Incident Overview
The aircraft was departing when the pilots felt a thump accompanied by a slight left nose pull, prompting them to abort the takeoff. After taxiing clear of the runway and coming to a stop, several flight crews on the ground reported over the tower frequency that the incident airplane's left engine was on fire. The captain initiated an evacuation of the airplane.
Firefighting Response
Airport Rescue and Fire Fighting (ARFF) personnel reported that the engine fire was confined to the tailpipe area. No further spread of fire was noted.
Engine Damage
Turbine blades had separated from the number 4 turbine disk, penetrated the engine case, and subsequently damaged the engine pylon and empennage area.
Teardown Examination
A teardown examination of the engine revealed that the Low Pressure Turbine (LPT) shaft was deformed and fractured into two pieces. Heavy coke deposits were identified on both the outer diameter of the LPT shaft and the inner diameter of the center tube. The two pieces of the LPT shaft were twisted and subjected to considerable permanent deformation, with the amount of plastic deformation indicative of exposure to high temperatures. Additionally, the High Pressure Turbine shaft was found with a missing 4 1/2 bearing stack retention pin, one of three such pins.