Ethiopian Airlines 737MAX crashes enroute to Nairobi Q1 2019

PW100 · Sat Apr 06, 2019 10:07 pm

morrisond wrote:
SomebodyInTLS wrote:
I can't understand why when it's been pointed out dozens of times already.

1) they followed all of the memory items according to the AD issued after the Lion Air crash, however they had not fully corrected the MCAS trim with electric trim during this process (referred to as manual electric trim in the preliminary report)
2) at the end of this (trim switches cut off) they were physically trying to apply more manual trim using the wheels but were unable to presumably due to aerodynamic forces from the high speed (blowback)
3) they switched electric trim back on to try and correct the trim with "manual electric" again, but their trim corrections were less than those in the opposite direction by the re-connected MCAS

So the issue is why their manual electric trim was repeatedly less than sufficient - it now seems possible that the electric trim was also having issues with blowback.
Then the question is why they didn't reduce airspeed - well they didn't have pitch control and couldn't simply reduce thrust since they were very close to the ground

From the printed conversation it appears they only tried manual trim for 8 seconds and it was probably only one of them.
They were 8,000’ AGL - which while low is still sufficient altitude to try a few things - they were not 1,000’ AGL as speculated and repeated to me before this thread was started.

When they threw the cut out switches (MCAS deactivated, 05:40:40) they were at around 1000 ft AGL (Altitude Rad Disp).
When they re-instated electric trimming (05:43:10), they were at around 7000 ft AGL (Altitude Rad Disp).

A significant reduction in thrust would cause some nose down effect, thus it would take quite some time for speed to bleed off.
Allowing the nose to drop (reduce back force on control column), combined with reduction of thrust (rollercoaster / Yoyo trim technique) could have done the job. Wonder whether 7000 ft would be enough to do so? At normal operating speed perhaps, but what about 400 kts?

PW100 · Sat Apr 06, 2019 10:12 pm

AirlineCritic wrote:
MD80Ttail wrote:
MCAS was “working properly”—by that it was doing what it was designed to do.

To be honest, this may (but only may -- see below) be true. But it feels like a planted distraction. Of course there are many aspects of this accident, some things worked some things did not, and in the end the cheese holes sadly lined up. But why emphasise that the MCAS worked as designed? Why don't you start listing that it was badly designed, badly informed about, procedures for it were possibly badly designed, and it was possibly imperfectly maintained and used (but maybe understandable, given lack of info and bad processes).

Furthermore, I do not believe it has been proved even that MCAS worked as designed. I haven't looked at the latest FDR logs, maybe there's some new information. But I've assumed from the start that one possible reason for the failures is that something else than the sensor failed, e.g., the MCAS software or some computer component. That would have explained, for instance, how the problems continued even after the Lion Air maintenance reportedly fixed or replaced sensors from previous flight. Of course there's other possible reasons for the maintenance problems, but this just goes to show that there can be other issues than design issues.

Fixed that for you . . . . : Was the system working as it was ~~designed~~ intended to do?

Grizzly410 · Sat Apr 06, 2019 10:14 pm

Since preliminary report is issued I see a lot of focus on the latest part of the short flight but as a layman I have a (dumb?) questions about the first crew action. There :
"At 05:38:44 [...] the left stick shaker activated and remained active until near the end of the recording"
"At 05:38:58 [...] an autopilotvwarning is recorded."
"At 05:39:01 and about 630 ft radio altitude, a second autopilot warning is recorded."
"At 05:39:22 and about 1,000 feet the left autopilot (AP) was engaged (it disengaged about 33 seconds later), the flaps were retracted."

It seems to me the flaps rectractation dictated by the AP is a key moment that led to the crash, one layer of the cheese model.
My question is on the AP activation, is this normal to engage the AP less than a minute after take off with the stick shaking and two warnings? (I admit I´m not sure what is an "autopilot warning")
Didn't they recognise the IAS situation ? And even, how could the AP engage for 33s with an AoA disagree ?

Planetalk wrote:

Just want to say thank you Mandala for all the time and information you give us here, your insights are incredibly valuable and your patience frankly incredible. I imagine LionAir was tough on you so just wanted to say thanks and that you are appreciated.

Yeah, me too.
Mandala and to some others which are an invaluable assets in the threads during this "crisis" and in the forum in general I say THANK YOU.

scbriml · Sat Apr 06, 2019 10:18 pm

MD80Ttail wrote:
MCAS was “working properly”—by that it was doing what it was designed to do.

Sure. Just a shame for 346 people that it was designed to work off a single, failed sensor. :banghead:

mzlin · Sat Apr 06, 2019 10:21 pm

To clear up confusion, here is a good description of why MCAS was implemented (to meet longitudinal stability requirements):
http://newsinflight.com/2019/03/29/what ... -to-stall/
(This was also first pointed out by Bjorn at leehamnews after the Lion Air crash.)

MCAS was passed off as a STS modification to the FAA and hidden from the manual, which appears to have been done in order to keep common type certification with the 737NG (at least that would seem to be the only motivation strong enough to piggyback MCAS on the non-redundant STS structure and hide a safety-impacting system from the manual)

PW100 · Sat Apr 06, 2019 10:29 pm

morrisond wrote:
That's not quite what was said.

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.

To me that could very well be the Pilot asking the FO to Manually try the electric trim. But it's not a great sentence so it could be interpreted many ways.

In any case he only tried for 8 seconds and the FO never asked the Pilot to help try cranking - which you assume he would if it was too hard to move.

I agree that the report is a bit vague on this manual trimming issue. Ideally, we'd like a full CVR transcript, as well as some other FDR data to continue our own little investigation . . . :-)

I'll offer two possible explanations as to why "the FO never asked the Pilot to help try cranking":
1) The report does not show all conversations. So it might be that they did discuss such, but the conversation didn't end up in the interim report for whatever reason;
2) Pilot flying needed ALL of his physical strength on the control column just to keep the nose up. Try doing that, bend forward, reach for the trim wheel, flipping out the handle, and apply rotational force on the trim wheel. And during all of that that, all the time, maintain maximum back force on the control column.

PW100 · Sat Apr 06, 2019 10:36 pm

Moose135 wrote:
sgrow787 wrote:
If there wasn't a stability issue inherent in the Max, then why was MCAS introduced for an airframe that is identical to previous 737 models? Because it's identical with exception to the engine size and placement on the wings.

MCAS was added so that the Max handled the same as the NG, which the airlines wanted so that it could be flown with the same type rating. Without MCAS, the Max would still be safe, but pilots would need additional training and certification, something that operators didn't want to spend money on. That has been explained a number of times in these threads.

It has also been suggested, way up thread (or in the grounding thread), and in a Leeham and/or Ostrower blog, that MAX needed MCAS in order to meet some specific FAR requirements with respect to control column force gradient as a function of AoA and/or airspeed. And thus could not be certified without MCAS.

Did we get a final answer on that already (apologies in advance if I have missed that)?

speedking · Sat Apr 06, 2019 10:50 pm

I wonder why Boeing designed the Final Gatekeeper, the manual trim wheel system, so poorly that it is impossible to use in the whole flight envelope and a bit more to really make sure that you can save the plane if all automation and electrical system fails?
What if you are in the high end of the envelope and you get a real trim runaway and cannot use the electric trim to bring the trim back to neutral before hitting the cut off switches?
Now the system seems to be like a Russian-made anal vibrator. Doesn't fit in and doesn't vibrate.

mjoelnir · Sat Apr 06, 2019 11:01 pm

speedking wrote:
I wonder why Boeing designed the Final Gatekeeper, the manual trim wheel system, so poorly that it is impossible to use in the whole flight envelope and a bit more to really make sure that you can save the plane if all automation and electrical system fails?
What if you are in the high end of the envelope and you get a real trim runaway and cannot use the electric trim to bring the trim back to neutral before hitting the cut off switches?
Now the system seems to be like a Russian-made anal vibrator. Doesn't fit in and doesn't vibrate.

Perhaps 60 years ago they did not know better? And grandfathering something is more important than that things actually work?

