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

[Nusa]

It's interesting that in the Lufthansa flight, individual AOA sensor data can be switched off.

They didn't have the precision to turn off individual sensor data. They had the ability to turn off one of the computers that handled that sensors data, which disabled about a third of the various sensors on the aircraft. Basically masking a sensor fault with an intentional computer fault. Not something to be done lightly, especially if one isn't sure of their diagnosis/solution.

[Emo]

Isn't there one option missing? In case the plane has a relative high speed and thus the manual trim is hardly usable because of the high forces on the elevator, the pilot would benefit by switching off the MCAS system/correction but not the electrical activated trim switches on the joke.

PS On the MCAS side input "rules" on the sensors were missing. A 70 degree AOA should never be accepted at flying speeds

[KL27x]

PS On the MCAS side input "rules" on the sensors were missing. A 70 degree AOA should never be accepted at flying speeds

At 200 knots wind speed and AOA of 70, that would mean the plane is going roughly 585 knots, true vector speed. And that would make the plane's speed in the belly (relative downward) direction 550 knots. I wonder if the wings would stay on. Even if they did, the reading is obviously invalid if it were to remain stable at 70. The plane would be in the middle of a somersault, if the reading were correct. And stabilizer will be useless, anyhow, while the plane is spinning... even if the plane was temporarily "flying" like a pancake, it would not be controllable at that time.

Even with a lack of other sensor data, I wonder if some sort of tracking over time might be useful. If the AOA changes faster than possible (or remains impossibly stable in an extreme condition), it might be able to be noticed by the FCC that the sensor is screwy, or the plane is already crashed.

To put 70 degree AOA in perspective: in AF447, the plane never exceed 40 degrees AOA while in a stall for 3 minutes... while the PF was actively pulling back on the stick. 

[Brumby]

Isn't there one option missing? In case the plane has a relative high speed and thus the manual trim is hardly usable because of the high forces on the elevator, the pilot would benefit by switching off the MCAS system/correction but not the electrical activated trim switches on the joke.

While your point has some validity, it is that sort of difference in the function of an aircraft that can lead to a separate Type Rating.  Establishing a new Type Rating means that any pilot that wants to fly such an aircraft will need to go through the full rating exercise.  This takes time, costs money and restricts the range of aircraft that an airline's pilots can fly unless they get the additional type rating.  It also means that pilots with more than one Type Rating have to keep each of them up to standard with ongoing training and assessment.

The objective of any new version of an aircraft is to keep it the same (as much as they possibly can) as previous versions - in the skills required to fly it.  This is why they still have the "No Smoking" switch on the 737NG models - even though it hasn't been active for years.

[Mechatrommer]

Isn't there one option missing? In case the plane has a relative high speed and thus the manual trim is hardly usable because of the high forces on the elevator, the pilot would benefit by switching off the MCAS system/correction but not the electrical activated trim switches on the joke.

surprising isnt it? engine and attitude can be controlled either manually or automatically at comfortable strength, ie servo or hydraulic booster activated on both mode. but not the elevator trim wheel, in manual mode, you need conan barbarian strength to rotate those wheel at probably hundreds of rotation from one end to the other.

[GeorgeOfTheJungle]

Had the pilot been a Sully, he would never have allowed the stabilizer to go full nose down (*), but these were young, "playstation" kind of pilots, they got lost the moment their xbox went nuts, and failed to keep under control 1) the speed (**) and 2) the control surfaces, a.k.a. the #1 rule: fly the plane.

(*) There's a dial next to the stabilizer wheel => you can see the angle and you are seeing it spinning in the wrong direction to further nose down => a self confident Sully kind of pilot would have just grabbed and stopped it immediately. The reason why it's got a clutch is to allow you to do exactly that.
(**) They totally neglected air speed, too.

[tooki]

Had the pilot been a Sully, he would never have allowed the stabilizer to go full nose down (*), but these were young, "playstation" kind of pilots, they got lost the moment their xbox went nuts

I think you need to sit down and shut up, old man, and learn about what pilots actually learn before you go badmouthing them.

