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keesje
Topic Author
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Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 5:50 pm

By Bjorn Fehrm

November 14, 2018, © Leeham News.: The automatic trim Boeing introduced on the 737 MAX, called MCAS, was news to us last week. Graver, it was news to the Pilots flying the MAX since 18 months as well.

Boeing and its oversight, the FAA, decided the Airlines and their Pilots had no need to know. The Lion Air accident can prove otherwise.


https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/#comment-242199
"Never mistake motion for action." Ernest Hemingway
 
Sooner787
Posts: 2567
Joined: Thu Jul 18, 2013 1:44 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 6:13 pm

I know there are some MAX customers that have yet to take delivery of their new jets ,
Alaska for instance..... Might AS decide to cancel their MAX orders , especially since they
now have A321NEOS on property. I would also guess Lion Air might be reconsidering
their Max order book as well.
 
BoeingGuy
Posts: 6314
Joined: Fri Dec 10, 2010 6:01 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 6:23 pm

Sooner787 wrote:
I know there are some MAX customers that have yet to take delivery of their new jets ,
Alaska for instance..... Might AS decide to cancel their MAX orders , especially since they
now have A321NEOS on property. I would also guess Lion Air might be reconsidering
their Max order book as well.


Isn’t that a little overly dramatic and childish? Airplane accidents have unfortunately occurred since the beginning of time. What, do you think every airline has cancelled orders for every model that’s had an accident? So I guess all A330 orders should be cancelled too?
Last edited by BoeingGuy on Wed Nov 14, 2018 6:33 pm, edited 1 time in total.
 
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Finn350
Posts: 1578
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 6:26 pm

Sooner787 wrote:
I know there are some MAX customers that have yet to take delivery of their new jets ,
Alaska for instance..... Might AS decide to cancel their MAX orders , especially since they
now have A321NEOS on property. I would also guess Lion Air might be reconsidering
their Max order book as well.


Not likely that there are any contractual clauses to justify deferrals or cancellations on 737 MAX orders based on this defect.
 
BoeingGuy
Posts: 6314
Joined: Fri Dec 10, 2010 6:01 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 6:34 pm

Finn350 wrote:
Sooner787 wrote:
I know there are some MAX customers that have yet to take delivery of their new jets ,
Alaska for instance..... Might AS decide to cancel their MAX orders , especially since they
now have A321NEOS on property. I would also guess Lion Air might be reconsidering
their Max order book as well.


Not likely that there are any contractual clauses to justify deferrals or cancellations on 737 MAX orders based on thuis defect.


Let’s be very clear. The defect was the AOA probe, not the airplane design.
 
LDRA
Posts: 281
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 6:34 pm

Finn350 wrote:
Sooner787 wrote:
I know there are some MAX customers that have yet to take delivery of their new jets ,
Alaska for instance..... Might AS decide to cancel their MAX orders , especially since they
now have A321NEOS on property. I would also guess Lion Air might be reconsidering
their Max order book as well.


Not likely that there are any contractual clauses to justify deferrals or cancellations on 737 MAX orders based on this defect.


Can be indirect. For example, one of the cert bodies does something to 737Max type certificate
 
kalvado
Posts: 2015
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 6:44 pm

BoeingGuy wrote:
Finn350 wrote:
Sooner787 wrote:
I know there are some MAX customers that have yet to take delivery of their new jets ,
Alaska for instance..... Might AS decide to cancel their MAX orders , especially since they
now have A321NEOS on property. I would also guess Lion Air might be reconsidering
their Max order book as well.


Not likely that there are any contractual clauses to justify deferrals or cancellations on 737 MAX orders based on thuis defect.


Let’s be very clear. The defect was the AOA probe, not the airplane design.

Airplane design included undisclosed features making a single point of failure undiagnosable and possibly unrecoverable by the crew due to lack of information. Moreover, single system failure brings airplane into non-certifiable condition as stability, required by FAR, is not there.
This is a design and certification issue. And while I cannot imagine what happens to Boeing once MAX certificate is suspended, I can clearly see that at least brought up by the FAA.
 
ScottB
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 7:02 pm

LDRA wrote:
Can be indirect. For example, one of the cert bodies does something to 737Max type certificate


Drama much? IMO, worst case is that Boeing is forced to issue a software update which disables the new safety feature completely or when there's a malfunction of one of the AOA sensors (or a disagreement is detected). Or the resolution may be what the emergency AD was intended to accomplish -- informing all pilots of how to respond to a potentially unsafe condition caused by an AOA sensor malfunction.

Otherwise we would have seen the A330 TC suspended as a result of AF 447 given that the BEA pointed to the Human Computer Interface of the A330 being a potential contributing factor to the loss of that aircraft.
 