I also do not understand how Boeing got away with making the wheels smaller, long before the MAX, and so still more difficult to use it.

dragon6172 · Sat Apr 06, 2019 11:19 pm

PW100 wrote:
mandala499 wrote:
The autopilot disengaging is likely to be due to the MCAS wanting to engage. After all, if you set your autopilot to a selection where you would cause a stall, you'd want it to disengage... not sure of the detailed logic of the 737 Autopilot in the realms of near stall, plus the addition of MCAS on the Max on top... but just by common sense, you'd want the MCAS to disengage the A/P and then command trim nose down if you're in an actual stall... especially if the A/T isn't disengaged.
SheikhDjibouti wrote:
Captain Hindsight with a possible answer here;
1. Re-engage stab trim cut-out
2. Immediately (or even sooner than that!) use thumb switches, and continue to depress the thumb switch to prevent MCAS function.(*)
3. Now, in conjunction with the electric motor attempting to move the stabiliser, both pilots crank the manual trim wheel
4. You now have one electric motor plus two pilots attempting to move the jackscrew
5. If that fails; pray.
You mean 1 = provide power back to the stab trim?
I really wonder what Boeing was thinking, having the yoke in the aft (nose up) position and trying to manually crank the trim wheel (especially with heavier than normal forces), isn't an easy walk in the park for some.
What the crew of 302 tried to do was probably what you said above, except for #3, because I think just use the thumb switch for the electric trim should be enough but they needed to do it immediately after reengaging power to the stab trim.
I think the investigation will go deeper into this...

I think they did just that, as seeing TWO instances of uptrim before MCAS kicked in again, but this electric uptrimming did not provide the desired result. Perhaps that threw them off in thinking that electric (up)trimming was not working, thus MACS down trimming would also be not working . . .

mandala499 wrote:
MD80Ttail wrote:
Two. Why didn’t the pilots up trim inputs time out MCAS allowing for the electric trim to be shut off after the pilots had commanded an acceptable trim condition? When conditions changed and the pilots needed more trim ok from what I’ve read and learned the manual trim wheel maybe was useless. That’s a Huge concern. No plane should ever be designed that can’t be manually trimmed.

I think the AD was badly worded that caused pilots reading it, to think, "OK I'll cut it off immediately"... and then lower down, it says, "you may use electric trim to reduce the load forces" (or something like that)... BUT HECK! YOU TOLD ME TO CUT IT OFF !!!!

The lack of emphasis to retrim the aircraft prior to cutting out the stab trim within the AD's wording and content structure, is my guess as being the culprit.

Oh hang on, is someone going to accuse me of being on Boeing's or FAA's payroll for saying that?

The FDR clearly shows a good deal of uptrimming prior to cut out switches. Its not that the crew did not try that. Its that all of their uptrimming was cut short before the control column was pitch balanced. Why is that? Why would the crew stop uptriming if there is still considerable back force required on the column? That just does not make any sense whatsoever. Even for a ~~200 hrs~~ 361 hrs FO. It very much seems there was another mechanism in play, unknown to the crew, that prevented them somehow from reaching balanced pitch trim condition.

The uptrimming stopped because the switches were released. The FDR shows trim commands, in other words switch position. If it doesnt show a trim up command, then the pilots didnt have the switches moved in the trim up position.

Now, why that is the case is the question. I dont think the pilots were incompetent. I'd guess the investigation will find some physiological/psychological factor that caused it.

lifecomm · Sun Apr 07, 2019 12:16 am

mwmav8r01 wrote:
I think people are putting too much on one spot or another. There seems to be a lot going on here.

I am a 737 typed pilot with 15000 hrs, i just want to highlight one possible scenario.

The people saying the manual trim didnt work... Do we know that they tried the trim wheel? Im not blaming lack of training or experience just the possibility... In the fog of war its very easy to get tunnel vision. Just maybe they tried the trim switches as the manual trim and not the wheel. It could have happened. I know when i had 300 hrs on the 737 it felt lime my seat was in the aft lav

It also seems that when they trimmed with the switches on it countered the MCAS as it was supposed to. Did they stop trying to trim or did something else happen?

Thanks for your time, and now I will be bashed by Boeing haters and people who want to call me a racist.

mwmav8r01, thank you for your insight. This point totally puzzles me. From the report:

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.

Did the pilot forget the trim cutout switches had been switched to the cutoff position? Was he asking for the FO to use the manual electric trim? The FO should have stated the trim switches were in the cutoff position. Did the FO forget? Only the wheel can be used at this point. It seems that both pilots either forgot or were unsure if the manual electric trim would work with the trim switches in the cutoff position

When the FO asks if he can try it manually (If the FO was meaning to turn the wheel and it was too hard to turn) saying "it's not working" is not clear. "It's jammed" or "I need help to turn it" or similar would be in order. So your comments might make sense. I am further puzzled by the report:

At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out.

mwmav8r01, question: why didn't either pilot comment on or request the use of the manual trim wheels at this point? Would that be in order? Also, Is it true that there are instances where the wheels must be held by hand to prevent them from turning?

MD80Ttail · Sun Apr 07, 2019 12:54 am

PW100 wrote:
MD80Ttail wrote:
marcelh wrote:
I repeat my statement: if lack of training/hours is so criminal, why don’t we read that a NG or A320 has made a crater?

Too many to list.

OK, I'll bite.
I'm curious at your list of NG or A320 craters with 200 hrs FO in the pointy end.

Thanks.

PS. Just to be clear, I'm not arguing with you that 200 hrs FO should not be in the cockpit of a commercial airliner (BTW, this FO had 361 hrs, of which 207 in 737, of which 56 in MAX). Just not (yet) convinced if his junior status was in any way a factor in this accident.

PS2. Regardless of total hours, what do you think of a 151 hrs NG pilot (even if he had 10000 hrs on different type, say A320) converting to MAX?

PS3. In my mind, FIRST we should establish if there were any issues with crew performance. If so, that would be the point we should start looking at FO proficiency, in regards with his limited total hours.
Since that FIRST is a looong way from being certain, discussing FO hrs at this stage is just producing noise and distracting us from establishing FIRST in the first place.

https://www.sbs.com.au/news/comment-ris ... re-crashes

mwmav8r01 · Sun Apr 07, 2019 1:27 am

SimonL wrote:
mwmav8r01 wrote:
MSPNWA wrote:

What do you see in the report that makes you think that?

I dont see it. I coulda missed it.

Do you agree thats plausable? Ive never heard the trim wheel not working. Though it isnt used much.

When they captain asks if the trim is working and the the FO replies "no, should i try manual trim", its clearly suggests that they did try the wheel since they only have 2 ways to trim the plane. And its also a bit too basic to forget.

And as was shown earlier: the trim wheels are under certain conditions very hard to use.

Good to know you were there and knew what they did and didnt do. Its possible either way. When you get task saturated it is easy to forget simple things. To say with 100% confidence either way is foolish.

mwmav8r01 · Sun Apr 07, 2019 1:30 am

morrisond wrote:
mwmav8r01 wrote:
MSPNWA wrote:

What do you see in the report that makes you think that?

I dont see it. I coulda missed it.

Do you agree thats plausable? Ive never heard of the trim wheel not working. Though it isnt used much.

Hi mwmav8r01 - Yes that is plausible. The time from when the Pilot asked the Co-pilot to try Manual was only 8 seconds. The pilots eyes would have been on the Instruments or outside the cockpit and not looking at what the FO was doing.

You would have to think if he(FO) was having physical difficulty moving it he would have asked for help and not given up after 8 seconds - just like the pilot was asking for help with the control column from time to time.

As a 15,000 hour 737 Pilot what do you think of my possible scenario from the previous page?

Copied below:

Sorry - but Colgan crashed because the Pilot followed the incorrect stall recovery procedure - he didn't know how to fly a T-tail - they were most likely going down even without the flaps being raised.

However It does bring up a good point - The Pilot didn't know what the first officer was doing or vice-versa.

In the case of ET302 that could have been what transpired in the last few seconds in the reverse.

I'm not saying this happened but it is Plausible and fits the timeline as they were faced with an impossible situation - please take this as a discussion topic and not me blaming the pilots. I'm really just trying to understand what happened and what could be done better - through better training.

