The FAA has issued an Airworthiness Directive, effective immediately, seeking to prevent failure of a critical component found on GE GEnx-series engines after one failed on a B787 Dreamliner during ground testing. The failure was contained and the engine threw debris out of its tailpipe. The source of the failure was determined to be the engine's fan mid shaft, which fractured. Less than one month later, in August, an ultrasonic inspection found the same part in another 787's engine exhibited cracking. The FAA has determined that cracks are likely to exist or develop in fan mid shaft within other engines of the same design. The new AD, published Friday, supersedes an earlier Service Bulletin (SB) and requires inspection before further flight, but does not resolve the problem. Further action is expected.
The SB required an initial inspection "within 30 days" of its date of issuance where the AD now requires inspection of the fan mid shaft prior to flight. The cause of the cracking is yet undetermined, but according to the FAA it "is likely due to environmentally assisted cracking; a type of corrosive cracking that is time-dependent." The agency is requiring repetitive inspections at an interval of not more than 90 days. The current AD has been enacted as a final rule and the FAA is soliciting comments through Oct. 22. It "may amend this AD because of those comments." Complete text of the AD is available online, here.