Event Summary
Following takeoff, the airplane was climbing through 6,200 feet mean sea level over the ocean when the crew heard a loud bang. Simultaneously, the number one engine fire annunciator light illuminated. The engine power decreased to zero. The crew secured the engine and the flight returned to the departure airport, landing without further problems. There was no fire, and passengers disembarked at the terminal gate.
Examination Findings
Post-flight examination revealed that the engine had sustained an uncontained failure of the high pressure compressor. The 6th stage disk of the 3-to-9 compressor spool was missing completely from the engine. The airplane received minor damage.
Background on Similar Failures
Similar disk failures have been attributed to a phenomenon known as dwell time fatigue. This may occur when titanium crystals form into microstructure colonies during the forging and manufacturing process. The disk has not been recovered, and the exact failure mode has not been determined.