AD/JT9D/27 - Fan Exit Case Cover Modification

A Boeing 747 aircraft experienced an in-flight engine shut down due to loss of oil.

Subsequent investigation identified loss of retention of the angle gearbox tower shaft cover as the cause of failure. In this instance failure of a threaded insert allowed the angle gearbox cover to migrate from its location recess resulting in a substantial oil leak.

The modification introduces a rubber bumper to the fan exit case access panel that abuts the angle gearbox tower shaft cover to prevent migration of the cover in the event that a cover bolt/insert fails.