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PW100
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 8:49 pm

morrisond wrote:
Who knows who is right - however the ET document does show a revision date of Feb .21 - it took them almost 4 months to revise it and then did they actually distribute it? Taking 4 months to revise something is not indicative of a strong safety environment.


Four months does not sound unreasonable.
In my organistaion, an AD or TR (Temporary Revision) is added to a manual within a couple days (or even hours, depending on urgency). The full revision adopting that same information into normal manual format can take upto 90 days.
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 8:51 pm

lexiion wrote:
XRAYretired wrote:
lexiion wrote:

The suspicion here is not the AoA sensor itself, but rather the wiring, ADIRU, etc. That has been mentioned a couple of times in the previous thread.

LEXiiON


Also mentioned that no one has come up with a sceanario that works for ADIRU or wiring, but AOA problem fits the data we have comfortably.


Ray


From AVherald:

....Prior to flight JT-43 the left AoA sensor (which was still the one mounted by Boeing during aircraft assembly) was replaced by LionAir maintenance due to repetitive similiar malfunctions on the flights before JT-43, the new AoA sensor on flights JT-43 and JT-610 however showed repetitive malfunctions again, on JT-43 the crew was able to correct, on JT-610 the crew however was not able to correct and crashed....
....On Apr 27th 2019 it became known, that four independent whistleblowers, current and former Boeing employees, had called the FAA hotline for whistleblowers regarding aviation safety concerns on Apr 5th 2019. The concerns reported were wiring damage to the AoA related wiring as result of foreign object damage as well as concerns with the TRIM CUTOUT switches. The FAA believes these reports may open completely new investigative angles into the causes of the two crashes in Indonesia and Ethiopia.......

I still believe the incorrect AoA data did not come from a faulty sensor. But we'll know when we have the final reports, I guess.

Some here has spend many time searching for scenarios that fit the available data and shared there views in the previous threads. The two consecutive defective AoA sensors was one of that scenarios, the falsification of the AoA sensor replacement was an other scenario, ADIRU fault was yet an another scenario, and so on... I think there was a few more ideas of scenarios shared. All those scenarios have there part of verifiable data and there part of speculative data., at least at this time. Everyone is free to ponder each parts as it like, but there are still some kind of "score" that each particular scenario can hit.

It look like a fault that makes erroneous AoA data on the two AoA links hit a very high score in explaining the FDR and CVR contents, and that no other scenario is actually likely to give a comparable score, as the two AoA links provides data to different paths in the avionic down to different observable consequence in the FDR. This can be induced by the two consecutive defective AoA sensors scenario, but the wiring fault or perturbation scenario could induced that too. An ADIRU fault on the contrary is a scenario that fit well only the observable data of a single link, and an another failure is probably necessary to explain the observable data on the other link.

There are missing and contradicting information posted. The JT043 AoA FDR trace is not published at this time. Some source say that the AoA FDR trace is not the same on the JT610 compared to the JT043. Some source say that the AoA that was replaced from that flight is defective, while other source say that is was serviceable. Time will tell...
 
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7BOEING7
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 8:56 pm

morrisond wrote:
kalvado wrote:
morrisond wrote:
"These pitch and power settings provide a simple reference setting for the crew to use for a short period of time while the initial steps of the checklist are accomplished. These settings do not ensure a level flight or constant airspeed at any particular altitude/airspeed/weight combination. However, they do ensure that at any and all weight/altitude combinations, the aircraft will accelerate from low speeds, and slow from a high speeds, as we cannot assume the aircraft is in stable flight when the NNC is run. It is more likely that the crew or the autopilot has destabilized the airplane as a result of erroneous airspeed indications prior to identification of the need to run the NNC. These memory item pitch and power settings often result in a significant climb (from lower altitudes) and can also result in a gradual descent (from higher altitudes).

zeke wrote:

Probably in excess of 10%, not relevant to the discussion.


Honestly speaking, things don't quite add up.
Boeing doesn't guarantee climb, while Zeke talks about 200-2500 fpm; and that is for a heavy plane right after takeoff.
I suspect it is "climb not guaranteed" is the core reason to hesitate.


Flaps down 10 Degree Pitch up and 80% N1 would have produced a significant climb at Airfield elevation to where they got too. 94% was TOGA thrust not climb thrust.


?????

Maintenance had all night to troubleshoot and read out any error codes in the Adiru, etc.
 
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 8:57 pm

morrisond wrote:
PW100 wrote:
morrisond wrote:

I believe AVherald (Which has a fantastic reputation) a lot more than I believe the Airline who was possibly responsible for not training there pilots properly.

Of course ET is going to say that - what do you expect them to publicly admit they never taught there pilots the proper procedures to deal with a runaway MCAS failure?


What training did the pilots not get? Did Boeing define any MCAS related training/instructions?
It is my impression that only after the groundung Boeing started working on MCAS instructions and training. The last official message from Boeing prior to the grounding, was reminder (!) to use Trim Cut Out Switches. Which was followed by the ET crew. Which strongly suggests that they did get this message . . .


So you are still absolving the pilots from reading the whole procedure where they had the option of returning the plane to In-trim using Electric before turning the swtiches off? Okay then...


No.

I'm just not (yet) convinced that the uptrim stopped because of pilot intervention (ie Cut Out Switches). I find it very suspicious that ALL four uptrim actions after MCAS first activation, stopped at exactly the same stabelizer pitch angle (2.3 degrees). That suggests that there may be a factor that we do not yet understand, that limited the uptrimming.

But you seem to be comfortable to put this on the crew, that they managed four times to stop uptrimming intentionally at 2.3 deg stabelizer angle. Despite very heavy control column. Okay then . . . .
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:02 pm

morrisond wrote:
PW100 wrote:
morrisond wrote:
What Pilot competency standard should Airbus and Boeing have to design too?

If Boeing is not lying they designed to the existing standard. The crew are allowed as a back up system in all modern designs by all Manufacturers.


Which was apparently the case before the MCAS parameters were drastically changed during the flight test program. However MCAS authority and speed was increased to such levels, that using pilots as back-up system was no longer valid as your average airline pilot is not expected to observe, trouble shoot and understand the safety critical effects of MCAS failure in timely fashion.

So Boeing perhaps did design to the existing standard, but that was not how the final product was delivered.


Unknown at this time.

Factually correct, your remark.
But the same appliues to "Boeing is not lying they designed/delivered to the existing standard".

Seems you have less problems accepting unknowns from Boeing PR department.
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XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:04 pm

PixelFlight wrote:
lexiion wrote:
XRAYretired wrote:

Also mentioned that no one has come up with a sceanario that works for ADIRU or wiring, but AOA problem fits the data we have comfortably.


Ray


From AVherald:

....Prior to flight JT-43 the left AoA sensor (which was still the one mounted by Boeing during aircraft assembly) was replaced by LionAir maintenance due to repetitive similiar malfunctions on the flights before JT-43, the new AoA sensor on flights JT-43 and JT-610 however showed repetitive malfunctions again, on JT-43 the crew was able to correct, on JT-610 the crew however was not able to correct and crashed....
....On Apr 27th 2019 it became known, that four independent whistleblowers, current and former Boeing employees, had called the FAA hotline for whistleblowers regarding aviation safety concerns on Apr 5th 2019. The concerns reported were wiring damage to the AoA related wiring as result of foreign object damage as well as concerns with the TRIM CUTOUT switches. The FAA believes these reports may open completely new investigative angles into the causes of the two crashes in Indonesia and Ethiopia.......

I still believe the incorrect AoA data did not come from a faulty sensor. But we'll know when we have the final reports, I guess.

