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

[tooki]

Boeing's response- blaming the pilots, not their shit MCAS software and AoA sensors, is the problem.
Blaming the victim minimizes the criminal act.

Well, many people have wondered why they didn't execute the "uncontrolled stabilizer trim" checklist in both flights. It's not "blaming", it's wondering.

Even if it was the crew's error, no (undocumented) system should be designed to rely on "a memory item" to stop a fatal dive.

I think that thou dost not understand the point of an emergency checklist. They're not for routine use, they're for, you know, when things aren't working right.

[Brumby]

Even if it was the crew's error, no (undocumented) system should be designed to rely on "a memory item" to stop a fatal dive.

I think that thou dost not understand the point of an emergency checklist. They're not for routine use, they're for, you know, when things aren't working right.

Nor do they understand WHY there are such things as "memory items".

[djacobow]

Even if it was the crew's error, no (undocumented) system should be designed to rely on "a memory item" to stop a fatal dive.

I think that thou dost not understand the point of an emergency checklist. They're not for routine use, they're for, you know, when things aren't working right.

Nor do they understand WHY there are such things as "memory items".

Yes, these are things the pilots are supposed to know, cold. As in no thinking, no puzzling, just doing. And furthermore, I think it is very reasonably, very very reasonable, to expect that pilots are, when confronted with a strange situation, to be able to do some aerodynamic reasoning of their own AFTER having completed the memory items and checked them with the emergency checklist. This is what pilots call "airmanship." So far, it's looking like the pilots of these two aircraft did not demonstrate such airmanship, and that is tragic.

However, I definitely have sympathy for flooby's point that no system should rely on a memory item to stop a fatal dive. I think that is essentially true. The electronic systems should be designed to avoid emergencies, not casually drop pilots into emergencies and expect pilots to fly their way out of them. If they designed stuff that way, then the "defense in depth" benefit of having astute pilots is lost, since you are relying on that as your first line of defense, not your last.

That said, I still find all these people saying that MAX is fatally flawed, that the aircraft is unstable in normal flight, that the 737 should not have been revamped once more, that the idea of MCAS is inherently bad and dangerous, that MCAS is shit, etc rather absurd -- at least very much premature given what we know.  Instead, I think the evidence is coming in that MCAS has a correctable design flaw. We will see how many people suspected that design flaw and signed off on it anyway. But fundamentally, it looks like bad engineering judgment was involved (what we used to call "a mistake") and that mistake will be corrected.

None of that makes it less tragic that so many people have died. And it will be doubly tragic if it turns out this is because Boeing engineers made a mistake that had previously been made by someone else. And triply so, if they did in knowingly. But none of that is established at this point.

[AG6QR]

Boeing's response- blaming the pilots, not their shit MCAS software and AoA sensors, is the problem.
Blaming the victim minimizes the criminal act.

Well, many people have wondered why they didn't execute the "uncontrolled stabilizer trim" checklist in both flights. It's not "blaming", it's wondering.

Even if it was the crew's error, no (undocumented) system should be designed to rely on "a memory item" to stop a fatal dive.

I think that thou dost not understand the point of an emergency checklist. They're not for routine use, they're for, you know, when things aren't working right.

Correct.  A pilot is one who is required to consult a written checklist when he is doing tasks which he does several times each day, but is required to commit to memory the tasks which are not expected to be used in an entire career.  Emergency items are committed to memory, because there's no time to locate and refer to a paper checklist.

Can an "average person" be trained well enough to accomplish the tasks that might be required of an average airline flight, in good weather, where the equipment works as it's supposed to, and no memorized checklists are required?  Possibly, with some time and effort. 

But being prepared for an average flight is not what the piloting job is about.  They have to be able to handle all the unusual and bad things that can happen.  For example, they have to know what instruments will be affected, and how, if all the pitot tubes are iced up at once, so that they can diagnose the condition, ignore the failed instruments, and safely fly using the remaining instruments.  They have to know how to handle engine failures.  They have to always know what airports are within gliding distance, and if there are none (as was the case for Sully's "Miracle on the Hudson") they have to recognize that quickly, and take the best available option rather than coming up short when trying to glide to a runway that is unreachable.