LDRA
Posts: 281
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 7:05 pm

ScottB wrote:
LDRA wrote:
Can be indirect. For example, one of the cert bodies does something to 737Max type certificate


Drama much? IMO, worst case is that Boeing is forced to issue a software update which disables the new safety feature completely or when there's a malfunction of one of the AOA sensors (or a disagreement is detected). Or the resolution may be what the emergency AD was intended to accomplish -- informing all pilots of how to respond to a potentially unsafe condition caused by an AOA sensor malfunction.

Otherwise we would have seen the A330 TC suspended as a result of AF 447 given that the BEA pointed to the Human Computer Interface of the A330 being a potential contributing factor to the loss of that aircraft.


When you withheld critical and required information, the question is not technology, it is process and trust. E.g. What else did you withheld?
 
LDRA
Posts: 281
Joined: Fri Jan 15, 2016 3:01 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 7:09 pm

And yes, there are definitely known technology issues, which software fix may or may not satisfy cert bodies.
 
kalvado
Posts: 2015
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 7:16 pm

ScottB wrote:
LDRA wrote:
Can be indirect. For example, one of the cert bodies does something to 737Max type certificate


Drama much? IMO, worst case is that Boeing is forced to issue a software update which disables the new safety feature completely or when there's a malfunction of one of the AOA sensors (or a disagreement is detected). Or the resolution may be what the emergency AD was intended to accomplish -- informing all pilots of how to respond to a potentially unsafe condition caused by an AOA sensor malfunction.

Otherwise we would have seen the A330 TC suspended as a result of AF 447 given that the BEA pointed to the Human Computer Interface of the A330 being a potential contributing factor to the loss of that aircraft.

Disabling the feature possibly makes plane non-certifiable, and definitely pilot training has to be significantly changed for different handling. Bye-bye common type rating.
Biggest issue here is that mandated parameters were achieved via a poorly designed code. Software redesign may be more involved than it looks. Possibly back to recertification, worst comes to worst. Bye-bye cash cow...
 
PSAatSAN4Ever
Posts: 848
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 7:38 pm

Once again, I will point out that we have been through this before: December 27, 1991, SK 751. Despite following all procedures correctly, the flight crew discovered that every time they reduced engine power, something was reversing their actions and turned the thrust up. Every time they reduced, the thrust returned higher, until it burned up the engines and left the plane a glider. Fortunately in that incident, everyone survived. The cause of the engine surges? A piece of software McDonnell Douglas installed to prevent stalling that they didn't tell SAS about. The pilot of that flight never flew again, not being able to trust an airplane ever again.

What we have with Lion Air is the same thing: Boeing adjusted but didn't inform the airlines nor the pilots. This one, sadly, ended with a great loss of life.

I hope that this incident will ensure that NO pilot will ever find him/herself in a situation where they are fighting the plane. There is absolutely no reason to not inform flight crews about changes in operational systems that ended as this one did.
 
kalvado
Posts: 2015
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 7:47 pm

Dantepel wrote:
Sometimes posters on the site remind me of my kids. They post what they hope will happen as what the think will happen.

Thing is, this seems to be a more fundamental issue than most of situations brought up in these threads. Boeing altered some fundamental properties of the frame, so software patch may be a bit less than situation calls for. It is to be seen how involved things would be. It is no longer about the single crash or control in some marginal conditions - possibly this is about basic design assumptions.
 
bgm
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Joined: Fri Sep 11, 2009 9:37 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 7:50 pm

BoeingGuy wrote:
Finn350 wrote:
Sooner787 wrote:
I know there are some MAX customers that have yet to take delivery of their new jets ,
Alaska for instance..... Might AS decide to cancel their MAX orders , especially since they
now have A321NEOS on property. I would also guess Lion Air might be reconsidering
their Max order book as well.


Not likely that there are any contractual clauses to justify deferrals or cancellations on 737 MAX orders based on thuis defect.


Let’s be very clear. The defect was the AOA probe, not the airplane design.


Let’s be even more clear: 189 people died because of that fault. The AoA probe is part of the 737 design, whether you like it or not.
████ ███ █ ███████ ██ █ █████ ██ ████ [redacted]
 
fadecfault
Posts: 164
Joined: Mon Nov 05, 2007 8:44 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 7:51 pm

I've reposted this a few times but here it is again
Here is the procedure for Runaway trim from my companies MAX QRH. The revision Date is July 2017.