Some here has spend many time searching for scenarios that fit the available data and shared there views in the previous threads. The two consecutive defective AoA sensors was one of that scenarios, the falsification of the AoA sensor replacement was an other scenario, ADIRU fault was yet an another scenario, and so on... I think there was a few more ideas of scenarios shared. All those scenarios have there part of verifiable data and there part of speculative data., at least at this time. Everyone is free to ponder each parts as it like, but there are still some kind of "score" that each particular scenario can hit.

It look like a fault that makes erroneous AoA data on the two AoA links hit a very high score in explaining the FDR and CVR contents, and that no other scenario is actually likely to give a comparable score, as the two AoA links provides data to different paths in the avionic down to different observable consequence in the FDR. This can be induced by the two consecutive defective AoA sensors scenario, but the wiring fault or perturbation scenario could induced that too. An ADIRU fault on the contrary is a scenario that fit well only the observable data of a single link, and an another failure is probably necessary to explain the observable data on the other link.

There are missing and contradicting information posted. The JT043 AoA FDR trace is not published at this time. Some source say that the AoA FDR trace is not the same on the JT610 compared to the JT043. Some source say that the AoA that was replaced from that flight is defective, while other source say that is was serviceable. Time will tell...


The JT043 FDR trace, including AoA, is in the JT610 Preliminary Report - Figure 7 - and shows a similar consistent 20deg. offset as JT610. The replaced AoA sensor was from flight prior to JT043. The Indonesian Investigation chief is quoted as saying this was deemed faulty by Rosemount.

Ray
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:08 pm

PW100 wrote:
morrisond wrote:
PW100 wrote:

What training did the pilots not get? Did Boeing define any MCAS related training/instructions?
It is my impression that only after the groundung Boeing started working on MCAS instructions and training. The last official message from Boeing prior to the grounding, was reminder (!) to use Trim Cut Out Switches. Which was followed by the ET crew. Which strongly suggests that they did get this message . . .


So you are still absolving the pilots from reading the whole procedure where they had the option of returning the plane to In-trim using Electric before turning the swtiches off? Okay then...


No.

I'm just not (yet) convinced that the uptrim stopped because of pilot intervention (ie Cut Out Switches). I find it very suspicious that ALL four uptrim actions after MCAS first activation, stopped at exactly the same stabelizer pitch angle (2.3 degrees). That suggests that there may be a factor that we do not yet understand, that limited the uptrimming.

But you seem to be comfortable to put this on the crew, that they managed four times to stop uptrimming intentionally at 2.3 deg stabelizer angle. Despite very heavy control column. Okay then . . . .


That is suspicious that it stopped at exactly the same value. I don't think anybody has a good explanation for it other than chance they ended up at the same value.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:10 pm

PW100 wrote:
morrisond wrote:
PW100 wrote:

Which was apparently the case before the MCAS parameters were drastically changed during the flight test program. However MCAS authority and speed was increased to such levels, that using pilots as back-up system was no longer valid as your average airline pilot is not expected to observe, trouble shoot and understand the safety critical effects of MCAS failure in timely fashion.

So Boeing perhaps did design to the existing standard, but that was not how the final product was delivered.


Unknown at this time.

Factually correct, your remark.
But the same appliues to "Boeing is not lying they designed/delivered to the existing standard".

Seems you have less problems accepting unknowns from Boeing PR department.


No - I said they might be lying. I did not say they are not lying.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:12 pm

PW100 wrote:
morrisond wrote:
Who knows who is right - however the ET document does show a revision date of Feb .21 - it took them almost 4 months to revise it and then did they actually distribute it? Taking 4 months to revise something is not indicative of a strong safety environment.


Four months does not sound unreasonable.
In my organistaion, an AD or TR (Temporary Revision) is added to a manual within a couple days (or even hours, depending on urgency). The full revision adopting that same information into normal manual format can take upto 90 days.


That's pathetic if that is acceptable in aviation safety. I though that is why it was an Emergency AD.
 
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:14 pm

morrisond wrote:
PW100 wrote:
morrisond wrote:
It turned out, that only very cursory knowledge about the stab trim runaway procedure exists amongst the flight crew of Ethiopian Airlines even 5 months after the EAD was distributed. In particular, none of the conditions suggesting an MCAS related stab trim runaway was known with any degree of certainty. In that context the recommendation by the accident flight's first officer to use the TRIM CUTOUT switches suggests, that he was partially aware of the contents of the EAD and reproduced some but not all of the provisions and not all of the procedure, which may or may not explain some of the obvious omissions in following the procedure in full."


There is no evidence the crew had "only very cursory knowledge about the stab trim runaway procedure".
Also, that is not what the EAD was about. The AD was just a reminder to use that procedure at certain conditions.
And thirdly, the ET crew DID use the Trim Cut Out Switches. Which strongly suggests that they DID receive the EAD message.


Those were AVHeralds words - not mine.

I know the ET crew did use the Trim cut out switches and suggested that as the Co-pilot had just gone through the SIM that is why he might have known about it. The pilot sure didn't seem to know anything about it.
However if MCAS was taught in the SIM - he for sure forgot about putting the plane back in trim before hitting the swtiches to turn it of.


That is a very poor excuse. If you did not agree with the words, why bring them up? I have yet to read anything remotely critical from your end on those AVHerald words.
Also, by adding your words "Ït turned out", suggests that you put quite some weight to those AVHeralds words.

Why would you bring up MCAS simulator training, when the current proposed training scheme by Boeing to unground the MAX does not even include MCAS simulator training?
You can't seriously bring that up against ET or their crew to suggest that they were not properly trained. Which airline in the world had MCAS sim-training at that time?
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:18 pm

XRAYretired wrote:
PixelFlight wrote:
lexiion wrote:

From AVherald:

....Prior to flight JT-43 the left AoA sensor (which was still the one mounted by Boeing during aircraft assembly) was replaced by LionAir maintenance due to repetitive similiar malfunctions on the flights before JT-43, the new AoA sensor on flights JT-43 and JT-610 however showed repetitive malfunctions again, on JT-43 the crew was able to correct, on JT-610 the crew however was not able to correct and crashed....
....On Apr 27th 2019 it became known, that four independent whistleblowers, current and former Boeing employees, had called the FAA hotline for whistleblowers regarding aviation safety concerns on Apr 5th 2019. The concerns reported were wiring damage to the AoA related wiring as result of foreign object damage as well as concerns with the TRIM CUTOUT switches. The FAA believes these reports may open completely new investigative angles into the causes of the two crashes in Indonesia and Ethiopia.......

I still believe the incorrect AoA data did not come from a faulty sensor. But we'll know when we have the final reports, I guess.

Some here has spend many time searching for scenarios that fit the available data and shared there views in the previous threads. The two consecutive defective AoA sensors was one of that scenarios, the falsification of the AoA sensor replacement was an other scenario, ADIRU fault was yet an another scenario, and so on... I think there was a few more ideas of scenarios shared. All those scenarios have there part of verifiable data and there part of speculative data., at least at this time. Everyone is free to ponder each parts as it like, but there are still some kind of "score" that each particular scenario can hit.

It look like a fault that makes erroneous AoA data on the two AoA links hit a very high score in explaining the FDR and CVR contents, and that no other scenario is actually likely to give a comparable score, as the two AoA links provides data to different paths in the avionic down to different observable consequence in the FDR. This can be induced by the two consecutive defective AoA sensors scenario, but the wiring fault or perturbation scenario could induced that too. An ADIRU fault on the contrary is a scenario that fit well only the observable data of a single link, and an another failure is probably necessary to explain the observable data on the other link.

There are missing and contradicting information posted. The JT043 AoA FDR trace is not published at this time. Some source say that the AoA FDR trace is not the same on the JT610 compared to the JT043. Some source say that the AoA that was replaced from that flight is defective, while other source say that is was serviceable. Time will tell...