[floobydust]

MCAS relying on a single sensor and being undocumented, optional AoA disagree indicator, are just a few of the many horrific errors contributing to these tragedies.
All the noise deflecting blame from Boeing and the FAA, protecting investor's and the stock- can't absolve this multi-billion dollar turd or return the 356 lost lives.

The Senate subcomittee hearing was tough to watch. The FAA acting Admin was horrible: "I am confident in the AOA veins that are produced and put on airplanes and I am confident in the MCAS system."

Are we saying the planes are safe and should be back up in the air? Just need another few minutes of pilot training on an iPad 

JT043, JT610, ET302 problems with AoA sensors
A very good read and sleuth work there. In 2006 it was incorrect assembly- a loose set screw on a 747-400 AoA sensor problem.
Today, a detail this small could be the root cause but here we are blaming the pilots.

[djacobow]

Today, a detail this small could be the root cause but here we are blaming the pilots.

I think you are having a hard time understanding why planes crash. There is not one reason. There is never "one" reason.

Aviation accidents are almost always the results of long chains of failures. To say the pilots could have saved the aircraft is not to "blame" them but to point out the obvious: that this was a link, among many, in the chain.

If these accidents were being investigated by the US NTSB, they would officially identify "proximate causes" and "contributing factors", but even this belies the reality that it takes a lot of things to go wrong to crash a plane. Some of those things would happen years earlier at an engineer's desktop workstation, during a test flight, in the assembly hangar, in a boardroom, during a regular maintenance check, and yes, in the cockpit.

[floobydust]

What I'm on about is the focus should be on finding the cause(s), the contributing factors for the crashes.
Instead, it's gets corrupted in order to protect Boeing and the FAA. Blame the humans when the automation system intended to save them, kills them.

Ethiopian Airlines preliminary report is due this week.
Just in WSJ: "Ethiopian Airlines Pilots Initially Followed Boeing’s Required Emergency Steps to Disable 737 MAX System"

I guess that trim wheel was their fault, right. "memory item"? No it's a "gymnasium item".

[GeorgeOfTheJungle]

Blame the humans when the automation system intended to save them, kills them.

@floobydust : knowing what you know, do you think you would have turned off those two switches or not?

[BradC]

I think you are having a hard time understanding why planes crash. There is not one reason. There is never "one" reason.

My initial reaction to your statement was "Hell no, I'll refute that". But I can't. Doesn't matter which Aviation disaster I'd like to cite, it is *always* a case of there being more than one factor and having to have the "stars align" in a particularly bastardly way for the plane to fall out of the sky. I keep going back to the 737 rudder reversal, but again it's a long chain.

And the reality is the same for pretty much any form of loss of life if you examine the issue closely enough. Maybe getting hit by a meteor would qualify, but then I don't know of any planes that have been knocked out of the sky like that.

That then goes back to the (actually scarily high) number of disasters that have been averted by competent jockeys up the front (BA-9 anyone?). I want my pilots to know how to fly a (not fatally like Alaska 261) broken aircraft. Although if you watched "Flight" you might suspend belief and think a skillful pilot might have saved that one also.

[PartialDischarge]

@floobydust : knowing what you know, do you think you would have turned off those two switches or not?

All over this thread everyone has been assuming that the pilots did not do this or that, some even suggesting that these pilots were basically unexperienced and clueless about planes,  without really knowing what happened, especially since software is involved and software tends to have a life of its own.

