The Federal Aviation Administration on Friday issued an emergency Airworthiness Directive (AD) for 2,000 Boeing 737s that have been parked.
The FAA issued the directive after inspectors found compromised air check valves when bringing the aircraft out of storage, agency spokesman Lynn Lunsford said. Corrosion on the "fifth stage bleed air check valve'' could result in dual-engine failure, he said.
Airlines must inspect the planes for valve corrosion, and if it is found, they must be replaced before the plane is returned to service, he said.
The FAA took the action after four recent reports of single-engine shutdowns due to check valves being stuck open, according to the Airworthiness Directive. It did not detail the incidents or name the airlines operating them, but Alaska Airlines confirmed one of its planes suffered an "engine shutdown issue'' on a July 15 flight from Seattle to Austin, Texas. Spokesman Ray Lane said the "safety of the flight was not compromised.'' The 737 made an emergency landing in Austin and the engine was replaced, he said.
"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 FAA said. "Corrosion of these valves on both engines could result in a dual-engine power loss without the ability to restart.''
If both engines are lost and can't be restarted, the FAA said, it could result in an emergency "off airport'' landing.
"The FAA is issuing this AD because the agency evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design,'' the directive says.
Boeing spokesman Peter Pedraza issued this statement in response to the FAA directive:
“Out of an abundance of caution, Boeing has advised operators of 737 Classic airplanes (series -300 to -500) and Next-Generation 737s (series -600 to -900) to inspect an engine valve for corrosion,'' the statement said. "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 is providing inspection and replacement information to fleet owners if they find an issue.”
The directive does not include the Boeing 737 Max, which has been grounded since March 2019 following two fatal crashes in less than six months.
Southwest Airlines, which only operates Boeing 737s, has not experienced the "conditions'' described in the directive but is reviewing the directive to see how it impacts its fleet. The airline has 100 Boeing 737s in storage, including 34 Max aircraft, spokesman Brian Parrish said.
"Currently, we do not anticipate any disruption to our operation as we work to review the aircraft in storage that are affected by the AD,'' Parrish said in a statement.
American Airlines has 304 Boeing 737 NGs in its fleet, including 19 parked in Roswell, New Mexico, spokesman Ross Feinstein said.
Four of American's 737 NGs recently back in service after storage were inspected and no issues were found, he said.
The planes still in storage will be inspected as they come out, he said, and the airline does not expect any impact on its operations.
United has 28 Boeing 737s that are out of storage and being checked, spokeswoman Leslie Scott said. Planes still in storage will be checked as they return to service, she said.
She said United also does not expect any impact on its operation from the inspections.
Delta Air Lines spokesman Morgan Durrant said the airline will comply with the directive and does not expect any impact to its operation or flight schedule as a result of the directive.
This article originally appeared on USA TODAY: FAA orders emergency inspections of 2,000 Boeing 737s for corrosion