The JT043 FDR trace, including AoA, is in the JT610 Preliminary Report - Figure 7 - and shows a similar consistent 20deg. offset as JT610. The replaced AoA sensor was from flight prior to JT043. The Indonesian Investigation chief is quoted as saying this was deemed faulty by Rosemount.

Ray

Oops, you are right. I have wrote from memory, I should have checked again: the unpublished FDR traces are for the replaced AoA sensor before te JT043.
The quote of the Indonesian Investigation chief is disputed by some (not me, as Rosemount/Boeing/FAA never denied that public claim)
 
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:26 pm

morrisond wrote:
PW100 wrote:
morrisond wrote:
Who knows who is right - however the ET document does show a revision date of Feb .21 - it took them almost 4 months to revise it and then did they actually distribute it? Taking 4 months to revise something is not indicative of a strong safety environment.


Four months does not sound unreasonable.
In my organistaion, an AD or TR (Temporary Revision) is added to a manual within a couple days (or even hours, depending on urgency). The full revision adopting that same information into normal manual format can take upto 90 days.


That's pathetic if that is acceptable in aviation safety. I though that is why it was an Emergency AD.


You are not understanding me correctly. The AD or TR is put in in matter of days or hours.

Usually an AD (FAA/EASA document), and every TR (OEM document) is followed up by a revision of the manual. That revision usually contains the exact same info as the AD or TR, but in regular format of such manual.

So the information is there from day one. And after some time (usually 10 - 20 days, but max 90 days) the AD/TR is removed from the manual and replaced by normal revision containing same info.

There is nothing pathetic about that. It is a generally accepted procedure, approved by EASA, FAA and TCCA amongst others. And no, this is not overseen by those agencies, as they take control of Maintenance Data very seriuously, and therefore this procedure is reviewed and checked durinmg every audit by these agencies.
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Cdydatzigs
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:30 pm

FluidFlow wrote:
Say you have an aircraft A that has 60 year old design and for example hydraulic controls and the amount of force to move the elevator is 20N.


In fairness, the only thing on the 737 that is "60-years old" is the shape of the nose. Everything else has been changed/updated by now, has it not?
 
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:36 pm

Cdydatzigs wrote:
FluidFlow wrote:
Say you have an aircraft A that has 60 year old design and for example hydraulic controls and the amount of force to move the elevator is 20N.


In fairness, the only thing on the 737 that is "60-years old" is the shape of the nose. Everything else has been changed/updated by now, has it not?


Ground clearance comes to mind . . .
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SEU
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 9:56 pm

zeke wrote:
SEU wrote:

Hardly, the plane trimmed itself into the ground. That's the million dollar question.


If they had followed the procedures for stick shaker, MCAS would never have activated.


The MCAS shouldve worked regardless of whether you think that the pilots should have done something. The MAX flew its pilots and PAX nose first into the ground (twice) due to the MCAS not doing its job properly. You focusing on "it wouldnt of activated if XYZ so its the pilots fault" it's just complete utter nonsense.

That is like saying that someone who was driving a car and was going over the speed limit, the breaks didnt work and they crash and died, it was the fault of the driver because they were speeding. No its because the breaks failed.

Edit: And to top it off, it was a fault to start with in your arguement, so the MAX had a fault, the pilots according to A.net posters, should have done something and because they didnt, the plane then flew itself into the ground, twice, because a malfunctioning MCAS, that was not fully disclosed to pilots or FAA, so it has to be the pilots fault....

Please lets stay on topic.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 10:28 pm

PW100 wrote:
morrisond wrote:
PW100 wrote:

There is no evidence the crew had "only very cursory knowledge about the stab trim runaway procedure".
Also, that is not what the EAD was about. The AD was just a reminder to use that procedure at certain conditions.
And thirdly, the ET crew DID use the Trim Cut Out Switches. Which strongly suggests that they DID receive the EAD message.


Those were AVHeralds words - not mine.

I know the ET crew did use the Trim cut out switches and suggested that as the Co-pilot had just gone through the SIM that is why he might have known about it. The pilot sure didn't seem to know anything about it.
However if MCAS was taught in the SIM - he for sure forgot about putting the plane back in trim before hitting the swtiches to turn it of.


That is a very poor excuse. If you did not agree with the words, why bring them up? I have yet to read anything remotely critical from your end on those AVHerald words.
Also, by adding your words "Ït turned out", suggests that you put quite some weight to those AVHeralds words.

Why would you bring up MCAS simulator training, when the current proposed training scheme by Boeing to unground the MAX does not even include MCAS simulator training?
You can't seriously bring that up against ET or their crew to suggest that they were not properly trained. Which airline in the world had MCAS sim-training at that time?


I did not say MCAS simulator training I know they don't exist - however it would have been easy to simulate an erroneous MCAS input in any sim - the sim operator would put the sim nose down out of trim and then the crew would have to return it to in-trim using electriC, hit the cutoff switches and then continue with manual trim wheel. BTW they would have flunked the exercise if they didn't keep the speed in normal ranges.

The co- pilot was the only one that went through the sim between Nov 9 and the flight and is the only one who seemed to know anything about the procedure so he might have picked it up in the sim.

Or the EAD was actually distributed and he was the only one to read it.
Last edited by morrisond on Thu May 02, 2019 10:34 pm, edited 1 time in total.
 
airnorth
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 10:28 pm

SEU wrote:
zeke wrote:
SEU wrote:

Hardly, the plane trimmed itself into the ground. That's the million dollar question.


If they had followed the procedures for stick shaker, MCAS would never have activated.


The MCAS shouldve worked regardless of whether you think that the pilots should have done something. The MAX flew its pilots and PAX nose first into the ground (twice) due to the MCAS not doing its job properly. You focusing on "it wouldnt of activated if XYZ so its the pilots fault" it's just complete utter nonsense.

That is like saying that someone who was driving a car and was going over the speed limit, the breaks didnt work and they crash and died, it was the fault of the driver because they were speeding. No its because the breaks failed.

Edit: And to top it off, it was a fault to start with in your arguement, so the MAX had a fault, the pilots according to A.net posters, should have done something and because they didnt, the plane then flew itself into the ground, twice, because a malfunctioning MCAS, that was not fully disclosed to pilots or FAA, so it has to be the pilots fault....

Please lets stay on topic.

You can't go on an off topic rant about car brakes, (not breaks), and then ask others to stay on topic.
I think it is clear that something in the MCAS system failed, and the design was bad, but, it also brings up some questions about flying. So again, lots of people and systems played some part in these fatal crashes.
There seems to be some consensus from pilots that procedures were not followed.
Read the posts, stay objective and open to facts and knowledgeable people, and yes, please, stay on topic.

Airnorth
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu May 02, 2019 11:22 pm

airnorth wrote:

There seems to be some consensus from pilots that procedures were not followed.

Yet months after the first accident, I still read (with high attention) pilots debating here what procedures should be followed.
 
PStechPaul
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 12:02 am

As for blaming the pilots for keeping thrust at 94% and overspeeding, wasn't auto-throttle engaged? And shouldn't that be configured to reduce thrust when maximum speed is reached?
 
airnorth
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 12:18 am

PixelFlight wrote:
airnorth wrote:

There seems to be some consensus from pilots that procedures were not followed.

Yet months after the first accident, I still read (with high attention) pilots debating here what procedures should be followed.

This all comes back to facts versus opinions. Unfortunately we do not know all of the facts yet, so we have opinions, and some facts.
I do really enjoy the contribution of civilized discussion around the different opinions, and I think the popular opinion is that there were some odd decisions made in the cockpit. This doesnt mean that the blame lies with the pilots, but it does mean more questions.

