[CorvusCrypto]

I was definitely one who thought it should be so simple to follow a standard stab trim runaway and made several comments to it too. But the more it drags on the more I'm learning from the data that the procedure to correct is just bullshit.

Boeing is now in unsaveable waters for this situation and all doubt is being removed. I still am upset that any airline was able to in good faith say "nah we don't want all the safety options not worth it" but here it doesn't seem it would have helped much the more data comes out.

[sokoloff]

Since I’m in your old boat (so to speak), what additional evidence suggests that the Ethiopian flight was not saveable by a crew who flew the airplane away under the stick shaker, reduced thrust, and then fixed the trim at altitude? (I’m not saying that is easy or even “par”, but it does seem like they had a salvageable situation until they turned the stab trim back on after correctly putting it in cutout and then left it on and let it run the trim nearly full nose down.)

[tigershark]

https://news.ycombinator.com/item?id=19902068 Even the simulator proves that it was impossible to save the plane using Boeing suggested procedures. Now imagine doing that while you know that you are going to die soon and there is your answer.

[sokoloff]

The content on that link suggests that it is in fact possible to save the airplane (and on the fatal flight, the Ethiopian Air crew got the airplane climbing and I believe exceeded 8000’ before losing control as they fought the bad hand they were dealt).

Possible to save the airplane doesn’t mean that it’s expected, but it’s quite a bit farther from “the simulator proves that it was impossible”.

[salawat]

So the extra detail can be found in the flight data from the flights FDR, and CVR, and is laid out in the crash report.

If you combine that with a bit of knowledge with regards to the basic physics involved, and complications introduced by not fully briefing pilots on the system, it becomes obvious the crew was fighting a losing battle without the information we have now.

https://www.tailstrike.com/100319.html

The prelim report, and summary of the event can be found at the link above.

To lay things out, ET302 ended up having an AoA sensor malfunction.

One of the Appendicies includes a page from the flight manual, there are several pages mentioning the possibility of runaway stabilizer, along with a list of other symptoms that may be experienced due to a failed AoA sensor input to the Flight Control Computer.

There is also the page on which the Stabilizer Trim Runaway checklist is printed, which also specifically characterizes a Stabilizer Trim Runaway as an uncommanded continuous stabilizer trim activation event with mucho emphasis.

The page containing the closest thing to a hint as to the existence of MCAS (page 29), gives a small blurb that the flight computer does something, and that maybe you should be ready to run through the Stab Trim Runaway checklist.

Now. Look at the list of associated symptoms.

IAS Airspeed disagree is one of those items.

There is a memory item for 737 for airspeed unreliable, which if run through before the Stab Trim Runaway can greatly exacerbate the difficulty of recovering from the out of trim condition.

Which checklist gets remembered first then, can have a drastic effect on whether you can recover the plane, and the checklist to solve the problem that MCAS caused, if committed to memory entirely, doesn't even characterize the entry point for the checklist in a manner consistent with MCAS malfunction.

This is without even taking into account what actually happened, mind. I'm just pointing out documentation/communication failures that could contribute to a pilot not making the connection in time, while trying to parse the cacophony of alerts to ascertain what his plane is trying to tell him.

This is coupled with his autopilot being unable to hold things stable so he can troubleshoot, his FEEL DIFF PRESS light indicates the haptic feedback provided by the computer may not be appropriate to actual conditions, so the finely tuned muscle memory that pilots can rely on as a recall aid may be inaccurate or downright dangerous.

In short, nothing about this situation feels right, the pilot who has had it ground into them to trust their instruments over their own senses is actually dropped into a situation where almost all of their instruments are lying, because the computer is correcting actual readings with garbage AoA data.

Again, we've not even touched on what actually happened. This is just enumerating what could have happened, which constitutes possibilities that a pilot would have to navigate in that moment to successfully come to a conclusion about what was going on. Without the luxury of priming by knowing that's what you're going into the simulator to practice today, and with the additional entropy and complacency that comes from having flown uneventful flights 100's of times before.

Now, take into account that a highly experienced pilot, clued into the possibility of the Stabilizer runaway, did manage to troubleshoot, but was left in a bad spot.

The torque required to actuate against the airstream at the speeds the flight had achieved were such that they needed the electrical trim motor to overcome the resistance. So they turned it back on, and re trimmed. However, they were unaware they would need to keep signalling with the trim switches to keep the MCAS system from kicking in 5 seconds later.

This was a system, snuck in, under the radar, and documented in a completely inconsistent manner to the catastrophic outcomes that could arise from a malfunction.

I'm not a legit Aeronautics Engineer. Just a polymath with a penchant for running down and understanding things without having the benefit of having someone explain them to me in good faith. (Immensely important skill for auditing purposes).

I don't want you to just take my word for anything. Go back through most of my posts on 737 MAX topics if you'd like, and do your own research.

-The relationship between Boeing and it's regulatory framework, was of so much concern, the Office of the Inspector General was calling it out.

-The A320neo taking them by surprise.

-The work culture at Boeing

-the reprioritization of shareholder value over product quality

All of these to any Quality Engineer only leads to one variety of outcome. It's a really pervasive pattern.