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FAA orders inspections of 9,300 Boeing 737s over fears altitude pressure switch failure could lead to dangerously low oxygen levels in cabins over 10,000ft

 The Federal Aviation Administration on Thursday issued a directive to operators of all Boeing 737 series airplanes to conduct inspections to address possible failures of cabin altitude pressure switches. 

The directive, covering 2,502 U.S.-registered airplanes and 9,315 airplanes worldwide, requires operators to conduct repetitive tests of the switches and replace them if needed.  

Included in the directive was the 737 MAX. The jet returned to service in November after being grounded for 19 months following two crashes in 2018 and 2019 killed a total of 346 people.

The order came after an operator reported that both pressure switches had failed on-wing functional tests on three different 737 models in September. 

The FAA said failure of the switches could result in the cabin altitude warning system not activating when cabin moves past 10,000ft, which is when oxygen levels become dangerously low.  Such a scenario could incapacitate cabin crew and pilots.

The FAA found that three models of Boeing's 737 airplanes failed the pressure switch test in September

The FAA found that three models of Boeing's 737 airplanes failed the pressure switch test in September 

Airplane cabins are pressurized at no more than 8,000ft . 

Boeing said it supports 'the FAA's direction, which makes mandatory the inspection interval that we issued to the fleet in June.'

The FAA directive did not report any in-flight failures of the switches.

The FAA also said Thursday that tests must be conducted within 2,000 flight-hours since the last test of the cabin altitude pressure switches, before airplanes have flown 2,000 hours, or within 90 days of the directive's effective date.

Boeing initially reviewed the issue, including the expected failure rate of the switches, and found it did not pose a safety issue.

Subsequent investigation and analysis led the FAA and Boeing to determine in May that 'the failure rate of both switches is much higher than initially estimated, and therefore does pose a safety issue.' 

Chicago-based Boeing declined to say what the failure rate was.

The error results in the plane's altitude warning system to failing to activate when reaching altitudes where oxygen levels become dangerously low in the cabin

The error results in the plane's altitude warning system to failing to activate when reaching altitudes where oxygen levels become dangerously low in the cabin

The FAA added it 'does not yet have sufficient information to determine what has caused this unexpectedly high failure rate.'

Due to the importance of functions provided by the switch, the FAA in 2012 mandated all Boeing 737 airplanes utilize two switches to provide redundancy in case of one switch's failure.

The directive is unrelated to any issues related to the 737 MAX's return to service in November. 

It was discovered that a safety feature on the MAX meant to stop the plane from climbing too fast and stalling had improperly forced the nose of the plane down, causing the crashes. 

2 comments:

  1. hmmm how do we make a problem where no problem exists and pretend we solve a problem... Fucking Clowns.

    ReplyDelete
  2. Still safer than the Juden vax could be a good advertising slogan

    ReplyDelete