The Federal Aviation Administration (FAA) has ordered that more than 2,600 Boeing 737 aircraft are checked, over concerns oxygen masks may not fully function during a depressurization event.
The FAA said it was adopting a new airworthiness directive (AD) after receiving “multiple reports of oxygen generators shifting out of position”.
“Boeing has investigated the condition and found that the oxygen generator retention failures were caused by a failure of the pressure-sensitive adhesive (PSA) material on certain generator strap thermal pads,” the FAA said.
The FAA estimates that the AD affects 2,612 planes on the US registry including Boeing 737-700, 737-800, and 737-900ER aircraft and the 737 MAX 8, 737 MAX 8-200, and MAX 9 jets.
If not addressed the condition could result in oxygen generators becoming “non-functional” which could result in an “inability to provide supplemental oxygen” to passengers.
In Boeing’s Special Attention Requirements Bulletins, approved by the FAA on June 17, 2024, it instructed operators to carry out visual inspections of the oxygen generator installation.
According to Reuters, Boeing instructed operators to update a subset of the retention straps used on the oxygen generator after it found a new adhesive introduced five years ago, under certain circumstances, allowed the unit to shift less than an inch.
Boeing told Reuters that it had returned to the “original adhesive” for all new deliveries to ”ensure the generators remain firmly in place”.
The planemaker added that inspections of undelivered planes and those already flying had not discovered any units not working properly. The AD also prohibits the installation of affected parts by operators.
The FAA decided that due to the “risk to the flying public” it had forgone notice and comment prior to adoption of this rule.
In the most recent high-profile incident in which oxygen masks failed to deploy an Alaska Airlines Boeing 737 MAX suffered a sudden depressurization after a door plug separated from the fuselage shortly after takeoff on January 5, 2024.