I get frustrated reading the pages and pages of passionate posts that have already concluded the investigation, and everyone else is wrong.
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 12:21 am

PW100 wrote:
Cdydatzigs wrote:
FluidFlow wrote:
Say you have an aircraft A that has 60 year old design and for example hydraulic controls and the amount of force to move the elevator is 20N.


In fairness, the only thing on the 737 that is "60-years old" is the shape of the nose. Everything else has been changed/updated by now, has it not?


Ground clearance comes to mind . . .


No slides from the wings to the ground for an emergency. I saw pictures of passengers standing on the wing looking down and wondering what to do next.
 
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7BOEING7
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 12:41 am

PStechPaul wrote:
As for blaming the pilots for keeping thrust at 94% and overspeeding, wasn't auto-throttle engaged? And shouldn't that be configured to reduce thrust when maximum speed is reached?


Since the thrust setting did not change throughout the flight the autothrottle either wasn't engaged for takeoff or was disengaged after takeoff (either crew action or related to the failures they were seeing). Under normal circumstances the autopilot would have prevented the overspeed. Note that stall recovery procedures call for disengaging the autopilot and auto throttle.
 
Chemist
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 2:26 am

FluidFlow wrote:
Chemist wrote:
FluidFlow wrote:

They definitely wanted to make it more efficient, the complete product seems to be worse than the NG as it is less safe.

They unfortunately did not make it handle the same Boeing only augmented it, on an aircraft that is grandfathered from a sixty-year-old concept.

In my opinion, the aircraft was too old for that step.


Please explain how the age of the aircraft design had anything to do with whether you can augment handling on a new revision.


Say you have an aircraft A that has 60 year old design and for example hydraulic controls and the amount of force to move the elevator is 20N.
Aircraft B is built after the design of aircraft B but has different aerodynamic forces due to new engines and it needs 40N to move the elevator.
To make them feel the same you need a tool to make both need 20N input force even a/c B actually needs 40N. You would build in an additional servo to help you (like a powersteering).

This complicates things and if it has to apply in certain situations only you need to also figure out when this help is needed and rely on sensors for functions you have not before. This leads to a long trail of possible error sources, as observed with MCAS.

If Boeing will build a 787 MAX in the future with new engines that are placed differently and generate different forces you only have to change the code that converts stick input into elevator movement.


This example doesn't work for me at all. It feels contrived to fit your argument but doesn't seem to have a basis in reality.
You could put bigger engines on a 5 yo plane and have force differences. The age of the plane has nothing to do with it.
 
FluidFlow
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 4:38 am

Chemist wrote:
FluidFlow wrote:
Chemist wrote:

Please explain how the age of the aircraft design had anything to do with whether you can augment handling on a new revision.


Say you have an aircraft A that has 60 year old design and for example hydraulic controls and the amount of force to move the elevator is 20N.
Aircraft B is built after the design of aircraft B but has different aerodynamic forces due to new engines and it needs 40N to move the elevator.
To make them feel the same you need a tool to make both need 20N input force even a/c B actually needs 40N. You would build in an additional servo to help you (like a powersteering).

This complicates things and if it has to apply in certain situations only you need to also figure out when this help is needed and rely on sensors for functions you have not before. This leads to a long trail of possible error sources, as observed with MCAS.

If Boeing will build a 787 MAX in the future with new engines that are placed differently and generate different forces you only have to change the code that converts stick input into elevator movement.


This example doesn't work for me at all. It feels contrived to fit your argument but doesn't seem to have a basis in reality.
You could put bigger engines on a 5 yo plane and have force differences. The age of the plane has nothing to do with it.


I specificly wrote in the second part about the 787 and yes its 10 years old but that should not make it any different.
 
FluidFlow
Posts: 290
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 4:45 am

planecane wrote:
FluidFlow wrote:
nikeherc wrote:

I don't think that the goal was to make the MAX=NG. Clearly the goal was to make the Max better than the NG. A subsidiary goal was to make the Max fly and handle like the NG. There is nothing wrong with this. The problem was in the execution.


They definitely wanted to make it more efficient, the complete product seems to be worse than the NG as it is less safe.

They unfortunately did not make it handle the same Boeing only augmented it, on an aircraft that is grandfathered from a sixty-year-old concept.

In my opinion, the aircraft was too old for that step.

Morrisond listed nicely that incidents on the FBW aircrafts from Airbus only happened with elevator inputs and it was no problem to recover from it. MCAS does change trim significantly and that can crash aircrafts rather fast. In my opinion, the mixture of FBW feature on an ancient non FBW aircraft does not work and the MAX seems to prove that.

The fault must have happened during the design. (I don’t know how the design with Boeing went but here would be the chain on the stuff I worked on)

The designers improved the aerodynamics of the NG at the drawing board. Then they put the new engines in the only position that allowed enough clearing. A model (1:3 or 1:4) was built and cramped with sensors and put into the wind tunnel.
The collected data was used in a computer simulation and that gave the result that the aircraft was not certifiable under current regulations.

There were now two options:
1) Back to the drawing board, redesign the H-stab, or the nacelles, or the main landing gear, etc.), build another model and test it again in the wind tunnel. Then another simulation and see if the result is certifiable. This would have cost a lot and would have probably taken 6 to 24 months depending on the changes necessary and if the step hat to be repeated.
2) Use a software solution to compensate for the change in aerodynamics. Cheap and fast. That is also were the first deflection in the MCAS came from. Simulations are not perfect and during flight tests it seems that more trim was needed. Instead of making a proper risk analysis at this point and return to step 1) as the input was extreme they went with it and just hoped it will all be fine. Now in the new version they want to go back to the pre-flight-testing settings but that was not enough in the first place. Will be fun to see how they justify that.

We know now which route was taken. Long story short, it would have been cheaper to delay the aircraft by the time it would have taken to redesign.


The only thing inherently wrong with MCAS is that it was poorly implemented, first relying on a single sensor, second for having essentially unlimited authority and third for not stopping when a pilot does something to directly counteract it (trimming opposite).

There is nothing wrong with the concept or unsafe when the sensor is working.

All this garbage about the 737 being too old to be updated is just agenda driven. If Boeing had made a 757MAX and required an MCAS-like system but designed it as poorly the same issues would have happened and the 757 design isn't much older than the A320. I used the 757 hypothetical because it is non-FBW.


Sorry I dont want to make it about age but it is bad design if you need a FBW like system to compensate on a non-FBW aircraft because you run out of options to do it with a mechanical/hydraulic solution and are to cheap to design the stab properly.

Boeing builds fantastic aircraft but they already cut corners what lead to the 787 grounding and now they cut the corner even more and they have tje 737 grounding and 350 bodybags. That should not happen and i wish the next aircraft, the 777 will take off with ease as the management hopefully learned from the mistakes made.
 
ctrabs0114
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 4:48 am

SomebodyInTLS wrote:
Agree about pushing the Ethiopian thread to here as well. But on the other point - I see no need at all for there to be a new thread! You only see a page of 50 replies each time, and if you're following it you go to the newest unread posting - so the thread could be 500,000 pages long and it would make literally no difference to me logging on and seeing the twenty new replies since I last logged in!

On the old forum software, people had trouble viewing long threads (apparently - my browser never had an issue with them) so that's where this thread-breaking moderation behaviour comes from - but it's totally unnecessary on the current software, and actually makes it harder to keep track!

(Also, no other forum I use does this...)