[KL27x]

https://leehamnews.com/wp-content/uploads/2019/04/Preliminary-Report-B737-800MAX-ET-AVJ.pdf

What I find very curious in this preliminary report:
There are a couple instances where the report states the duration of the MCAS trim adjustments in seconds and in units.
But there are NO instances, anywhere in this doc, were the duration of the pilots' manual power trim inputs are ever reported. The only thing that is reported is the corresponding movement of the stabilizer.

In addition:

At 05:40:41, approximately five seconds after the end of the ANU stabilizer motion, a third instance
of AND automatic trim command occurred without any corresponding motion of the stabilizer,
which is consistent with the stabilizer trim cutout switches were in the ‘’cutout’’ position

This statement suggests that
1. The data recorder doesn't know the position of the stab cutout switches
2. The data recorder doesn't know if/when the trim motors are actually powered or not; the conclusion is made based on the actual movement of the stabilizer.

So we can't know if the power trim was working, properly, in this plane under these conditions, from the info in this report. Either this info was omitted/withheld intentionally, or it was not recorded.

AFAIC, it is completely possible that the pilots did not make appropriate trim inputs under the conditions. It is also completely possible that they did, but the stabilizer did not make the corresponding change. It is further possible they grabbed the trim wheel and successfully stopped the wheel from turning further down... but the stabilizer/jackscrew moved, anyway. Pulling back on the yoke puts  a high force that wants to push the entire stabilizer into a further nose down position (ref Alaska Air 261)*. AFAIC, this mechanism is probably belt driven, and at some point belts slip. Gears or chains are possible, but not likely, IMO (and a snapped jackscrew or chain is also no good). There is potentially a point where cutting stab trim is the only way to prevent the MCAS from moving the trim further down despite grabbing the wheel, physically.... and that there is no way to move the trim back up without doing a roller coaster maneuver.

*I picture the stabilizer rotating around an axle that is near its midpoint. As long as the elevator is neutral, it doesn't matter what load is on the stabilizer; it can still rotate freely under power or manual trim. But an extreme elevator position can put enough torque that the stabilizer cannot be rotated against this force, anymore... though it might still be possible that the motor (MCAS) could turn the stabilizer in the other direction.

[GeorgeOfTheJungle]

Had the pilot been a Sully, he would never have allowed the stabilizer to go full nose down (*), but these were young, "playstation" kind of pilots, they got lost the moment their xbox went nuts

I think you need to sit down and shut up, old man, and learn about what pilots actually learn before you go badmouthing them.

And you should stop watching the TV because there are professional pilots saying just that in forums all over the internet, e.g. at pprune.org

[GeorgeOfTheJungle]

[KL27x]

^I'm curious where this guy gets his information. How does he know this stuff? Particularly the part about pilots not being able to tell the difference with MCAS off... and why can you disable MCAS in a simulator and not in an actual plane?

Anyhow
1. "MCAS isn't antistall... it just gives the plane a little nose down nudge to make it handle like the NG."

10 seconds and 2.6 degrees of trim every 5 seconds is not a small nudge.

2. "This proved too big. In simulator testing it (when fired erroneously, I presume) can put the plane into an unrecoverable situation in as little as 40 seconds."

According to the Seattle Times article, Boeing initially told FAA that the stabilizer adjustment was only 0.4 degrees. But they had to  increase it based on real test flights. Boeing didn't increase this response, by over 4x without informing the FAA, for no good reason.

At an actual high AOA, that huge amount of trim has been (presumably) shown to actually be needed in real test flights. But when it happens erroneously, at lower AOA, this adjustment is obviously enormous. This is to be expected due to how the aerodynamic problem caused by the engine manifests. The nose up force increases as the AOA increases. At high AOA, you need an extreme stabilizer position. At normal AOA, this stabilizer adjustment will be ridiculous. Is what it is. "Small nudge" is optimistic.

[floobydust]

Only Boeing shills will push the "blame the pilots" narrative.
No system should be so obfuscated, undisclosed to pilots, and ultimately such a shit design.
"... Boeing is now working on and testing changes to the software “because the original software was designed in a hideous manner.” as the Pilots Association says. “MCAS was a monster”.

How about the class action lawsuits against Boeing:
"...claims the plane maker “effectively put profitability and growth ahead of airplane safety and honesty.”
"Boeing withheld necessary safety features from the Boeing 737 Max unless airlines purchased them as ‘extras’ or ‘optional features’ in order to keep the price down” to compete with Airbus.

