Airlines are being advised by the Federal Aviation Administration (FAA) to examine their Boeing 737 fleets for defective altitude pressure valves that might pose a safety concern.
The switches are part of a mechanism that alerts flight crews if the cabin is depressurized. Two cabin altitude pressure switches are installed on planes as a backup in case one fails. Switch failures, on the other hand, are not communicated to the crew or maintenance staff.
The FAA warns that if both switches fail while the plane is over 10,000 feet in the air, the cabin altitude warning system may not activate. “Oxygen levels might get dangerously low” in that situation.
“A latent failure of both pressure switches could result in the loss of cabin altitude warning, which could delay flight crew recognition of a lack of cabin pressurization, and result in in-flight crew incapacitation due to hypoxia (a lack of oxygen in the body), and consequent loss of airplane control,” the agency said.
Around 2,500 planes in the United States are affected by the FAA directive, including the Boeing 737 Max and 737 NextGen. The instruction does not require any planes to be taken out of service, and it has nothing to do with the 737 Max flight control system problems that have been linked to two recent tragic disasters.
Inspections and switch replacements must be completed within 90 days or every 2,000 flight hours. Inspections can take anywhere from 30 to 60 minutes, with replacements taking approximately 15 minutes. Previously, these switches had to be inspected every 6,000 flying hours.
According to the FAA, Boeing concluded in November that the failures were not a safety problem.
However, “following further investigation and analysis, the FAA and the airplane manufacturer determined, in May of 2021, that the failure rate of both switches is much higher than initially estimated, and thus does pose a safety issue,” the FAA said, adding that “addressing these failures requires immediate action.”
In response to the findings, Boeing recommended that all Boeing 737s have their switch inspections increased.
“Safety is our first priority, and we completely support the FAA’s guidance, which makes the inspection interval that we gave to the fleet in June obligatory,” Boeing said in an ABC News statement.