From earlier in the flight we do know that it was the FO who brought up "both Trim Cutoff Switches to Off"

Thereafter there is no discussion of MCAS - the Memo or anything which is very weird. Wouldn't a normal reaction after you figure something out to remark to basically say Eureka! I figured it out - it was MCAS just like Lionair. There is no discussion at all. You would think something like this would be in the discussion of the flight history.

It is possible the Captain was not familiar with the Memo and due to the FO's lack of experience he was reticent to bring it up as he probably assumed the Captain knew all about it.

There is no back and forth in the cockpit according to the printed flight history in the report - the FO just waited for commands from the Pilot.

The First Officer had just been through the Sim (end of Jan) so presumably got some training on MCAS procedures. The Pilot was scheduled too after the fateful flight.

So you have one person in the cockpit who possibly knew the procedures (FO) and one who possibly didn't and really didn't understand what was going on which is understandable if they didn't have the proper training.

Then in the final seconds the Pilot not knowing that turning on Electric Trim again was a big no-no and the FO who can't see what the Captain is doing or bowing to Authority and not speaking up says nothing when the Captain reaches over and reenergizes the Electric trim and tries it again - the Captian not knowing that he should turn it off right away (the Co-Pilot might have assumed he would) but by that time it is too late.

As they are travelling so fast there is no time to react from MCAS again.

One final comment - it is mentioned in the crash report that the throttle levers were never moved from 94% N1 the whole flight.

Over on the other forum a 737 Pilot did point out that small changes in throttle (a few percent) would have literally no effect on the nose pitching down.

I know they were faced with an impossible situation - but with all the overspeed warnings - don't you think they would have tried to pull it back a least a few percent to see the effect when they could both pull to offset it and if didn't work they could have pushed the throttle up again? They did have about 6'500' of altitude at that point.

Again - I am not blaming the pilots - I consider this Boeing's big screwup along with a fault in the Worldwide training system.

Please take this as a discussion topic to help us all understand better what happened.

100% plausible. I dont know... Its all a head scratcher. Things happen. I know with such a low time FO (first year or so I consider low time). Puts a lot more stress on the Captain.

mwmav8r01 · Sun Apr 07, 2019 1:50 am

lifecomm wrote:
mwmav8r01 wrote:
I think people are putting too much on one spot or another. There seems to be a lot going on here.

I am a 737 typed pilot with 15000 hrs, i just want to highlight one possible scenario.

The people saying the manual trim didnt work... Do we know that they tried the trim wheel? Im not blaming lack of training or experience just the possibility... In the fog of war its very easy to get tunnel vision. Just maybe they tried the trim switches as the manual trim and not the wheel. It could have happened. I know when i had 300 hrs on the 737 it felt lime my seat was in the aft lav

It also seems that when they trimmed with the switches on it countered the MCAS as it was supposed to. Did they stop trying to trim or did something else happen?

Thanks for your time, and now I will be bashed by Boeing haters and people who want to call me a racist.

mwmav8r01, thank you for your insight. This point totally puzzles me. From the report:

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.

Did the pilot forget the trim cutout switches had been switched to the cutoff position? Was he asking for the FO to use the manual electric trim? The FO should have stated the trim switches were in the cutoff position. Did the FO forget? Only the wheel can be used at this point. It seems that both pilots either forgot or were unsure if the manual electric trim would work with the trim switches in the cutoff position

When the FO asks if he can try it manually (If the FO was meaning to turn the wheel and it was too hard to turn) saying "it's not working" is not clear. "It's jammed" or "I need help to turn it" or similar would be in order. So your comments might make sense. I am further puzzled by the report:

At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out.

mwmav8r01, question: why didn't either pilot comment on or request the use of the manual trim wheels at this point? Would that be in order? Also, Is it true that there are instances where the wheels must be held by hand to prevent them from turning?

In my opinion... I think thats what happened. The Captain asked the FO if it was working and he tried his yoke switch. But there is absolutely no way to know. You can hear the handle come out on the trim wheel... It would be interesting to hear it to see if you can hear it click. I just feel like they would have used the word jammed or stuck. Or try your wheel. I just dont know.

As to the people bashing the common type. Ill add my two cents. I have flown the 737-300 & -500, NG and MAX, the difference between the classics and NGs is fsr less than the NG and MAX. I think you can take that back to the jurrasic too. Theres a reason the FAA wouldnt allow pilots to fly the classic and MAX... Too big of a difference. The posters suggesting that time in a NG isnt as important as Airbus time an NG is very similar to a MAX. The FOs lack of experience isnt the sole cause, but I dont think it should be completely discredited either. Yes there are differences in a NG and MAX, is there difference in MD88s and MD90s? 757s and 767s? They are all the same type too. This isnt just a 737 thing.

Sorry to ramble. This thread is getting hard to follow.

trex8 · Sun Apr 07, 2019 1:56 am

mwmav8r01 wrote:
[
You would have to think if he(FO) was having physical difficulty moving it he would have asked for help and not given up after 8 seconds - just like the pilot was asking for help with the control column from time to time.

The First Officer had just been through the Sim (end of Jan) so presumably got some training on MCAS procedures. The Pilot was scheduled too after the fateful flight.

Werent they fighting against a very heavy yoke? And one has to take at least one hand off to help turn the trim wheel?

MCAS training at least for the American majors its been reported was only either an ipad or other computer course. Even with ET having a Max sim, would a sim check involve any Mcas training at that point in time? I think its quite probable even today the only sims capable of mcas training are at Boeing.

mwmav8r01 · Sun Apr 07, 2019 2:03 am

trex8 wrote:
mwmav8r01 wrote:
[
You would have to think if he(FO) was having physical difficulty moving it he would have asked for help and not given up after 8 seconds - just like the pilot was asking for help with the control column from time to time.

The First Officer had just been through the Sim (end of Jan) so presumably got some training on MCAS procedures. The Pilot was scheduled too after the fateful flight.

Werent they fighting against a very heavy yoke? And one has to take at least one hand off to help turn the trim wheel?

MCAS training at least for the American majors its been reported was only either an ipad or other computer course. Even with ET having a Max sim, would a sim check involve any Mcas training at that point in time? I think its quite probable even today the only sims capable of mcas training are at Boeing.

Yes you need one hand to trim. You can also use your legs, etc.

Do you think we train for every possible situation in sim training? We do a lot. But not everything. Training told us the ways to disable and counteract it. I am confident that a MCAS or any other trim runaway issue would be easier to deal with than other scenarios just because of these accidents bringing them to the foreground.

dragon6172 · Sun Apr 07, 2019 2:18 am

I find it interesting that during the time that electric trim is turned off and they are unable to trim and fighting to raise the nose they find time to change the altitude setting and then the selected heading. Those dont seem real important when you're having flight control problems. Any insight on this? I assume these changes came from the FO since the captain was pulling on the control column?

planecane · Sun Apr 07, 2019 2:29 am

PW100 wrote:
mandala499 wrote:
mzlin wrote:
It is the final paragraph in this directive which is a restatement of the runaway stabilizer memory checklist:

Thanks... I think we have a problem in how this MCAS thing is trained...
I think the crew of ET followed this AD...
Going from the top to bottom.. Cutout... was told to cut out for the remainder of the flight... and then down at the bottom, "by the way, you can use the electric stabilizer before the cutout if it feels heavy or hard to move the stab trim"... Oh, OK, let's try that... then MCAS starts acting up...

PW100 wrote:
As you can see in ALL of my posts, I continue asking questions as to why the crew did this, did that, stopped uptrimming way before the control column was balanced in pitch. Why they reinstated electric trimming. Trying to find answers.
The only thing I see from you, is that crew made a lot of mistakes. I have not seen one single effort from your side trying to answer these important questions.

See the above (and the reply by MZLIN at $4492)

Hi 499,
Not sure what you were suggesting here.
My post was a reaction to some that implied the crew made several mistakes:
1) Not performing electric uptrim prior to hitting the cut out switches (as [i] suggested[i] by the AD);
2) Re-instating MCAS by reversing cut-out switches (in direct conflict with the AD);
3) Trim-control issues were a result of the crew allowing the aircraft to exceed Vmo.

I replied to that that I'm not sure we can conclude that as mistakes, perhaps they had no other choice. Please allow me to explain.

