The Federal Aviation Administration is ordering emergency inspections of about 2,000 Boeing 737 airplanes because of a possible engine valve problem that could lead to engine failure.
The FAA's emergency air worthiness directive orders inspections of older 737 Classic and Next Generation planes that may have been in storage as a result of sharply reduced air travel demand during the COVID-19 pandemic.
The directive, dated Thursday, was prompted by four recent reports of single-engine failures due to problems with a critical air check valve. Inspectors found corrosion on some engine air check valves, which can lead the valves to become stuck open and potentially cause both of a plane's engines to lose power and prevent them from restarting.
"If this valve opens normally at takeoff power, it may become stuck in the open position during flight and fail to close when power is reduced at top of descent, resulting in an unrecoverable compressor stall and the inability to restart the engine," the directive states. "Corrosion of these valves on both engines could result in a dual-engine power loss without the ability to restart. This condition, if not addressed, could result in compressor stalls and dual-engine power loss without the ability to restart, which could result in a forced off-airport landing."
The directive requires airlines and other aircraft owners and operators to inspect the valves on all of their 737 Classics and 737 NGs that have not been in operation for seven or more consecutive days.
In a statement, Boeing says that "with airplanes being stored or used infrequently due to lower demand during the COVID-19 pandemic, the valve can be more susceptible to corrosion."
Boeing says it is providing inspection and replacement information to fleet owners if they discover an issue.
The valve problem is not related to Boeing's grounded 737 Max aircraft.