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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 12:21 pm

XRAYretired wrote:
PixelFlight wrote:
XRAYretired wrote:
Objective of 2 is achieved by implementing 3 i.e. the maximum deflection is limited to 2.5deg which is less than the maximum elevator authority.

I agree that you might be right on this, but I am unable to find a document that confirm this. If you have, please share.
My reading is that the 737 uk fix number 2 description is that the 0.6 degree and 2.5 degree was part of the text that describes MCAS v0 ("In its original report, Boeing said") and MCAS v1 ("However, after the Lion Air crash, it told airlines"). So the MCAS v2 fix number 2 description strip down to "To limit how much MCAS can move the horizontal stab to guarantee sufficient handling capability using elevator alone". There is no mention anymore of a given number of degree. To me the MCAS v2 fix number 3 is unrelated to the fix number 2. Please correct me where I am wrong.

Suggest you go back to the Boeing released , layman terms, outline:

'The additional layers of protection include:
-Flight control system will now compare inputs from both AOA sensors. If the sensors disagree by 5.5 degrees or more with the flaps retracted, MCAS will not activate. An indicator on the flight deck display will alert the pilots.
-If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
-MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column. The pilots will continue to always have the ability to override MCAS and manually control the airplane.'


The final statement equates to item 2 in the Chris Brady write up. This s a description of achievement of limiting activation to one cycle if the AoA has not dropped below the trigger value.

The rate of change of trim was specified as 0.27deg/sec noes down for V1.0, (and a cycle length of 9.26 seconds). This was the rate arrived at to induce the desired effect. Unless the aerodynamics have changed (and nobody knows about it), it does not change. In any case the total deflection is equivalent to 2.5deg nose down in one cycle and is within the authority of elevator to counteract, so there is no reason to change anything else if MCAS activation is limited to one cycle.

Sorry, but if limiting the rate and time to 0.27deg/sec and 9.26 seconds effectively limit the displacement of 2.5deg, this do not take in account the initial position of the stab trim, and it could anywhere already, including near the elevator authority limit.

The second thing I found curious is that according to your description, the fix "elevator authority" (in normal condition) would then depend on the fix "only one input per AoA event in non-normal condition". My understanding is that in normal condition the MCAS v2 is still allowed to provides multiple inputs, so it is still able to take authority overt the elevator if not limited by something else. In normal condition this should be the right thing to do, but this do not match the fix description. Confusing for me.

I would not be surprised that the actual implementation of the MCAS v2 is a bit more complex to grant the elevator authority (in normal condition).
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 12:30 pm

PixelFlight wrote:
Sorry, but if limiting the rate and time to 0.27deg/sec and 9.26 seconds effectively limit the displacement of 2.5deg, this do not take in account the initial position of the stab trim, and it could anywhere already, including near the elevator authority limit.

The second thing I found curious is that according to your description, the fix "elevator authority" (in normal condition) would then depend on the fix "only one input per AoA event in non-normal condition". My understanding is that in normal condition the MCAS v2 is still allowed to provides multiple inputs, so it is still able to take authority overt the elevator if not limited by something else. In normal condition this should be the right thing to do, but this do not match the fix description. Confusing for me.

I would not be surprised that the actual implementation of the MCAS v2 is a bit more complex to grant the elevator authority (in normal condition).


On the initial position of the stab trim are you assuming it's out of trim for that AOA or way out of trim for that AOA?

If it is in-trim the elevator still has the same the same authority.

If it is well out of trim and the elevator is fully deflected to maintain the desired AOA then yes it could have not authority to counteract - but why would you do that?

Non-normal would be referring to climbing at much higher than normal AOA's approaching stall.

MCAS would never trigger in normal conditions.
 
dtw2hyd
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 12:31 pm

morrisond wrote:
...
You are all taking the JATR report where they say things like "may be considered" as "it is". You also have to to remember that the JATR report was not a consensus report. If one of the members had a thought or recommendation it went into the report.


If a handpicked like-minded group couldn't produce a consensus report, it is a failure on team selection. BTW, how are these regulators selected?
All posts are just opinions.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 12:38 pm

kalvado wrote:
morrisond wrote:
Noshow wrote:
Could anything physical be added to the aircraft surface to change the slow flight behavior? Strakes, stall strips, vortex generators and such? How much would it "cost" by added drag and fuel burn to "ruin" the airflow around the nacelles with maybe bypass doors and such to prevent them lifting the nose into some stall?


Yes it could - and apparently they tried and it either didn't work or as you correctly identified the extra drag was just too expensive in fuel. It would have been a huge hit to efficiency for something that doesn't really do much to improve overall safety so they went for the software solutiuon.

I really just seems like Boeing did MCAS as an afterthought - and put minimal resources into it as it wasn't considered a big deal as it really wasn't going to meaningfully increase safety. However as we now know that minimal effort and failure to consider the "What if that one sensor fails" led to tragedies.

The FAA should have caught it as well.

I wonder how many more of such afterthoughts poorly trained Boeing engineers added to the project? And since FAA picks from generally the same engineering pool, are they capable to catch these?
The most flabbergasting thing is that even hindsight is well below 20/20, as the issue was barely noticed even after the crash...


Oh they noticed it - hence the new procedure and FCOM bulletin - they just assumed that should be enough for any pilot to identify MCAS activation and simply deactivate while they worked on a solution.

Luckily MAX was somewhat minimal change - I suspect they have thoroughly reviewed all changes that were made from the NG.

WIth all the recommendations from the FAA, NTSB, and JATR with Boeing's own internal changes I'm sure they will do the proper second order analysis going forward. It will be more about procedure than engineering brilliance. At least until such time as these crashes are forgotten and things go slack again.

I'm sure there will be some very interesting unintended consequences when Artificial Intelligence (AI) makes it's way into a cockpit. They program the AI to minimize carbon emissions - AI conclusion - turn off engines and put the plane into the ground as those pesky humans are going to kill the planet.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 12:39 pm

morrisond wrote:
You are all taking the JATR report where they say things like "may be considered" as "it is". You also have to to remember that the JATR report was not a consensus report. If one of the members had a thought or recommendation it went into the report.

The letter is clear that only the recommendations might not be a consensus:
The members of the JATR team wish to
thank you for the opportunity to conduct this review and to share our observations and findings. You also
invited JATR members to submit recommendations whether or not they represented a consensus.

Yet there was not contradiction identified to date in the recommendations submitted in the review.

The only non conclusive finding identified to date if the already famous F3.5-C:
Finding F3.5-C: The JATR team considers that the STS/MCAS and EFS
functions could be considered as stall identification systems or stall protection
systems, depending on the natural (unaugmented) stall characteristics of the
aircraft. From its data review, the JATR team was unable to completely rule out
the possibility that these augmentation systems function as a stall protection
system.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 12:48 pm

morrisond wrote:
MCAS would never trigger in normal conditions.

From JATR:
Observation O3.4-A: The original implementation of MCAS was driven primarily
by its ability to provide the B737 MAX with FAA-compliant flight characteristics
at high speed. An unaugmented design would have been at risk of not meeting
14 CFR part 25 maneuvering characteristics requirements due to aerodynamics.

Observation O3.4-B: Extension of MCAS to the low-speed and 1g environment
during the flight program was due to unacceptable stall characteristics with STS
only. The possibility of a pitch-up tendency during approach to stall was
identified for the flaps-up configuration prior to the implementation of MCAS.

The two situations are in normal condition: all the surfaces, engines, sensors, computers, actuators, etc.. are working all fine.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
Amiga500
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 12:53 pm

morrisond wrote:
WIth all the recommendations from the FAA, NTSB, and JATR with Boeing's own internal changes I'm sure they will do the proper second order analysis going forward. It will be more about procedure than engineering brilliance.


I'll just correct you there.

Engineering brilliance is having a great idea and then stepping it through all procedures to make sure its watertight from every angle. Otherwise you are just a philosopher.
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 1:10 pm

PixelFlight wrote:
XRAYretired wrote:
PixelFlight wrote:
I agree that you might be right on this, but I am unable to find a document that confirm this. If you have, please share.
My reading is that the 737 uk fix number 2 description is that the 0.6 degree and 2.5 degree was part of the text that describes MCAS v0 ("In its original report, Boeing said") and MCAS v1 ("However, after the Lion Air crash, it told airlines"). So the MCAS v2 fix number 2 description strip down to "To limit how much MCAS can move the horizontal stab to guarantee sufficient handling capability using elevator alone". There is no mention anymore of a given number of degree. To me the MCAS v2 fix number 3 is unrelated to the fix number 2. Please correct me where I am wrong.

Suggest you go back to the Boeing released , layman terms, outline:

'The additional layers of protection include:
-Flight control system will now compare inputs from both AOA sensors. If the sensors disagree by 5.5 degrees or more with the flaps retracted, MCAS will not activate. An indicator on the flight deck display will alert the pilots.
-If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
-MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column. The pilots will continue to always have the ability to override MCAS and manually control the airplane.'


The final statement equates to item 2 in the Chris Brady write up. This s a description of achievement of limiting activation to one cycle if the AoA has not dropped below the trigger value.

The rate of change of trim was specified as 0.27deg/sec noes down for V1.0, (and a cycle length of 9.26 seconds). This was the rate arrived at to induce the desired effect. Unless the aerodynamics have changed (and nobody knows about it), it does not change. In any case the total deflection is equivalent to 2.5deg nose down in one cycle and is within the authority of elevator to counteract, so there is no reason to change anything else if MCAS activation is limited to one cycle.