1)
Per the FDR chart, every instance of uptrim (after flap retraction) ended well before the control column was balanced in pitch. Why did they stop trimming before the control column was balancedin pitch? There were a total of four electric uptrim events when the control column was heavy. But each instance stopped/ was cut-out well before the control column was anywhere near being balanced (if I may extrapolate Ctrl Column Pos to control column force). Why would the PF stop electric uptrim if with a heavy control column?

Also, the observation was that throwing the cut-out switches was preceeded with the longest recorded uptrim was performed. So this seem to be very much in line with the AD and instruction to use electric uptrim prior to hitting the cut out switches. But again, why did the PF stop uptrimming before the control column was balance din pitch? I offered two theroies:
a) the PF was in fact still uptrimming, but the cut-out switches were thrown (by PM) while trimming was still in progress. This could be seen as a crew CRM issue, lack of communication;
b) Could it be that the uptrim was stopped as the motor reached its max torque limit, due to aerodynamic loading of the elevator? Such mechanism has now been reported by Leeham as well as Ostrower.
Conclusion: crew mistake? Not sure, in fact, don't think so.

2)
Why did they re-instate electric trimming? Offered theory was that the crew started reaching their physical limitations in maintain back force on control column (lactic acid setting in their muscles) and they were desperately searching for option to reduce control column back force. Re-instating electric trimming would do that (theoretically). And we can see two (very short) up trim commands at 05:43:10. But these were both very short. Again, WHY? Why on earth would the crew stop uptrimming if there was so much back force on the control column? Possible answer, as per 1) above: electric trim motor could not overcome aerodynamic forces?
Conclusion? Crew error? Probably not. More an act of desperation, rather than "not following AD procedures".

3)
It was suggested that since the crew allowed the plane to exceed Vmo, they found themselves in a opposition that both electric trimming, as well as manual trimming were non-functional (due to excessive aerodynamic loading of elevator). I believe that the ineffectiveness of electric/manual trimming was already present before exceeding Vmo, a shown by the FDR chart. Both uptrim commands at 05:40:15 and 05:40:30 stop way short of control column being balanced. At this stage Vmo had not been reached, and the aircraft was still within the certified flight envelope. Even here, trimming was apparently not effective in balancing the control column in pitch.
Conclusion: Perhaps the crew should not have allowed the plane to exceed Vmo, but that was inconsequential in the grand scheme of things as they "lost" pitch trim control before reaching Vmo.

So I guess my main question was, and still is, why were the uptrim commands cut short, well before the control column was anywhere near being pitch balanced?

The one that makes no sense to me is the second manual Electric trim that occurred after MCAS kicked in. The trim was moving significantly in the nose up direction. It was at this point that they threw the cutout switches. But why would they do that before getting back to neutral trim? I would say they didn't know it would disable the manual electric trim but they seemed to stop pressing the trim switch at the same time. All they had to do was keep trimming for a few more seconds then hit the cutout switches

speedking · Sun Apr 07, 2019 2:41 am

mwmav8r01 wrote:
trex8 wrote:
mwmav8r01 wrote:
[
You would have to think if he(FO) was having physical difficulty moving it he would have asked for help and not given up after 8 seconds - just like the pilot was asking for help with the control column from time to time.

The First Officer had just been through the Sim (end of Jan) so presumably got some training on MCAS procedures. The Pilot was scheduled too after the fateful flight.

Werent they fighting against a very heavy yoke? And one has to take at least one hand off to help turn the trim wheel?

MCAS training at least for the American majors its been reported was only either an ipad or other computer course. Even with ET having a Max sim, would a sim check involve any Mcas training at that point in time? I think its quite probable even today the only sims capable of mcas training are at Boeing.

Yes you need one hand to trim. You can also use your legs, etc.

Do you think we train for every possible situation in sim training? We do a lot. But not everything. Training told us the ways to disable and counteract it. I am confident that a MCAS or any other trim runaway issue would be easier to deal with than other scenarios just because of these accidents bringing them to the foreground.

This starts to sound weirder and weirder. Very heavy yokes, trim wheels, with one had or legs. How much a pilot has to be able to bench press to safely operate a 737? Should I, as a passenger, worry if the pilot is a woman? In a 21st century airplane?

mwmav8r01 · Sun Apr 07, 2019 4:07 am

speedking wrote:
mwmav8r01 wrote:
trex8 wrote:
Werent they fighting against a very heavy yoke? And one has to take at least one hand off to help turn the trim wheel?

MCAS training at least for the American majors its been reported was only either an ipad or other computer course. Even with ET having a Max sim, would a sim check involve any Mcas training at that point in time? I think its quite probable even today the only sims capable of mcas training are at Boeing.

Yes you need one hand to trim. You can also use your legs, etc.

Do you think we train for every possible situation in sim training? We do a lot. But not everything. Training told us the ways to disable and counteract it. I am confident that a MCAS or any other trim runaway issue would be easier to deal with than other scenarios just because of these accidents bringing them to the foreground.

This starts to sound weirder and weirder. Very heavy yokes, trim wheels, with one had or legs. How much a pilot has to be able to bench press to safely operate a 737? Should I, as a passenger, worry if the pilot is a woman? In a 21st century airplane?

If you put yourself behind the 8ball you will need more strength. I like others dont understand while its trimming in the correct direction why it was turned off then. Trim in opposite direction stops any speed trimming for 5 seconds... Trim it get it in a safer area and shut it off. But a lot was going on... Not enough people are talking about the constant warnings going off in the cockpit. This makes it a lot harder to communicate and can be dostracting.

Jetty · Sun Apr 07, 2019 4:46 am

mjoelnir wrote:
speedking wrote:
I wonder why Boeing designed the Final Gatekeeper, the manual trim wheel system, so poorly that it is impossible to use in the whole flight envelope and a bit more to really make sure that you can save the plane if all automation and electrical system fails?
What if you are in the high end of the envelope and you get a real trim runaway and cannot use the electric trim to bring the trim back to neutral before hitting the cut off switches?
Now the system seems to be like a Russian-made anal vibrator. Doesn't fit in and doesn't vibrate.

Perhaps 60 years ago they did not know better? And grandfathering something is more important than that things actually work?

I also do not understand how Boeing got away with making the wheels smaller, long before the MAX, and so still more difficult to use it.

Exactly. Especially as there are many more female pilots flying. Nothing against that, but on average their upper body strength is only about half that of males. If anything, they should have made the wheel twice as big. The 737 doesn't only need skillful pilots, as it is it needs strong pilots as well.

mwmav8r01 · Sun Apr 07, 2019 5:07 am

Jetty wrote:
mjoelnir wrote:
speedking wrote:
I wonder why Boeing designed the Final Gatekeeper, the manual trim wheel system, so poorly that it is impossible to use in the whole flight envelope and a bit more to really make sure that you can save the plane if all automation and electrical system fails?
What if you are in the high end of the envelope and you get a real trim runaway and cannot use the electric trim to bring the trim back to neutral before hitting the cut off switches?
Now the system seems to be like a Russian-made anal vibrator. Doesn't fit in and doesn't vibrate.

Perhaps 60 years ago they did not know better? And grandfathering something is more important than that things actually work?

I also do not understand how Boeing got away with making the wheels smaller, long before the MAX, and so still more difficult to use it.

Exactly. Especially as there are many more female pilots flying. Nothing against that, but on average their upper body strength is only about half that of males. If anything, they should have made the wheel twice as big. The 737 doesn't only need skillful pilots, as it is it needs strong pilots as well.

I must be Arnold Schwarzenegger. Its not hard to more the trim wheel. Takes a while longer than electric.

RickNRoll · Sun Apr 07, 2019 5:13 am

Jetty wrote:
mjoelnir wrote:
speedking wrote:
I wonder why Boeing designed the Final Gatekeeper, the manual trim wheel system, so poorly that it is impossible to use in the whole flight envelope and a bit more to really make sure that you can save the plane if all automation and electrical system fails?
What if you are in the high end of the envelope and you get a real trim runaway and cannot use the electric trim to bring the trim back to neutral before hitting the cut off switches?
Now the system seems to be like a Russian-made anal vibrator. Doesn't fit in and doesn't vibrate.