Well, bombshell, pilots followed emergency procedures that were laid out by Boeing. This Boeing fkup could be even bigger than expected, and yet many will still blame the pilots 

https://edition.cnn.com/2019/04/03/africa/ethiopian-airlines-emergency-procedures-intl/index.html

[BradC]

Well, bombshell, pilots followed emergency procedures that were laid out by Boeing. This Boeing fkup could be even bigger than expected, and yet many will still blame the pilots 
https://edition.cnn.com/2019/04/03/africa/ethiopian-airlines-emergency-procedures-intl/index.html

"Citing unnamed sources familiar with the investigation, the WSJ reported that despite following the steps, which included turning off an automated flight-control system, pilots could not regain control of the Boeing 737 MAX 8.
CNN has not been able to confirm details of the report."

Let's wait and see 'eh?

[GeorgeOfTheJungle]

I'd bet they did turn off the autopilot but NOT the trim cutout switch...

[GeorgeOfTheJungle]

It can't do anything if you cut power to the jackscrew motor with the stab trim cutout switches.



See: https://www.eevblog.com/forum/chat/lion-air-crash-jakarta-boeing-737-had-prior-instrument-error/msg2302188/#msg2302188

[G7PSK]

This is interesting as when the power failed on this Russian plane the pilots used a glass of water in order to keep the right attitude. I guess they may have had more time to sort things but they were also trained in what to do if the electronic system did fail perhaps these days there is not so much training and it certainly looks like the manufacturers make no allowances for total failure of the systems. It begins to look like they might even be trying to lock the pilots out of the systems now.

https://youtu.be/JUfcL1Muz6M

[PartialDischarge]

It can't do anything if you cut power to the jackscrew motor with the stab trim cutout switches.

You sure? Post the cockpit wiring diagram and I'll check....

[GeorgeOfTheJungle]

100% sure.

[GeorgeOfTheJungle]

I don't think so.

[dzseki]

After all Boeing can say it's not needed to modify anything, since even the passangers know how to cut-off trim power now...

[djacobow]

This is interesting as when the power failed on this Russian plane the pilots used a glass of water in order to keep the right attitude. I guess they may have had more time to sort things but they were also trained in what to do if the electronic system did fail perhaps these days there is not so much training and it certainly looks like the manufacturers make no allowances for total failure of the systems. It begins to look like they might even be trying to lock the pilots out of the systems now.

https://youtu.be/JUfcL1Muz6M

This is a cool story, but some of those details seem very dubious. For example, a glass of water cannot be used as a substitute attitude indicator***  for the same reason your ear cannot be used for such: it can make no distinction between the acceleration of gravity and other sources of acceleration. Hence, you can easily "death spiral" an aircraft all the while with the water level. In any case, the video makes it clear that they dropped below the ceiling in order to see the ground; at that point they would not really need an AI anyway.

I also notice the wikipedia page for the incident mentions no glass of water.

I see how the loss of electricity caused them to lose their nav capabilities. I wonder, though, why they didn't still have use of primary instruments. Airspeed indicator, altimeter and vertical speed indicator do not need power at all. AI and DG are usually vacuum driven, but I can imagine them being electric in an airliner. But it would be a poor design choice indeed for that electric system not to be backed up by something non-electric. Turn coordinator usually is electric, so that would go.

Of course, on a modern airliner these sensors are all integrated onto screens, but if you look around you can usually find some or all of them duplicated somewhere on an old steam gauge.

*** notwithstanding the Tales of the Gold Monkey episode where the heroic captain keeps the aircraft level in hard IMC with a half drunk bottle of whiskey.

[djacobow]

I don't think so.

George is right. These switches cut electric power. They do not go to a computer or other logic -- though I would not be surprised to find out that they actually control solenoid relays that handle the heavier load of the trim motors.

[floobydust]

It looks like the stab trim wheel is too difficult to turn. The stabilizer and elevator forces combine to make high force on the jackscrew.
1982 737 manual says let go of the stick to crank the trim wheel, the "roller coaster technique", to remove elevator forces from the jackscrew.

