Incident Overview
During a climb through flight level 240, the No. 1 engine experienced a fan disk separation. This resulted in the separation of the inlet, fan rotor assembly, fan containment case, and portions of the thrust reverser. The airplane reversed course and landed without further incident.
Damage Inspection
Postincident examination revealed minor damage to the aft portion of the fuselage and empennage. Examination of the remaining airplane systems revealed no anomalies. Recovered portions of the fan disk were examined.
Investigation Findings
Examination of the fan disk revealed fatigue striations emanating from the aft bore corner. The striations originated from an area exhibiting characteristics consistent with arc-out damage. This damage was the result of improper assembly and marking procedures during the electrochemical etching process. The manufacturer's quality assurance process failed to detect this damage. Additionally, the operator did not detect the damage during inspections prescribed by required airworthiness directives because the inspection procedures were not detailed enough, and maintenance personnel did not receive appropriate training.
Corrective Actions
Following the incident, the manufacturer issued alert service bulletins, and the FAA issued an airworthiness directive to address the issues.