Says Engine Marking Procedure Led To Fan Disk Failure

Less than one month after a Mesa Airlines regional airliner suffered an inflight uncontained fan disk failure in one of its engines, the FAA has issued an emergency Airworthiness Directive requiring operators of the type to perform inspections on their engines.

As Aero-News reported, the CRJ-200 experienced failure of its number one engine January 25, approximately 70 nm from Denver International Airport, while climbing through 24,000 feet. The failure took out the forward engine cowling, but the aircraft was otherwise unscathed. The flight returned uneventfully to Denver and none of the 55 persons aboard was injured.

In its Airworthiness Directive, the FAA states an inspection of the GE CF34-3B1 engine showed the front section of the engine failed, resulting in the fan, forward cowlings, and fan reverser departing from the engine. A subsequent inspection of the recovered segments of the fan disk, found an electrical arc-out defect at the fracture origin site.

The FAA adds the fan disk was marked using the electro-chemical etchmarking (ECM) procedure during engine assembly. If the ECM procedure is performed incorrectly, an arc-out defect can occur. This arc-out defect, caused during part marking, resulted in the uncontained failure.

Operators of affected aircraft may refer to GE Alert Service Bulletin (ASB) No. CF34-BJ S/B 72-A0213, dated February 15, 2007, and GE ASB No. CF34-AL S/B 72-A0232, dated February 15, 2007 for procedures for visual and tactile inspection of certain areas of certain serial number (SN) fan disks, to determine if those fan disks are similarly affected.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/