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#4469004 - 04/05/19 10:52 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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Originally Posted by Alicatt
Preliminary report is now out:

http://www.ecaa.gov.et/documents/20...1EQS914Wm-ECeoSDCJVmaSKHUCOxUHDZHikoIF8s

Not read it yet, just about to start.

Accordng to the cockpit voice recorder (page 11) they used the "stab trim cut-out" at 5:40:35, and the flight data recorder (page 26) indicates a few seconds later an automatic trim down command that gets supressed (no change in stab position) => cut-out does its job.
At 5:41:30 they try stab trim again, and I assume that's supposed to be manual electrical input, but there is no such input indicated in the FDR plot. Correction, not by trim but pitch up by pulling the stick, I guess. The pilot then asks the co-pilot whether trim is working, which he answers no and then tries to trim manually, which seems not to work either.
But then at 5:43:20, short before the end (no indication that they would have reverted the cut-out, but the switch position seems not to be part of the FDR plot), they trim again, two short manual electric up inputs are indicated in the FDR, ~5secs after the last manual input followed by a longer automatic down - that's the last inputs before the crash.

I am a bit confused that right after the cut-out the FDR still recorded the suppressed automatic trim input, but it later does not indicate the apparently attempted manual electric at 5:41:30 (I guess there might still have been such an attempt before the co-pilot said that trim doesn't work and tried manually). So it seems supressed automatic inputs are recorded, but supressed manual electric inputs are not recorded?
Question is, did they revert the cut-out before the last manual electric trim inputs?

Trying to put the quoted excerpt from the report into a quote or spoiler here, but the forum does not accept the post in that way...


Last edited by WhoCares; 04/05/19 12:27 PM.
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#4469006 - 04/05/19 10:59 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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As separate post it does - sorry for chain post...
ANU: aircraft nose up
AND: aircraft nose down
At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.
At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and co-pilot confirmed stab trim cut-out.
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.
...
At 05:41:30, the Captain requested the First-Officer to pitch up with him and the First-Officer acknowledged.
...
At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working.
...
At 05:43:04, the Captain asked the First Officer to pitch up together and said that pitch is not enough.
At 05:43:11, about 32 seconds before the end of the recording, at approximately 13,400 ft, two momentary manual electric trim inputs are recorded in the ANU direction. The stabilizer moved in the ANU direction from 2.1 units to 2.3 units.
At 05:43:20, approximately five seconds after the last manual electric trim input, an AND automatic trim command occurred and the stabilizer moved in the AND direction from 2.3 to 1.0 unit in approximately 5 seconds. The aircraft began pitching nose down. Additional simultaneous aft column force was applied, but the nose down pitch continues, eventually reaching 40° nose down. The stabilizer position varied between 1.1 and 0.8 units for the remainder of the recording.


Last edited by WhoCares; 04/05/19 12:14 PM.
#4469009 - 04/05/19 11:38 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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Originally Posted by Haggart
Boeing Co. Chief Executive Dennis Muilenburg Apologizes for Loss of Life & Promises a Software Fix Soon
https://www.marketwatch.com/story/b...eks-away-2019-04-04?mod=mw_theo_homepage


Already posted by Chaz. It is a few posts before the one you posted.


There was only 16 squadrons of RAF fighters that used 100 octane during the BoB.
The Fw190A could not fly with the outer cannon removed.
There was no Fw190A-8s flying with the JGs in 1945.
#4469010 - 04/05/19 11:41 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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Yikes. What a major clusterfu** for Boeing.


I'm sure Airbus will be benefiting from this.


“Whoever fights monsters should see to it that in the process he does not become a monster. And if you gaze long enough into an abyss, the abyss will gaze back into you.”
#4469015 - 04/05/19 12:28 PM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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I guess for Military Aircraft it makes sense to build airfoils and designs that are inherently so unstable it needs software to fly (F-117 was the first of the sort, no?).

But for airliners, there should be a law that the aircraft needs to be inherently stable. Fixing a design problem with a sensor and software was just asking for this tragedy.