Sorry, but if limiting the rate and time to 0.27deg/sec and 9.26 seconds effectively limit the displacement of 2.5deg, this do not take in account the initial position of the stab trim, and it could anywhere already, including near the elevator authority limit.

The second thing I found curious is that according to your description, the fix "elevator authority" (in normal condition) would then depend on the fix "only one input per AoA event in non-normal condition". My understanding is that in normal condition the MCAS v2 is still allowed to provides multiple inputs, so it is still able to take authority overt the elevator if not limited by something else. In normal condition this should be the right thing to do, but this do not match the fix description. Confusing for me.

I would not be surprised that the actual implementation of the MCAS v2 is a bit more complex to grant the elevator authority (in normal condition).

Trim, and 'neutral elevator' is managed by STS (and its equivalent in A/P) during normal operation so there is no reason for significant out of trim to be present. If this is present, you are already in a serious fault condition. If in significant nose up, then activation may well be useful, if in significant nose down, you are not going to be able to pull up to AoA trigger point.

V2.0 will only provide multiple inputs if the AoA drops below the trigger point and resets MCAS ready for any future excursion. If AoA remains above the trigger value, MCAS will not be reset. This applies to both normal AoA condition and in fault condition. I cant actually envisage any scenario where high AoA (above trigger value) will be maintained for 9.26 seconds, in the presence of nose down trim by MCAS, that is not a fault condition or is being commanded by the pilot through the yoke.

Ray.

Ray
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 1:24 pm

PixelFlight wrote:
morrisond wrote:
MCAS would never trigger in normal conditions.

From JATR:
Observation O3.4-A: The original implementation of MCAS was driven primarily
by its ability to provide the B737 MAX with FAA-compliant flight characteristics
at high speed. An unaugmented design would have been at risk of not meeting
14 CFR part 25 maneuvering characteristics requirements due to aerodynamics.

Observation O3.4-B: Extension of MCAS to the low-speed and 1g environment
during the flight program was due to unacceptable stall characteristics with STS
only. The possibility of a pitch-up tendency during approach to stall was
identified for the flaps-up configuration prior to the implementation of MCAS.

The two situations are in normal condition: all the surfaces, engines, sensors, computers, actuators, etc.. are working all fine.


Non-normal can also be defined as outside of the normal operating range - getting close to stall where MCAS would activate is an AOA way above where you would normally operate the aircraft. Things would be flying all over the cabin.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 1:41 pm

morrisond wrote:
Non-normal can also be defined as outside of the normal operating range

The two MCAS functions are there to give "FAA-compliant flight characteristics", so within the normal operating range.

From the JATR it look like that "normal operation" is defined as "not considering failure cases"
Observation O3.18-A: The high-speed MCAS function was reviewed, and for normal
operation (not considering failure cases) no concerns were noted.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 1:58 pm

XRAYretired wrote:
-If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
[...]
V2.0 will only provide multiple inputs if the AoA drops below the trigger point and resets MCAS ready for any future excursion. If AoA remains above the trigger value, MCAS will not be reset. This applies to both normal AoA condition and in fault condition.

From the Boeing text it's clear that the limitation to "one input for each elevated AOA event" is only in case of "non-normal conditions". In normal condition MCAS v2 will still be able to provides multiple inputs to the stab trim actuator without waiting that "the AoA drops below the trigger point and resets MCAS". So according to Boeing description, in normal condition if AoA remains above the trigger value, MCAS will be reset.

XRAYretired wrote:
I cant actually envisage any scenario where high AoA (above trigger value) will be maintained for 9.26 seconds, in the presence of nose down trim by MCAS, that is not a fault condition or is being commanded by the pilot through the yoke.

There is not guarantee that the initial stab position was not already near the limit of the elevator authority. The MCAS might not even know what the elevator position actually is when it give input to the stab trim actuator. I would not be confident in a safety assessment that miss a such important possibility.
Last edited by PixelFlight on Tue Oct 15, 2019 2:02 pm, edited 1 time in total.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
kalvado
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Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 2:01 pm

morrisond wrote:
kalvado wrote:
morrisond wrote:

Yes it could - and apparently they tried and it either didn't work or as you correctly identified the extra drag was just too expensive in fuel. It would have been a huge hit to efficiency for something that doesn't really do much to improve overall safety so they went for the software solutiuon.

I really just seems like Boeing did MCAS as an afterthought - and put minimal resources into it as it wasn't considered a big deal as it really wasn't going to meaningfully increase safety. However as we now know that minimal effort and failure to consider the "What if that one sensor fails" led to tragedies.

The FAA should have caught it as well.

I wonder how many more of such afterthoughts poorly trained Boeing engineers added to the project? And since FAA picks from generally the same engineering pool, are they capable to catch these?
The most flabbergasting thing is that even hindsight is well below 20/20, as the issue was barely noticed even after the crash...


Oh they noticed it - hence the new procedure and FCOM bulletin - they just assumed that should be enough for any pilot to identify MCAS activation and simply deactivate while they worked on a solution.

Luckily MAX was somewhat minimal change - I suspect they have thoroughly reviewed all changes that were made from the NG.

WIth all the recommendations from the FAA, NTSB, and JATR with Boeing's own internal changes I'm sure they will do the proper second order analysis going forward. It will be more about procedure than engineering brilliance. At least until such time as these crashes are forgotten and things go slack again.

I'm sure there will be some very interesting unintended consequences when Artificial Intelligence (AI) makes it's way into a cockpit. They program the AI to minimize carbon emissions - AI conclusion - turn off engines and put the plane into the ground as those pesky humans are going to kill the planet.

Noticed and brushed off. Cost of poorly trained engineers in workforce for Boeing: $10B and counting... All those recommendations don't make up for drunk college parties instead of studying...
And your AI example is exactly why proper training of engineers is a must for proper design of complex systems!
 
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aerolimani
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 2:04 pm

morrisond wrote:
Many of you above (but not all) still don't understand what MCAS was for. It was not to point the nose down.

It was too intentionally mistrim the aircraft so it took more effort on the control column to pull the aircraft into a stall and meet the stick force regs.

It had to act at a relatively quick speed to make it harder fast enough so it didn't fall under the value needed.

It is not an anti-stall system as no regulation was required for it to be one. It just unintentionally acted like one when the AOA values went way too high when the vanes failed. Very bad design.

MCAS 2.0 won't defacto operate as an anti-stall system at all as due to the once per cycle limitation you will be able to pull through the heavier control feel and still put it into a stall if you are determined too.

If it was meant to be an anti-stall system it would suck at it.

You are all taking the JATR report where they say things like "may be considered" as "it is". You also have to to remember that the JATR report was not a consensus report. If one of the members had a thought or recommendation it went into the report.

Is it not curious that in order to meet the FAR, the way devised to do so involved manipulating the control surfaces in a way which produces a nose down result? Surely, a stick pusher seems like a simpler solution? Ah, right, but then you’d have to add hardware, and certification would be more complicated. Nonetheless, even the textbook description of a stick pusher describes it as an anti-stall device.

While you’re in the business of “reminding us” of how you feel we should all think, please also remind us of the title of the FAR whose requirements MCAS was created to satisfy. Also, please remind us of the intention behind that FAR.

At the very least, MCAS is a system designed to help pilots not miss the fact they are nearing a stall. And why would that be important? Maybe it’s so that the pilot can then avoid putting the plane into a stall.

By your logic, none of the other stall warning systems are anti-stall systems either. If they’re not there to help prevent a stall from happening, then what are those warnings for?

By all means, discuss/debate the technical details of MCAS, but this business of “it’s not an anti-stall system” is just towing the line of Boeing PR. While I’m not accusing you of being a paid shill, as you continue like this, that does seem to be the function you are serving.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 2:05 pm

kalvado wrote:
morrisond wrote:
kalvado wrote:
I wonder how many more of such afterthoughts poorly trained Boeing engineers added to the project? And since FAA picks from generally the same engineering pool, are they capable to catch these?
The most flabbergasting thing is that even hindsight is well below 20/20, as the issue was barely noticed even after the crash...


Oh they noticed it - hence the new procedure and FCOM bulletin - they just assumed that should be enough for any pilot to identify MCAS activation and simply deactivate while they worked on a solution.

Luckily MAX was somewhat minimal change - I suspect they have thoroughly reviewed all changes that were made from the NG.

WIth all the recommendations from the FAA, NTSB, and JATR with Boeing's own internal changes I'm sure they will do the proper second order analysis going forward. It will be more about procedure than engineering brilliance. At least until such time as these crashes are forgotten and things go slack again.

I'm sure there will be some very interesting unintended consequences when Artificial Intelligence (AI) makes it's way into a cockpit. They program the AI to minimize carbon emissions - AI conclusion - turn off engines and put the plane into the ground as those pesky humans are going to kill the planet.

Noticed and brushed off. Cost of poorly trained engineers in workforce for Boeing: $10B and counting... All those recommendations don't make up for drunk college parties instead of studying...
And your AI example is exactly why proper training of engineers is a must for proper design of complex systems!


Good luck on designing the perfect system. It will never happen.
 
kalvado
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Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 2:08 pm

morrisond wrote:
kalvado wrote:
morrisond wrote:

Oh they noticed it - hence the new procedure and FCOM bulletin - they just assumed that should be enough for any pilot to identify MCAS activation and simply deactivate while they worked on a solution.

Luckily MAX was somewhat minimal change - I suspect they have thoroughly reviewed all changes that were made from the NG.