How about Trump desperately tweeting “FIX the Boeing 737 MAX, add some additional great features, & REBRAND the plane with a new name.”
Anything to save the huge political donations Boeing gives the Republican Party, and the thousands of jobs at risk.
He has no idea that it takes a very long time to engineer out the bullshit and may not even be possible, if the aircraft needs hardware changes.

[KL27x]

Oh, it is possible that it was pilot error, but we don't know that. As a conspiracy theorist, I can imagine

1. Jakarta was potentially a true accident and might have been partly due to pilot error.
2. ET302 was crashed intentionally. I can't guess the motive other than some damage to the US and/or the UN. (Many UN members were onboard). And the pilots were both in their twenties... young men are most susceptible to being martyrs for idealistic reasons. You could even wonder if it really comes down to money... Airbus investors involved.

This is seemingly ridiculous, but wherever hundred of billions of dollars hang in the balance, every angle must be investigated to the very end. Let alone the deaths of the 150 people onboard.

[GeorgeOfTheJungle]

They and Boeing, both are to blame. It's hard to have to blame the poor dead pilots too, but they didn't do it right. Sorry but that's the sad truth. Hundreds of lives lost due to 1) Boeing and 2) two young pilots who should have known better after the Lion Air 610 crash.

[KL27x]

It's hard to have to blame the poor dead pilots too, but they didn't do it right. Sorry but that's the sad truth.

If you know that, great. I don't know it, despite anything you or any "real" pilot has posted. Jakarta: yeah, let's say they shoulda cut the stab trim. But even if the pilots had cut the stab trim, it still doesn't mean the plane would not have subsequently crashed.

[GeorgeOfTheJungle]

They were incapable to (un)trim and to keep the speed within limits, when the means to untrim and to control the speed were there. Had your son been in that plane, you'd call that a fail, wouldn't you?

[floobydust]

They and Boeing, both are to blame. It's hard to have to blame the poor dead pilots too, but they didn't do it right. Sorry but that's the sad truth. Hundreds of lives lost due to 1) Boeing and 2) two young pilots who should have known better after the Lion Air 610 crash.

You can't move the stabilizer once you shut off power. You get a few seconds after switching stab trim power on, until MCAS takes over again. I think this is why ET302 kept flipping power on and off, trying to stop the dive.... after the emergency procedure failed them. The manual trim wheels need the Hulk to turn them.
I can't fault the pilots for something so complicated, secretive and ultimately a futile endeavour.

[GeorgeOfTheJungle]

They and Boeing, both are to blame. It's hard to have to blame the poor dead pilots too, but they didn't do it right. Sorry but that's the sad truth. Hundreds of lives lost due to 1) Boeing and 2) two young pilots who should have known better after the Lion Air 610 crash.

You can't move the stabilizer once you shut off power. You get a few seconds after switching stab trim power on, until MCAS takes over again. I think this is why ET302 kept flipping power on and off, trying to stop the dive.... after the emergency procedure failed them. The manual trim wheels need the Hulk to turn them.
I can't fault the pilots for something so complicated, secretive and ultimately a futile endeavour.

No, no... please re-read the preliminary report it's here: https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg2321457/#msg2321457

At 5:40:00 they should have corrected trim with the yoke's trim button (electrical trim) and then flip the cutout switches to off for the rest of the flight and they would all be still alive.

[Nusa]

As a conspiracy theorist,

https://en.wikipedia.org/wiki/Conspiracy_theory

A conspiracy theory is the fear of a nonexistent or alleged conspiracy or the unnecessary assumption of conspiracy when other explanations are more probable. Evidence showing it to be false, or the absence of proof of the conspiracy, is interpreted by believers as evidence of its truth, thus insulating it from refutation.

closely related to, in more modern terminology:

https://www.urbandictionary.com/define.php?term=Trolling

Trolling – (verb), as it relates to internet, is the deliberate act, (by a Troll – noun or adjective), of making random unsolicited and/or controversial comments on various internet forums with the intent to provoke an emotional knee jerk reaction from unsuspecting readers to engage in a fight or argument

The real question is how useful and/or desirable this behavior is.

[KL27x]

At 5:40:00 they should have corrected trim with the yoke's trim button (electrical trim) and then flip the cutout switches to off for the rest of the flight and they would all be still alive.

