Lion Air crash: Jakarta Boeing 737 'had prior instrument error'

[GeorgeOfTheJungle]

Yes, it is true that button overrides MCAS. It is clearly visible in the flight recorder data. Did they knew/notice or not - that's the question which is unanswered.

But the emergency directive says... "Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT" Hadn't they read it?

[ogden]

But the emergency directive says... "Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT" Hadn't they read it?

Apparently not. Who knows. Anyway sitting in our armchairs we can only speculate or guess - what did they know and what did they think during those critical moments. Those answers are up-to professional investigators.

[Nusa]

You really should stop invoking Sully. He's an excellent pilot, but the incident he's famous for didn't involve malfunctioning controls of any kind. What Sully did was handle one of the most-practiced problems in all of aviation (multiple engine failure) and live to tell the tale. If he'd been able to make it to an airport, it wouldn't even be that famous. Ditching in water is also a training scenario, so I'd suggest that most airline pilots would be able to pull that off if they had to.

[KL27x]

If it's true that the (electric) trim button overrides the MCAS trim commands it follows that they just had to keep pushing it longer. The emergency directive quite clearly suggests that too:

Do you know that the stabilizer was responding to the button press like it should? Maybe they stopped pressing it because something was wrong. You assume only the manual method of trimming the plane can stick.

The ET302 prelim does NOT include the duration of the manual trim input button presses. We have that information for Jarkarta, not for ET302. This is strange. So we don't know how long they pressed the buttons.

At one point, the Capt requests the FO to press the trim up button with him, at the same time. This suggests that the Captain perceived that the trim was not responding the way he expected it to from his trim button. Was he confused by MCAS? Maybe. At this point the yoke/elevator is responding exactly like he expects. It is sufficient to control the plane, so far. And like a good Capt Sully, he relies on what works as expected. And perhaps he is unaware that this is going to be woefully inadequate in the very near future at the rate of acceleration of the plane in this attitude.

Do you know what happens if the pilots overcorrect the trim? Or let's say, do you know how much over-correction can be done without causing a new and dangerous problem? I don't either. There is perhaps a reason to be conservative in making this adjustment. And with the FO pressing the trim and the Capt pulling the yoke, the FO did not have that feedback and was conservative.

After initially running through the checklist, correcting the trim not quite enough, and doing stab trim cutout... The only thing left in the procedure it to manually trim. This did not work. If they knew how to do it (roller coaster maneuver), then they might have been able to perform manual trim rather than breaking protocol and turning stab trim power back on.

If copilot were allowed to touch buttons without a 30 second song and dance of verbal poetry and permissions, maybe he would have flipped stab trim power back off after correcting the plane the second time, without a second thought, like GoJ's perception of "a Sully." Perhaps Capt was tongue twistered out to figure out how to properly state the exact sequence fast enough in real-time and/or didn't even want it recorded on the voice recorder because he knew it was against protocol. And maybe the Captain left trim power on, on purpose, seeing as how he can "simply press the up button" to fix the problem according to GoJ simplified view... (at higher speeds and low enough altitude, this may not be the case).

[ogden]

The ET302 prelim does NOT include the duration of the manual trim input button presses.  We have that information for Jarkarta, not for ET302. This is strange. So we don't know how long they pressed the buttons.

We *do* have manual trim information for ET302, graphs in page 26 of prelim report. You can estimate button press times quite precisely:

[KL27x]

^Ahh ok, interesting. The most obvious oddity in this part of the recording is that they do not appear to realize when the MCAS re-activation occurs. There is no attempt to interrupt or to immediately correct it.

Perhaps the capt is hearing the clicks and believes that the copilot is making further up correction and/or vice versa? Too many chefs in the kitchen? The Captain's perception and communication that his trim control is not working as expected and the sharing of responsibility over trim control to the FO who has no yoke feedback was perhaps a significant domino in this outcome. Copilots of both crashes may have underestimated the danger of mistrim, as well. Seeing how calm the captain handled it (breaking out the manual even, in the Jakarta case) but not realizing how the increase in speed has affected things and increased the stakes.

I'd like to try corelate the button presses with the resulting trim changes as measured at the elevator, but I can't find the link. Gonna dig back through this thread to find it and try that later.