1 Control column. . . . . . . . . . . . . . . . . Hold firmly
2 Autopilot (if engaged) . . . . . . . . . . . . .Disengage
Do not re-engage the autopilot.
Control aircraft pitch attitude manually with
control column and main electric trim as
needed.
3 Autothrottle (if engaged). . . . . . . . . . .Disengage
Do not re-engage the autothrottle.
4 If the runaway stops after the autopilot is
disengaged.
■ ■ ■ ■
5 If the runaway continues after the autopilot is
disengaged:
STAB TRIM CUTOUT
switches (both) . . . . . . . . . . . . . . . . CUTOUT
If the runaway continues:
Stabilizer
trim wheel . . . . . . . . . . Grasp and hold
6 Stabilizer . . . . . . . . . . . . . . . . . . . Trim manually
7 Anticipate trim requirements.
- - - - - - - - - - - - - -

That procedure WILL stop MCAS or any trim from operating the trim motor. MCAS is also described in my MAX maintenance training manuals.
The views and opinions written here are my own and do not reflect those of my employer.
 
kevin5345179
Posts: 97
Joined: Sat Feb 10, 2018 4:08 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 7:52 pm

the only thing that's certain is if this happen to AA, WN, or UA, we'll certainly see bigger move from FAA
 
User avatar
Finn350
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 7:53 pm

BoeingGuy wrote:
Finn350 wrote:
Sooner787 wrote:
I know there are some MAX customers that have yet to take delivery of their new jets ,
Alaska for instance..... Might AS decide to cancel their MAX orders , especially since they
now have A321NEOS on property. I would also guess Lion Air might be reconsidering
their Max order book as well.


Not likely that there are any contractual clauses to justify deferrals or cancellations on 737 MAX orders based on thuis defect.


Let’s be very clear. The defect was the AOA probe, not the airplane design.


As you must be a reasonable man, I am sure you understand it is not just the AOA probe. The defect is the trim stabilizer system design in certain malfunctions.
 
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seahawk
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:00 pm

It is all speculation until we have all facts. It would be strange if only the failure of MCAS caused the crash, as pilots should be able to handle it, but we must consider the possibility of multiple sensor or system failures and then things might get complicated.
 
LDRA
Posts: 281
Joined: Fri Jan 15, 2016 3:01 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:04 pm

seahawk wrote:
It is all speculation until we have all facts. It would be strange if only the failure of MCAS caused the crash, as pilots should be able to handle it, but we must consider the possibility of multiple sensor or system failures and then things might get complicated.


The criteria as to whether runaway trim procedure is considered enough to mitigate hazard depend on how much pitch control authority MCAS has under "false activate" failure condition
 
boerje
Posts: 35
Joined: Tue Jan 09, 2018 9:16 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:15 pm

PSAatSAN4Ever wrote:
Once again, I will point out that we have been through this before: December 27, 1991, SK 751. Despite following all procedures correctly, the flight crew discovered that every time they reduced engine power, something was reversing their actions and turned the thrust up. Every time they reduced, the thrust returned higher, until it burned up the engines and left the plane a glider. Fortunately in that incident, everyone survived. The cause of the engine surges? A piece of software McDonnell Douglas installed to prevent stalling that they didn't tell SAS about. The pilot of that flight never flew again, not being able to trust an airplane ever again.


SAS had been informed about Automatic Thrust Restoration (ATR).

"However, ATR was described in manuals by the aircraft manufacturer which every operator is obliged to know. Even though the system was developed for use in procedures not applied by SAS, a sufficiently careful study of the manuals should have led to SAS noting the system and training its pilots in its function."

https://en.wikipedia.org/wiki/Scandinavian_Airlines_Flight_751
https://www.havkom.se/assets/reports/English/C1993_57e_Gottrora.pdf
Last edited by boerje on Wed Nov 14, 2018 8:18 pm, edited 1 time in total.
 
garf25
Posts: 32
Joined: Sun Sep 18, 2005 8:26 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:15 pm

BoeingGuy wrote:
Finn350 wrote:
Sooner787 wrote:
I know there are some MAX customers that have yet to take delivery of their new jets ,
Alaska for instance..... Might AS decide to cancel their MAX orders , especially since they
now have A321NEOS on property. I would also guess Lion Air might be reconsidering
their Max order book as well.


Not likely that there are any contractual clauses to justify deferrals or cancellations on 737 MAX orders based on thuis defect.


Let’s be very clear. The defect was the AOA probe, not the airplane design.


Boeing guy, it would seem that you may be wrong with your quote.

It seems primary cause of this terrible incident was loss of control of the aircraft. That is why it crashed.
There may be numerous contributory factors, such as potential defective probes and potential lack of knowledge of the auto trim system. There could be many more contributory factors but let's not speculate.