WIth all the recommendations from the FAA, NTSB, and JATR with Boeing's own internal changes I'm sure they will do the proper second order analysis going forward. It will be more about procedure than engineering brilliance. At least until such time as these crashes are forgotten and things go slack again.

I'm sure there will be some very interesting unintended consequences when Artificial Intelligence (AI) makes it's way into a cockpit. They program the AI to minimize carbon emissions - AI conclusion - turn off engines and put the plane into the ground as those pesky humans are going to kill the planet.

Noticed and brushed off. Cost of poorly trained engineers in workforce for Boeing: $10B and counting... All those recommendations don't make up for drunk college parties instead of studying...
And your AI example is exactly why proper training of engineers is a must for proper design of complex systems!


Good luck on designing the perfect system. It will never happen.

Of course. And we're in this discussion because certain company has poorly trained engineering workforce designing faulty systems - and we all keep praying (without too much faith) that MCAS quality is not a new normal for that certain company...
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 2:16 pm

morrisond wrote:
Good luck on designing the perfect system. It will never happen.

We are talking about the modifications to be done on a particular design to go from the state of killing 346 innocents to the state reaching full compliance with actual commercial aircraft safety regulation.
It will not be a "perfect system", but I hope for Boeing that a successful re-certification will happen.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 2:26 pm

aerolimani wrote:
morrisond wrote:
Many of you above (but not all) still don't understand what MCAS was for. It was not to point the nose down.

It was too intentionally mistrim the aircraft so it took more effort on the control column to pull the aircraft into a stall and meet the stick force regs.

It had to act at a relatively quick speed to make it harder fast enough so it didn't fall under the value needed.

It is not an anti-stall system as no regulation was required for it to be one. It just unintentionally acted like one when the AOA values went way too high when the vanes failed. Very bad design.

MCAS 2.0 won't defacto operate as an anti-stall system at all as due to the once per cycle limitation you will be able to pull through the heavier control feel and still put it into a stall if you are determined too.

If it was meant to be an anti-stall system it would suck at it.

You are all taking the JATR report where they say things like "may be considered" as "it is". You also have to to remember that the JATR report was not a consensus report. If one of the members had a thought or recommendation it went into the report.

Is it not curious that in order to meet the FAR, the way devised to do so involved manipulating the control surfaces in a way which produces a nose down result? Surely, a stick pusher seems like a simpler solution? Ah, right, but then you’d have to add hardware, and certification would be more complicated. Nonetheless, even the textbook description of a stick pusher describes it as an anti-stall device.

While you’re in the business of “reminding us” of how you feel we should all think, please also remind us of the title of the FAR whose requirements MCAS was created to satisfy. Also, please remind us of the intention behind that FAR.

At the very least, MCAS is a system designed to help pilots not miss the fact they are nearing a stall. And why would that be important? Maybe it’s so that the pilot can then avoid putting the plane into a stall.

By your logic, none of the other stall warning systems are anti-stall systems either. If they’re not there to help prevent a stall from happening, then what are those warnings for?

By all means, discuss/debate the technical details of MCAS, but this business of “it’s not an anti-stall system” is just towing the line of Boeing PR. While I’m not accusing you of being a paid shill, as you continue like this, that does seem to be the function you are serving.


MCAS v 1.0 was not intended to be an Anti-stall - it was due to it's piss poor design that unfortunately it acted like one.

That is why MCAS v2.0 is not required to be one either.

A stick pusher would be an anti-stall system. It was not required for certification.

There is no anti-stall on the NG or MAX. All the systems were there to provide warnings for the pilots.

There is nothing on an 737 NG or MAX to keep the pilot from intentionally putting it into a stall. None of the other systems will prevent a stall. You can pull right through them.

MCAS was required to meet the FAR's for stall characteristics to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.

I don't know how more plainly it can be said.

If you were flying the MAX in manual mode and were maintaining a certain angle of attack per the instruments or outside visual reference and MCAS fired once - you would feel the elevator getting a little heavier. You wouldn't let the nose drop by not counteracting that force unless you were being completely inattentive to what the aircraft was supposed to be doing - which is your job as you are flying an airplane in manual mode.

What else do you expect the pilot to be doing if they are trying to fly at way higher than normal AOA's? Going for a coffee or texting on there phone and not paying attention to what the aircraft is doing?
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 2:34 pm

PixelFlight wrote:
morrisond wrote:
Good luck on designing the perfect system. It will never happen.

We are talking about the modifications to be done on a particular design to go from the state of killing 346 innocents to the state reaching full compliance with actual commercial aircraft safety regulation.
It will not be a "perfect system", but I hope for Boeing that a successful re-certification will happen.


I hope it's successful as well - but my comment was about the future and engineers or others who think engineers will be perfect.

It reminds me of a great Scotty Quote from Star Trek - when Scotty disables the new Wonder Ship the Excelsior so it can't follow the Entreprise. A little out of context but something to keep in mind as systems get more and more complex.

"Aye, sir. The more they overthink the plumbing, the easier it is to stop up the drain. Here, Doctor, souvenirs from one surgeon to another. I took them out of her main transwarp computer drive."
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 2:42 pm

morrisond wrote:
I hope it's successful as well - but my comment was about the future and engineers or others who think engineers will be perfect.

Nobody have wrote this in the recent posts.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 2:50 pm

PixelFlight wrote:
morrisond wrote:
I hope it's successful as well - but my comment was about the future and engineers or others who think engineers will be perfect.

Nobody have wrote this in the recent posts.


Kalvado wrote in response to my talking about AI's trying to kill us.

"And your AI example is exactly why proper training of engineers is a must for proper design of complex systems!"

And I wrote

"Good luck on designing the perfect system. It will never happen."
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 3:24 pm

PixelFlight wrote:
XRAYretired wrote:
-If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
[...]
V2.0 will only provide multiple inputs if the AoA drops below the trigger point and resets MCAS ready for any future excursion. If AoA remains above the trigger value, MCAS will not be reset. This applies to both normal AoA condition and in fault condition.

From the Boeing text it's clear that the limitation to "one input for each elevated AOA event" is only in case of "non-normal conditions". In normal condition MCAS v2 will still be able to provides multiple inputs to the stab trim actuator without waiting that "the AoA drops below the trigger point and resets MCAS". So according to Boeing description, in normal condition if AoA remains above the trigger value, MCAS will be reset.

XRAYretired wrote:
I cant actually envisage any scenario where high AoA (above trigger value) will be maintained for 9.26 seconds, in the presence of nose down trim by MCAS, that is not a fault condition or is being commanded by the pilot through the yoke.

There is not guarantee that the initial stab position was not already near the limit of the elevator authority. The MCAS might not even know what the elevator position actually is when it give input to the stab trim actuator. I would not be confident in a safety assessment that miss a such important possibility.

No. "one input for each elevated AOA event" means precisely what it says. If AoA drops below the trip value, MCAS is disengaged and reset to await the next excursion (with at least a 5 sec delay) in all conditions. It will not be reset if the AoA remains above the trip value. If it is a you suggest, then you are back to the ridiculous only once per A/C power up.

Now, I am not sure I have enough knowledge of the systems to talk multiple fault scenarios with any confidence. However, we would have to have a significant nose down trim that cannot be corrected by STS, cannot be corrected by Electrical manual trim or manual wheel trim or is otherwise commanded by the pilot or otherwise commanded by FCC somehow and stab trim cut-out switches are still in normal plus dual channel AoA failure high with a probability likely in the order E-10. Hopefully, Boeing will have reviewed the S & MF activity and picked some of these up.

Ray
 
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 3:29 pm

morrisond wrote:
PixelFlight wrote:
morrisond wrote:
I hope it's successful as well - but my comment was about the future and engineers or others who think engineers will be perfect.

Nobody have wrote this in the recent posts.


Kalvado wrote in response to my talking about AI's trying to kill us.

"And your AI example is exactly why proper training of engineers is a must for proper design of complex systems!"

And I wrote

"Good luck on designing the perfect system. It will never happen."

I stop here. I don't want to got an another "board warning" in that such impossible talk.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 3:39 pm

morrisond wrote:
PixelFlight wrote:
morrisond wrote:
I hope it's successful as well - but my comment was about the future and engineers or others who think engineers will be perfect.

Nobody have wrote this in the recent posts.


Kalvado wrote in response to my talking about AI's trying to kill us.

"And your AI example is exactly why proper training of engineers is a must for proper design of complex systems!"

And I wrote

"Good luck on designing the perfect system. It will never happen."

There had been some people at Boeing who had designed 777 a quarter century ago, if you will. A pretty successful project in terms of reliability to say the least.
Nobody expect perfect performance - except you wishing such for pilots. Imperfection is balanced by procedures, attitude, cross-checks. Setting up and following proper procedures is an important part.
Unlike pilots fighting aircraft, engineers generally have the luxury of peer review, coordination, discussion and what not - all with coffee breaks and at zero airspeed.
Where Boeing failed - and multiple times repeating the same! - is failing to follow (or even establishing!) those procedures for design - that is where JATR makes some comments; and definitely failed to establish procedures - aka explain system operation to pilots (and I wonder, if anyone at Boeing still knows how 737 operates as a big picture).
That is an extent of poor training at Boeing - it is not about using Comsol/ANSYS/whatever is cool thing today; it is cultural thing. Something that has to be carefully developed starting at first day of college - and keep it going until retirement. Too bad it is lost, may take decades to rebuild.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 3:46 pm

kalvado wrote:
morrisond wrote:
PixelFlight wrote:
Nobody have wrote this in the recent posts.