[ogden]

Do not recall - link was in this thread or not. 
Here it is: http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+,(ET-AVJ).pdf

[GeorgeOfTheJungle]

Do you know what happens if the pilots overcorrect the trim? Or let's say, do you know how much over-correction can be done without causing a new and dangerous problem? I don't either. There is perhaps a reason to be conservative in making this adjustment. And with the FO pressing the trim and the Capt pulling the yoke, the FO did not have that feedback and was conservative.

There's a dial next to the stabilizer trim wheel, if they didn't know the proper takeoff trim range (how the hell can a pilot NOT know that?), it's marked in green so they could have looked at it. Obviously, should have kept pressing nose up until the dial was well into the green... then flip cutout, end of problem.



BTW, see the flap lever next to the trim wheel? Could also have put that in position 1 to accelerate the (un)trim and disable MCAS.

[KL27x]

Funny I was just typing a post about this.

In this low altitude with mountainous terrain, perhaps the copilot is incorrectly fixating his view out the windshield rather than on the controls. The view of the controls are very cramped, and I imagine it is disorienting to change view/focus between miles and inches.

In a fighter jet, the navigator has no view out the front of the plane, at all. Perhaps some sort of electrically darkening windshield (yeah, what could go wrong?) would be useful in a commercial plane so that both pilots don't redundantly fixate on the horizon/terrain. Copilot would have nothing better to look at than the controls and instruments. To see which way wheel is turning, where the trim indicator is at, and what the air speed and pitch is. This could perhaps also improve instrument-only flight competence/confidence. Like blinders for a horse. Don't worry about things that the other guy has control over.

Obviously, should have kept pressing nose up until the dial was well into the green... then flip cutout, end of problem.

MP simulation:
https://youtu.be/xixM_cwSLcQ?t=1154
Captain doesn't specify numbers/rotations/duration. Neither pilot ever looks down at the indicator. All very relative and by feel. I think it is possible pilots develop a habit of not looking at the trim indicator or the wheel during flight. It's an awkward location and the wheel turns rather frequently with the autopilot on. It's perhaps something that has been habituated. I.e., totally ignored. Heck, reading the amount of trim isn't even part of the memory items.... the only criteria is if the wheel is moving by itself or not. The only communication relating to absolute trim position in this video is "it's getting quite heavy, now."

[tooki]

You really should stop invoking Sully. He's an excellent pilot, but the incident he's famous for didn't involve malfunctioning controls of any kind. What Sully did was handle one of the most-practiced problems in all of aviation (multiple engine failure) and live to tell the tale. If he'd been able to make it to an airport, it wouldn't even be that famous. Ditching in water is also a training scenario, so I'd suggest that most airline pilots would be able to pull that off if they had to.

Thank you! I, too, was tiring of GotJ's constant invoking of Sully as some kind of aviation deity*. Skilled pilot? Yes. Lucky? Lucky as hell.


*Reminds me of how non-tech-historians "discovered" Nikola Tesla a few years ago (thanks, Elon...  ) and ascribe to him things that go far beyond his (already significant) legitimate accomplishments. (And yes, I resent the "cool" kids evoking Tesla's good name for hipster points, even though when I was a kid, they bullied me for being a nerd who knew about people like Edison, Watt, Marconi... and Tesla.)

[GeorgeOfTheJungle]

It's sad, but you don't have to be a Sully to understand that they royally screwed up. Very very sad. As they say, shit happens.

[tooki]

It's sad, but you don't have to be a Sully to understand that they royally screwed up. Very very sad. As they say, shit happens.

I don’t think you realized that the comment above (and the one I quote) are talking about you. Enough with the Sully.

[GeorgeOfTheJungle]

I don’t think you realized that the comment above (and the one I quote) are talking about you. Enough with the Sully.

Oh, yes, I do realize, perfectly! And I wonder what makes some people think they can go around telling others to shut up. Tip of the day: If you disagree with someone, that's alright, get over it, life is like that.

Sincerely,
Have a nice day!

[KL27x]

It's sad, but you don't have to be a Sully to understand that they royally screwed up.

