FAA orders inspections of 737s over oxygen masks

The Federal Aviation Administration (FAA) has ordered the inspection of 737 aircraft due to concerns over oxygen masks potentially failing to supply oxygen to passengers during a depressurisation event. The airworthiness directive (AD) is adopted for Boeing model 737-8, 737-9, 737-8200 and model 737-700, -800, and -900ER series airplanes. It is estimated to impact around 2,612 aircraft of US registry. The FAA read in its AD: ""This AD was prompted by multiple reports of passenger service unit (PSU) oxygen generators shifting out of position within their associated PSU assemblies because of a retention failure."" It added: ""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 AD requires a general visual inspection of the oxygen installation to determine the configuration of the thermal pads of the retention straps followed by any required actions. On June 17, Boeing told airlines in a bulletin that airlines should visually inspect the oxygen generators, according to the FAA's AD. The FAA said it has ""determined the unsafe condition"" is ""likely to exist or develop in other products of the same type design"" and thus issued the AD. The agency estimated the costs for the inspection on US operators to cost $222,020. The replacement of a PSU oxygen generator is estimated to cost up to $1,459 as well as estimating the replacement of PSA retention strap thermal pads to cost around $153 per pad, with each PSU oxygen generator having two pads. On average, a 737 has 61 oxygen generators. The AD prohibits the installation of potentially defective parts. Boeing said in a statement: ""In June 2024, Boeing shared detailed instructions for operators to update a subset of the restraining straps on 737 oxygen generators. A new adhesive introduced on the straps in August 2019 has been found, under certain circumstances, to have allowed units to shift up to three quarters of an inch. ""We have gone back to the original adhesive for all new deliveries to ensure the generators remain firmly in place, as intended."" Boeing's inspections of the in-service fleet and undelivered jets did not uncover any units that failed to operate properly. The AD will be published in the US federal register on July 10, 2024, 15 days after which it will become effective.