Your name suggests you may be overly biased here. Let's hope for a factual investigation into this terrible event.
Thoughts to all on board and their families!!
 
JayinKitsap
Posts: 1479
Joined: Sat Nov 26, 2005 9:55 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:17 pm

This plane had problems on 4 previous flights, it was serviced at least twice. The previous flight's pilot to a picture of the maintenance request so he had the proof he wrote one, probably angry that the prior service did not fix the problem. There may have been incorrect pitot tube replacements and work on the AOA sensor. This plane may have had 3 different speed readings so the pilots could not tell which two were correct, also the AOA sensor has been reported as the problem. So multiple failures are known to be present, much harder to determine if the controls operated poorly in this situation.

How the software performs with multiple sensor failures was likely not tested, but yes this MCAS control should have been better documented.

The accident happened with Lion Air, an airline that had been banned from flying for a number of years to the EU and has a worrisome safety reputation. Because of this we need to wait until the facts are out before condemning the MAX, it would be different if a Blue Chip airline like BA had this accident.
 
iahcsr
Posts: 4777
Joined: Fri Jun 04, 1999 2:59 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:19 pm

Question; Was/is this software change listed in the Max maintenance manuals that techops use and simply not referenced in flightops manuals? This wasn’t a deliberate attempt to hide the information. Someone(s) at Boeing (And FAA?) just thought it wasn’t worth mentioning. The saying “Hindsight is 20/20” clearly applies here. This event is so eerily similar to the crash of a NZ A320 some years ago. In that case the AOA also failed and software did what it thought was the right thing.
Working Hard, Flying Right Friendly....
 
LDRA
Posts: 281
Joined: Fri Jan 15, 2016 3:01 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:25 pm

iahcsr wrote:
Question; Was/is this software change listed in the Max maintenance manuals that techops use and simply not referenced in flightops manuals? This wasn’t a deliberate attempt to hide the information. Someone(s) at Boeing (And FAA?) just thought it wasn’t worth mentioning. The saying “Hindsight is 20/20” clearly applies here. This event is so eerily similar to the crash of a NZ A320 some years ago. In that case the AOA also failed and software did what it thought was the right thing.


There are two separate but possibly related issues

1. MCAS not documented in flight manual

2. Boeing withheld MCAS failure mode information to FAA
 
smartplane
Posts: 1024
Joined: Fri Aug 03, 2018 9:23 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:29 pm

If changes to an aircraft are so significant, they alter it's 'natural' flying characteristics, which require software to mask same, which is undocumented, surely correction / rectification involves a bit more than changing procedures and writing some new code?
 
User avatar
N14AZ
Posts: 3800
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:41 pm

ScottB wrote:
Otherwise we would have seen the A330 TC suspended as a result of AF 447 given that the BEA pointed to the Human Computer Interface of the A330 being a potential contributing factor to the loss of that aircraft.

??? Where did you read this?

The final words of the AF447-crew pretty much summarize what went wrong:

02:13:40 (Robert) Climb... climb... climb... climb...
02:13:40 (Bonin) But I've had the stick back the whole time!
[At last, Bonin tells the others the crucial fact whose import he has so grievously failed to understand himself.]
02:13:42 (Captain) No, no, no… Don’t climb… no, no.
02:13:43 (Robert) Descend, then… Give me the controls… Give me the controls!

[Bonin yields the controls, and Robert finally puts the nose down. The plane begins to regain speed. But it is still descending at a precipitous angle. As they near 2000 feet, the aircraft's sensors detect the fast-approaching surface and trigger a new alarm. There is no time left to build up speed by pushing the plane's nose forward into a dive.
 
PSAatSAN4Ever
Posts: 848
Joined: Thu Sep 13, 2018 5:38 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:46 pm

boerje wrote:
PSAatSAN4Ever wrote:
Once again, I will point out that we have been through this before: December 27, 1991, SK 751. Despite following all procedures correctly, the flight crew discovered that every time they reduced engine power, something was reversing their actions and turned the thrust up. Every time they reduced, the thrust returned higher, until it burned up the engines and left the plane a glider. Fortunately in that incident, everyone survived. The cause of the engine surges? A piece of software McDonnell Douglas installed to prevent stalling that they didn't tell SAS about. The pilot of that flight never flew again, not being able to trust an airplane ever again.


SAS had been informed about Automatic Thrust Restoration (ATR).

