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.

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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.

FMI: www.geae.com, www.faa.gov/regulations_policies/airworthiness_directives/