GoJ: I realize the thread was started 5 months ago, and that it started due to this Jakarta crash. But the big hubbub is over the more recent Ethiopian airlines crash that occurred just 5 months after Jakarta. And AFTER airlines and pilots were given specific training on how to handle an AOA sensor failure causing erroneous MCAS activation. ET302 pilots reportedly received this training.

Nusa, lol. 

[GeorgeOfTheJungle]

GoJ: I realize the thread was started 5 months ago, and that it started due to this Jakarta crash. But the big hubbub is over the more recent Ethiopian airlines crash that occurred just 5 months after Jakarta. And AFTER airlines and pilots were given specific training on how to handle an AOA sensor failure causing erroneous MCAS activation. ET302 pilots reportedly received this training.

The report I'm referring to is of the ET302 crash, at 5:40:00 they should have (un)trimmed but they did not do it. That was their first chance to save the plane, but not the only one nor the last.

[KL27x]

^My bad, I just read "jakarta" in that link and thought you were talking about the other crash.

As for "they shoulda untrimmed," if you look carefully at this report, there's nothing in it that proves the pilots did not do what you are suggesting they should have done. The report does not include the duration of the pilots' trim inputs. Only the resultant change at the stabilizer. It is quite possible that the pilots pressed the button appropriately, but the stabilizer did not move the amount that would be expected, due to extreme elevator load. It appears they may have "neglected" to switch the power back off, though. 

After the Alaskan Airlines 261 accident, the NTSB has suggested that in a case where the trim is not working, properly, that no further attempt should be made to correct the trim. So what they "should have" done is not exactly clear without having been there, unless you have a crystal ball. Even if there were able to maintain level flight at that point, with no further trim adjustments, that doesn't guarantee the plane could bank to return to the airport without losing too much altitude or that they could land the plane, safely, in this condition. They may have had to land at a much higher than normal speed, and they might not be able to stop on the runway or they might break the front landing gear. Depending on the airport, this might mean crashing into buildings or a mountain... or falling off the edge of a cliff. This airport has been described as a shoebox in the mountains.

*I find it rather curious that the report states the duration of the MCAS response a couple of times, but nowhere does it state the length of trim input from the pilots. I find it hard to believe this is not recorded by the black box. Perhaps the response was not appropriate, and the airline is intentionally omitting this information to keep this data hidden for a bit longer.

[tooki]

Had the pilot been a Sully, he would never have allowed the stabilizer to go full nose down (*), but these were young, "playstation" kind of pilots, they got lost the moment their xbox went nuts

I think you need to sit down and shut up, old man, and learn about what pilots actually learn before you go badmouthing them.

And you should stop watching the TV because there are professional pilots saying just that in forums all over the internet, e.g. at pprune.org

Aww, honeybear, I literally do not even have TV. (I do not have cable or antenna, nor do I subscribe to any internet TV service. Just netflix for movies, and youtube.)

My point was, at no point EVER has flying been like video games. Are younger pilots more inexperienced? Sure. Age lets you gain experience. But it’s complete and utter bullshit to act as though pilots today are not trained well. If you actually followed working airline pilots, and not just general aviation pilots, you’d know this.

[Brumby]

... and why can you disable MCAS in a simulator and not in an actual plane?

If you just think for a second, that should be extremely obvious.

Simulators are used for training - and that includes training for adverse situations.  Flick a switch and you can have an engine fire to deal with - or a failed instrument - or a faulty hydraulic system.  I don't think these will be options on a real plane.

Same way you could flick a switch to kill the MCAS, but not affect anything else.


Simples.

[dzseki]

Had the pilot been a Sully, he would never have allowed the stabilizer to go full nose down (*), but these were young, "playstation" kind of pilots, they got lost the moment their xbox went nuts

I think you need to sit down and shut up, old man, and learn about what pilots actually learn before you go badmouthing them.

And you should stop watching the TV because there are professional pilots saying just that in forums all over the internet, e.g. at pprune.org

I also think that bringing up the pilot’s age can't serve for any judgement.
Experienced pilots make fatal mistakes as well -> Captain Lutz with close to 20k hours flight experience crashed Crossair 3597

https://en.wikipedia.org/wiki/Crossair_Flight_3597