The right hand second stage HPT fractured into four pieces with the engines at full power, as the aircraft was passing through 128 knots. The aircraft
was at 134 knots when power was retarded and brake pressure began to rise. It took 25 seconds to stop the aircraft.
One of the fractures showed signs of a fatigue failure and began at an inclusion on the forward side of the hub.
It was a defect that caused the #2 engine on United 232 to come apart, but that was the only one. It all depends on what caused it. There was a
turboprop aircraft that had the prop come off and embed in the wing, because of the cleaning process for the engine and prop. In that case, they found
several engines with issues.
They'll probably end up mandating inspections beyond a certain number of cycles, which will require borescope inspections.
GE has recommended ultrasonic inspections of the first and second high pressure turbine disks produced before 2000, in their CF6-80C2 engines. New
documents show that the second stage HPT disk ruptured, due to cracks that formed from an "anomaly" under the surface of the disk. The pilots
reported reaching 80 knots, and then there was a "ka-boom" from the engine and a bump. Fragments from the ruptured turbine went through the dry bay
above the engine, and ruptured the main fuel line, allowing the fire to start.
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