#4469020 - 04/05/19 01:28 PM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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The same pilot posted earlier in this thread, talking us through the report. He assumes that the pilots indeed may have reverted the cut-off. Also interesting his explanation why the manual trim attempt may have failed.

Last edited by WhoCares; 04/05/19 01:31 PM.
#4469097 - 04/05/19 06:45 PM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: PanzerMeyer]  
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Originally Posted by PanzerMeyer
Yikes. What a major clusterfu** for Boeing.


I'm sure Airbus will be benefiting from this.


Airbus has had its share of issues as well. The Air France crash in the South Atlantic, and these:

https://en.m.wikipedia.org/wiki/Qantas_Flight_72

https://avherald.com/h?article=47d74074

https://en.m.wikipedia.org/wiki/Indonesia_AirAsia_Flight_8501

All it takes is a small error in soldering on a circuit board..


In all my years I've never seen the like. It has to be more than a hundred sea miles and he brings us up on his tail. That's seamanship, Mr. Pullings. My God, that's seamanship!
#4469110 - 04/05/19 09:28 PM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: RSColonel_131st]  
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Originally Posted by RSColonel_131st
I guess for Military Aircraft it makes sense to build airfoils and designs that are inherently so unstable it needs software to fly (F-117 was the first of the sort, no?).

But for airliners, there should be a law that the aircraft needs to be inherently stable. Fixing a design problem with a sensor and software was just asking for this tragedy.


+1


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#4469116 - 04/05/19 10:16 PM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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I really rhink Boeing has blood on its hands. Air Lion we can say was a tragedy. The fact that Ethiopian air happened after that was completely inexcusable. They were probably presureing FAA not ground the 737 MAX even after both disasters too behind the scenes.

People should go to jail over this.


"No power in the 'verse can stop me!!!"
#4469158 - 04/06/19 04:21 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: WhoCares]  
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Originally Posted by WhoCares
As separate post it does - sorry for chain post...
ANU: aircraft nose up
AND: aircraft nose down
At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.
At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and co-pilot confirmed stab trim cut-out.
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.
...
At 05:41:30, the Captain requested the First-Officer to pitch up with him and the First-Officer acknowledged.
...
At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working.
...



Was it broken or was it that he didn't know how much strength it would take to move it at 250 knots?

Did the captain try to move it with the first officer?

The conversation here doesn't seem to mention turning the cutout switches back on, how is it that it autotrimmed with the switches on CUTOUT? is this one of the flaws in the design, or did they flip the cutouts back to the normal positions?

incidentally, one of the techniques taught in that fantastic AA training course was unloading the aircraft to restore control of the aircraft after malfunction of a control surface or trim failure.. Really, everyone should watch it..

#4469165 - 04/06/19 08:27 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: VF9_Longbow]  
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Originally Posted by VF9_Longbow
Originally Posted by WhoCares
As separate post it does - sorry for chain post...
ANU: aircraft nose up
AND: aircraft nose down
At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.
At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and co-pilot confirmed stab trim cut-out.
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.
...
At 05:41:30, the Captain requested the First-Officer to pitch up with him and the First-Officer acknowledged.
...
At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working.
...



Was it broken or was it that he didn't know how much strength it would take to move it at 250 knots?

Did the captain try to move it with the first officer?

The conversation here doesn't seem to mention turning the cutout switches back on, how is it that it autotrimmed with the switches on CUTOUT? is this one of the flaws in the design, or did they flip the cutouts back to the normal positions?

incidentally, one of the techniques taught in that fantastic AA training course was unloading the aircraft to restore control of the aircraft after malfunction of a control surface or trim failure.. Really, everyone should watch it..

There was a mention of the captain asking the co-pilot to help pull back on the control,

The aircraft was at 340knots and getting faster, final speed before the end of the recording was over 500knots, so a lot of resistance to moving the controls/ trim and they did not have the height above ground level to unload the aircraft to trim manually.


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#4469168 - 04/06/19 09:00 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Alicatt]  
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The pilot in the yt video explains the unloading as well - not sure whether they knew about this technique. But the question is whether it would really be applicable, because they didn't really have the luxury of altitude to unload the aircraft.