Kalvado wrote in response to my talking about AI's trying to kill us.

"And your AI example is exactly why proper training of engineers is a must for proper design of complex systems!"

And I wrote

"Good luck on designing the perfect system. It will never happen."

There had been some people at Boeing who had designed 777 a quarter century ago, if you will. A pretty successful project in terms of reliability to say the least.
Nobody expect perfect performance - except you wishing such for pilots. Imperfection is balanced by procedures, attitude, cross-checks. Setting up and following proper procedures is an important part.
Unlike pilots fighting aircraft, engineers generally have the luxury of peer review, coordination, discussion and what not - all with coffee breaks and at zero airspeed.
Where Boeing failed - and multiple times repeating the same! - is failing to follow (or even establishing!) those procedures for design - that is where JATR makes some comments; and definitely failed to establish procedures - aka explain system operation to pilots (and I wonder, if anyone at Boeing still knows how 737 operates as a big picture).
That is an extent of poor training at Boeing - it is not about using Comsol/ANSYS/whatever is cool thing today; it is cultural thing. Something that has to be carefully developed starting at first day of college - and keep it going until retirement. Too bad it is lost, may take decades to rebuild.


I was waiting for the Boeing is evil rant - at least this one is well written and I don't disagree with a lot of it.

Yes Boeing really screwed up - but you will never be able to design the perfect airplane - that is why you need pilots and not systems operators.

Yes following procedures properly and cross checks are a must for engineers as well as pilots.

All I'm asking for from Pilots - is if they don't understand what is going on - they have ability/foresight to turn things off and actually fly the plane. That does not require perfection or sky god skills.

It is the first thing they (should)learn as pilots.

This approach would probably result in a lot better outcomes than trying to master a 1300 Page POH.
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 3:50 pm

morrisond wrote:
kalvado wrote:
morrisond wrote:

Kalvado wrote in response to my talking about AI's trying to kill us.

"And your AI example is exactly why proper training of engineers is a must for proper design of complex systems!"

And I wrote

"Good luck on designing the perfect system. It will never happen."

There had been some people at Boeing who had designed 777 a quarter century ago, if you will. A pretty successful project in terms of reliability to say the least.
Nobody expect perfect performance - except you wishing such for pilots. Imperfection is balanced by procedures, attitude, cross-checks. Setting up and following proper procedures is an important part.
Unlike pilots fighting aircraft, engineers generally have the luxury of peer review, coordination, discussion and what not - all with coffee breaks and at zero airspeed.
Where Boeing failed - and multiple times repeating the same! - is failing to follow (or even establishing!) those procedures for design - that is where JATR makes some comments; and definitely failed to establish procedures - aka explain system operation to pilots (and I wonder, if anyone at Boeing still knows how 737 operates as a big picture).
That is an extent of poor training at Boeing - it is not about using Comsol/ANSYS/whatever is cool thing today; it is cultural thing. Something that has to be carefully developed starting at first day of college - and keep it going until retirement. Too bad it is lost, may take decades to rebuild.


I was waiting for the Boeing is evil rant - at least this one is well written and I don't disagree with a lot of it.

Yes Boeing really screwed up - but you will never be able to design the perfect airplane - that is why you need pilots and not systems operators.

Yes following procedures properly and cross checks are a must for engineers as well as pilots.

Good thing we can agree on something. Problem is I don't see a good cure for such cultural problems...
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 4:07 pm

XRAYretired wrote:
-If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
[...]

No. "one input for each elevated AOA event" means precisely what it says. If AoA drops below the trip value, MCAS is disengaged and reset to await the next excursion (with at least a 5 sec delay) in all conditions. It will not be reset if the AoA remains above the trip value. If it is a you suggest, then you are back to the ridiculous only once per A/C power up.

Sorry, but I still have a problem to understand how an activation in "non-normal conditions" is equal to an activation in "all conditions". This hit too hard my basic logic.
In my basic logic and by reading Boeing fix description to negate the condition, I got this:
"If the MCAS v2 is activated NOT in non-normal condition it will NOT only provide one input for each elevated AOA event."
Now I could make an error in interpreting 'NOT in "non-normal condition"' as a "normal condition", or by interpreting 'NOT only provide one input' as "provide multiple inputs", but it still look reasonable to me.
I agree that I could be wrong, but I want to understand why.

XRAYretired wrote:
Now, I am not sure I have enough knowledge of the systems to talk multiple fault scenarios with any confidence. However, we would have to have a significant nose down trim that cannot be corrected by STS, cannot be corrected by Electrical manual trim or manual wheel trim or is otherwise commanded by the pilot or otherwise commanded by FCC somehow and stab trim cut-out switches are still in normal plus dual channel AoA failure high with a probability likely in the order E-10. Hopefully, Boeing will have reviewed the S & MF activity and picked some of these up.

Well, this is exactly the basis of my concern from a safety assessment point of view: to make a statement like "MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column" unequivocally true, you can have two approaches:
1) Prove that all the possible initial situations before the activation cannot result in a loss of elevator authority with some margin after the maximum activation.
2) Design a system that measure/compute the elevator authority and stop the activation with some margin to grant it, regardless of the initial situation.
I suspect that the first path is a really hard to do.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 4:15 pm

morrisond wrote:
Non-normal can also be defined as outside of the normal operating range - getting close to stall where MCAS would activate is an AOA way above where you would normally operate the aircraft. Things would be flying all over the cabin.


The approved flight envelope is (much) larger than the (what you would consider) normal flight envelope.

I sure hope as a passenger that the airplane is safe over the full approved flight envelope, and not just the normal flight envelope.

To me it seems that MCAS was designed to operate in the approved flight envelope, as it would come alive way before stick shaker and stall warning.
I therefore do not understand your fixation on "normal operating range".
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 4:21 pm

PW100 wrote:
morrisond wrote:
Non-normal can also be defined as outside of the normal operating range - getting close to stall where MCAS would activate is an AOA way above where you would normally operate the aircraft. Things would be flying all over the cabin.


The approved flight envelope is (much) larger than the (what you would consider) normal flight envelope.

I sure hope as a passenger that the airplane is safe over the full approved flight envelope, and not just the normal flight envelope.

To me it seems that MCAS was designed to operate in the approved flight envelope, as it would come alive way before stick shaker and stall warning.
I therefore do not understand your fixation on "normal operating range".

We had comments saying that MCAS activates "way after stick shaker activation". Whatever that worth, this is a plausible scenario.
And that pretty much means that MCAS legit activation happens when real emergency is underway. While no definite scenarios were published, to me it sounds like "we're going to crash, pray for this bird doing impossible to save us" things - like last second CFIT or mid-air avoidance.
 
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 4:33 pm

morrisond wrote:
PW100 wrote:
. . . .


If MCAS is working correctly and it fires once to arrest an approach to stall when the aircraft is at a big angle of attack this is not going to put it into a dive - it will just make the controls heavier - there will be sufficient elevator authority to overcome and worst case if the pilots decide to put no pressure on the control column you will probably then just be climbing at a shallower angle - just remember to pull back the throttles or disengage AT or you may exceed Vmo.

If you choose to keep climbing at way too high of an AOA then you can use the Electric trim to zero out the control forces.
It took multiple applications of MCAS to result in a situation where the Elevator could not offset the Horizontal stabilizer on both Lionair and ET.
The retrimming of the Horizontal Stabilizer just puts the plane out of trim making the controls heavier to meet the regs.


That's all fine and well, but how would you explain finding F3.5-B . . . ?

JTAR Final Report wrote:
Finding F3.5-B: The FAA-accepted Boeing flight test technique of freezing column deflection at the onset of EFS was perceived by the JATR team as possibly not meeting the requirements of § 25.201 for natural stall identification from nose-down pitch, not readily arrested. Column/elevator deflection data indicates that there may be an insufficient column input to attempt to arrest the nose-down pitch created by system augmentation.
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XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 4:46 pm

PixelFlight wrote:
XRAYretired wrote:
-If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
[...]

No. "one input for each elevated AOA event" means precisely what it says. If AoA drops below the trip value, MCAS is disengaged and reset to await the next excursion (with at least a 5 sec delay) in all conditions. It will not be reset if the AoA remains above the trip value. If it is a you suggest, then you are back to the ridiculous only once per A/C power up.

Sorry, but I still have a problem to understand how an activation in "non-normal conditions" is equal to an activation in "all conditions". This hit too hard my basic logic.
In my basic logic and by reading Boeing fix description to negate the condition, I got this:
"If the MCAS v2 is activated NOT in non-normal condition it will NOT only provide one input for each elevated AOA event."
Now I could make an error in interpreting 'NOT in "non-normal condition"' as a "normal condition", or by interpreting 'NOT only provide one input' as "provide multiple inputs", but it still look reasonable to me.
I agree that I could be wrong, but I want to understand why.

XRAYretired wrote:
Now, I am not sure I have enough knowledge of the systems to talk multiple fault scenarios with any confidence. However, we would have to have a significant nose down trim that cannot be corrected by STS, cannot be corrected by Electrical manual trim or manual wheel trim or is otherwise commanded by the pilot or otherwise commanded by FCC somehow and stab trim cut-out switches are still in normal plus dual channel AoA failure high with a probability likely in the order E-10. Hopefully, Boeing will have reviewed the S & MF activity and picked some of these up.

