Boeing and FAA late Friday warned Boeing 737NG operators of a failure mode in elevator tab control mechanisms that could lead to attach lug failures. From FAA's emergency directive:
The FAA received a report of failure of the aft attach lugs on the left elevator tab control mechanism, which resulted in severe elevator vibration. The flightcrew diverted from the intended route and made an uneventful landing. Subsequent investigation revealed extensive damage to the elevator tab control system. Severe vibration in this attach point is suspected of allowing rapid wear of the joint, and resulted in failure of the attach lugs.
We have reviewed Boeing Alert Service Bulletin 737-27A1296, dated March 12, 2010. The service bulletin describes procedures for a detailed inspection to detect discrepancies of the inboard and outboard aft attach lugs of the elevator tab control mechanism. Discrepancies include movement or rotation of the spacer, and gaps between the swage ring and the aft attach lug or between the spacer and the aft attach lug.
Operators have either 12 or 30 days to check for "discrepancies of the inboard and outboard aft attach lugs of the elevator tab control mechanism," per a Boeing Alert Service Bulletin issued Friday.
Read the full AD here