Incident Overview
A McDonnell Douglas DC-10 Series 10 aircraft suffered an uncontained failure of the number 1 engine while in the cruise climb phase of flight. The failure originated from the 14th through 16th stage compressor spool.
Previous Damage and Repair
Approximately 11 years before the incident, the compressor spool had been damaged beyond the limits specified in the maintenance manual. The damage consisted of a 360-degree rub on the aft rim surface (designated Surface Q) of the 16th stage compressor. Following the damage, the spool was placed into storage for a period of five years. After storage, it was repaired and subsequently returned to service.
Stress Analysis
The engine manufacturer conducted an analysis of flight profile stresses. According to the manufacturer, peak stresses in the aft rim region (Surface Q) occur at the same point in the flight profile as the uncontained failure. This correlation is noted in the investigation findings.
Conclusion
The uncontained failure of the number 1 engine was directly associated with the prior damage and subsequent repair of the compressor spool, with stress analysis indicating that peak operational stresses aligned with the failure event.