Perhaps 60 years ago they did not know better? And grandfathering something is more important than that things actually work?

I also do not understand how Boeing got away with making the wheels smaller, long before the MAX, and so still more difficult to use it.

Exactly. Especially as there are many more female pilots flying. Nothing against that, but on average their upper body strength is only about half that of males. If anything, they should have made the wheel twice as big. The 737 doesn't only need skillful pilots, as it is it needs strong pilots as well.

The NG trim wheels were made smaller than the Classic trim wheels to fit the new, larger instrement panel. When electric trim was added a damper had to be placed on the manual trim to stop springback. Both changes added to the physical load on the pilot trying to manually trim.

sgrow787 · Sun Apr 07, 2019 5:18 am

mzlin wrote:
Planetalk wrote:
Perhaps worth reposting this for a fuller insight https://www.seattletimes.com/business/b ... air-crash/

The article gives a clear picture of why the whole thing is under criminal investigation and Boeing have accepted they bear some responsibility which is actually very unusual for a manufacturer after a crash. Although some will still insist there is nothing wrong with the plane.

Great post. Would be nice if everybody could read that Seattle Times article before asking the same questions or spreading the same wrong guesses/assumptions repeatedly.

I thought I had read all the articles from Seattle Times. I'm still not clear on what the min and max of operating range the horizontal stabilizer can travel to, as well as how fast it is allowed to travel. The FDR preliminary report showed about 2.5 degrees over 9-10 seconds. So the rate is 0.25-0.27 deg per second.

Anyway, Peter Lemme, a former Boeing flight controls engineer, says the MCAS design was single sensor and he doesn't know why Boeing didn't go with two. From the diagrams presented in the ET302 Preliminary Report it's clear that both AOAs had a data path to the FCC. So I find it hard to believe that a company would come up with a business case for a reused airframe with new engines, would skimp on the one system - MCAS - that allowed that business case to work. Hence I'm not convinced that it was a single sensor design. I think it's more probable that they had an intended two sensor design that had a bug that they missed because they fast tracked the testing and certification, which is a much more systemic problem than a single bad design decision by systems engineers.

Note that Boeing has extensive experience with multi-sensor redundancy design. The actual task of making MCAS use multi-sensor redundancy is just a matter of reusing existing redundancy models, and tweaking filters and hysteresis to make it work.

speedbored · Sun Apr 07, 2019 5:25 am

mwmav8r01 wrote:
But a lot was going on... Not enough people are talking about the constant warnings going off in the cockpit. This makes it a lot harder to communicate and can be dostracting.

Yes.

I think the most obvious sign that a few of the posters here are not the experienced commercial pilots that they are claiming to be, is the fact that they are talking about what the pilots should have been doing, or how easy it should have been to save the aircraft, without making any allowances whatsoever for just how busy it can get for the crew when things go "none normal".

Jetty · Sun Apr 07, 2019 5:29 am

mwmav8r01 wrote:
Jetty wrote:
mjoelnir wrote:

Perhaps 60 years ago they did not know better? And grandfathering something is more important than that things actually work?

I also do not understand how Boeing got away with making the wheels smaller, long before the MAX, and so still more difficult to use it.

Exactly. Especially as there are many more female pilots flying. Nothing against that, but on average their upper body strength is only about half that of males. If anything, they should have made the wheel twice as big. The 737 doesn't only need skillful pilots, as it is it needs strong pilots as well.

I must be Arnold Schwarzenegger. Its not hard to more the trim wheel. Takes a while longer than electric.

It’s not hard in good conditions. But in bad conditions it can be, as is shown by the ET pilot not being able to get it moving. Arnold Schwarzenegger in the right seat might actually have been able to save this plane. Assuming normal deviations in strength among pilots quite some are 4 times as strong as others. When strength can be such a big factor in safely operating a plane as the 737 that shouldn’t be ignored. Yet it is completely

MSPNWA · Sun Apr 07, 2019 5:42 am

Jetty wrote:
It’s not hard in good conditions. But in bad conditions it can be, as is shown by the ET pilot not being able to get it moving.

More completely unknown details stated as known fact. We have no proof they even touched the trim wheels, let alone couldn't turn them.

whiplash · Sun Apr 07, 2019 6:03 am

MD80Ttail wrote:
PW100 wrote:
MD80Ttail wrote:

Too many to list.

OK, I'll bite.
I'm curious at your list of NG or A320 craters with 200 hrs FO in the pointy end.

Thanks.

PS. Just to be clear, I'm not arguing with you that 200 hrs FO should not be in the cockpit of a commercial airliner (BTW, this FO had 361 hrs, of which 207 in 737, of which 56 in MAX). Just not (yet) convinced if his junior status was in any way a factor in this accident.

PS2. Regardless of total hours, what do you think of a 151 hrs NG pilot (even if he had 10000 hrs on different type, say A320) converting to MAX?

PS3. In my mind, FIRST we should establish if there were any issues with crew performance. If so, that would be the point we should start looking at FO proficiency, in regards with his limited total hours.
Since that FIRST is a looong way from being certain, discussing FO hrs at this stage is just producing noise and distracting us from establishing FIRST in the first place.

https://www.sbs.com.au/news/comment-ris ... re-crashes

I am not somebody who comments on this website and have been a silent witness as this thread has grown.

Firstly, to quash the stupid article that you have quoted here; I'd like to say that the American crash in 2001 was attributed to incorrect training on part of American Airlines. That has been well documented.

Second, the Pinnacle Airlines crash was attributed to stupid people trying to do stupid things in an otherwise empty jet. And I quote "unprofessional behavior and disregard for training and procedures.

Third, the Colgan crash which infamously brought the 1500 hour rule in the US is just ridiculous. The Captain had 3400 hours and the co-pilot had 2300.

And lastly, the German Airwings crash - Come on, pilot suicide related to low experience? Do I even need to write anything more?

Rest of the world is not the US, Canada or Australia. General aviation is not such a big thing everywhere else. There is almost no place for young budding pilots to build their hours, considering that the only ones flying in those countries are full-fledged airlines. Unless you are willing to give all these people 5-6 years of flying in a country like the US, there is no way for them to ever have the experience you require them to fly a larger jet. Your measly number of crashes that you attribute to low hours is nothing in comparison to the absolutely massive number of crashes caused by mature veterans.

I am a pilot myself on the A320. I have seen people with 5000 hours absolutely panic during a simulator check, where I have also seen a 200 hours-on-type first officer perform wonderfully. Civil Airline authorities in other countries are not bumbling idiots who do not make sure how qualified someone is before making them sit on the right seat.

Jetty · Sun Apr 07, 2019 6:03 am

MSPNWA wrote:
Jetty wrote:
It’s not hard in good conditions. But in bad conditions it can be, as is shown by the ET pilot not being able to get it moving.

More completely unknown details stated as known fact. We have no proof they even touched the trim wheels, let alone couldn't turn them.

It’s well known that it can be difficult in certain scenario’s, this was even covered by the manual of the 737 classic. Thus strength matters. I’ll agree that it isn’t certain if it mattered in this specific flight but given the preliminary report their’s at least a strong likelihood it did. I shouldn’t have stated this as fact, but saying it is ‘completely unknown’ is just as wrong.

mandala499 · Sun Apr 07, 2019 6:23 am

morrisond wrote:
Serves me right for going off of memory and trying to follow and respond to something on my phone.

Don't worry... no one is immune from such mistakes, no matter how many thousands of hours one spends on the phone

Planetalk wrote:
I imagine LionAir was tough on you so just wanted to say thanks and that you are appreciated.

It was, and with that not finished and ET302 following, not having an easy time... however, I can breathe a sigh of relief in that after ET302 "foreign pressure" and attempts to railroad my comments in the media, have subsided. I just wish I could just say, "didn't I say those things a while back?"

smartplane wrote:
Hands up those working for a crisis / reputation management PR specialist.

Some have stopped posting since ET302 because probably their "employers" realized it wasn't going to work... at least some of those who accused of me being on the payroll of whoever they were supposed to go after, have stopped throwing accusations against me too...

Who would have thought this could happen to a.net forums 5 years ago...

PW100 wrote:
My post was a reaction to some that implied the crew made several mistakes:

No doubt. But yeah, let's not discuss it in a way that demonizes and blames them... Dead pilots can't talk to defend themselves...

