AD NUMBER: PL2006-06-51
MANUFACTURER: General Electric
SUBJECT: Airworthiness Directive PL2006-06-51
SUMMARY: This emergency AD results from two failures of the No. 3 bearing in GEAE CT7-8A engines. Bearing contamination by Aluminum Oxide caused the first failure. The Aluminum Oxide contamination is a hard-particle contamination, left in the air cavity of the front frame core after cleaning, that entered the bearing and caused damage and metal loss at the roller ball and race interface. The loss of metal caused a warning light for an electrical chip detector to illuminate in the cockpit. The pilot reduced power to the engine. Inspection found the bearing unserviceable. The engine accumulated 458 flight hours-since-new before the failure. Improper use of a bearing support tool at production assembly caused the second failure. Damage from improper use of a bearing support tool caused bearing metal loss at the roller ball and race interface. The loss of metal caused a warning light for an electrical chip detector to illuminate in the cockpit and signaled an impending oil bypass. The pilot performed an in-flight shutdown of the engine. The engine accumulated 686 hours since-new. This condition, if not corrected, could result in failures of the No. 3 bearings and possible dual in-flight shutdowns of the engines.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/