Well, this is exactly the basis of my concern from a safety assessment point of view: to make a statement like "MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column" unequivocally true, you can have two approaches:
1) Prove that all the possible initial situations before the activation cannot result in a loss of elevator authority with some margin after the maximum activation.
2) Design a system that measure/compute the elevator authority and stop the activation with some margin to grant it, regardless of the initial situation.
I suspect that the first path is a really hard to do.

You are trying to read a press release designed to address the known deficiencies of V1.0 by indicating the intended change as a technical requirement definition of the change. Your logic is leading you to a solution that is ridiculous.

Ray
 
rheinwaldner
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 4:52 pm

morrisond wrote:
MCAS v 1.0 was not intended to be an Anti-stall - it was due to it's piss poor design that unfortunately it acted like one.

That is why MCAS v2.0 is not required to be one either.

A stick pusher would be an anti-stall system. It was not required for certification.

There is no anti-stall on the NG or MAX. All the systems were there to provide warnings for the pilots.

There is nothing on an 737 NG or MAX to keep the pilot from intentionally putting it into a stall. None of the other systems will prevent a stall. You can pull right through them.

MCAS was required to meet the FAR's for stall characteristics to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.

I don't know how more plainly it can be said.

If you were flying the MAX in manual mode and were maintaining a certain angle of attack per the instruments or outside visual reference and MCAS fired once - you would feel the elevator getting a little heavier. You wouldn't let the nose drop by not counteracting that force unless you were being completely inattentive to what the aircraft was supposed to be doing - which is your job as you are flying an airplane in manual mode.

What else do you expect the pilot to be doing if they are trying to fly at way higher than normal AOA's? Going for a coffee or texting on there phone and not paying attention to what the aircraft is doing?

Why are you reversing the truth? Not many sentences in this huge post are correct. The red ones are wrong, the yellow ones are contradicting and the green ones are not relevant to judge whether MCAS is to prevent stalls.

You continue to provide some platitudes as answers but never reach the answer to the final "why is this?"...

E.g. (picking just some of your statements)
- Why is there a certification requirement that demands particular stick forces when approaching a stall? Final answer: to prevent stalls....
- Why are there systems to provide warnings to the pilots? Final answer: to help avoiding stalls.
- Why was the MAX required to meet certain stall characteristics? Final answer: to help avoiding stalls (<- if that is not a no brainer, then maybe questions about ones brain should be asked)
- Why pilots must identify that they are approaching a stall by not letting the stick force fall below a certain value? Final answer: to help avoiding stalls.
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 5:01 pm

PixelFlight wrote:
Please respond to the author of that speculation.
I presented a fairly simple logic about a speculation (MCAS v1 retrimming is required to meet the regs) that was not from me.


I did.

The logic was too simple (false dilemma). You presented it as fact when it's not known to us as fact.

morrisond wrote:
You are all taking the JATR report where they say things like "may be considered" as "it is". You also have to to remember that the JATR report was not a consensus report. If one of the members had a thought or recommendation it went into the report.


Indeed. I'm also seeing "may be" findings taken as "it is". I also think that fact that the recommendations are not a consensus opinion is very important. I was surprised and disappointed when I read that, and that fact needs to be respected. The JATR report is not a gospel, and considering the range of parties involved, we have to tread carefully with its statements.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 5:10 pm

XRAYretired wrote:
PixelFlight wrote:
XRAYretired wrote:
-If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
[...]

No. "one input for each elevated AOA event" means precisely what it says. If AoA drops below the trip value, MCAS is disengaged and reset to await the next excursion (with at least a 5 sec delay) in all conditions. It will not be reset if the AoA remains above the trip value. If it is a you suggest, then you are back to the ridiculous only once per A/C power up.

Sorry, but I still have a problem to understand how an activation in "non-normal conditions" is equal to an activation in "all conditions". This hit too hard my basic logic.
In my basic logic and by reading Boeing fix description to negate the condition, I got this:
"If the MCAS v2 is activated NOT in non-normal condition it will NOT only provide one input for each elevated AOA event."
Now I could make an error in interpreting 'NOT in "non-normal condition"' as a "normal condition", or by interpreting 'NOT only provide one input' as "provide multiple inputs", but it still look reasonable to me.
I agree that I could be wrong, but I want to understand why.

XRAYretired wrote:
Now, I am not sure I have enough knowledge of the systems to talk multiple fault scenarios with any confidence. However, we would have to have a significant nose down trim that cannot be corrected by STS, cannot be corrected by Electrical manual trim or manual wheel trim or is otherwise commanded by the pilot or otherwise commanded by FCC somehow and stab trim cut-out switches are still in normal plus dual channel AoA failure high with a probability likely in the order E-10. Hopefully, Boeing will have reviewed the S & MF activity and picked some of these up.

Well, this is exactly the basis of my concern from a safety assessment point of view: to make a statement like "MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column" unequivocally true, you can have two approaches:
1) Prove that all the possible initial situations before the activation cannot result in a loss of elevator authority with some margin after the maximum activation.
2) Design a system that measure/compute the elevator authority and stop the activation with some margin to grant it, regardless of the initial situation.
I suspect that the first path is a really hard to do.

You are trying to read a press release designed to address the known deficiencies of V1.0 by indicating the intended change as a technical requirement definition of the change. Your logic is leading you to a solution that is ridiculous.

Ok, the press release is really not the best source of technical information, but do we have something better to analyse ? If no, I fail to see how your interpretation is fundamentally better than mine.
And yes, I expect that at some point in the design process there will be a corresponding requirement regarding the elevator authority claim, properly certified by the safety agencies.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 5:26 pm

PW100 wrote:
morrisond wrote:
Non-normal can also be defined as outside of the normal operating range - getting close to stall where MCAS would activate is an AOA way above where you would normally operate the aircraft. Things would be flying all over the cabin.


The approved flight envelope is (much) larger than the (what you would consider) normal flight envelope.

I sure hope as a passenger that the airplane is safe over the full approved flight envelope, and not just the normal flight envelope.

To me it seems that MCAS was designed to operate in the approved flight envelope, as it would come alive way before stick shaker and stall warning.
I therefore do not understand your fixation on "normal operating range".


How about Normal airline operating range where you don't upset the babies or the older people in the back of the aircraft. MCAS would be above that and probably just before stick shaker - where the stick force can't fall off.

I don't know the precise values but at Take-off thrust you probably wouldn't probably go much past 15-16degrees Angle up - whereas stall would probably be a bunch higher than 30 degrees especially at light weights and full thrust.

That is a huge difference. Try walking up a 30 degree hill.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 5:28 pm

kalvado wrote:
PW100 wrote:
morrisond wrote:
Non-normal can also be defined as outside of the normal operating range - getting close to stall where MCAS would activate is an AOA way above where you would normally operate the aircraft. Things would be flying all over the cabin.


The approved flight envelope is (much) larger than the (what you would consider) normal flight envelope.

I sure hope as a passenger that the airplane is safe over the full approved flight envelope, and not just the normal flight envelope.

To me it seems that MCAS was designed to operate in the approved flight envelope, as it would come alive way before stick shaker and stall warning.
I therefore do not understand your fixation on "normal operating range".

We had comments saying that MCAS activates "way after stick shaker activation". Whatever that worth, this is a plausible scenario.
And that pretty much means that MCAS legit activation happens when real emergency is underway. While no definite scenarios were published, to me it sounds like "we're going to crash, pray for this bird doing impossible to save us" things - like last second CFIT or mid-air avoidance.


I'm pretty sure it's before stick shaker. But I don't know for sure.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 5:34 pm

kalvado wrote:
morrisond wrote:
kalvado wrote:
There had been some people at Boeing who had designed 777 a quarter century ago, if you will. A pretty successful project in terms of reliability to say the least.
Nobody expect perfect performance - except you wishing such for pilots. Imperfection is balanced by procedures, attitude, cross-checks. Setting up and following proper procedures is an important part.
Unlike pilots fighting aircraft, engineers generally have the luxury of peer review, coordination, discussion and what not - all with coffee breaks and at zero airspeed.
Where Boeing failed - and multiple times repeating the same! - is failing to follow (or even establishing!) those procedures for design - that is where JATR makes some comments; and definitely failed to establish procedures - aka explain system operation to pilots (and I wonder, if anyone at Boeing still knows how 737 operates as a big picture).
That is an extent of poor training at Boeing - it is not about using Comsol/ANSYS/whatever is cool thing today; it is cultural thing. Something that has to be carefully developed starting at first day of college - and keep it going until retirement. Too bad it is lost, may take decades to rebuild.


I was waiting for the Boeing is evil rant - at least this one is well written and I don't disagree with a lot of it.

Yes Boeing really screwed up - but you will never be able to design the perfect airplane - that is why you need pilots and not systems operators.

Yes following procedures properly and cross checks are a must for engineers as well as pilots.

Good thing we can agree on something. Problem is I don't see a good cure for such cultural problems...


Yes - that will take some fixing.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 5:47 pm

rheinwaldner wrote:
morrisond wrote:
MCAS v 1.0 was not intended to be an Anti-stall - it was due to it's piss poor design that unfortunately it acted like one.

That is why MCAS v2.0 is not required to be one either.

A stick pusher would be an anti-stall system. It was not required for certification.

There is no anti-stall on the NG or MAX. All the systems were there to provide warnings for the pilots.

There is nothing on an 737 NG or MAX to keep the pilot from intentionally putting it into a stall. None of the other systems will prevent a stall. You can pull right through them.

MCAS was required to meet the FAR's for stall characteristics to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.

I don't know how more plainly it can be said.