PW100 wrote:
1) Not performing electric uptrim prior to hitting the cut out switches (as [i] suggested[i] by the AD);

I disagree on this point. While I know this is implicit in the AD, in my opinion the AD was ambiguous and unclear on this... ie: poorly written.

PW100 wrote:
2) Re-instating MCAS by reversing cut-out switches (in direct conflict with the AD);

Again, I think the AD is poorly written. It said, "cut it out"... and later at the end it said, "oh, if you find difficulty in manual trimming, you could use electric trim prior to cutting it out"... Poorly written in my opinion.

The above 2 points, are just different ways of reaching the same question as you had later, that were:

PW100 wrote:
Conclusion: crew mistake? Not sure, in fact, don't think so.

and

PW100 wrote:
Conclusion? Crew error? Probably not. More an act of desperation, rather than "not following AD procedures".

We have the same questions, but perhaps differing routes on how we got there.

PW100 wrote:
3) Trim-control issues were a result of the crew allowing the aircraft to exceed Vmo.

This I agree and I think this should be questioned on what factors influencing the crew prior to the flight to allow this to happen on the flight... ie: perhaps the way they were instructed, or aviate prioritization philosophies, etc, that may differ from other carriers/countries... because the major difference between JT043 and JT610 and ET302 is the speed.

PW100 wrote:
PS. Just to be clear, I'm not arguing with you that 200 hrs FO should not be in the cockpit of a commercial airliner (BTW, this FO had 361 hrs, of which 207 in 737, of which 56 in MAX). Just not (yet) convinced if his junior status was in any way a factor in this accident.

I think this is 261 hours on the 737 AND Max, as they are put in as separate entries.
The way I see it is:
TOTAL 361 Hours which includes 207 hours in 737s that is not a MAX, and 56 hours in a Max.
I raised this in an earlier reply but it seems no one has picked up on it...
If he has 361 total hours, how many hours did he spend in flying school?
My version: 361-207-56 = 98 hours
If I understand yours correctly, your version would be 154 hours.
If the guy does a standard training path (ie: non-MPL), 154 hours would get you PPL CPL with no ME and perhaps with no IR, and 98 hours... heck, that's a PPL and 50% of a CPL with no ME and no IR.
Even before going into total experience, I question the basic foundation for the FO... this is not to blame the FO, but the carrier's recruitment standards. And if the guy is MPL, then I want to know his total simulator hours.

In Indonesia we've stopped recruiting guys with less than 210 hrs because of excessive sim training requirements to bring these guys up to standards (mostly CPLSEIR), and are now beginning to only recruit those with more than 200hrs and ideally, more than 240hrs (the latter being with CPLMEIR)... because we consistently a huge difference in quality (and accident/incident rates have plummetted since this move), thanks also to a slowing in the market growth here allowing carriers to be more selective.

So, just what was the license path of the FO and his total training hours?
From experience over here, those with over 200hrs of pre-jet flight experience, the easier it is to train on CRM in abnormal situations on the 737 and 320.

I've heard too many lawn dart episodes in 737/320 simulators for those who applied to airlines with less than 200hrs...

Sorry for this "noise", but while I disagree with conclusions of guys with less than 1000hrs hours in a jet is criminal, for many of us who disagree with that, would however conclude that putting someone in a jet with less than 200hrs of total flying experience, is a "corporate misadventure" (to put it politely). However, we need to know in order to understand the FO and what his thinking process might be in contrast to the Captain's.

PW100 wrote:
I think they did just that, as seeing TWO instances of uptrim before MCAS kicked in again, but this electric uptrimming did not provide the desired result. Perhaps that threw them off in thinking that electric (up)trimming was not working, thus MACS down trimming would also be not working . . .

This is the right question to ask.
Did they reengage the power to the stab trim prior to these 2 instances or not?
If yes, and the trim didn't work, we have an ever bigger design issue then...

If no, then task saturation under an overly stressed cockpit situation, can explain... including why "only 2 very short trim command actions" instead of the longer ones they did earlier.

What we can assume at the moment is that power to the trim was available after that. I think arguments for "did the MCAS engage the trim after the stab trim cutout" is misleading... we have an instance of automatic trim command (assumed MCAS) with no trim movement, so the cutout did what it did.

Let me go back to this:

planecane wrote:
PW100 wrote:
The FDR clearly shows a good deal of uptrimming prior to cut out switches. Its not that the crew did not try that. Its that all of their uptrimming was cut short before the control column was pitch balanced. Why is that? Why would the crew stop uptriming if there is still considerable back force required on the column? That just does not make any sense whatsoever.

If you look at the combination of altitude, pitch attitude display, and control column inputs, I think it is possible that the crew felt that they the slight reduction in column input force required, made a big difference in their perception of where "neutral is"... call it adrenalin, or "heat of the moment" or whatever... But yeah, this is definitely far from conclusive and complete.

---
By the way, anyone tried to pulling the manual trim up while having 1/2 to 2/3 aft column input, while flying at Vmo, in the 737NG sim?

flybucky · Sun Apr 07, 2019 6:26 am

mwmav8r01 wrote:
I must be Arnold Schwarzenegger. Its not hard to more the trim wheel. Takes a while longer than electric.

Here's a video of pilots demonstrating manual wheel trim in a parked 737-800 NG. They set the trim to 0 units (full nose down) and attempted the manual wheel to trim back to normal 5 units.

That was in a parked 737 with no aerodynamic forces on the stabilizer. The FO struggled and was only able to trim 1 unit in 1 minute, and was exhausted afterwards. Using the left hand may have been a factor. There have been several experts that have said that the aerodynamic forces on an out-of-trim stabilizer when the elevator is up (which it was, because the FDR Control Column Position was 5-10º nose up for most of the flight) at high speed would likely make it impossible for the manual wheel to be able to trim up.

Even the Captain in the demo, who had no problems turning the manual trim wheel, took 30 seconds to trim back to normal 5 units. According to the Preliminary Report graph, ET302 crashed ~20 seconds after the final MCAS command.

marcelh · Sun Apr 07, 2019 6:33 am

MD80Ttail wrote:
PW100 wrote:
MD80Ttail wrote:

Too many to list.

OK, I'll bite.
I'm curious at your list of NG or A320 craters with 200 hrs FO in the pointy end.

Thanks.

PS. Just to be clear, I'm not arguing with you that 200 hrs FO should not be in the cockpit of a commercial airliner (BTW, this FO had 361 hrs, of which 207 in 737, of which 56 in MAX). Just not (yet) convinced if his junior status was in any way a factor in this accident.

PS2. Regardless of total hours, what do you think of a 151 hrs NG pilot (even if he had 10000 hrs on different type, say A320) converting to MAX?

PS3. In my mind, FIRST we should establish if there were any issues with crew performance. If so, that would be the point we should start looking at FO proficiency, in regards with his limited total hours.
Since that FIRST is a looong way from being certain, discussing FO hrs at this stage is just producing noise and distracting us from establishing FIRST in the first place.

https://www.sbs.com.au/news/comment-ris ... re-crashes

Way too easy - again

flybucky · Sun Apr 07, 2019 6:51 am

mwmav8r01 wrote:
The people saying the manual trim didnt work... Do we know that they tried the trim wheel?

morrisond wrote:
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.

To me that could very well be the Pilot asking the FO to Manually try the electric trim. But it's not a great sentence so it could be interpreted many ways.

We know that FO did not try Electric Trim during that time because the FDR Electric Trim Command showed no activity during that time (the FDR data would have shown Electric Trim Command even if the Stab Trim was cutout). So we can infer that the FO was referring to the manual wheel when the FO "asked if he could try it manually" and "it is not working".

morrisond wrote:
In any case he only tried for 8 seconds and the FO never asked the Pilot to help try cranking - which you assume he would if it was too hard to move.

It is likely the Captain was using both hands to pull the yoke back and did not have free hands to assist.

B777LRF · Sun Apr 07, 2019 6:56 am

PW100 wrote:
MD80Ttail wrote:
marcelh wrote:
I repeat my statement: if lack of training/hours is so criminal, why don’t we read that a NG or A320 has made a crater?

