WASHINGTON—The Federal Aviation Administration (FAA) on Thursday issued a directive to operators of all Boeing Co 737 collection airplanes to conduct inspections to handle attainable failures of cabin altitude strain switches.
The directive requires operators to conduct repetitive assessments of the switches and change them if wanted. The directive covers 2,502 U.S.-registered airplanes and 9,315 airplanes worldwide.
It was prompted after an operator reported in September that each strain switches failed the on-wing practical check on three totally different 737 fashions.
The FAA mentioned failure of the switches might end result within the cabin altitude warning system not activating if the cabin altitude exceeds 10,000 ft (3,050 m), at which level oxygen ranges might grow to be dangerously low.
Airplane cabins are pressurized to the equal of no more than 8,000 ft (2438 m).
Boeing mentioned it helps “the FAA’s route, which makes necessary the inspection interval that we issued to the fleet in June.” The FAA directive didn’t report any in-flight failures of the switches.
The FAA mentioned on Thursday that assessments have to be performed inside 2,000 flight hours because the final check of the cabin altitude strain switches, earlier than airplanes have flown 2,000 hours, or inside 90 days of the directive’s efficient date.
Boeing initially reviewed the difficulty, together with the anticipated failure fee of the switches, and located it didn’t pose a security problem.
Subsequent investigation and evaluation led the FAA and Boeing to find out in Might that “the failure fee of each switches is way greater than initially estimated, and due to this fact does pose a security problem.” Boeing declined to say what the failure fee was.
The FAA added it “doesn’t but have adequate data to find out what has brought about this unexpectedly excessive failure fee.”
As a result of significance of capabilities supplied by the swap, the FAA in 2012 mandated all Boeing 737 airplanes make the most of two switches to supply redundancy in case of 1 swap’s failure.
The directive covers all variations of the 737 jetliners, together with the MAX, however is unrelated to any points associated to the MAX’s return to service final November.
By David Shepardson