Incident Overview
During a climb through flight level 210, the flight crew heard an explosion and observed flames emanating from the tailpipe of the No.3 engine. The crew promptly secured the engine, and the aircraft landed without further incident.
Examination Findings
A post-incident examination revealed an uncontained failure of the engine. Investigators identified a preexisting crack in the No.12 blade on the 4th stage turbine wheel. The crack was not noted during a recent dye penetrant inspection of the wheel, as documented in the maintenance records.
Engine Service History
At the time of the failure, the engine had accumulated 99 cycles and 66 hours of operation over a period of 13 days since the last inspection. The inspection had not detected any cracks or anomalies.
Conclusion
The investigation concluded that the uncontained failure was the result of a preexisting crack in the turbine blade, which remained undetected during a previous maintenance inspection.