NTSB: failed airline engine disk had fatigue cracking

WASHINGTON  — Investigators say an engine disk that broke apart forcing an American Airlines jet to abort a takeoff in Chicago last week shows signs of fatigue cracking.

A preliminary National Transportation Safety Board report says a high pressure turbine disk in the Boeing 767’s right engine broke into pieces that shot out of the engine’s housing. The report says an examination of the disk shows evidence of an anomaly where the fatigue cracking begins.

Metallurgical examinations of the disk are underway to determine what caused the cracking.

Disk pieces were spewed up to a half mile away and a fierce fire enveloped one side of the plane after the failure.

Such “uncontained” engine failures are rare and serious events that can cause extensive damage to the aircraft.