AD #: 2020-16-51 Boeing Company Model 737-300, -400, -500, -600, -700, -700c, -800, -900, And -900er Series Airplanes

The FAA has issued an emergency AD, "prompted by 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 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 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.

AD Requirements: This AD requires 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.

FMI: www.regulations.gov