April 04, 2013
The FAA today will mandate a Boeing-recommended fix to install new elevator components on all 737 Next Generation aircraft that addresses a problem linked to at least two instances of inflight elevator vibrations.
The airworthiness directive (AD 2013-06-05), based on a Boeing service bulletin issued in April 2012, gives operators 60 months to replace left and right elevator tab control mechanisms with pieces with modified attach lugs, or modifying the lug assemblies alone.
Boeing says that two operators reported lug failures, which caused “unwanted elevator freeplay.” The manufacturer traced the problem to lug bearings “likely installed such that they may become loose and migrate.” The redesigned lug mitigates the problem, Boeing says.
The directive affects 1,096 U.S.-registered 737s, the FAA says in the AD. Compliance costs could be $62,400 per aircraft if the entire elevator mechanism is swapped out or $13,500 if operators just modify the lug assemblies, the FAA estimates.
It is not clear how many operators have complied with Boeing’s April bulletin, or how many will opt for the less expensive modifications.
The directive supersedes a previous order from September 2010 that required repetitive inspections of the old-design lugs. The new directive terminates the need for repetitive checks.