B737 etter lengre tids lagring kan få motorproblemer - Curt Lewis / AVweb

FAA requires additional post-storage B737 engine inspections after several in-flight shutdown incidents

24 July 2020

The U.S. FAA is requiring operators of Boeing 737 aircraft to inspect engine bleed air valves of aircraft that have been stored after several incidents of in-flight engine shutdowns.

Many airlines are restarting flights following groundings related to the COVID-19 pandemic. The FAA received four recent reports of single-engine shutdowns due to engine bleed air 5th stage check valves being stuck open. Corrosion of the engine bleed air 5th stage check valve internal parts during airplane storage may cause the valve to stick in the open position. 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. Corrosion of these valves on both engines could result in a dual-engine power loss without the ability to restart.

This led the FAA to issue an Emergency Airworthiness Directive AD 2020-51, requiring inspections of the engine bleed air 5th stage check valve on each engine and replacement of the engine bleed air 5th stage check valve if any inspection is not passed. The EAD applies to all Boeing 737-300, -400, -500, -600, -700, -700C, -800, and -900 models in storage on or after the date of receipt of this AD, and any airplane that, as of the date of receipt of the AD, has been operated for 10 or fewer flight cycles since returning to service from the most recent period of storage.

Emergency AD Affects 2000 Stored 737s

Russ Niles

July 25, 2020

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The FAA issued an emergency AD affecting more than 2,000 second- and third-generation Boeing 737s that have been parked since the COVID-19 pandemic took hold in March. The AD requires immediate inspection of the fifth stage bleed air check valve to check for corrosion. The corroded valves don’t close after the engine is throttled back from climb power. “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 in a news release. “Corrosion of these valves on both engines could result in a dual-engine power loss without the ability to restart.”The agency said there have been four reported incidents and one of them may have occurred July 15 when an Alaska Airlines flight lost an engine and made an uneventful emergency landing in Austin. The airline told USA Today the 737 had an “engine shutdown issue” but didn’t elaborate on the cause. Most of the aircraft are still in storage so the inspections and potential replacement of the valves shouldn’t affect any operations. The 737 MAX is not included in the AD.