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seahawk
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 2:33 pm

OldAeroGuy wrote:
seahawk wrote:
ET crew as in the end they also did the normal procedure for unreliable airspeed indications.


What evidence do you have that the ET302 applied the "Unreliable Airspeed" procedures?


From the FDR data from the preliminary report. It looks very much as if they were aiming for the suggested 10° with Flaps 5 and 4-5° with Flaps up.
 
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PW100
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 2:34 pm

OldAeroGuy wrote:
Unfortunately, I'll probably now be tagged as part of the "Boeing PR" machine.


Well, as far as I'm concerned, that's not the case. I find many of your contributions very helpful, and well thought out.

However, these kind of posts are not helping your case . . . :
OldAeroGuy wrote:
Interested wrote:
We keep reading that the initial pitch down command of 0.6 was changed to 2.5 at some stage of design
Why would something so severe be needed oldaeroguy?
Isn't that a concern for everybody?


I'm much more concerned about the apparent AoA vane signal failure rate.


. . . evading an important question, by raising a new question . . .
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Interested
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 2:47 pm

OldAeroGuy wrote:
Interested wrote:
OldAeroGuy wrote:

I'm much more concerned about the apparent AoA vane signal failure rate.


But why do none of the Boeing defenders who tell is MCAS isn't really needed evert answer that question above. Why did it have to be changed to be so powerful late on in the design process?


Have I ever said that MCAS isn't needed?


But once again you haven't answered the question. None of the Boeing defenders do on here. Some say MCAS isn't needed - some say we don't have a serious problem to fix. Some say the Max737 is a great design. Some say everything is fine.

NOBODY ever answers the question as to what went wrong to result in an initial plan/design of 0.6 nose down to be changed to 2.5 behind closed doors?

Why?

What went wrong to make that happen? Why so extreme?
What is it preventing for all of us to stay safe in these planes?

What is the big problem it had to fix?

Let's get some honest answers ?

Stop avoiding this question every time?

What's wrong guys? Haven't Boeing being able to write up a PR answer for this yet?
Last edited by Interested on Mon Apr 22, 2019 2:58 pm, edited 1 time in total.
 
OldAeroGuy
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 2:53 pm

seahawk wrote:
OldAeroGuy wrote:
seahawk wrote:
ET crew as in the end they also did the normal procedure for unreliable airspeed indications.


What evidence do you have that the ET302 applied the "Unreliable Airspeed" procedures?


From the FDR data from the preliminary report. It looks very much as if they were aiming for the suggested 10° with Flaps 5 and 4-5° with Flaps up.


The QRH "Airspeed unreliable" procedure calls for both Attitude and Thrust adjustments.

The ET302 crew did not adjust thrust, keeping it at the takeoff rating throughout the accident.

Flaps down attitude varied from 10 deg initially and decreasing to 4 deg at Flap retraction. There is no evidence the crew tried to maintain a constant attitude prior to Flap retraction.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
OldAeroGuy
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 3:06 pm

PW100 wrote:
OldAeroGuy wrote:
Unfortunately, I'll probably now be tagged as part of the "Boeing PR" machine.


Well, as far as I'm concerned, that's not the case. I find many of your contributions very helpful, and well thought out.

However, these kind of posts are not helping your case . . . :
OldAeroGuy wrote:
Interested wrote:
We keep reading that the initial pitch down command of 0.6 was changed to 2.5 at some stage of design
Why would something so severe be needed oldaeroguy?
Isn't that a concern for everybody?


I'm much more concerned about the apparent AoA vane signal failure rate.


. . . evading an important question, by raising a new question . . .


I really am more concerned about the AoA vane failure rate as it has the potential to impact many airplane fault trees and FMEA's.

The change from 0.6 to 2.5 may only represent flight test tuning. In normal operation at high AoA, it's probably not a major issue. With an AoA vane signal failure at low AoA, it becomes more important due to high dynamic pressure.

The important point is to have MCAS not activate at low AoA. That's why high AoA vane signal failure rate is a more important concern.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
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SomebodyInTLS
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 3:30 pm

ArgentoSystems wrote:
rheinwaldner wrote:
OldAeroGuy wrote:
And once again, MCAS was not a stall prevention device. The pilot could still stall the MAX with MCAS operating. MCAS was designed to make sure the stall entry stick force did not "lighten" duding the stall entry.