I would respectfully disagree with this point. A lot of the "regional" airport threads (ie. the DAL/DFW, PIT, etc.) launch new threads every year; others, such as the Irish aviation forum, start new threads monthly. I can only speak for myself, but I'm fine with launching a new thread every so often depending on the situation.
2019: DAL, MCI, PHX, LAS, DFW, SAT, ORD, SLC, SEA, DTW, PHL, MIA, LAX; B73G (WN x3), B738 (WN, AA, DL), A20N (NK), MD83 (AA), B788 (AA x2), CS1 (DL), B739 (DL), B712 (DL), B752 (AA), B763 (AA), B77W (AA), B789 (AA)
Next: TBA
 
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AirlineCritic
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 5:19 am

morrisond wrote:
I suspect Crew training standards were improving for quite some time on that graph along with more reliable safe designs. Crew training standards just seem to have taken a nosedive in the last 20 years.


Heh.

Based on evidence, it seems to me that the crew training nosedived right around the introduction of MAX. Or perhaps at the time when lots of posters (or one poster making lots of posts) needed to explain away in the best light for their favourite manufacturer. Or place of employment. Or the CEO who felt there was no technical mistake or process mistake and nothing was done wrong.

To be clear, I think the crew does share part of the blame here. But equally, and given the expectation of a professional, safe, design that we have come to know Boeing can do:
Boeing failed miserably here. They failed to understand the multiple error situation crews would be experiencing. They did not appreciate the danger of a repetitive system running on unchecked inputs. They failed to understand what throwing many serious things at the crew at the most critical phase of flight would mean. Boeing failed to grasp the meaning of and tell the crews about the limitations of the manual backups. They failed to document any of this. Their published procedures are still unclear and in need of revision, for instance about the order of trim corrections and cutout.

So, I think safe aircraft design has nosedived in the last few years, badly. I know it will be fixed. Perhaps already has. But admitting the nosedive in the design failures would be a good start.
 
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SomebodyInTLS
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 5:22 am

ctrabs0114 wrote:
SomebodyInTLS wrote:
Agree about pushing the Ethiopian thread to here as well. But on the other point - I see no need at all for there to be a new thread! You only see a page of 50 replies each time, and if you're following it you go to the newest unread posting - so the thread could be 500,000 pages long and it would make literally no difference to me logging on and seeing the twenty new replies since I last logged in!

On the old forum software, people had trouble viewing long threads (apparently - my browser never had an issue with them) so that's where this thread-breaking moderation behaviour comes from - but it's totally unnecessary on the current software, and actually makes it harder to keep track!

(Also, no other forum I use does this...)


I would respectfully disagree with this point. A lot of the "regional" airport threads (ie. the DAL/DFW, PIT, etc.) launch new threads every year; others, such as the Irish aviation forum, start new threads monthly. I can only speak for myself, but I'm fine with launching a new thread every so often depending on the situation.


But there's no need for it, that was my point.

And it's one thing to stay a new thread for the new year, or this month... But the thread was randomly cut towards the end of April yet labelled Q2...
"As with most things related to aircraft design, it's all about the trade-offs and much more nuanced than A.net likes to make out."
 
oschkosch
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 5:38 am

I guess we might know more after 15 May...

https://www.kktv.com/content/news/House ... 94861.html

A U.S. House subcommittee has scheduled a May 15 hearing on the Boeing 737 Max airliner.

The Aviation Subcommittee of the Transportation and Infrastructure Committee will hold the hearing at 10 a.m.

The committee's website says the hearing will be on the "status of the Boeing 737 Max."

Witnesses were not announced, but the committee is likely to summon representatives from Boeing as well as the Federal Aviation Administration and the National Transportation Safety Board. They'll be asked about how the FAA certified the plane to be airworthy.
 
art
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 10:19 am

Boeing has given its former general counsel the new job of providing legal advice on matters related to the two recent Boeing 737 Max crashes.


Luttig “will manage all legal matters associated with the Lion Air flight 610 and Ethiopian Airlines flight 302 accidents", says Boeing.


Before joining Boeing, Luttig was a judge on the US Court of Appeals and assistant attorney general at the US Department of Justice, according to Boeing.


https://www.flightglobal.com/news/artic ... 37-457885/

I see this as Boeing setting up extremely strong defensive forces (ex-Appeals Court judge etc) to fight any claims for justice regarding MAX crashes. What's the line going to be with relatives of the victims? We're not liable: it was the pilots who crashed a safe plane (FAA said it was) so we're not to blame?
 
axio
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 10:59 am

For the folks who are asking whether X happened, the preliminary report is available here: http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+%2C(ET-AVJ).pdf
It includes a number of FDR parameters and a timeline.

In response to a recent post, the report does not mention the auto-throttle state, indicating only that "From this point [take-off] for most of the flight,the N1 Reference remained about 94% and the throttles did not move" (section 1 para 4).

It also states (section 2):
- After the autopilot disengaged, the DFDR recorded an automatic aircraft nose down (AND) trim command four times without pilot’s input. As a result, three motions of the stabilizer trim were recorded. The FDR data also indicated that the crew utilized the electric manual trim to counter the automatic AND input.
- The crew performed runaway stabilizer checklist and put the stab trim cutout switch to cutout position and confirmed that the manual trim operation was not working
Time for a new viewing deck at AKL!
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 11:19 am

AirlineCritic wrote:
morrisond wrote:
I suspect Crew training standards were improving for quite some time on that graph along with more reliable safe designs. Crew training standards just seem to have taken a nosedive in the last 20 years.


Heh.

Based on evidence, it seems to me that the crew training nosedived right around the introduction of MAX. Or perhaps at the time when lots of posters (or one poster making lots of posts) needed to explain away in the best light for their favourite manufacturer. Or place of employment. Or the CEO who felt there was no technical mistake or process mistake and nothing was done wrong.

To be clear, I think the crew does share part of the blame here. But equally, and given the expectation of a professional, safe, design that we have come to know Boeing can do:
Boeing failed miserably here. They failed to understand the multiple error situation crews would be experiencing. They did not appreciate the danger of a repetitive system running on unchecked inputs. They failed to understand what throwing many serious things at the crew at the most critical phase of flight would mean. Boeing failed to grasp the meaning of and tell the crews about the limitations of the manual backups. They failed to document any of this. Their published procedures are still unclear and in need of revision, for instance about the order of trim corrections and cutout.

So, I think safe aircraft design has nosedived in the last few years, badly. I know it will be fixed. Perhaps already has. But admitting the nosedive in the design failures would be a good start.


I have never not said there were serious problems in design. It's just whether or not they rise to the level of criminality or violated the regs (which if they didn't the regs should be changed as they are not robust enough).

On training - please see when 150 -200 Hour Wonder button pushers were let into the cockpit of Modern Airliners. It was well before the MAX.

On the Limitations on the manual backups - someone else posted it's in the MAX training manuals including the procedure that you may need to unload the control surfaces to get them to work in certain situations and that excessive speed is bad. Which is the same as it would be on an Airbus.

People keep attacking me for posting so much - it's because people keep asserting things that have already been discussed 10x and shown not to be true or there is serious doubt about their validity.

It would be nice to have a summary at the beginning so this doesn't keep happening. However the odds of everyone agreeing on it would be very low.
Last edited by morrisond on Fri May 03, 2019 11:31 am, edited 2 times in total.
 
axio
Posts: 258
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 11:22 am

Something that puzzles me in the preliminary report is:
"At 05:43:11, about 32 seconds before the end of the recording, at approximately 13,4002ft, two momentary manual electric trim inputs are recorded in the ANU (aircraft nose up) direction. The stabilizer moved in the ANU direction from 2.1 units to 2.3 units."
If I understand correctly, if the stab trim is cutout, then the electric trim is disconnected ("If either switch is positioned to CUTOUT, both the autopilot and main electric trim inputs are disconnected from the stabilizer trim motor."). Does that mean that the stab trim was no longer cutout, or is manual electric trim different to main electric trim?

