 and 767, the Airbus A300 and
A310, and McDonnell Douglas MD-11.
To comply with the directive, airlines must remove the engines
from the affected aircraft and conduct a metallurgical examination
of the turbine disk... which involves running electrical current
over the component to detect hairline fractures.
*****
AD NUMBER: 2006-16-06
MANUFACTURER: General Electric
SUBJECT: Airworthiness Directive 2006-16-06
SUMMARY: The
FAA is superseding an existing airworthiness directive (AD) for GE
CF6-80 series turbofanengines with certain stage 1 high-pressure
turbine (HPT) rotor disks. That AD currently requires an initial
inspection as a qualification for the mandatory rework procedures
for certain disks, andrepetitive inspections only for certain disks
for which the rework procedures were not required. That action also
requires reworking certain disks before further flight, and removes
certain CF6-80 E1 series disks from service. This AD requires the
same actions but shortens the compliance schedule for HPT disks
that have not been previously inspected using AD 2004-04-07, which
this AD supersedes. This AD results from a recent report of an
uncontained failure of a stage 1 HPT disk. We are issuing this AD
to detect and prevent cracks in the bottoms of the dovetail slots
that could propagate to failure of the disk and cause an
uncontained engine failure.
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