"However, ATR was described in manuals by the aircraft manufacturer which every operator is obliged to know. Even though the system was developed for use in procedures not applied by SAS, a sufficiently careful study of the manuals should have led to SAS noting the system and training its pilots in its function."

https://en.wikipedia.org/wiki/Scandinavian_Airlines_Flight_751
https://www.havkom.se/assets/reports/English/C1993_57e_Gottrora.pdf


Page 72 of the report, point 2.2.3: "At the time of the accident there was no knowledge of ATR (Automatic Thrust Recovery) within SAS. The pilots were therefore not trained on ATR and information was not included in their operational documentation". It further states that if they had been trained, they would have switched settings and recovered. In this case, SAS' training did not include this particular setting, leading to the accident. That to me seems to be what happened in the Lion Air accident, where a change by the manufacturer was not passed on sufficiently to the pilots.
 
dtw2hyd
Posts: 7110
Joined: Wed Jan 09, 2013 12:11 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:47 pm

BoeingGuy wrote:
...
Let’s be very clear. The defect was the AOA probe, not the airplane design.


To be specific it is the software. Physical components are bound to failure. It is the redundancy and software capability which should result in a positive outcome.
 
fadecfault
Posts: 164
Joined: Mon Nov 05, 2007 8:44 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:49 pm

iahcsr wrote:
Question; Was/is this software change listed in the Max maintenance manuals that techops use and simply not referenced in flightops manuals? This wasn’t a deliberate attempt to hide the information. Someone(s) at Boeing (And FAA?) just thought it wasn’t worth mentioning. The saying “Hindsight is 20/20” clearly applies here. This event is so eerily similar to the crash of a NZ A320 some years ago. In that case the AOA also failed and software did what it thought was the right thing.


I do not know the reason why it may not have been in the flight crew training but MCAS is performing a similar function as speed trim. This is not a totally different system. I do not know what pilots were trained but both the NG and MAX QRH calls for stab cutout to be enabled. NOT to pull back the column like Mr.Bjorn Fehrm says.
The views and opinions written here are my own and do not reflect those of my employer.
 
bob75013
Posts: 882
Joined: Tue Jun 23, 2015 5:05 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:57 pm

fadecfault wrote:
I've reposted this a few times but here it is again
Here is the procedure for Runaway trim from my companies MAX QRH. The revision Date is July 2017.

1 Control column. . . . . . . . . . . . . . . . . Hold firmly
2 Autopilot (if engaged) . . . . . . . . . . . . .Disengage
Do not re-engage the autopilot.
Control aircraft pitch attitude manually with
control column and main electric trim as
needed.
3 Autothrottle (if engaged). . . . . . . . . . .Disengage
Do not re-engage the autothrottle.
4 If the runaway stops after the autopilot is
disengaged.
■ ■ ■ ■
5 If the runaway continues after the autopilot is
disengaged:
STAB TRIM CUTOUT
switches (both) . . . . . . . . . . . . . . . . CUTOUT
If the runaway continues:
Stabilizer
trim wheel . . . . . . . . . . Grasp and hold
6 Stabilizer . . . . . . . . . . . . . . . . . . . Trim manually
7 Anticipate trim requirements.
- - - - - - - - - - - - - -

That procedure WILL stop MCAS or any trim from operating the trim motor. MCAS is also described in my MAX maintenance training manuals.



Now now, now -- don't confuse the haters with facts.
 
User avatar
glideslope
Posts: 1553
Joined: Sun May 30, 2004 8:06 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 8:59 pm

Desperately need to find and recover the CVR.
To know your Enemy, you must become your Enemy.” Sun Tzu
 
XT6Wagon
Posts: 2723
Joined: Tue Feb 13, 2007 4:06 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 9:20 pm

N14AZ wrote:
ScottB wrote:
Otherwise we would have seen the A330 TC suspended as a result of AF 447 given that the BEA pointed to the Human Computer Interface of the A330 being a potential contributing factor to the loss of that aircraft.

??? Where did you read this?

The final words of the AF447-crew pretty much summarize what went wrong:

02:13:40 (Robert) Climb... climb... climb... climb...
02:13:40 (Bonin) But I've had the stick back the whole time!
[At last, Bonin tells the others the crucial fact whose import he has so grievously failed to understand himself.]
02:13:42 (Captain) No, no, no… Don’t climb… no, no.
02:13:43 (Robert) Descend, then… Give me the controls… Give me the controls!

[Bonin yields the controls, and Robert finally puts the nose down. The plane begins to regain speed. But it is still descending at a precipitous angle. As they near 2000 feet, the aircraft's sensors detect the fast-approaching surface and trigger a new alarm. There is no time left to build up speed by pushing the plane's nose forward into a dive.