Also interesting is "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-Office replied that it is not working.". They had confirmed stab trim cutout one minute earlier, so does this mean the Captain had forgotten (understandable in the situation, and possibly a double-check)? Or is this manual-electric as opposed to manual-manual (i.e. getting the handle out and manipulating the wheel)?
Time for a new viewing deck at AKL!
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 11:31 am

axio wrote:
For the folks who are asking whether X happened, the preliminary report is available here: http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+%2C(ET-AVJ).pdf
It includes a number of FDR parameters and a timeline.

In response to a recent post, the report does not mention the auto-throttle state, indicating only that "From this point [take-off] for most of the flight,the N1 Reference remained about 94% and the throttles did not move" (section 1 para 4).

It also states (section 2):
- After the autopilot disengaged, the DFDR recorded an automatic aircraft nose down (AND) trim command four times without pilot’s input. As a result, three motions of the stabilizer trim were recorded. The FDR data also indicated that the crew utilized the electric manual trim to counter the automatic AND input.
- The crew performed runaway stabilizer checklist and put the stab trim cutout switch to cutout position and confirmed that the manual trim operation was not working


It's debatable whether or not they tried the actual manual trim wheels and didn't just try to Manually operate the the electric trim. There are pages on it in the previous thread.
 
FluidFlow
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 11:38 am

morrisond wrote:
On the Limitations on the manual backups - someone else posted it's in the MAX training manuals including the procedure that you may need to unload the control surfaces to get them to work in certain situations and that excessive speed is bad. Which is the same as it would be on an Airbus.


The FBW has an High-speed protection, which pitches the aircraft up if it reaches a certain threshold velocity. So even if Alpha-protection pitches the aircraft down, high-speed protection would pitch it up again. As they would counteract I suggest the aircraft would change to alternate law and both protections would be disabled and replaced by the stability laws. That would result in pilot regaining command over the pitch.

http://www.airbusdriver.net/airbus_fltlaws.htm

Therefore it is not possible (by design) to get a similar situation as on the MAX. The Airbus FBW system could only fly the aircraft within the speed limits into ground, or switch to direct law (EDIT: or alternate law) and then get stalled by confused pilots (AF447).
 
frmrCapCadet
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 12:21 pm

I am suspecting Boeing and the two airlines will be offering survivors of those who died a very generous settlements, using a formula for who is entitled to what, as well as vigorous defense with those not accepting. Boeing will likewise be offering airlines compensation -particularly if they stay loyal to Boeing. This all will be a complicated and slow moving legal dance. Boeing is wise to turn this over to a legal czar. I would expect the recently appointed attorney to be picking referees, as he is a Boeing person.

CEO and key MAX figures really need to apologize and resign, and probably key figures in the two airlines. Anyone know what the legal status of the FAA is likely to be? And I wonder to what extent government officials of the three countries involved will need to step in. This is somewhat of an unprecedented situation.
Buffet: the airline business...has eaten up capital...like..no other (business)
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 1:15 pm

frmrCapCadet wrote:
I am suspecting Boeing and the two airlines will be offering survivors of those who died a very generous settlements, using a formula for who is entitled to what, as well as vigorous defense with those not accepting. Boeing will likewise be offering airlines compensation -particularly if they stay loyal to Boeing. This all will be a complicated and slow moving legal dance. Boeing is wise to turn this over to a legal czar. I would expect the recently appointed attorney to be picking referees, as he is a Boeing person.

CEO and key MAX figures really need to apologize and resign, and probably key figures in the two airlines. Anyone know what the legal status of the FAA is likely to be? And I wonder to what extent government officials of the three countries involved will need to step in. This is somewhat of an unprecedented situation.

I'm afraid we've been here before and got the T-shirt. It will be de ja vu for many.

Favours will be called in.
Palms will be greased.
Deals will be done.
Litigations will be settled out of court.
NDAs will be issued.
The dead will be pilloried.
Campaigns will be bankrolled.
MAX will be back in service and no one will care.

There will be some hold-outs but they will be relegated to flat-earthers and conspiracy theorist realms. Swamp gas may even get a mention.

40 or 50 years hence, some TV conglomerate will do an EPIC on 100 years of the 737 and will all come out. Those organisations responsible will profess their profound regrets for something that happened a long, long time ago in a galaxy far, far away but things are much better now, in this brave new world, and they are concentrating their attention on getting the anti-grav. reactor in the 737 frame (just minor linearity problem in the extremes of quantum gravity field envelope) to save the world from global warming.

Ray
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 1:17 pm

FluidFlow wrote:
morrisond wrote:
On the Limitations on the manual backups - someone else posted it's in the MAX training manuals including the procedure that you may need to unload the control surfaces to get them to work in certain situations and that excessive speed is bad. Which is the same as it would be on an Airbus.


The FBW has an High-speed protection, which pitches the aircraft up if it reaches a certain threshold velocity. So even if Alpha-protection pitches the aircraft down, high-speed protection would pitch it up again. As they would counteract I suggest the aircraft would change to alternate law and both protections would be disabled and replaced by the stability laws. That would result in pilot regaining command over the pitch.

http://www.airbusdriver.net/airbus_fltlaws.htm

Therefore it is not possible (by design) to get a similar situation as on the MAX. The Airbus FBW system could only fly the aircraft within the speed limits into ground, or switch to direct law (EDIT: or alternate law) and then get stalled by confused pilots (AF447).


I am not trying to be argumentative - just trying to understand. See this for what I am referring too https://avherald.com/h?article=47d74074

On LH 1829 the Alpha Protection kicked in and the flight lost 4,000' of Altitude. They don't don't mention the High Speed Protection kicking in - is that because the probes were blocked and the computers confused?

It sounds like the Pilot only got control of the plane by disconnecting the second ADIRU. Until then they had no elevator authority (I'm assuming because of the full nose down excess thrust and speed over the control surfaces). It doesn't sound like the plane saved itself with High speed protection.

It also appears that the thrust was pulled way back as the Mach number comes back in the dive.

If this had happened a few thousand feet over ADD airport what would the result have been? How long would it have taken them to recover if they hadn't pulled the thrust back (assuming I'm reading the traces right and they pulled it back)?
 
WIederling
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 1:23 pm

OldAeroGuy wrote:
With continuous stick shaker, all the MAX crews elected to continue their missions with continuous stick shaker.

Both crews initiated a return, didn't they. Only they never made it. entangled by a bad product :-)
Murphy is an optimist
 
FluidFlow
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 1:54 pm

morrisond wrote:
FluidFlow wrote:
morrisond wrote:
On the Limitations on the manual backups - someone else posted it's in the MAX training manuals including the procedure that you may need to unload the control surfaces to get them to work in certain situations and that excessive speed is bad. Which is the same as it would be on an Airbus.


The FBW has an High-speed protection, which pitches the aircraft up if it reaches a certain threshold velocity. So even if Alpha-protection pitches the aircraft down, high-speed protection would pitch it up again. As they would counteract I suggest the aircraft would change to alternate law and both protections would be disabled and replaced by the stability laws. That would result in pilot regaining command over the pitch.

http://www.airbusdriver.net/airbus_fltlaws.htm

Therefore it is not possible (by design) to get a similar situation as on the MAX. The Airbus FBW system could only fly the aircraft within the speed limits into ground, or switch to direct law (EDIT: or alternate law) and then get stalled by confused pilots (AF447).


I am not trying to be argumentative - just trying to understand. See this for what I am referring too https://avherald.com/h?article=47d74074

On LH 1829 the Alpha Protection kicked in and the flight lost 4,000' of Altitude. They don't don't mention the High Speed Protection kicking in - is that because the probes were blocked and the computers confused?


