NTSB Identification: DEN07IA055.
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Scheduled 14 CFR operation of MESA AIRLINES INC
Incident occurred Thursday, January 25, 2007 in Cripple Creek, CO
Probable Cause Approval Date: 01/31/2008
Aircraft: Bombardier, Inc. CL-600-2B19, registration: N17337
Injuries: 54 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

While climbing through FL 240, the No. 1 engine experienced a fan disk separation, which resulted in the separation of the inlet, fan rotor assembly, the fan containment case, and portions of the thrust reverser. The airplane reversed course and landed without further incident. Postincident examination revealed minor damage to the aft portion of the fuselage and empennage. An examination of the remaining airplane systems revealed no anomalies. Portions of the fan disk were recovered and examination of the fan disk revealed fatigue striations emanating from the aft bore corner of the fan disk. The striations came from an area that exhibited characteristics consistent with arc-out damage, which was the result of improper assembly and marking procedures during the electrochemical etching process. This damage was not detected during the manufacturer's quality assurance process used by the manufacturer. Further, the operator did not detect this damage while conducting the inspections prescribed through required airworthiness directives because the inspection procedures required were not detailed enough to detect the arc-out damage and the maintenance personnel did not receive appropriate training. Following the incident, the manufacturer issued alert service bulletins and the FAA issued an airworthiness directive to resolve these issues.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

A fatigue fracture, which resulted in the separation of the No.1 engine fan disk. Contributing factors in the accident were the operators' maintenance personnel lack of training to be able to detect arc-out damage on the fan disk, and the fan disk manufacturer's inadequate electro-chemical etch match marking process of the fan disk to forward fan shaft that allowed for the initiation of a fatigue point that was undetected at the time of original manufacture.

Full narrative available

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