Boeing’s 737 is at risk of an engine failure that could potentially leave the jet powerless after takeoff, the FAA has warned airlines, after multiple incidents were observed as previously grounded fleets return to active service. The US Federal Aviation Administration says it has four recent reports of 737-series jets experiencing a stuck valve that, if unchecked, could lead to disastrous results.
The Emergency Airworthiness Directive (AD) requires all owners and operatives of Boeing 737-300, -400, -500, -600, -700, -700C, -800, -900, and -900ER series planes to check the engine bleed air 5th stage check valve. If it’s faulty – like getting stuck in the open position, for instance – it must be replaced.
“This emergency AD was prompted by four recent reports of single-engine shutdowns due to engine bleed air 5th stage check valves being stuck open,” the FAA explains [pdf link]. “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.”
While the four reported cases have involved a single engine shutting down and proving unable to restart, the concern is that valves on both 737 engines could be affected. Were that the case, the FAA warns, it could leave the jet without power while in the air.
“Corrosion of these valves on both engines could result in a dual-engine power loss without the ability to restart,” the FAA points out. “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.”
In this case, “forced off-airport landing” sounds a whole lot like FAA-speak for “unexpected crash landing,” which is not something you want to think about when you’re getting on a jet. The issue is believed to be a result of 737 fleets being temporarily grounded during the COVID-19 pandemic, as operators reduced services around the country. Any aircraft that has gone without operation in flight for 7 or more consecutive days is considered to have been in “storage,” by the FAA’s definition.
The only real exception to the check being carried out before the next flight is if the plane needs to be moved to a different location where that assessment and repairs could be carried out. Even then, the FAA says that one engine’s valve must be locked closed during that flight, out of caution. There are approximately 2,000 impacted jets in the US.
It’s another stroke of bad news for Boeing, which is still feeling the pinch after the 737 MAX crisis that began last year. Earlier this month, the aircraft-maker confirmed “significant impacts of COVID-19” on deliveries, with only 20 planes handed over to customers in Q2 2020 versus 50 in the previous quarter.