I assume they never reached speeds that would have triggered High-speed protection, that is why it was also not mentioned, it was not noteworthy. The additional mention of:

When Alpha Prot is activated due to blocked AOA probes, the flight control laws order a continuous nose down pitch rate that, in a worst case scenario, cannot be stopped with backward sidestick inputs, even in the full backward position. If the Mach number increases during a nose down order, the AOA value of the Alpha Prot will continue to decrease. As a result, the flight control laws will continue to order a nose down pitch rate, even if the speed is above minimum selectable speed, known as VLS.

Does not state what happens if you reach Over-speed but in general the pilots will avoid over-speed and therefore the "fight of the computer" should normally never happen. But if the gravitational acceleration exceeds the drag then the aircraft will speed up no matter how much the thrust is reduced.

It sounds like the Pilot only got control of the plane by disconnecting the second ADIRU. Until then they had no elevator authority (I'm assuming because of the full nose down excess thrust and speed over the control surfaces). It doesn't sound like the plane saved itself with High speed protection.


The first part updated at: Dec 28th 2014 22:22Z seems to be not correct as the events in the second part published at: Mar 24th 2015 20:43Z state:

The aircraft however continued to pitch down, inputs to counter the pitch down remained without effect. About 45 seconds after the nose down began the first officer alerted the captain who took control of the aircraft, that at this time had reached a rate of descent of 4000 feet per minute and a pitch of -3.5 degrees. The captain provided a maximum nose up input which caused the aircraft to pitch up again and the rate of descent decreased and the aircraft entered level flight.

The captain was able to maintain altitude by providing a continuous nose up input deflecting the side stick about 50% of its travel. The autopilot could not be engaged again, and a manual nose up trim was not possible.


Which leads to the conclusion that the aircraft was controllable but the FO did not provide maximum side stick input and the captain did, what brought the aircraft back to level flight.

Disconnecting the ADIRU just made managing the aircraft easier as no more input was needed for level flight.

It also appears that the thrust was pulled way back as the Mach number comes back in the dive.


Probably, that is why no over speed occurred.



If this had happened a few thousand feet over ADD airport what would the result have been? How long would it have taken them to recover if they hadn't pulled the thrust back (assuming I'm reading the traces right and they pulled it back)?


That is really hypothetical because we do not know if normal law is disengaged if alpha protection and high speed protection is triggered the same time. But as full side stick input was able to control the aircraft there would have been no crash as I imagine if they were closer to the ground the FO would have given full input aswell and the aircraft would have lost less than 4000ft.
 
OldAeroGuy
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 2:04 pm

[threeid][/threeid]
WIederling wrote:
OldAeroGuy wrote:
With continuous stick shaker, all the MAX crews elected to continue their missions with continuous stick shaker.

Both crews initiated a return, didn't they. Only they never made it. entangled by a bad product :-)


Unfortunately, if you abuse any product, it can turn out badly.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
ArgentoSystems
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 2:07 pm

Boeing’s Own Test Pilots Lacked Key Details of 737 MAX Flight-Control System


https://www.wsj.com/articles/boeings-ow ... 1556877600
 
art
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 2:32 pm

ArgentoSystems wrote:
Boeing’s Own Test Pilots Lacked Key Details of 737 MAX Flight-Control System


https://www.wsj.com/articles/boeings-ow ... 1556877600


The start of the article says:

Boeing Co. limited the role of its own pilots in the final stages of developing the 737 MAX flight-control system implicated in two fatal crashes, departing from a longstanding practice of seeking their detailed input, people familiar with the matter said.

As a result, Boeing test pilots and senior pilots involved in the MAX’s development didn’t receive detailed briefings about how fast or steeply the automated system known as MCAS could push down a plane’s nose, these people said.


I thought it was the test pilots who recommended 2;5 degree pitch down per MCAS iteration ather than the original 0.6 degree (as reported). How could that be the case if they were not briefed on it? To me something does not stack up here.
 
ArgentoSystems
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 2:38 pm

art wrote:
I thought it was the test pilots who recommended 2;5 degree pitch down per MCAS iteration ather than the original 0.6 degree (as reported). How could that be the case if they were not briefed on it? To me something does not stack up here.

Yep, lot's of contradictory info floats around. Stall prevention-not stall prevention, now this...

Interesting comments under the article. One claims that Boeing was under pressure to make its s/w team more 'diverse', even at cost of losing some experience. Not sure if that is true, but I can say with certainty that MCAS was written not by a brightest bunch.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 2:46 pm

FluidFlow wrote:
morrisond wrote:
FluidFlow wrote:

The FBW has an High-speed protection, which pitches the aircraft up if it reaches a certain threshold velocity. So even if Alpha-protection pitches the aircraft down, high-speed protection would pitch it up again. As they would counteract I suggest the aircraft would change to alternate law and both protections would be disabled and replaced by the stability laws. That would result in pilot regaining command over the pitch.

http://www.airbusdriver.net/airbus_fltlaws.htm

Therefore it is not possible (by design) to get a similar situation as on the MAX. The Airbus FBW system could only fly the aircraft within the speed limits into ground, or switch to direct law (EDIT: or alternate law) and then get stalled by confused pilots (AF447).


I am not trying to be argumentative - just trying to understand. See this for what I am referring too https://avherald.com/h?article=47d74074

On LH 1829 the Alpha Protection kicked in and the flight lost 4,000' of Altitude. They don't don't mention the High Speed Protection kicking in - is that because the probes were blocked and the computers confused?


I assume they never reached speeds that would have triggered High-speed protection, that is why it was also not mentioned, it was not noteworthy. The additional mention of:

When Alpha Prot is activated due to blocked AOA probes, the flight control laws order a continuous nose down pitch rate that, in a worst case scenario, cannot be stopped with backward sidestick inputs, even in the full backward position. If the Mach number increases during a nose down order, the AOA value of the Alpha Prot will continue to decrease. As a result, the flight control laws will continue to order a nose down pitch rate, even if the speed is above minimum selectable speed, known as VLS.

Does not state what happens if you reach Over-speed but in general the pilots will avoid over-speed and therefore the "fight of the computer" should normally never happen. But if the gravitational acceleration exceeds the drag then the aircraft will speed up no matter how much the thrust is reduced.

It sounds like the Pilot only got control of the plane by disconnecting the second ADIRU. Until then they had no elevator authority (I'm assuming because of the full nose down excess thrust and speed over the control surfaces). It doesn't sound like the plane saved itself with High speed protection.


The first part updated at: Dec 28th 2014 22:22Z seems to be not correct as the events in the second part published at: Mar 24th 2015 20:43Z state:

The aircraft however continued to pitch down, inputs to counter the pitch down remained without effect. About 45 seconds after the nose down began the first officer alerted the captain who took control of the aircraft, that at this time had reached a rate of descent of 4000 feet per minute and a pitch of -3.5 degrees. The captain provided a maximum nose up input which caused the aircraft to pitch up again and the rate of descent decreased and the aircraft entered level flight.

The captain was able to maintain altitude by providing a continuous nose up input deflecting the side stick about 50% of its travel. The autopilot could not be engaged again, and a manual nose up trim was not possible.


Which leads to the conclusion that the aircraft was controllable but the FO did not provide maximum side stick input and the captain did, what brought the aircraft back to level flight.

Disconnecting the ADIRU just made managing the aircraft easier as no more input was needed for level flight.

It also appears that the thrust was pulled way back as the Mach number comes back in the dive.


Probably, that is why no over speed occurred.



If this had happened a few thousand feet over ADD airport what would the result have been? How long would it have taken them to recover if they hadn't pulled the thrust back (assuming I'm reading the traces right and they pulled it back)?


That is really hypothetical because we do not know if normal law is disengaged if alpha protection and high speed protection is triggered the same time. But as full side stick input was able to control the aircraft there would have been no crash as I imagine if they were closer to the ground the FO would have given full input aswell and the aircraft would have lost less than 4000ft.



