General Discussion

Due to the critical nature of the fan disk, maintenance practices require that it be subjected to regular, detailed inspections to look for various types of damage, or indications that the disk is no longer serviceable. The #2 fan disk on the accident airplane had been inspected several times prior to the accident, and no damage had been discovered. The NTSB estimated that the crack which led to the disk failure had been approximately one-half inch long at the time of failure. It was assumed that the detailed, regular inspections would result in detection of a flaw that would require removal of the disk from service prior to failure.

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