The Federal Aviation Administration issued an airworthiness directive Monday requiring replacement of defective attachment pins in the horizontal tails of more than 1,000 Boeing 737s flying in the U.S.
The directive requires airlines to inspect the pins that connect the rear spar of the jet’s horizontal tail to the fuselage, and to replace all pins that came from a Boeing supplier during a two-year period.
The FAA said an incorrect procedure was used by the supplier to apply a surface coating to the pins to protect against wear and corrosion.
Pilots adjust moveable panels on the horizontal tail — or horizontal stabilizer, as it is called in the industry — to push the jet’s nose up or down.
No accidents have been attributed to the defect. But the FAA’s directive warns that without replacement, the defective pins could fail prematurely in service, potentially “resulting in loss of control of the airplane.”
Boeing issued a service bulletin recommending the pin replacements a year ago. The FAA in September proposed issuing a mandatory directive.
Airlines must now complete the work before 56,000 total flight cycles or within 3,000 flight cycles after the directive takes effect on May 20.
The FAA estimates the cost to U.S. airlines at just over $10 million, with 39 hours of work on each airplane.
Boeing may cover some of those costs under warranty, the FAA said.
The defective pins were installed on most new airplanes delivered between August 2006 and July 2008, and also were distributed by Boeing as spares.
During that timeframe, Boeing delivered fewer than 700 of the 737 jets worldwide — and less than 300 in the U.S.
But, because pins may have been swapped out during maintenance, it’s possible that defective pins may have been installed on other jets. So the FAA is demanding that all 737NGs delivered before the 2012 Boeing service bulletin be inspected.
While the FAA directive applies only to U.S. airlines, it indicates that this issue applies to more than 3,500 jets worldwide.
Aviation regulators around the globe typically follow the FAA lead and will likely mandate the same pin inspection and replacement regimen.