If you were flying the MAX in manual mode and were maintaining a certain angle of attack per the instruments or outside visual reference and MCAS fired once - you would feel the elevator getting a little heavier. You wouldn't let the nose drop by not counteracting that force unless you were being completely inattentive to what the aircraft was supposed to be doing - which is your job as you are flying an airplane in manual mode.

What else do you expect the pilot to be doing if they are trying to fly at way higher than normal AOA's? Going for a coffee or texting on there phone and not paying attention to what the aircraft is doing?

Why are you reversing the truth? Not many sentences in this huge post are correct. The red ones are wrong, the yellow ones are contradicting and the green ones are not relevant to judge whether MCAS is to prevent stalls.

You continue to provide some platitudes as answers but never reach the answer to the final "why is this?"...

E.g. (picking just some of your statements)
- Why is there a certification requirement that demands particular stick forces when approaching a stall? Final answer: to prevent stalls....
- Why are there systems to provide warnings to the pilots? Final answer: to help avoiding stalls.
- Why was the MAX required to meet certain stall characteristics? Final answer: to help avoiding stalls (<- if that is not a no brainer, then maybe questions about ones brain should be asked)
- Why pilots must identify that they are approaching a stall by not letting the stick force fall below a certain value? Final answer: to help avoiding stalls.


It seems like we are arguing about the English language. I'll admit some of what I type is pretty bad sometimes so I apologize if it's ever confusing.

I'll try once more.

The systems on the Max help to give the pilots clues to prevent inadvertently entering a stall - but none of them will actually cause the stall to not happen like a FBW design in Normal Law with all safeties working. They will not "prevent a stall" automatically. They still require the correct action from the pilot. They are helping the pilot to avoid a stall by giving them clues.

A properly functioning Stick Shaker, MCAS, or Audio alarm will not stop a stall from happening.

The probably only automatic thing on a non-FBW aircraft that would prevent(stop) a stall from happening would be a stick pusher that can't be countermanded by the pilot.

The MAX or NG do not have any anti-stall (meaning will automatically stop a stall from happening) systems. They just have systems to help avoid stalls by giving the pilot tactile and Audio clues - MCAS would be included in that category - it gives the pilots clues to help avoid stalls. it won't stop a stall from happening. MCAS gives tactile clues like a stick shaker would.

Ray - help!
 
hivue
Posts: 2076
Joined: Tue Feb 26, 2013 2:26 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 5:54 pm

kalvado wrote:
We had comments saying that MCAS activates "way after stick shaker activation". Whatever that worth, this is a plausible scenario.
And that pretty much means that MCAS legit activation happens when real emergency is underway. While no definite scenarios were published, to me it sounds like "we're going to crash, pray for this bird doing impossible to save us" things - like last second CFIT or mid-air avoidance.


If this is true (which I don't think it is) then it would be clear to everyone that MCAS would definitely require simulator time as part of training for the MAX, and keeping MCAS secret (as Boeing basically did) would be a more egregious mistake than even the worst Boeing haters in this thread have been accusing them of.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
kalvado
Posts: 2817
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 6:09 pm

hivue wrote:
kalvado wrote:
We had comments saying that MCAS activates "way after stick shaker activation". Whatever that worth, this is a plausible scenario.
And that pretty much means that MCAS legit activation happens when real emergency is underway. While no definite scenarios were published, to me it sounds like "we're going to crash, pray for this bird doing impossible to save us" things - like last second CFIT or mid-air avoidance.


If this is true (which I don't think it is) then it would be clear to everyone that MCAS would definitely require simulator time as part of training for the MAX, and keeping MCAS secret (as Boeing basically did) would be a more egregious mistake than even the worst Boeing haters in this thread have been accusing them of.

viewtopic.php?f=3&t=1426007&start=2250#p21594133
If my memory serves me right, @7BOEING7 is a Boeing employee
Whatever that worth
 
User avatar
aerolimani
Posts: 1321
Joined: Tue Jun 18, 2013 5:46 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 6:12 pm

morrisond wrote:
aerolimani wrote:
morrisond wrote:
Many of you above (but not all) still don't understand what MCAS was for. It was not to point the nose down.

It was too intentionally mistrim the aircraft so it took more effort on the control column to pull the aircraft into a stall and meet the stick force regs.

It had to act at a relatively quick speed to make it harder fast enough so it didn't fall under the value needed.

It is not an anti-stall system as no regulation was required for it to be one. It just unintentionally acted like one when the AOA values went way too high when the vanes failed. Very bad design.

MCAS 2.0 won't defacto operate as an anti-stall system at all as due to the once per cycle limitation you will be able to pull through the heavier control feel and still put it into a stall if you are determined too.

If it was meant to be an anti-stall system it would suck at it.

You are all taking the JATR report where they say things like "may be considered" as "it is". You also have to to remember that the JATR report was not a consensus report. If one of the members had a thought or recommendation it went into the report.

Is it not curious that in order to meet the FAR, the way devised to do so involved manipulating the control surfaces in a way which produces a nose down result? Surely, a stick pusher seems like a simpler solution? Ah, right, but then you’d have to add hardware, and certification would be more complicated. Nonetheless, even the textbook description of a stick pusher describes it as an anti-stall device.

While you’re in the business of “reminding us” of how you feel we should all think, please also remind us of the title of the FAR whose requirements MCAS was created to satisfy. Also, please remind us of the intention behind that FAR.

At the very least, MCAS is a system designed to help pilots not miss the fact they are nearing a stall. And why would that be important? Maybe it’s so that the pilot can then avoid putting the plane into a stall.

By your logic, none of the other stall warning systems are anti-stall systems either. If they’re not there to help prevent a stall from happening, then what are those warnings for?

By all means, discuss/debate the technical details of MCAS, but this business of “it’s not an anti-stall system” is just towing the line of Boeing PR. While I’m not accusing you of being a paid shill, as you continue like this, that does seem to be the function you are serving.


MCAS v 1.0 was not intended to be an Anti-stall - it was due to it's piss poor design that unfortunately it acted like one.

That is why MCAS v2.0 is not required to be one either.

A stick pusher would be an anti-stall system. It was not required for certification.

There is no anti-stall on the NG or MAX. All the systems were there to provide warnings for the pilots.

There is nothing on an 737 NG or MAX to keep the pilot from intentionally putting it into a stall. None of the other systems will prevent a stall. You can pull right through them.

MCAS was required to meet the FAR's for stall characteristics to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.

I don't know how more plainly it can be said.

If you were flying the MAX in manual mode and were maintaining a certain angle of attack per the instruments or outside visual reference and MCAS fired once - you would feel the elevator getting a little heavier. You wouldn't let the nose drop by not counteracting that force unless you were being completely inattentive to what the aircraft was supposed to be doing - which is your job as you are flying an airplane in manual mode.

What else do you expect the pilot to be doing if they are trying to fly at way higher than normal AOA's? Going for a coffee or texting on there phone and not paying attention to what the aircraft is doing?


active stall prevention = anti-stall
…but,
anti-stall ≠ active stall prevention

Anti simply means against.

Let’s consider your phrasing that MCAS is “to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.” Why would we want that? The reason is so that pilots don’t inadvertently stall the plane. A system which helps pilots to avoid stalls is still anti-stall.

Anyhow… there’s plenty of accredited experts out there now, perfectly willing to label MCAS as an anti-stall measure. You can go on calling it whatever you like. Just know that it comes across as whitewashing.
 
morrisond
Posts: 2715
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 6:25 pm

hivue wrote:
kalvado wrote:
We had comments saying that MCAS activates "way after stick shaker activation". Whatever that worth, this is a plausible scenario.
And that pretty much means that MCAS legit activation happens when real emergency is underway. While no definite scenarios were published, to me it sounds like "we're going to crash, pray for this bird doing impossible to save us" things - like last second CFIT or mid-air avoidance.


If this is true (which I don't think it is) then it would be clear to everyone that MCAS would definitely require simulator time as part of training for the MAX, and keeping MCAS secret (as Boeing basically did) would be a more egregious mistake than even the worst Boeing haters in this thread have been accusing them of.


It wasn't in the iPad conversion course or the POH but it was in the maintenance manuals. So it wasn't secret - the information was just not readily available to the pilots. The FAA agreed the pilots had no need to know.
 
kalvado
Posts: 2817
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 6:30 pm

aerolimani wrote:
morrisond wrote:
aerolimani wrote:
Is it not curious that in order to meet the FAR, the way devised to do so involved manipulating the control surfaces in a way which produces a nose down result? Surely, a stick pusher seems like a simpler solution? Ah, right, but then you’d have to add hardware, and certification would be more complicated. Nonetheless, even the textbook description of a stick pusher describes it as an anti-stall device.

While you’re in the business of “reminding us” of how you feel we should all think, please also remind us of the title of the FAR whose requirements MCAS was created to satisfy. Also, please remind us of the intention behind that FAR.

At the very least, MCAS is a system designed to help pilots not miss the fact they are nearing a stall. And why would that be important? Maybe it’s so that the pilot can then avoid putting the plane into a stall.

By your logic, none of the other stall warning systems are anti-stall systems either. If they’re not there to help prevent a stall from happening, then what are those warnings for?

By all means, discuss/debate the technical details of MCAS, but this business of “it’s not an anti-stall system” is just towing the line of Boeing PR. While I’m not accusing you of being a paid shill, as you continue like this, that does seem to be the function you are serving.


MCAS v 1.0 was not intended to be an Anti-stall - it was due to it's piss poor design that unfortunately it acted like one.