Too many to list.

OK, I'll bite.
I'm curious at your list of NG or A320 craters with 200 hrs FO in the pointy end.

Thanks.

The short of the long is, there is no long list of NG or A320 craters caused by 200 hour pilots. For the last 10+ years, virtually every single FO in Europe has entered the cockpit with 200 hours and either a frozen ATPL or a MPL, and that has not resulted in any measurable decrease in flight safety. In fact, it has had no measurable effect at all.

Now I'm not particularly fond of the idea either, but this industry is supposed to be driven by data and cold, hard, facts - not feelings. And the cold, hard, facts does not in any way support your statement.

XRAYretired · Sun Apr 07, 2019 7:08 am

sgrow787 wrote:
mzlin wrote:
Planetalk wrote:
Perhaps worth reposting this for a fuller insight https://www.seattletimes.com/business/b ... air-crash/

The article gives a clear picture of why the whole thing is under criminal investigation and Boeing have accepted they bear some responsibility which is actually very unusual for a manufacturer after a crash. Although some will still insist there is nothing wrong with the plane.

Great post. Would be nice if everybody could read that Seattle Times article before asking the same questions or spreading the same wrong guesses/assumptions repeatedly.

I thought I had read all the articles from Seattle Times. I'm still not clear on what the min and max of operating range the horizontal stabilizer can travel to, as well as how fast it is allowed to travel. The FDR preliminary report showed about 2.5 degrees over 9-10 seconds. So the rate is 0.25-0.27 deg per second.

Anyway, Peter Lemme, a former Boeing flight controls engineer, says the MCAS design was single sensor and he doesn't know why Boeing didn't go with two. From the diagrams presented in the ET302 Preliminary Report it's clear that both AOAs had a data path to the FCC. So I find it hard to believe that a company would come up with a business case for a reused airframe with new engines, would skimp on the one system - MCAS - that allowed that business case to work. Hence I'm not convinced that it was a single sensor design. I think it's more probable that they had an intended two sensor design that had a bug that they missed because they fast tracked the testing and certification, which is a much more systemic problem than a single bad design decision by systems engineers.

Note that Boeing has extensive experience with multi-sensor redundancy design. The actual task of making MCAS use multi-sensor redundancy is just a matter of reusing existing redundancy models, and tweaking filters and hysteresis to make it work.

It has been established many times that MCAS is incompetent single sensor design.Part of the Boeing fix is to implement a two sensor design.Are you just muddying the waters?

Ray

trauha · Sun Apr 07, 2019 7:11 am

Seattle Times has several good articles on this.
Professional journalism can be quite different from forum postings.
Read the many articles. But here is a good start:
https://www.seattletimes.com/business/b ... air-crash/

And this:

https://www.seattletimes.com/business/b ... an-flight/

scbriml · Sun Apr 07, 2019 7:45 am

MD80Ttail wrote:
https://www.sbs.com.au/news/comment-rising-number-of-inexperienced-pilots-may-lead-to-more-crashes

That doesn't support your argument at all.

Must try harder, see me after class.

mwmav8r01 wrote:
I must be Arnold Schwarzenegger. Its not hard to more the trim wheel. Takes a while longer than electric.

Have you tried it in a MAX in the same situation as ET302?

MSPNWA wrote:
More completely unknown details stated as known fact. We have no proof they even touched the trim wheels, let alone couldn't turn them.

Even without knowing if they attempted to use the trim wheel, we have evidence from Bjorn at Leeham supporting the fact that the trim wheel becomes incredibly heavy to turn at high aerodynamic loads. Even more so when pulling back on the yoke for all you're worth.

flybucky · Sun Apr 07, 2019 7:51 am

sgrow787 wrote:
I'm still not clear on what the min and max of operating range the horizontal stabilizer can travel to, as well as how fast it is allowed to travel. The FDR preliminary report showed about 2.5 degrees over 9-10 seconds. So the rate is 0.25-0.27 deg per second.

737 stabilizer range is 0 units (-4.2º nose down) to 17 units (12.9º nose up).
Stabilizer rate is 0.27º/s for MCAS, 0.2º/s for Electric Trim.

sgrow787 wrote:
I'm not convinced that it was a single sensor design. I think it's more probable that they had an intended two sensor design that had a bug that they missed because they fast tracked the testing and certification, which is a much more systemic problem than a single bad design decision by systems engineers.

The previously existing autotrim systems (Speed Trim and Mach Trim) were based on single sensor design, so MCAS probably just piggybacked off the same model. The difference is that Speed Trim and Mach Trim made small adjustments that pilots could easily counter with the yoke (in fact, the yoke had an automatic cutout when opposing those autotrims), whereas as MCAS made aggressive adjustments that the pilots could not counter with the yoke (no column cutout).

Elshad · Sun Apr 07, 2019 8:00 am

Why isn’t removing MCAS completely being considered as a solution? The only problem would be a tendency to pitch up in a small portion of the flight envelope, which can easily be countered by pushing forward on the yoke or using electric trim. Seems a lot more logical and also easier to train pilots for, rather than teaching various procedures to manage a system that frequently goes deranged.

If it’s a matter of reducing crew workload then any pilot who can’t figure out that moderate forward pressure on the yoke will help pitch the plane down probably shouldn’t be flying.

zeke · Sun Apr 07, 2019 8:00 am

Grizzly410 wrote:
My question is on the AP activation, is this normal to engage the AP less than a minute after take off with the stick shaking and two warnings? (I admit I´m not sure what is an "autopilot warning")
Didn't they recognise the IAS situation ? And even, how could the AP engage for 33s with an AoA disagree ?

AOA is not an AP arming requirement on the 737. Different flight control architecture to what you are used to.

mzlin wrote:
MCAS was passed off as a STS modification to the FAA and hidden from the manual, which appears to have been done in order to keep common type certification with the 737NG (at least that would seem to be the only motivation strong enough to piggyback MCAS on the non-redundant STS structure and hide a safety-impacting system from the manual)

MCAS is implemented almost exactly the same way as STS is, however the 737NG when initially certified by the FAA did not have STS. STS was only installed at the insistance of JAA (now EASA) after the FAA had certified the 737NG, and was added as a modification to existing aircraft.

PW100 wrote:
It has also been suggested, way up thread (or in the grounding thread), and in a Leeham and/or Ostrower blog, that MAX needed MCAS in order to meet some specific FAR requirements with respect to control column force gradient as a function of AoA and/or airspeed. And thus could not be certified without MCAS.

I find it as being a very odd way of implementing that. The loads felt by the pilots on the 737 are artificial, they are generated by the elevator feel computer. If all they wanted to do was to change the feel to the pilots they should have just been able to change the programming in the elevator feel computer without changing the stabilizer trim. Hence I think there is much more to MCAS than just changing the "feel".

trex8 wrote:
MCAS training at least for the American majors its been reported was only either an ipad or other computer course. Even with ET having a Max sim, would a sim check involve any Mcas training at that point in time? I think its quite probable even today the only sims capable of mcas training are at Boeing.

No, as far as I know there is no simulator in the world programmed with such a failure, even the ones at Boeing. It was not required to be developed as MCAS differences was deemed not to require any training from the NG.

rheinwaldner · Sun Apr 07, 2019 8:06 am

mwmav8r01 wrote:
In my opinion... I think thats what happened. The Captain asked the FO if it was working and he tried his yoke switch. But there is absolutely no way to know.

Why? Check the FDR plot.
Hint: there is no electric trim input visible so we absolutely know that he did not continue using the yoke switch.

mxaxai · Sun Apr 07, 2019 8:59 am

rheinwaldner wrote:
mwmav8r01 wrote:
In my opinion... I think thats what happened. The Captain asked the FO if it was working and he tried his yoke switch. But there is absolutely no way to know.

Why? Check the FDR plot.
Hint: there is no electric trim input visible so we absolutely know that he did not continue using the yoke switch.

