This is a issue that may also affect Airbus aircraft, but so far, it has only caused problems on two Boeing planes. Like MCAS, it was not disclosed to pilots, prompting the FAA to recommend design changes and notify flight crews.
Unfortunately, it seems that the internal FAA recommendations were not allowed to make their way into any kind of airworthiness directive.
The recommendations include very basic procedure changes that mitigate the near term risks without any significant impact to operation, as well as recommendations for what probably amounts to a software change and upgrades to some of the pilot oxygen masks to effect a permanent fix.
The only reason that we even know about the internal recommendations is that they were leaked to the press.
Boeing released a pilot bulletin that basically says to go through the checklist quickly and to treat smoke in the cabin as a major failure, but stops short of recommending some very, very simple steps in aircraft configuration prior to takeoff that would completely mitigate the issue without negatively effecting flight performance.
The major recommendation in the internal FAA bulletin is to use the APU bleed instead of the main engine bleed air to power the air conditioning and cabin pressurisation during the takeoff phase of flight, below 3000 feet AGL. I can see no reason to drag feet on this recommendation, other than the uncomfortable suggestion that perhaps this issue should have been addressed during certification. (It is yet another difference from older 737 design , like the deadly MCAS system, that was not disclosed to pilots transitioning to the new aircraft)
> […] stops short of recommending some very, very simple steps in aircraft configuration prior to takeoff that would completely mitigate the issue […]
Well, the configuration changes during takeoff mitigate the issue if it happens during takeoff. If it happens at any other time then they don’t do anything to help.
> I can see no reason to drag feet on this recommendation […]
I can. Perhaps the FAA believes that it is better to minimize change fatigue. Since the problem can apparently be fixed in software, and Boeing has decided to make that fix, they might want to write just one airworthiness directive requiring everyone to install it instead of two, one telling pilots to adopt some procedure followed by another telling them to abandon it.
> (It is yet another difference from older 737 design , like the deadly MCAS system, that was not disclosed to pilots transitioning to the new aircraft)
Keep in mind that for most aircraft the airline can pick and choose between different engines. The pilots don’t have to learn the myriad different engineering decisions that go into those engines; from the pilot’s perspective they are supposed to be interchangeable.
> Well, the configuration changes during takeoff mitigate the issue if it happens during takeoff. If it happens at any other time then they don’t do anything to help.
he covers this in the video, but both engines have the same LRD (Load reduction device), but it's more about how the bleed system is done on if it's an impact or not, and he doesn't know if the other planes have the same flaw or not.
Of course MCAS was disclosed to pilots, the idea that it wasn’t is ridiculous to the point of absurdity.
Boeing has gone off the rails, but the general lack of nuance in the common narrative about their failures is really over the top.
MCAS is how a fundamentally different plane behaves (in most cases) like a normal 737. The fact that such a system exists is described, and disclosed, in minute detail to pilots when they get their mandatory training on the 737-MAX.
The specific name wasn’t used in the training, and that’s where this ridiculous narrative came from.
The manual described Elevator Feel Shift, Speed Trim, and Stall Management Yaw Damper. It describes the scenarios in which each of these systems activate and what effect they have.
MCAS uses the same hardware but has different scenarios in which it activates and has a different effect. Not knowing of the existence of MCAS and not having a viable procedure to deactivate it if it went haywire was critical to the two accidents. I've looked into this a lot and to my knowledge this was never disclosed to pilots.
Can you provide a reference to MCAS being disclosed prior to the two accidents?
https://simpleflying.com/boeing-cfm-international-update-737...