#4469572 - 04/09/19 01:57 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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maybe not, but I have a suspicion the captain did not try to move the trim wheel with the fo, and that the inexperienced fo didn't realize that trim was going to be stiff because he'd probably never flown an airplane that fast besides the 737 using manual trim.

I really question why they didn't stop the wheel on the numerous, long chances they got, and most of all I wonder who and why the cutout switches were turned back to normal even though they knew the system was behaving badly.

for what it's worth, unloading an aircraft does not mean you have to lose altitude. if they had been quicker to notice that the nose was being pushed down, they would have been able to unload the aircraft and continue climbing. i haven't looked at the time stamps in super detail but iirc they didn't start looking at trim issues until the second or third instance of uncommanded nose down trim. they ignored a LOT of signals to let it get to that point. it's the difference between holding the yoke with your thumb and index finger and having to strain to pull back on the yoke to keep the nose from sinking. it's a huge oversight. alert pilots don't just miss that. then turning back on a system they knew was broken.. well come on, really?

it doesn't absolve boeing of their %hitty design which is a position i've always maintained, but they should have been watching like hawks, and they should have known every little detail of the mcas after the lionair crash. they didn't know that enabling AP would have disabled the mcas. fair enough, i didn't know that either, but then again i'm not a MAX captain. they didn't know that flaps down would have stopped mcas.

they SHOULD have known that changing power settings would have improved their maneuverability on manual controls. instead they crashed their jet with the throttles untouched at near max power settings. unbelievable. they SHOULD have known that turning on a bad system would compound problems, not improve them. they SHOULD have asked for help over the radio when they realized they didn't have a solution. someone on the air might have known what to do.

Last edited by VF9_Longbow; 04/09/19 07:31 AM.
#4469583 - 04/09/19 08:19 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: VF9_Longbow]  
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The pilot actually enabled the autopilot, from the pilots seat which at that time was already shaking for ~30secs as a stall warning (kept shaking until the end, only the pilots, not on the fo side), but AP was turned of again 33 seconds later, iirc, whether automatically due to the divergent AoA and other sensor readings from both sides, or manually is not documented in the report. Short before the autopilot was disengaged, the crew retracted the flaps as well. With autopilot off and flaps up MCAS finally "took control", triming down from 4.6 to 2.1 5secs after the AP was disengaged (1st).
"Don't sink" warning, followed first by pulling the stick and then electric trim up to 2.4. 5secs later MCAS trims down to 0.4 (2nd).
"Don't sink" warnings again, followed by electric trim up to 2.3, and stab trim cut-out. Thus before MCAS could do its thing the third time, they already reacted.

Last edited by WhoCares; 04/09/19 09:28 AM.
#4469584 - 04/09/19 08:31 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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As part of flight training in the Cessna 150/152 the instructor wound on full nose down trim to let me feel and react to an out of trim aircraft, now we were only flying at around 90kts but it took a lot of force to hold the little aircraft straight and level, the trim tabs on a little Cessna are not very big at all.


Chlanna nan con thigibh a so's gheibh sibh feoil
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#4469585 - 04/09/19 09:47 AM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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For most of the time they still managed to maintain a slight climb, up to ~9kft above ground. Then they requested and entered a turn to return to the airport.
At 5:42:04 both call out "Left alpha vane" (I guess realising that the AoA vane on the pilots side gives wrong input). Then the pilot asks the FO to pitch up with him again, but also adds that pitch is not enough. At that time they maintained altitude (probably as a result of the turn no longer climbing?!) until apparently the cutout was reverted. I'd guess that's coming as a reaction to that notion and not being able to trim manually, though I wonder why there were just two very short uptrim pulses. 5secs later MCAS triggers again, and the plane crashed <30secs later.
Already stating that pitch is not enough and not being able to trim manually, I guess reverting the cutoff is a measure of desperation, but as said, I wonder why after that they only gave very short uptrim pulses...