That is why MCAS v2.0 is not required to be one either.

A stick pusher would be an anti-stall system. It was not required for certification.

There is no anti-stall on the NG or MAX. All the systems were there to provide warnings for the pilots.

There is nothing on an 737 NG or MAX to keep the pilot from intentionally putting it into a stall. None of the other systems will prevent a stall. You can pull right through them.

MCAS was required to meet the FAR's for stall characteristics to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.

I don't know how more plainly it can be said.

If you were flying the MAX in manual mode and were maintaining a certain angle of attack per the instruments or outside visual reference and MCAS fired once - you would feel the elevator getting a little heavier. You wouldn't let the nose drop by not counteracting that force unless you were being completely inattentive to what the aircraft was supposed to be doing - which is your job as you are flying an airplane in manual mode.

What else do you expect the pilot to be doing if they are trying to fly at way higher than normal AOA's? Going for a coffee or texting on there phone and not paying attention to what the aircraft is doing?


active stall prevention = anti-stall
…but,
anti-stall ≠ active stall prevention

Anti simply means against.

Let’s consider your phrasing that MCAS is “to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.” Why would we want that? The reason is so that pilots don’t inadvertently stall the plane. A system which helps pilots to avoid stalls is still anti-stall.

Anyhow… there’s plenty of accredited experts out there now, perfectly willing to label MCAS as an anti-stall measure. You can go on calling it whatever you like. Just know that it comes across as whitewashing.

There was a discussion a few months ago. Some texbooks were produced.
The moral of the story, if I remember correctly, that someone defined "stall prevention system" as a system which prevents stall despite any pilot effort to stall. From there it goes - MCAS can be overcome, so it doesn't qualify.
A pretty straw-men argument, IMHO, as this is a very narrow use of word "prevention". But people get very irritated when you call things by their true names.
 
morrisond
Posts: 2715
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 6:32 pm

aerolimani wrote:
morrisond wrote:
aerolimani wrote:
Is it not curious that in order to meet the FAR, the way devised to do so involved manipulating the control surfaces in a way which produces a nose down result? Surely, a stick pusher seems like a simpler solution? Ah, right, but then you’d have to add hardware, and certification would be more complicated. Nonetheless, even the textbook description of a stick pusher describes it as an anti-stall device.

While you’re in the business of “reminding us” of how you feel we should all think, please also remind us of the title of the FAR whose requirements MCAS was created to satisfy. Also, please remind us of the intention behind that FAR.

At the very least, MCAS is a system designed to help pilots not miss the fact they are nearing a stall. And why would that be important? Maybe it’s so that the pilot can then avoid putting the plane into a stall.

By your logic, none of the other stall warning systems are anti-stall systems either. If they’re not there to help prevent a stall from happening, then what are those warnings for?

By all means, discuss/debate the technical details of MCAS, but this business of “it’s not an anti-stall system” is just towing the line of Boeing PR. While I’m not accusing you of being a paid shill, as you continue like this, that does seem to be the function you are serving.


MCAS v 1.0 was not intended to be an Anti-stall - it was due to it's piss poor design that unfortunately it acted like one.

That is why MCAS v2.0 is not required to be one either.

A stick pusher would be an anti-stall system. It was not required for certification.

There is no anti-stall on the NG or MAX. All the systems were there to provide warnings for the pilots.

There is nothing on an 737 NG or MAX to keep the pilot from intentionally putting it into a stall. None of the other systems will prevent a stall. You can pull right through them.

MCAS was required to meet the FAR's for stall characteristics to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.

I don't know how more plainly it can be said.

If you were flying the MAX in manual mode and were maintaining a certain angle of attack per the instruments or outside visual reference and MCAS fired once - you would feel the elevator getting a little heavier. You wouldn't let the nose drop by not counteracting that force unless you were being completely inattentive to what the aircraft was supposed to be doing - which is your job as you are flying an airplane in manual mode.

What else do you expect the pilot to be doing if they are trying to fly at way higher than normal AOA's? Going for a coffee or texting on there phone and not paying attention to what the aircraft is doing?


active stall prevention = anti-stall
…but,
anti-stall ≠ active stall prevention

Anti simply means against.

Let’s consider your phrasing that MCAS is “to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.” Why would we want that? The reason is so that pilots don’t inadvertently stall the plane. A system which helps pilots to avoid stalls is still anti-stall.

Anyhow… there’s plenty of accredited experts out there now, perfectly willing to label MCAS as an anti-stall measure. You can go on calling it whatever you like. Just know that it comes across as whitewashing.


I can't believe we are dwelling on this.

The definition of anti "anti. To be anti is to be opposed to or against something, like an action, political party, or government. If you are anti love scenes, you might prefer an action flick. The word anti comes from the prefix anti-, which means “against” or “opposite,” and is still used in English words, such as antibodies and anti-hero"

Answer this one simple question - will MCAS stop a stall from happening? Yes or no. If no then it is not anti-stall. If yes then it is Anti-stall.

Properly working it is no different than a stick shaker. It will not stop a stall from happening.
 
kalvado
Posts: 2817
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 6:35 pm

morrisond wrote:
aerolimani wrote:
morrisond wrote:

MCAS v 1.0 was not intended to be an Anti-stall - it was due to it's piss poor design that unfortunately it acted like one.

That is why MCAS v2.0 is not required to be one either.

A stick pusher would be an anti-stall system. It was not required for certification.

There is no anti-stall on the NG or MAX. All the systems were there to provide warnings for the pilots.

There is nothing on an 737 NG or MAX to keep the pilot from intentionally putting it into a stall. None of the other systems will prevent a stall. You can pull right through them.

MCAS was required to meet the FAR's for stall characteristics to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.

I don't know how more plainly it can be said.

If you were flying the MAX in manual mode and were maintaining a certain angle of attack per the instruments or outside visual reference and MCAS fired once - you would feel the elevator getting a little heavier. You wouldn't let the nose drop by not counteracting that force unless you were being completely inattentive to what the aircraft was supposed to be doing - which is your job as you are flying an airplane in manual mode.

What else do you expect the pilot to be doing if they are trying to fly at way higher than normal AOA's? Going for a coffee or texting on there phone and not paying attention to what the aircraft is doing?


active stall prevention = anti-stall
…but,
anti-stall ≠ active stall prevention

Anti simply means against.

Let’s consider your phrasing that MCAS is “to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.” Why would we want that? The reason is so that pilots don’t inadvertently stall the plane. A system which helps pilots to avoid stalls is still anti-stall.

Anyhow… there’s plenty of accredited experts out there now, perfectly willing to label MCAS as an anti-stall measure. You can go on calling it whatever you like. Just know that it comes across as whitewashing.


I can't believe we are dwelling on this.

The definition of anti "anti. To be anti is to be opposed to or against something, like an action, political party, or government. If you are anti love scenes, you might prefer an action flick. The word anti comes from the prefix anti-, which means “against” or “opposite,” and is still used in English words, such as antibodies and anti-hero"

Answer this one simple question - will MCAS stop a stall from happening? Yes or no. If no then it is not anti-stall. If yes then it is Anti-stall.

Properly working it is no different than a stick shaker. It will not stop a stall from happening.

You may look up other uses of "anti-" terms. Hint: antibiotics can be inefficient, so do anti-terrorism forces.
As for stick shaker - you may also notice that some control surfaces are moved by MCAS, not the case with stick shaker.
 
hivue
Posts: 2076
Joined: Tue Feb 26, 2013 2:26 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 6:48 pm

kalvado wrote:
hivue wrote:
kalvado wrote:
We had comments saying that MCAS activates "way after stick shaker activation". Whatever that worth, this is a plausible scenario.
And that pretty much means that MCAS legit activation happens when real emergency is underway. While no definite scenarios were published, to me it sounds like "we're going to crash, pray for this bird doing impossible to save us" things - like last second CFIT or mid-air avoidance.


If this is true (which I don't think it is) then it would be clear to everyone that MCAS would definitely require simulator time as part of training for the MAX, and keeping MCAS secret (as Boeing basically did) would be a more egregious mistake than even the worst Boeing haters in this thread have been accusing them of.

viewtopic.php?f=3&t=1426007&start=2250#p21594133
If my memory serves me right, @7BOEING7 is a Boeing employee
Whatever that worth


My comment was addressed to your "...to me it sounds like 'we're going to crash, pray for this bird doing impossible to save us' things - like last second CFIT or mid-air avoidance."

I believe 7BOEING7 is a retired Boeing production test pilot.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
kalvado
Posts: 2817
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 7:04 pm

hivue wrote:
kalvado wrote:
hivue wrote:

If this is true (which I don't think it is) then it would be clear to everyone that MCAS would definitely require simulator time as part of training for the MAX, and keeping MCAS secret (as Boeing basically did) would be a more egregious mistake than even the worst Boeing haters in this thread have been accusing them of.

viewtopic.php?f=3&t=1426007&start=2250#p21594133
If my memory serves me right, @7BOEING7 is a Boeing employee
Whatever that worth


My comment was addressed to your "...to me it sounds like 'we're going to crash, pray for this bird doing impossible to save us' things - like last second CFIT or mid-air avoidance."

I believe 7BOEING7 is a retired Boeing production test pilot.