You don't know anything about Sully except he was put in a tough situation and he ended up making a questionable decision. Some people believe he had time to make a better estimate and actually land at an airport.

Sully throws shade at Ethiopian Airlines, suggesting that the copilot's 200 hours was unacceptable in the US.  He also suggests that the pilots have to be experienced enough to read each other's minds. In order be able to handle a situation that a single sensor failure can lead to, you need two greatly experienced pilots with ESP? What if one of those pilots had been incapacitated? Personally, i'd rather be on a plane that doesn't do this. Give me two average professional pilots and a debugged plane, and you can have Capt Sully and his ESP flying partner personally flying you around on a plane that has been grounded. Maybe Goose is available.

GoJ, most everyone following this thread understands that the pilots probably could have saved the plane if they had reacted differently. Let's even say that this is the most likely scenario. No one needs Capt Obvious to paint this narrative, so we owe you a thanks for repeatedly doing it, anyway. It's god's work, my friend. Keep it up.

I have made a lot of reaching speculations. At least some, if not all, of which will prove to be wildly wrong. I'm not trying to paint a narrative as if I know what happened. It's possible we find out more in the next 9 months. I can still imagine scenarios where Boeing is morally vindicated (but the damage has already been done).

[langwadt]

It's sad, but you don't have to be a Sully to understand that they royally screwed up.

You don't know anything about Sully except he was put in a tough situation and he ended up making a questionable decision. Some people believe he had time to make a better estimate and actually land at an airport.

afaiu it was shown in the simulator that he could made it the airport and landed, but only just, so it required he instantly take the decision and getting it wrong could results in a crash in a populated area

[tautech]

It's sad, but you don't have to be a Sully to understand that they royally screwed up.

You don't know anything about Sully except he was put in a tough situation and he ended up making a questionable decision. Some people believe he had time to make a better estimate and actually land at an airport.

afaiu it was shown in the simulator that he could made it the airport and landed, but only just, so it required he instantly take the decision and getting it wrong could results in a crash in a populated area

This ^^^^
So much could have gone wrong so the safest plan was the Hudson.

[KL27x]

^ And he would have had only one chance at it. Come in too steep, and you have to make the best of it. At least the Hudson was the longest landing strip in the area. I don't think he made a bad decision, but it was not like the alternative was only better because of the cost of the plane and evacuation.

He also wasn't sure that everyone would make it off the plane. There could be people with disabilities. There could have been some panic in the egress. There could have been damage to the plane in the landing. He could have bugsplatted a couple crazy college kids in a canoe.

He knew he could land the plane in one piece on the Hudson. And he knew that perhaps a majority of the passengers could egress before the plane sank or caught fire, including himself if it came to it.

I think he made the right call, but there was nothing heroic about it. A pilot concerned only for his own life would have done the same thing. Usually, this decision is always going to be the same. This is why we don't give the pilot an ejection seat. No one should ever have to make that kind of choice. But notice in this case, the cabin is pretty damn close to an exit. I would also bet Capt Sully knows how to swim.

[Nusa]

But notice in this case, the cabin is pretty damn close to an exit. I would also bet Capt Sully knows how to swim.

Now you're actually being rude in trying to turn historical fact into unfounded speculation. Sully was one of the last people to leave the plane after the water landing. He even checked the plane himself to make sure everyone was out. Plenty of witnesses. You should know this unless you were completely brain-dead to the news ten years ago.

But since you're measuring distance from the exit: there are actually TWO window exits in the cockpit that are intended for emergency egress, one for each pilot. There are even ropes so they don't have to jump.

[KL27x]

Of course if the plane isn't in immediate danger, the captain will heroically be the last person to leave. Of course, he has every intention of being the last guy off the plane, even while it is sinking. Even if everybody was not going to make it. But that didn't happen. He didn't get to find out what he would have done. Intentions != actions, and I don't think you can accurately predict what anyone will do when that push comes to shove. Capt Sully had that option. He gets to stand right next to the exit, breathing freedom, whilst heroically intending to be the last guy off the plane. If the plane isn't sinking, do you think it takes a hero to do that? The guy tucked in the back of the plane away from an exit and waiting for the line of people in front of him to move... for that old lady to frikkin jump, already, and start swimming... he didn't have that option. If he did, he would trade places in a hearbeart, and he would stand there next to the exit, being a hero, too. At least right up until the last second where not everyone makes it. Then we don't know what he will do anymore than Capt Sully.