Last edited by WhoCares; 04/09/19 11:05 AM.
#4469635 - 04/09/19 03:45 PM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: VF9_Longbow]  
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Originally Posted by VF9_Longbow
... then turning back on a system they knew was broken.. well come on, really?

...they didn't know that flaps down would have stopped mcas.


I was following some discussion of actual 737 pilots, who were responding to some suggestions that the crew could have dropped flaps to disable MCAS. The pilots indicated two counters to this... A) modern air safety is largely supported by pilots following orderly procedures. Dropping flaps isn't apparently part of the procedures to counter the MCAS issue. and B) the aircraft was above rated speed for flap deployment anyway, and one pilot mentioned a lockout which would have prevented flap deployment above that speed, even if they had tried.

The general feeling I got about their conclusions was that the procedure following MCAS error, was followed, cutting out the system. However, this leaves the crew in a bad to worse situation, if the plane has been forcing nose down, and is descending at high speed (the manual trim forces at 400 to 500 mph are apparently quite high). Those comments I read seemed to indicate that a crew in such a position would need to nose down even farther to decrease manual trim forces, or re-enable power to the system to attempt powered adjustment.

This post is only intended as a response to the idea of deploying flaps as a fix. I welcome input and correction from anyone who knows better.

And of course, I will add all the usual internet required disclaimers to my post:
I am just me relaying what I've read elsewhere. I am not a pilot. I can't verify the guys I was reading were actually pilots, or that what they were posting was even correct.

Last edited by adlabs6; 04/10/19 12:00 AM. Reason: Clarity, or something like it.

WARNING: This post contains opinions produced in a facility which also occasionally processes fact products.
#4469654 - 04/09/19 06:12 PM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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There is also the suggestion floating around that they should have reduced the power to reduce the speed. I am no pilot, but I am tempted to think that this is not standard procedure in the climb phase after the start while the stick is rattling and warning of a potential stall condition. It's easy for us in hindsight to say it's clear that it's the "MCAS bug" causing them the troubles.

For the pilots the trouble started with the shaking stick at 5:38.44, MCAS only started to play its stab trim game after flaps got retracted and 5secs after the auto-pilot was disabled at 5:40:00. At 5:40:35 they used the cut-out switch - took them (just or loooong?) 35secs from the first MCAS trim action to them switching the stab trim off. And all the while the pilot has a shaking stick telling him about a (potential) stall risk. The next ~100s they maintain a slight climb by pulling the controls but also continuously build up speed. At 5:41:20 an overspeed clacker started. That's the point where you can start to argue that they should adjust the power settings. But what's a safe reduced power setting when you still try to climb but have a shaking stick telling you about a stall risk and without stab control? I hope a pilot that went through plenty of training has a good answer to that question - I am no pilot, I don't frown ... What do they teach in a simulator training in such a situation?! I wouldn't consider trying to go back to the airport the worst possible idea.

See, I'd love to give them reverting the cutout to get back stab control if they went ham applying a lot of uptrim - what I don't understand is why they do so but then give only very little trim input. I mean, they gave significant trim input from 0.4 to 2.3 units to revert the 2nd MCAS action, why now just 0.2 units...

Last edited by WhoCares; 04/09/19 06:52 PM.
#4469667 - 04/09/19 07:19 PM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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I still don't understand why these pilots were going ne as rly full throttle the whole time speed keeps going up amd up out of safety range.


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#4469690 - 04/09/19 09:25 PM Re: Another Boeing 737 Max 8 Flight Goes Down [Re: Haggart]  
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the question is, is the flaps thing something that all/most MAX pilots knew about before and after the LionAir crash. The first time I heard about it was after the second crash and it's not exactly intuitive.

Does putting flaps to the 1 or 2 or 5 position in a MAX cause a pitch up or a pitch down movement at the margins of the maximum flaps extension speed?

How does the MAX respond to a reduction in thrust while in a climb at high power settings and relatively high altitude? These are some questions that may help explain their thinking.

It looks to me like they diagnosed certain things with more accuracy than I gave them credit for, but the steps they took to resolve the problems..not the right steps.

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