Well, assuming MCAS is indeed coming after stick shaker. What can be the reason for pilot to keep pulling? I cannot see any non-emergency scenario requiring that. Emergencies tend to be one of a kind; and MCAS is there to make plane "feel right", whatever that mean. Probably giving plane "natural feel" is more important - and MCAS, as reported, does exactly that, makes things predictable
 
mzlin
Posts: 128
Joined: Sat Mar 31, 2012 6:32 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 7:12 pm

aerolimani wrote:
morrisond wrote:
aerolimani wrote:
Is it not curious that in order to meet the FAR, the way devised to do so involved manipulating the control surfaces in a way which produces a nose down result? Surely, a stick pusher seems like a simpler solution? Ah, right, but then you’d have to add hardware, and certification would be more complicated. Nonetheless, even the textbook description of a stick pusher describes it as an anti-stall device.

While you’re in the business of “reminding us” of how you feel we should all think, please also remind us of the title of the FAR whose requirements MCAS was created to satisfy. Also, please remind us of the intention behind that FAR.

At the very least, MCAS is a system designed to help pilots not miss the fact they are nearing a stall. And why would that be important? Maybe it’s so that the pilot can then avoid putting the plane into a stall.

By your logic, none of the other stall warning systems are anti-stall systems either. If they’re not there to help prevent a stall from happening, then what are those warnings for?

By all means, discuss/debate the technical details of MCAS, but this business of “it’s not an anti-stall system” is just towing the line of Boeing PR. While I’m not accusing you of being a paid shill, as you continue like this, that does seem to be the function you are serving.


MCAS v 1.0 was not intended to be an Anti-stall - it was due to it's piss poor design that unfortunately it acted like one.

That is why MCAS v2.0 is not required to be one either.

A stick pusher would be an anti-stall system. It was not required for certification.

There is no anti-stall on the NG or MAX. All the systems were there to provide warnings for the pilots.

There is nothing on an 737 NG or MAX to keep the pilot from intentionally putting it into a stall. None of the other systems will prevent a stall. You can pull right through them.

MCAS was required to meet the FAR's for stall characteristics to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.

I don't know how more plainly it can be said.

If you were flying the MAX in manual mode and were maintaining a certain angle of attack per the instruments or outside visual reference and MCAS fired once - you would feel the elevator getting a little heavier. You wouldn't let the nose drop by not counteracting that force unless you were being completely inattentive to what the aircraft was supposed to be doing - which is your job as you are flying an airplane in manual mode.

What else do you expect the pilot to be doing if they are trying to fly at way higher than normal AOA's? Going for a coffee or texting on there phone and not paying attention to what the aircraft is doing?


active stall prevention = anti-stall
…but,
anti-stall ≠ active stall prevention

Anti simply means against.

Let’s consider your phrasing that MCAS is “to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.” Why would we want that? The reason is so that pilots don’t inadvertently stall the plane. A system which helps pilots to avoid stalls is still anti-stall.

Anyhow… there’s plenty of accredited experts out there now, perfectly willing to label MCAS as an anti-stall measure. You can go on calling it whatever you like. Just know that it comes across as whitewashing.


While we are arguing over semantics, I would agree that MCAS is anti-stall, because as you point out the reason for longitudinal stability within the 'stall characteristics' FAR 25.203 is to avoid/discourage stalls, and anti- is a pretty general term that encompasses avoidance, discouragement, or prevention. However MCAS cannot fully prevent or protect against stalls, and Boeing seems eager to play down that expectation (perhaps so it doesn't get roped into making a robust automated protection system and can continue to put the onus of stall prevention on the pilots). So I would propose we agree that MCAS is for stall discouragement, and thereby is anti-stall loosely speaking.

BTW Peter Lemmle made the link between FAR 25.203 and MCAS here if you are looking for another source to link the two: https://www.satcom.guru/2019/03/regulat ... stems.html
Last edited by mzlin on Tue Oct 15, 2019 7:30 pm, edited 1 time in total.
 
User avatar
aerolimani
Posts: 1321
Joined: Tue Jun 18, 2013 5:46 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 7:24 pm

morrisond wrote:
aerolimani wrote:
morrisond wrote:

MCAS v 1.0 was not intended to be an Anti-stall - it was due to it's piss poor design that unfortunately it acted like one.

That is why MCAS v2.0 is not required to be one either.

A stick pusher would be an anti-stall system. It was not required for certification.

There is no anti-stall on the NG or MAX. All the systems were there to provide warnings for the pilots.

There is nothing on an 737 NG or MAX to keep the pilot from intentionally putting it into a stall. None of the other systems will prevent a stall. You can pull right through them.

MCAS was required to meet the FAR's for stall characteristics to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.

I don't know how more plainly it can be said.

If you were flying the MAX in manual mode and were maintaining a certain angle of attack per the instruments or outside visual reference and MCAS fired once - you would feel the elevator getting a little heavier. You wouldn't let the nose drop by not counteracting that force unless you were being completely inattentive to what the aircraft was supposed to be doing - which is your job as you are flying an airplane in manual mode.

What else do you expect the pilot to be doing if they are trying to fly at way higher than normal AOA's? Going for a coffee or texting on there phone and not paying attention to what the aircraft is doing?


active stall prevention = anti-stall
…but,
anti-stall ≠ active stall prevention

Anti simply means against.

Let’s consider your phrasing that MCAS is “to help the pilot identify they were approaching a stall by not letting the stick force fall below a certain value.” Why would we want that? The reason is so that pilots don’t inadvertently stall the plane. A system which helps pilots to avoid stalls is still anti-stall.

Anyhow… there’s plenty of accredited experts out there now, perfectly willing to label MCAS as an anti-stall measure. You can go on calling it whatever you like. Just know that it comes across as whitewashing.


I can't believe we are dwelling on this.

The definition of anti "anti. To be anti is to be opposed to or against something, like an action, political party, or government. If you are anti love scenes, you might prefer an action flick. The word anti comes from the prefix anti-, which means “against” or “opposite,” and is still used in English words, such as antibodies and anti-hero"

Answer this one simple question - will MCAS stop a stall from happening? Yes or no. If no then it is not anti-stall. If yes then it is Anti-stall.

Properly working it is no different than a stick shaker. It will not stop a stall from happening.

To answer your question above, as bolded by me. No, as far as we understand it, MCAS 2.0 will not stop a pilot from pulling through to a stall, but it will prevent one from doing it inadvertently.

Just to add to the list: antifreeze can be frozen.

Why do press I this issue? It’s because words matter. Going back to earliest grounding thread from months ago, it’s interesting reading all the posts saying how MCAS is “barely needed” or “only operates in a tiny margin of the flight envelope.” It’s a clear and steady effort to minimize the role of the aircraft’s design. I think the pushback against use of the term anti-stall is part of this same effort.

These threads are a constant evolution which began with “there’s nothing wrong with the plane, and grounding the MAX would be irresponsible” through to where we are now with “it’s not an anti-stall system.” In between, there’s a lot of “okay, fine, yes, that actually is bad, but what about this new thing I just thought of.”
Last edited by aerolimani on Tue Oct 15, 2019 7:26 pm, edited 1 time in total.
 
mzlin
Posts: 128
Joined: Sat Mar 31, 2012 6:32 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 7:24 pm

A little beside the point, but I learned something very interesting from this thread which is that the L1011 had a single-piece stabilator for trim and pitch control, instead of the whole stabilizer for trim and the smaller elevator section for pitch. This then led me to the incredible story of how astute pilots saved Delta Flight 1080, in which the L1011 left stabilator jammed in the fully pitch-up direction. It is really interesting to read about the emotions that the pilots went through as they first thought they were doomed but then recovered enough presence of mind to improvise a solution. Wikipedia has little detail on this but does link to this fascinating first-hand account: https://www.tristar500.net/library/flight1080.pdf.

Similar to UA232, an impressive example of airmanship... true understanding of the airplane and how it works. No panicked attempts to hit the autopilot button here. UA232 seems to get mentioned a lot on this site but I had never heard of DL1080. Both happened with trijets.

Relevant to this thread, the pilots talk about trying the electric trim switches and the manual wheel... so there's some insight into how trim issues can be troubleshooted (troubleshot?) in the hands of experienced pilots.
 
rheinwaldner
Posts: 1859
Joined: Wed Jan 02, 2008 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Oct 15, 2019 7:51 pm

morrisond wrote:
I'll try once more.

The systems on the Max help to give the pilots clues to prevent inadvertently entering a stall - but none of them will actually cause the stall to not happen like a FBW design in Normal Law with all safeties working. They will not "prevent a stall" automatically. They still require the correct action from the pilot. They are helping the pilot to avoid a stall by giving them clues.

A properly functioning Stick Shaker, MCAS, or Audio alarm will not stop a stall from happening.

The probably only automatic thing on a non-FBW aircraft that would prevent(stop) a stall from happening would be a stick pusher that can't be countermanded by the pilot.

The MAX or NG do not have any anti-stall (meaning will automatically stop a stall from happening) systems. They just have systems to help avoid stalls by giving the pilot tactile and Audio clues - MCAS would be included in that category - it gives the pilots clues to help avoid stalls. it won't stop a stall from happening. MCAS gives tactile clues like a stick shaker would.

Why should an anti stall system not do all that?

You even mention stick shaker all the time. Do you say, stick shaker does not exist to prevent stalls?

Stick shaker, as well as the stick force requirements (and therefore MCAS) do exist to prevent stalls. You need to look at the ultimate goal of a thing. Why does it exist? Really.

B.t.w. in this post again a lot of wrong things are written. MCAS gives no tactile clues approaching a stall. It just makes the aircraft behaving as natural, as an aerodynamically stable aircraft would (by correcting the "unnatural" stick force curve the MAX otherwise has).
Many things are difficult, all things are possible!

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