One of the issues is that increasing the airspeed turned ON the stall warning because it cut off below a certain airspeed. So pull back it turns off, push down and the stall warning comes on.
 
boerje
Posts: 35
Joined: Tue Jan 09, 2018 9:16 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 9:34 pm

PSAatSAN4Ever wrote:
boerje wrote:
PSAatSAN4Ever wrote:
Once again, I will point out that we have been through this before: December 27, 1991, SK 751. Despite following all procedures correctly, the flight crew discovered that every time they reduced engine power, something was reversing their actions and turned the thrust up. Every time they reduced, the thrust returned higher, until it burned up the engines and left the plane a glider. Fortunately in that incident, everyone survived. The cause of the engine surges? A piece of software McDonnell Douglas installed to prevent stalling that they didn't tell SAS about. The pilot of that flight never flew again, not being able to trust an airplane ever again.


SAS had been informed about Automatic Thrust Restoration (ATR).

"However, ATR was described in manuals by the aircraft manufacturer which every operator is obliged to know. Even though the system was developed for use in procedures not applied by SAS, a sufficiently careful study of the manuals should have led to SAS noting the system and training its pilots in its function."

https://en.wikipedia.org/wiki/Scandinavian_Airlines_Flight_751
https://www.havkom.se/assets/reports/English/C1993_57e_Gottrora.pdf


Page 72 of the report, point 2.2.3: "At the time of the accident there was no knowledge of ATR (Automatic Thrust Recovery) within SAS. The pilots were therefore not trained on ATR and information was not included in their operational documentation". It further states that if they had been trained, they would have switched settings and recovered. In this case, SAS' training did not include this particular setting, leading to the accident. That to me seems to be what happened in the Lion Air accident, where a change by the manufacturer was not passed on sufficiently to the pilots.


Scandinavian Airlines Flight 751

ATR was described in manuals by the aircraft manufacturer

Lion Air Flight 610

MCAS was not described in manuals by the aircraft manufacturer
 
salttee
Posts: 3149
Joined: Wed Jul 13, 2016 3:26 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 9:35 pm

seahawk wrote:
It is all speculation until we have all facts.
True, and the "facts" we currently have don't make any sense. No matter what else was happening, any pilot would pull back on the yoke when the nose starts pointing down. This of course leaves a stall as the possible cause for the descent, but how can a 737 flying on a level altitude at over 300kts stall? Next we have to consider an overspeed stall, which seemingly could only have come about as a result of unchallenged nose down flight; so we are back to why wouldn't a pilot pull back on the stick.

seahawk wrote:
It would be strange if only the failure of MCAS caused the crash, as pilots should be able to handle it,
Yes, even panicked pilots don't usually fail to pull back on the stick.

seahawk wrote:
but we must consider the possibility of multiple sensor or system failures and then things might get complicated.
We already have multiple sensors failure: airspeed and AOA.

How about if we make all future airline pilot candidates demonstrate the ability to make a half hour flight in a Cessna 140 without a functioning airspeed indicator or altimeter? :duck:
 
kalvado
Posts: 2015
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 9:39 pm

boerje wrote:
Scandinavian Airlines Flight 751

ATR was described in manuals by the aircraft manufacturer

Lion Air Flight 610

MCAS was not described in manuals by the aircraft manufacturer

Honestly speaking.. If you're at controls and machine is doing something very strange and you don't know what to do - do you care if this is manufacturer's fault, your boss fault, or you were just sick on the day of that class? It can be sorted out later, when (and actually if) you're at the office explaining what happened....
 
kalvado
Posts: 2015
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 9:43 pm

salttee wrote:

How about if we make all future airline pilot candidates demonstrate the ability to make a half hour flight in a Cessna 140 without a functioning airspeed indicator or altimeter? :duck:

Make sure you cut off 80% Cessna's stabilizer before that test flight - it would be a better approximation to the situation at hand. MCAS is there for reduced stability reasons.
 
djm18
Posts: 80
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 9:44 pm

I do not know the reason why it may not have been in the flight crew training but MCAS is performing a similar function as speed trim. This is not a totally different system. I do not know what pilots were trained but both the NG and MAX QRH calls for stab cutout to be enabled. NOT to pull back the column like Mr.Bjorn Fehrm says.


I am guessing that with all that was going on in the cockpit in those short minutes the pilots never imagined that this was creeping up on them until it was too late. In other words, it would seem to me that they may have never considered (or had time) going through the runaway trim procedure which may have led them to a different outcome."
 
WIederling
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 9:56 pm

BoeingGuy wrote:
Let’s be very clear. The defect was the AOA probe, not the airplane design.


A defective AoA probe exposed the basic design error Boeing made. And apparently some rather grave omissions.
Last edited by WIederling on Wed Nov 14, 2018 10:03 pm, edited 1 time in total.
Murphy is an optimist
 
salttee
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 9:57 pm

kalvado wrote:
Make sure you cut off 80% Cessna's stabilizer before that test flight - it would be a better approximation to the situation at hand. MCAS is there for reduced stability reasons.