I wonder, though, why MCAS gave one automatic AND input after the trim cut out switches had been flipped, then remained dormant, and only reactivated after (presumably) electric trim had been reactived. Could it be that inputs to the electric trim - either manually on the yoke or from MCAS - were not recorded while electric trim was off (after some initial transition time)?

mxaxai · Sun Apr 07, 2019 9:16 am

Elshad wrote:
Why isn’t removing MCAS completely being considered as a solution? The only problem would be a tendency to pitch up in a small portion of the flight envelope, which can easily be countered by pushing forward on the yoke or using electric trim. Seems a lot more logical and also easier to train pilots for, rather than teaching various procedures to manage a system that frequently goes deranged.

If it’s a matter of reducing crew workload then any pilot who can’t figure out that moderate forward pressure on the yoke will help pitch the plane down probably shouldn’t be flying.

I assume that there are some situations where the aircraft becomes unstable, so the pilot would have to react in a very short time to avoid an unrecoverable attitude.
At high AoA, the large nacelles of the MAX create a torque around the lateral axis that would make the aircraft pitch up even further, potentially pushing itself into a stall. Avoiding this would require additional aerodynamic surfaces, e. g. a larger horizontal stabilizer or tail strakes, that create a counteracting torque.
Extending flaps probably provides such aerodynamic effects, so MCAS is not required (and deactivated) while flaps are deployed.

giopan1975 · Sun Apr 07, 2019 10:23 am

What we understand so far is that a pilot flying can find himself in a situation where manual trimming the aircraft is very difficult/impossible.
The question is what would have saved them? Would it be possible to reengage A/P and throw mcas out of the equation? One thing is certain, they had very little room (altitude), very small margin to try different solutions.

We also understand that:
1) Boeing (a world class, leading aircraft manufacturer for many decades) are choosing to pay its highly ranked executives with billions of dollars in salaries and bonuses BUT at the same time choose to install poor quality critical components in their aircrafts.
2) The genious engineers of the same company (Boeing) after all those decades of evolution overlooked the scenario of physically impossible manually trimming in low altitude/high speed
3) And what we know from the beginning: Boeing decided to develop the max model doing patchwork (mcas) to conceal max's fundamental design flaws.

And of course, the sacrifice of hundreds of Ethiopians/Indonesians can easily be filed under statistically acceptable (as in collateral damage).
Αre we really in year 2019 or is this an illusion?

Elshad · Sun Apr 07, 2019 10:49 am

Would a small increase in horizontal stabiliser area make MCAS redundant? Obviously all frames would need to be retrofitted at great cost but it would be a real solution as opposed to an MCAS patch.

zeke · Sun Apr 07, 2019 10:54 am

sgrow787 wrote:
From the diagrams presented in the ET302 Preliminary Report it's clear that both AOAs had a data path to the FCC.

The diagram is high level. There is actually two FCCs, each receives one AOA input.

mxaxai wrote:
I wonder, though, why MCAS gave one automatic AND input after the trim cut out switches had been flipped, then remained dormant, and only reactivated after (presumably) electric trim had been reactived. Could it be that inputs to the electric trim - either manually on the yoke or from MCAS - were not recorded while electric trim was off (after some initial transition time)?

There presently is no direct way to actually turn off MCAS, the only way that I have seen to indirectly turn off MCAS is by selecting flap greater than zero. The AD that has been published just turns off power to the stabilizer, the actual command from the MCAS located in the FCC will continue to tell the aircraft to pitch nose down if the actuation conditions are met. Turning power back on to the stabilizer will enable the MCAS commands to start moving the stabilizer again.

morrisond · Sun Apr 07, 2019 11:05 am

PW100 wrote:
morrisond wrote:
That's not quite what was said.

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.

To me that could very well be the Pilot asking the FO to Manually try the electric trim. But it's not a great sentence so it could be interpreted many ways.

In any case he only tried for 8 seconds and the FO never asked the Pilot to help try cranking - which you assume he would if it was too hard to move.

I agree that the report is a bit vague on this manual trimming issue. Ideally, we'd like a full CVR transcript, as well as some other FDR data to continue our own little investigation . . .

I'll offer two possible explanations as to why "the FO never asked the Pilot to help try cranking":
1) The report does not show all conversations. So it might be that they did discuss such, but the conversation didn't end up in the interim report for whatever reason;
2) Pilot flying needed ALL of his physical strength on the control column just to keep the nose up. Try doing that, bend forward, reach for the trim wheel, flipping out the handle, and apply rotational force on the trim wheel. And during all of that that, all the time, maintain maximum back force on the control column.

Yes that is entirely plausible. You would have to guess though that they could have both held the control column with one hand and cranked with the other.

I did not know it was the full transcript - but if the Co-pilot had asked for help you think they would have noted that.

morrisond · Sun Apr 07, 2019 11:16 am

PW100 wrote:
Moose135 wrote:
sgrow787 wrote:
If there wasn't a stability issue inherent in the Max, then why was MCAS introduced for an airframe that is identical to previous 737 models? Because it's identical with exception to the engine size and placement on the wings.

MCAS was added so that the Max handled the same as the NG, which the airlines wanted so that it could be flown with the same type rating. Without MCAS, the Max would still be safe, but pilots would need additional training and certification, something that operators didn't want to spend money on. That has been explained a number of times in these threads.

It has also been suggested, way up thread (or in the grounding thread), and in a Leeham and/or Ostrower blog, that MAX needed MCAS in order to meet some specific FAR requirements with respect to control column force gradient as a function of AoA and/or airspeed. And thus could not be certified without MCAS.

Did we get a final answer on that already (apologies in advance if I have missed that)?

Here is the best description I have seen off the 737.org.uk site that has lots of great information on all generations of 737.

"MCAS is a longitudinal stability enhancement. It is not for stall prevention (although indirectly it helps) or to make the MAX handle like the NG (although it does); it was introduced to counteract the non-linear lift generated by the LEAP-1B engine nacelles at high AoA and give a steady increase in stick force as the stall is approached as required by regulation.

The LEAP engine nacelles are larger and had to be mounted slightly higher and further forward from the previous NG CFM56-7 engines to give the necessary ground clearance. This new location and larger size of nacelle cause the vortex flow off the nacelle body to produce lift at high AoA. As the nacelle is ahead of the C of G, this lift causes a slight pitch-up effect (ie a reducing stick force) which could lead the pilot to inadvertently pull the yoke further aft than intended bringing the aircraft closer towards the stall. This abnormal nose-up pitching is not allowable under 14CFR §25.203(a) "Stall characteristics". Several aerodynamic solutions were introduced such as revising the leading edge stall strip and modifying the leading edge vortilons but they were insufficient to pass regulation. MCAS was therefore introduced to give an automatic nose down stabilizer input during elevated AoA when flaps are up."

On interpretation of this is that it helps the controls feel stiffer as you get closer to the stall margins as additional warning before the stick shaker activates which is usually quite a bit before the stall. It was trying to make a safe aircraft safer and give pilots more warning.

Easy to do in a fly by wire aircraft harder to do in an Mechanical system. I would have to guess though that the NG has some parts of the flight envelope where it's controls are non-linear as well (or just passing through something like turbulence - air is not a constant medium and controls can load or unload) - it's not like driving a car on dry asphalt.

I don't recall any crashes being caused by non-linear control responses.

I don't believe the FAR existed when the NG was ceritified. There is good intent behind it and if Boeing had screwed it up so bad it would have made a safe plane safer.

When it is fixed it should make the MAX safer than the NG.

morrisond · Sun Apr 07, 2019 11:24 am

flybucky wrote:
mwmav8r01 wrote:
The people saying the manual trim didnt work... Do we know that they tried the trim wheel?

morrisond wrote:
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.

To me that could very well be the Pilot asking the FO to Manually try the electric trim. But it's not a great sentence so it could be interpreted many ways.

We know that FO did not try Electric Trim during that time because the FDR Electric Trim Command showed no activity during that time (the FDR data would have shown Electric Trim Command even if the Stab Trim was cutout). So we can infer that the FO was referring to the manual wheel when the FO "asked if he could try it manually" and "it is not working".

morrisond wrote:
In any case he only tried for 8 seconds and the FO never asked the Pilot to help try cranking - which you assume he would if it was too hard to move.

It is likely the Captain was using both hands to pull the yoke back and did not have free hands to assist.

I thought the same thing - but Would it have shown it though if the power was cut-off? MCAS shows when the trim was cut-off probably because it is powered on different circuit?

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