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This article seems to focus on things from a perspective of things from a small plane pilot. So a little wider perspective might be helpful. A 737 first off is

This article seems to focus on things from a perspective of things from a small plane pilot. So a little wider perspective might be helpful. A 737 first off is not a Cessna like the author mentions flying. You do not get to use direct inputs easily nor do you want to have to fight stab trim because the force on the stabilizer control surfaces is muuuch higher than those on a slower flying plane. Because of this, when the 737 came out there were designs for trim systems that can help. These systems work by adjusting the trim settings for pitch using motors (like the author mentioned). However sometimes these systems would give erroneous inputs to the trim. The system might be causing incorrect trim up or down depending on the failure. This is officially known as stabilizer trim runaway. The procedure for this has been well established as a memory item meaning all pilots of 737s must be able to correct this without referencing a checklist since it is so dangerous. And it is HARD to correct because of the aerodynamic forces on the stabilizer. You can find videos of training for it. Now they introduced MCAS. A system designed to adjust trim automatically to compensate for the shift in the moments acting on the plane due to powerplant placement, etc. This adjusts the trim as well to prevent to high of angle of attack that would allow these different moments to introduce a stall situation. So what procedure should you use if it starts giving incorrect inputs? That's right, the stab trim runaway procedures, which again should be a memory item all pilots of these 737s should know and be ready and able to execute. The differences between systems that cause it just means you are taking different systems out of the control loop. This is also why I believe the FAA said it was fine to forego full airframe certification requirements. The procedures for handling the plane just didn't change drastically enough. Yes there was negligence on Boeing's part, but I also think it's worrying that the reports seemed to indicate that the correct procedures for runaway stab trim were not followed which could have saved lives (e.g. turning MCAS back on while dealing with runaway stab trim). Also something to note is the plane in Ethiopian airways' crash was flying with "unusually high thrust settings". Remember the aerodynamic forces that make runaway stab trim a bitch to deal with? Well those forces get stronger with more speed. People are quick to point the finger at Boeing and surely they ARE at fault in some ways, but what's worrying to me is that there are pilots that are being trained that cannot perform the proper procedures that have been known since way before MCAS. Whats more is that the motors for trim from MCAS is limited to move at a rate of 2.5 degrees over 10 seconds with a pause of 5 seconds before the next adjustment. This is definitely slow enough to give pilots time to catch the runaway trim, cutout the stab trim and regain control. Anyway I am just surprised that the engineer, working for Boeing, couldn't be arsed to also give this info which allows an alternative perspective. It is bad that stab trim runaway is happening more with this system and Boeing acknowledged it and pushed patches. It is worse imo that pilots are forgetting or just not being trained on how to recognize and correct for stab trim. Edit: Any details or numbers about the systems I got wrong please post a comment so I can correct it.

Jonnax 7y ago
The question I have is: Would the plane have crashed if the plane was a non MAX 737? I don't think so, but I'm open to being proved wrong. In that case the root cause of the two crashes is Boeing trying to save money.
- CorvusCrypto 7y ago
  I think it's not just that question and this is what I dislike about the whole discussion. It's all about Boeing and no one is also asking "if proper procedure was performed for runaway stab trim (again, a generalized memory item) would the plane have crashed? And it does seem the sentiment is to hell with anyone suggesting pilots and airlines involved share part of the blame despite evidence. I could also ask, would the plane have crashed if it WASNT a max and another stab trim system failed? It's both. We need to look at everything otherwise we will end up solving only 1 part of the issue. Edit: To address something you mentioned about root cause (in aviation it's almost never a single root cause and I will give an example that shows such cases here). Let's look at another situation: Assume P&W designs an engine model a plane uses. The plane they are used in has in-air engine fire procedures that must be performed in order to mitigate disaster regardless of the engine model used. Now imagine the new engine design causes more engine fires. If pilots don't manage the problem appropriately when it occurs, what is the root cause? The poor engine design? Improper training from the pilot? In my opinion it's, again, both. Poor training coupled with higher chance of system issues.
  - im_down_w_otp 7y ago
    The pilots and the airlines didn't design, build, and release a semi-autonomous system which isn't resilient to erroneous data, despite the failure case for that problem being catastrophic. If an Automotive OEM released a vehicle with an adaptive cruise control system that refused to disable itself except by the human driver intervening through power cycling the vehicle, while driving, it's difficult to put much warranted blame on the driver. The OEM sold a potentially catastrophically faulty system, irrespective of that the fault can sometimes be managed into a fail-safe condition by the driver. The reason people put the blame on Boeing is because the system implementation didn't fail, the design did.

Jonnax 7y ago

The question I have is: Would the plane have crashed if the plane was a non MAX 737? I don't think so, but I'm open to being proved wrong. In that case the root cause of the two crashes is Boeing trying to save money.

CorvusCrypto 7y ago
I think it's not just that question and this is what I dislike about the whole discussion. It's all about Boeing and no one is also asking "if proper procedure was performed for runaway stab trim (again, a generalized memory item) would the plane have crashed? And it does seem the sentiment is to hell with anyone suggesting pilots and airlines involved share part of the blame despite evidence. I could also ask, would the plane have crashed if it WASNT a max and another stab trim system failed? It's both. We need to look at everything otherwise we will end up solving only 1 part of the issue. Edit: To address something you mentioned about root cause (in aviation it's almost never a single root cause and I will give an example that shows such cases here). Let's look at another situation: Assume P&W designs an engine model a plane uses. The plane they are used in has in-air engine fire procedures that must be performed in order to mitigate disaster regardless of the engine model used. Now imagine the new engine design causes more engine fires. If pilots don't manage the problem appropriately when it occurs, what is the root cause? The poor engine design? Improper training from the pilot? In my opinion it's, again, both. Poor training coupled with higher chance of system issues.
- im_down_w_otp 7y ago
  The pilots and the airlines didn't design, build, and release a semi-autonomous system which isn't resilient to erroneous data, despite the failure case for that problem being catastrophic. If an Automotive OEM released a vehicle with an adaptive cruise control system that refused to disable itself except by the human driver intervening through power cycling the vehicle, while driving, it's difficult to put much warranted blame on the driver. The OEM sold a potentially catastrophically faulty system, irrespective of that the fault can sometimes be managed into a fail-safe condition by the driver. The reason people put the blame on Boeing is because the system implementation didn't fail, the design did.