This plane wasn't in a flight region where MCAS intervention was appropriate. The MCAS intervened only because of a broken AOA sensor.

djm18 wrote:
I am guessing that with all that was going on in the cockpit in those short minutes the pilots never imagined that this was creeping up on them until it was too late. In other words, it would seem to me that they may have never considered (or had time) going through the runaway trim procedure which may have led them to a different outcome."

You don't need "procedures" to tell you to pull back on the yoke when the plane starts to nose down.


WIederling wrote:
A defective AoA probe exposed the basic design error Boeing made. And apparently some rather grave omissions.

If this was an Airbus you'd be singing a completely different song. You're the most provincial poster on A.net.
 
mm320cap
Posts: 302
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 10:06 pm

djm18 wrote:
I do not know the reason why it may not have been in the flight crew training but MCAS is performing a similar function as speed trim. This is not a totally different system. I do not know what pilots were trained but both the NG and MAX QRH calls for stab cutout to be enabled. NOT to pull back the column like Mr.Bjorn Fehrm says.


I am guessing that with all that was going on in the cockpit in those short minutes the pilots never imagined that this was creeping up on them until it was too late. In other words, it would seem to me that they may have never considered (or had time) going through the runaway trim procedure which may have led them to a different outcome."


Yup, this. IF the cause of this accident ends up being an MCAS event brought about by faulty AOA inputs, then it would be hard to fault the crew for not going to the “Runaway Stab Trim” QRC. During our stall training on the NG, there is no trim down bias. I was mighty surprised to hear that on the MAX (which we fly) there WILL be nose down trim applied and that if left unchecked it could become unrecoverable. I don’t think Boeing purposely left this out of the differences training; more likely they just didn’t think it was necessary to mention. Of course it looks necessary NOW with the benefit of 20/20 hindsight.

If the airplane is showing 3 different airspeeds, the stick shaker is going off (possibly at the same time as the clacker), there is probably a significant amount of confusion on the flight deck. This is something that can take awhile to digest and sort out. In the meantime, the airplane is constantly trimming nose down, which based on the training you’ve had you aren’t expecting. That’s a handful. I’m glad we are all aware of it now. But to except a crew to diagnose runaway stab trim as being the most serious fault at the time is asking a lot.
 
fadecfault
Posts: 164
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 10:10 pm

djm18 wrote:
I do not know the reason why it may not have been in the flight crew training but MCAS is performing a similar function as speed trim. This is not a totally different system. I do not know what pilots were trained but both the NG and MAX QRH calls for stab cutout to be enabled. NOT to pull back the column like Mr.Bjorn Fehrm says.


I am guessing that with all that was going on in the cockpit in those short minutes the pilots never imagined that this was creeping up on them until it was too late. In other words, it would seem to me that they may have never considered (or had time) going through the runaway trim procedure which may have led them to a different outcome."


Yes I agree, there's more to the story than just trim going awry (imo)
I also did find the MAX AOM is at odds with the MAX QRH. The AOM calls for just pulling back the column for runaway trim while the QRH says to hit the cutouts. The AOM does say to use manual trim if needed though.
The views and opinions written here are my own and do not reflect those of my employer.
 
alaskan9974
Posts: 111
Joined: Sat Oct 01, 2011 9:06 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 10:15 pm

Maybe this is more of a tech/ops question, but does the trim have the ability to override elevator inputs? I am not a 737 driver, but if it were to be trimmed full up or down, does that make control inputs ineffective in the opposite direction past a certain speed? Is the trim position dynamic based on speed or is the deflection angle always the same?
 
GalaxyFlyer
Posts: 3707
Joined: Fri Jan 01, 2016 4:44 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 10:16 pm

You don't need "procedures" to tell you to pull back on the yoke when the plane starts to nose down.


Pulling back maybe the worst thing to do when the nose starts down! It depends on lots of other factors—speed, attitude being the primary ones. Pull a plane straight up, it will run out of airspeed, flop over nose down at a very similar attitude it had going up, now down with no airspeed. Pull and it will stall.


GF
 
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Acey
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Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 10:20 pm

Sooner787 wrote:
I know there are some MAX customers that have yet to take delivery of their new jets ,
Alaska for instance..... Might AS decide to cancel their MAX orders , especially since they
now have A321NEOS on property. I would also guess Lion Air might be reconsidering
their Max order book as well.