The write up is pretty fuzzy - but I take it they either got control back by disengaging the computer - which took 45 seconds to a minute or the Captain pulled the thrust back and regained elevator authority and electric trim Authority which they did not have either. However how would the electric trim authority come back unless it was because the computers were turned off which took some time to figure out? Just pulling back on the stick should not have restored there function or could it?

When MCAS kicked on ET302 they were 1,000' AGL at about 8,500' Elevation. MCAS only did a partial nose down trim and they still had electric trim to counteract.

Somehow I doubt that LH1829 would have made it if the two AOA sensors had frozen at 1,000' and Alpha Protection had kicked in and provided full nose down input - they would not have had no time to react (unless the 320 has some sort of terrain avoidance system).

However if they were a super crew and managed to pull back throttle or disconnect the computers in that time (what 10-15 seconds) they could have made it - however if it was the ET302 crew which seemed to have an aversion to touching the thrust levers somehow I don't think the outcome would have been the same.

The FBW (relying on Faulty sensors - sound familiar?) would not have saved them and actually probably resulted in an earlier crash as the full nose down input and no Elevator or Electric Trim Authority would have been harder to counteract in the time available - 10-15 seconds.

At Initial MCAS activation ET still had some Elevator authority and Electric Trim still worked.
 
FluidFlow
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 3:07 pm

morrisond wrote:
The write up is pretty fuzzy - but I take it they either got control back by disengaging the computer - which took 45 seconds to a minute or the Captain pulled the thrust back and regained elevator authority and electric trim Authority which they did not have either. However how would the electric trim authority come back unless it was because the computers were turned off which took some time to figure out? Just pulling back on the stick should not have restored there function or could it?


The second version is from the official release of the BFU, so actually the captain gained control by pulling back on the side stick. The FO did not enough. The first part is not official just a prelim report by the BEA and therefore obsolete after the BFU report. So they always had authority.

Mach number increases strong when Pitch decreases as you can see in the graphs so the trust was not reduced or not enough, but the aircraft was not over-speeding and therefore control was possible. And even in Alpha-prot mode you can pull back and lift the nose as there is a margin between the set angle by the software and the maximal angle possible.

morrisond wrote:
When MCAS kicked on ET302 they were 1,000' AGL at about 8,500' Elevation. MCAS only did a partial nose down trim and they still had electric trim to counteract.

Somehow I doubt that LH1829 would have made it if the two AOA sensors had frozen at 1,000' and Alpha Protection had kicked in and provided full nose down input - they would not have had no time to react (unless the 320 has some sort of terrain avoidance system).


If the sensors froze at 1'000ft AGL nothing would have happened as alpha prot takes speed into account aswell. It took 11'000ft before alpha protection kicked in on the A321:

The BFU reported that according to flight data and cockpit voice recorder the first officer (35, ATPL, 6,473 hours total, 5,179 hours on type) was pilot flying, the captain (52, ATPL, 16,384 hours total, 12,414 hours on type) pilot monitoring. After the aircraft climbed clear of top of clouds at about FL200 the flight data recorder recorded a fixed value of +4.2 degrees for the left hand AoA sensor, less than a minute later the FDR began to record a fixed value of +4.6 degrees for the right hand AoA sensor.

the first officer observed an irregularity in the properties of the speed indication just prior to reaching FL310 and disengaged the autopilot, the aircraft in response began a descent that lasted for about one minute before the crew was able to stop the descent at FL270.

So it would not have caused a crash comparable to ET302 and probably not one at all if the sensors would have frozen at 1'000ft AGL.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 3:29 pm

FluidFlow wrote:
morrisond wrote:
The write up is pretty fuzzy - but I take it they either got control back by disengaging the computer - which took 45 seconds to a minute or the Captain pulled the thrust back and regained elevator authority and electric trim Authority which they did not have either. However how would the electric trim authority come back unless it was because the computers were turned off which took some time to figure out? Just pulling back on the stick should not have restored there function or could it?


The second version is from the official release of the BFU, so actually the captain gained control by pulling back on the side stick. The FO did not enough. The first part is not official just a prelim report by the BEA and therefore obsolete after the BFU report. So they always had authority.

Mach number increases strong when Pitch decreases as you can see in the graphs so the trust was not reduced or not enough, but the aircraft was not over-speeding and therefore control was possible. And even in Alpha-prot mode you can pull back and lift the nose as there is a margin between the set angle by the software and the maximal angle possible.

morrisond wrote:
When MCAS kicked on ET302 they were 1,000' AGL at about 8,500' Elevation. MCAS only did a partial nose down trim and they still had electric trim to counteract.

Somehow I doubt that LH1829 would have made it if the two AOA sensors had frozen at 1,000' and Alpha Protection had kicked in and provided full nose down input - they would not have had no time to react (unless the 320 has some sort of terrain avoidance system).


If the sensors froze at 1'000ft AGL nothing would have happened as alpha prot takes speed into account aswell. It took 11'000ft before alpha protection kicked in on the A321:

The BFU reported that according to flight data and cockpit voice recorder the first officer (35, ATPL, 6,473 hours total, 5,179 hours on type) was pilot flying, the captain (52, ATPL, 16,384 hours total, 12,414 hours on type) pilot monitoring. After the aircraft climbed clear of top of clouds at about FL200 the flight data recorder recorded a fixed value of +4.2 degrees for the left hand AoA sensor, less than a minute later the FDR began to record a fixed value of +4.6 degrees for the right hand AoA sensor.

the first officer observed an irregularity in the properties of the speed indication just prior to reaching FL310 and disengaged the autopilot, the aircraft in response began a descent that lasted for about one minute before the crew was able to stop the descent at FL270.

So it would not have caused a crash comparable to ET302 and probably not one at all if the sensors would have frozen at 1'000ft AGL.



Alpha protection doesn't work at lower speed? That doesn't seem to make a lot of sense for a stall prevention system. What are it's limits? I'm looking and can't find them.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 3:33 pm

zeke wrote:
FluidFlow

Stop feeding morrisond, I told him earlier on the thread he was wrong, provided the same reference that showed the crew were able to control the aircraft with elevator input.

They are trolling, this has nothing to do with MCAS, stop feeding their off topic lies and rants please.


Zeke - I'm not trolling - I'm trying to understand and you never answered my reply before - he brought it up not me. I'm trying to understand how an A321 FBW system would save the plane with two frozen AOA sensors at 1,000 AGL.

Why wouldn't Alpha protection kick in at 1'000 AGL - what are the limits? I know they changed things after the A320 demo Crash - but what did they change?
 
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Aesma
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 3:38 pm

morrisond wrote:
PixelFlight wrote:
morrisond wrote:

Yes - but it was an Airbus 330 with a FBW system where it tried to put the plane in the ground.

ADIRU fault generating unbelievable, still unexplained, repetitive spike data without triggering any integrity test + FC algorithm design error that was never catch before because nobody was able to think that a such repetitive spike data could be possible in reality. The algorithm was corrected. This ADIRU was analyzed but never sent such repetitive spike data anymore, nobody known why. Safety assessment was evaluated and found ok.


Yes a systems problem put the A330 into a dive and the crew was able to save it - Good crew.


Thank you for having mentioned this incident, it's true that I wasn't thinking about it.

It still proves that overall the Airbus system was much easier to recover.

In that case there was a failure to recognize one ADIRU was faulty, consequently the aircraft didn't change to alternate law.

From what I'm reading on the fault, if the pilots hadn't done anything, once pitched down, the aircraft itself would have recovered, as now two ADIRUs are seeing a low AoA, and one a high AoA. But that's just a theory.
New Technology is the name we give to stuff that doesn't work yet. Douglas Adams
 
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zeke
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Fri May 03, 2019 3:40 pm

This has nothing to do with the 737 max grounding, by definition that is trolling.
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