Capt Sully didn't do anything wrong. He performed under pressure, he executed, he kept control. Good and good and good. But he never had to really make a heroic decision. I bet Sully would be the first person to say it. He is just a pilot who did his job. The airline wants him to be a hero, because it's good for their reputation and lawsuits.

The helicopter tour pilot made it out alive after a perfectly executed water landing. Nothing wrong with that. If he couldn't save his passengers, why should he die?

[GeorgeOfTheJungle]

They had to react quickly, that's why experience counts, they had not much time to guess the proper sequence of actions. Here in a forum we have all the time in the world...

[tooki]

"Guessing"? Just what exactly do you think pilots do in their pilot training?? It's all about practicing how to deal with the unexpected, so that when it happens, they already know what to do and how to do it, because they've practiced it a bunch of times.

[GeorgeOfTheJungle]

And that's exactly why I said guess

[james_s]

Sully has said as much himself, he did his job, he's a highly competent and experienced pilot who remained calm during an emergency and did what he was trained to do. There was also a significant amount of luck involved, he had enough speed and altitude to get to a suitably open space to put it down, had he been elsewhere things would not have turned out as well. His performance was admirable but I don't think I'd go so far as to call him a hero. He did exactly what any competent pilot would try to do, and he pulled it off almost perfectly.

[tooki]

And that's exactly why I said guess

So, then, you really have no idea what pilots do...

[KL27x]

They had to react quickly, that's why experience counts, they had not much time to guess the proper sequence of actions. Here in a forum we have all the time in the world...

And that's exactly why I said guess

Ok, going back to ET302:
The only way a pilot would have significant experience with solving this problem is if they had been so incompetent to begin with that they had screwed up the trim way out of whack.* They would have gotten this experience by allowing a plane to become dangerously close to losing control... probably with a load of passengers on board. This grossly out of trim problem is so rare, they moved the diagnosis to a supplemental reference and deleted the solution, entirely, some decades ago. I suppose they figured anyone who would need the deleted info should really just not fly planes. Since the pilot is now experiencing it for the first time, with an intermittent runaway trim on top, and they don't have "all the time in the world" the way you do, do you think it's at least possible that Capt Sully and his experienced copilot could also have botched it?

*It's not like the pilots have many/any opportunities to intentionally pull stunts with their employers' 737's, even on the rare occasion they are flying a near empty plane with just a few other crew.

Also, the reason they undercorrected is perhaps not so strange. Every pilot is fully aware of the dangers of overcorrecting in this scenario. Some pilots are apparently unaware, at this point in time, of any significant danger of undercorrecting, thinking they can just eventually get the trim into adjustment in stages, without being aware of the other parameters which must be considered. Hopefully this is no longer the case.

I don't see any obvious reason Sully would have known any better. He was an experienced commercial passenger pilot, not a stunt pilot. This is like thinking an experienced bus driver will know what to do when the bus goes into a slide. We pick bus drivers that don't slide the bus in the first place. This trim problem is so far out of the regular "lines" it doesn't normally exist. And if we only let experienced Indy car racers drive buses, I don't think it would make travelling by bus any safer. Personality type and temperament might increase the accident rate.

GoJ: we've been around and around, so I will also say this:
The memory item says nothing about looking at the trim indicator and putting it back to green band by using the trim button before powering it off. It says the button CAN be used to correct trim before stab cutout. That makes it sound like it's optional. And that the "correct" amount of trim is just a judgement call which is not necessarily of vital importance but more for convenience of the pilot. Maybe the pilot has some other additional training/education that covers this stuff in more detail, and perhaps that additional education and training should have been adequate. But the emergency procedure should perhaps better cover the actual emergency and not just the malfunction that can lead to this emergency in the first place. Going back to Jakarta, the captain did not appear to realize how close he was to losing control of the plane. Like you, he thought, well, just press the up button. Give control to the copilot and start reading a manual.