It's sad what a useless place this forum has become thanks to posts like this.
If a man hasn't discovered something that he will die for, he isn't fit to live. -- Martin Luther King, Jr.
 
musman9853
Posts: 831
Joined: Mon May 14, 2018 12:30 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 10:22 pm

glideslope wrote:
Desperately need to find and recover the CVR.



iirc they found one, the other one lost signal.
Welcome to the City Beautiful.
 
salttee
Posts: 3149
Joined: Wed Jul 13, 2016 3:26 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 10:25 pm

salttee wrote:
GalaxyFlyer wrote:
You don't need "procedures" to tell you to pull back on the yoke when the plane starts to nose down.


Pulling back maybe the worst thing to do when the nose starts down! It depends on lots of other factors—speed, attitude being the primary ones. Pull a plane straight up, it will run out of airspeed, flop over nose down at a very similar attitude it had going up, now down with no airspeed. Pull and it will stall.


GF
In Lion 610 the airspeed was high and the attitude was level (at the start to the downward pitch). The rest of your post isn't worth responding to. It's as if you're a non-pilot who came over here from non-av just to argue.
 
WkndWanderer
Posts: 270
Joined: Sat Oct 21, 2017 6:36 pm

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 11:04 pm

boerje wrote:
PSAatSAN4Ever wrote:
boerje wrote:
Lion Air Flight 610

MCAS was not described in manuals by the aircraft manufacturer


Where are you getting that MCAS wasn't described or that Boeing delivered a plane without giving the customer information on how it worked? As another poster described, the MCAS is described in MAX maintenance manuals and procedures that address it are in at least some airline's MAX QRH's, do you think they just guessed?
 
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caoimhin
Posts: 449
Joined: Thu Oct 23, 2014 12:30 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 11:08 pm

iahcsr wrote:
Question; Was/is this software change listed in the Max maintenance manuals that techops use and simply not referenced in flightops manuals? This wasn’t a deliberate attempt to hide the information. Someone(s) at Boeing (And FAA?) just thought it wasn’t worth mentioning. The saying “Hindsight is 20/20” clearly applies here. This event is so eerily similar to the crash of a NZ A320 some years ago. In that case the AOA also failed and software did what it thought was the right thing.


For reference regarding the NZ/XL A320 crash: https://en.wikipedia.org/wiki/XL_Airway ... light_888T
 
ikramerica
Posts: 14901
Joined: Mon May 23, 2005 9:33 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 11:27 pm

Leeham claim contradicts Delta and others. How did Delta know about runaway trim and this system last year if Boeing didn't tell them? How is it in their manual?

I'm still of the belief that because it was a new type for Lion, not all pilots or maintenance staff knew about it because they didn't learn/retain it in difference training. With the plane have tech issues 3 previous flights that don't seem to have been addressed, where was the Lion call to Boeing for support? Where was any indication that they even thought of taking the aircraft out of service? Where was the abundance of caution that I see all the time with western airlines, where an aircraft goes tech to be on the safe side.

Whatever the cause, there is an undeniable truth: Lion did not err on the safe side.
Of all the things to worry about... the Wookie has no pants.
 
User avatar
Erebus
Posts: 1049
Joined: Tue Oct 20, 2015 2:40 am

Re: Boeing’s automatic trim for the 737 MAX was not disclosed to the Pilots

Wed Nov 14, 2018 11:28 pm

WkndWanderer wrote:
Where are you getting that MCAS wasn't described or that Boeing delivered a plane without giving the customer information on how it worked? As another poster described, the MCAS is described in MAX maintenance manuals and procedures that address it are in at least some airline's MAX QRH's, do you think they just guessed?


It is coming from AA and WN pilots. From the Seattle Times...

Jon Weaks, president of the Southwest Airlines Pilots Association, said Monday the airline and the pilots “were kept in the dark.”

“We do not like the fact that a new system was put on the aircraft and wasn’t disclosed to anyone or put in the manuals,” he said in an interview. What’s more, he noted, Boeing and the Federal Aviation Administration have now warned “that the system may not be performing as it should.”


Early Saturday morning, Capt. Mike Michaelis, chairman of the safety committee of the Allied Pilots Association (APA) at American Airlines, sent out a message to pilots informing them of details Boeing had shared with the airline about this new 737 MAX system — called MCAS (Maneuvering Characteristics Augmentation System).

“This is the first description you, as 737 pilots, have seen,” the message from the pilots association at American reads. “It is not in the American Airlines 737 Flight Manual … nor is there a description in the Boeing FCOM (Flight Crew Operations Manual). It will be soon.”


Either these guys are not reading their manuals fully or they have been given inadequate versions. In any case it is still disconcerting to have pilots claiming that they are unaware of it.

Question: are pilots expected to know everything that is described in a maintenance manual?

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