Can't imagine the near zero G dive, screaming passengers and an emergency procedure leading you to hand cranks the crew can't move. Flipping the cutout switches back on is the only option.
They might be "soft" switches and not actually physically disconnect power to the BLDC motors but who knows.

source: https://www.seattletimes.com/business/boeing-aerospace/boeings-emergency-procedure-for-737-max-may-have-failed-on-ethiopian-flight/

[GeorgeOfTheJungle]

They just had to correct trim with the yoke trim button BEFORE cutting power. The button on the yoke overrides the MCAS commands. The MCAS kicks in again (and again, that's the flaw) 5 seconds after the pilot releases the yoke's trim button, but that's plenty of time to flip the cutout switches. Many (well, a few, or some) pilots in previous 737 MAX flights have saved the day by doing just that. Why? How did they know? Because after the lion air 610 crash Boeing put out a safety technical bulletin explaining just that. We're going in circles in this thread...

[iMo]

..Many (well, a few, or some) pilots in previous 737 MAX flights have saved the day by doing just that. Why? How did they know? Because after the lion air 610 crash Boeing put out a safety technical bulletin explaining just that. We're going in circles in this thread...

Frankly, the fact the pilots had to manipulate the switches in order to save the day makes me pretty nervous (as a passenger). I do not want to fly in a plane where the pilots have to manipulate those switches in order to save my day.. 

[djacobow]

I do not want to fly in a plane where the pilots have to manipulate those switches in order to save my day.. 

I certainly wouldn't want to fly in a plane that didn't have those switches, but I also don't want to fly in a plane where needing to flip them is a regular occurrence.

That is, I don't want to fly in a plane where the automation sometimes malfunctions and requires to intervene, but the sad basic fact is that this is all airplanes. And this is also why we still have pilots.

[Nusa]

This is interesting as when the power failed on this Russian plane the pilots used a glass of water in order to keep the right attitude. I guess they may have had more time to sort things but they were also trained in what to do if the electronic system did fail perhaps these days there is not so much training and it certainly looks like the manufacturers make no allowances for total failure of the systems. It begins to look like they might even be trying to lock the pilots out of the systems now.

https://youtu.be/JUfcL1Muz6M

This is a cool story, but some of those details seem very dubious. For example, a glass of water cannot be used as a substitute attitude indicator***  for the same reason your ear cannot be used for such: it can make no distinction between the acceleration of gravity and other sources of acceleration. Hence, you can easily "death spiral" an aircraft all the while with the water level. In any case, the video makes it clear that they dropped below the ceiling in order to see the ground; at that point they would not really need an AI anyway.

I also notice the wikipedia page for the incident mentions no glass of water.

I see how the loss of electricity caused them to lose their nav capabilities. I wonder, though, why they didn't still have use of primary instruments. Airspeed indicator, altimeter and vertical speed indicator do not need power at all. AI and DG are usually vacuum driven, but I can imagine them being electric in an airliner. But it would be a poor design choice indeed for that electric system not to be backed up by something non-electric. Turn coordinator usually is electric, so that would go.

Of course, on a modern airliner these sensors are all integrated onto screens, but if you look around you can usually find some or all of them duplicated somewhere on an old steam gauge.

*** notwithstanding the Tales of the Gold Monkey episode where the heroic captain keeps the aircraft level in hard IMC with a half drunk bottle of whiskey.

The video itself shows cockpit shots. It's obvious it's NOT a glass cockpit, so most of the primary instruments would have been unaffected. Nor were the primary flight controls, which were engine-driven hydraulic. Basic navigation could be done manually, that was not a show-stopper. By far the most critical lost system was the fuel-transfer pump, which meant the engines were going to die as soon as the holding tanks emptied. Otherwise, they could have made it to a proper airport.

There may have been a glass of water and/or coffee in the cockpit, but I doubt the pilots actually relied on it as an instrument. Maybe the flight engineer had time to look at such things. Most likely its just some layman's idea of embellishing the story.