The internal FAA memo, reviewed by The Seattle Times, is highly critical of Boeing for not informing pilots about the existence of the engine component that activates when the engine is severely damaged, called the load reduction device, or LRD.
This device is new on the MAX’s LEAP engine, which is designed and built by CFM International, a joint venture of GE Aerospace and Safran of France. It was not part of the engine on the prior 737 model.
Various models of the 777, 747 and 787 also have such an engine component. So does the larger version of LEAP engine on the Airbus A320neo jet family.
No similar incidents have been reported on the A320neo jets. Although their engines are similar in design, the way the airflow from the engines is controlled can be different.
As far as I can tell, the issue is a combination of:
The LRD design which many newer-generation turbofan engines share
These specific engines spraying oil all through the engine and creating a big toxic-fume nebulizer when that happens, which is “working as designed” although clearly not fully thought through
The specific way in which the 737 MAX draws bleed air from the engines. It’s not clear to me whether the A320neo which shares this engine isn’t vulnerable to the same “it happens every time” behavior that the MAX has, or if they’ve just been lucky so far.
The plane’s systems not being set up to detect the situation and deal with it automatically (by shutting off bleed air when the LRD breaks for example). This seems like a blatant oversight and I’m not sure why fixing it is not mandated, or why Boeing doesn’t want to fix it until someone from outside orders them to.
The pilots not being trained about any of this until it almost killed the flight crew that one time and everyone realized it was a problem
I don’t think it’s fair to say that every turbofan engine does this. And regardless, setting up the plane’s systems to prevent the situation is obviously the right thing to do, instead of just leaving it to the pilots to wait until they start choking and can’t see, and remember what switch they need to hit when that happens.
https://www.seattletimes.com/business/boeing-aerospace/faa-team-recommends-boeing-max-design-change-and-notify-pilots/
As far as I can tell, the issue is a combination of:
I don’t think it’s fair to say that every turbofan engine does this. And regardless, setting up the plane’s systems to prevent the situation is obviously the right thing to do, instead of just leaving it to the pilots to wait until they start choking and can’t see, and remember what switch they need to hit when that happens.