Answer this question: why is it not allowed to lighten during stall entry? What would be the risk if it does lighten? Do you see why many are saying, it is ultimately to prevent stalls?


Was going to ask the same.


I keep making this point and it keeps getting ignored...
"As with most things related to aircraft design, it's all about the trade-offs and much more nuanced than A.net likes to make out."
 
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SomebodyInTLS
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 3:37 pm

OldAeroGuy wrote:
I really am more concerned about the AoA vane failure rate as it has the potential to impact many airplane fault trees and FMEA's.


And I've been saying this since a couple of weeks after the Lion Air crash - during that first thread it became clear that a fault downstream in the avionics looked like the possible failure which triggered everything, and Ethiopian fits the same scenario.
"As with most things related to aircraft design, it's all about the trade-offs and much more nuanced than A.net likes to make out."
 
OldAeroGuy
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 3:42 pm

SomebodyInTLS wrote:
ArgentoSystems wrote:
rheinwaldner wrote:
Answer this question: why is it not allowed to lighten during stall entry? What would be the risk if it does lighten? Do you see why many are saying, it is ultimately to prevent stalls?


Was going to ask the same.


I keep making this point and it keeps getting ignored...


ArgentoSystems and SomebodyinTLS, I hope you've read my Reply #5800.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
ArgentoSystems
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 3:47 pm

OldAeroGuy wrote:
By eliminating "stick lightening", MCAS makes inadvertent stalls less likely as required by certification regulations.

As I said above, MCAS is not a stall prevention device since the pilot can still stall the airplane with MCAS in operation.

LOL. Are you listening to yourself? It is like saying that collision avoidance system on my Subaru (that brakes automatically if I'm heading for an obstacle) is not really a collision avoidance system because I still can make a collision while driving this vehicle. Even when the system is activated.

Your statement does not make much sense.

The keyword here is inadvertent. Obviously MCAS won't work against deliberate attempt to stall, same as my CAS won't work against deliberate attempt to crash a vehicle. But that does not change the purpose of the system. If you deny that, you have to admit that MCAS serves no purpose whatsoever.
Last edited by ArgentoSystems on Mon Apr 22, 2019 3:53 pm, edited 3 times in total.
 
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Francoflier
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 3:48 pm

OldAeroGuy wrote:
The important point is to have MCAS not activate at low AoA. That's why high AoA vane signal failure rate is a more important concern.


I disagree.

Aircraft systems, especially those that directly impact the airplane's flight controls and trajectory, are meant to be fault tolerant, usually multiple-fault tolerant.

High AoA failure rate is obviously not good, but zero failure rate is simply unachievable. The systems that depend on that signal should be able to tolerate that failure without adversely affecting the airplane's flight path. This is airplane design 101, and whoever came up with MCAS failed that class hard...

...either that or they were under immense pressure to push that thing through.

That being said, as mentioned above, there is still no conclusive proof that the faulty AoA signal was coming from the probe itself. There might still be an issue laying deeper in the air data system.
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
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zeke
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 4:13 pm

PixelFlight wrote:
zeke wrote:
PixelFlight wrote:
Conclusion: AoA.-> SMYD -> FDAU -> FDR


So more than enough to know that the FDR does not actually record the raw sensor values, it records the values after being processed by at least two other boxes. But we still don’t know where the MAX gets it AOA values from, you only gave NG.

The reality is the fault could have been in the ADIRU, SYMD, or the EFDAU, or the new wiring looms.

What has been said to me by others is to look at where the FDR gets its information from for clues. The main reason they were suggesting that is they had the belief the AOA probes on the JT aircraft were serviceable, and something else was causing the speed and altitude issues.

Apparently there is a full set of paperwork for the probe that was installed showing it had passed all bench tests required before being released for flight (that is from an avionics shop in the US).

I am also told there is a way to check the ADIRU and SYMD in the FDR data, something about the relationships between data.

There are at least 5 sources of information about the erratic AoA values and related consequences:
1) The AoA erratic value
2) The airspeed disagree due to erratic AoA value in the correction algorithm.
3) The MCAS action due to erratic AoA value.
4) The tab trim position due to erratic AoA value and MCAS command.
5) The stick shaker activation due to erratic AoA value.
But not all those FDR recorded facts come from the same AoA link:
AoA
| |            /---------------------------------------------------------\
| \---> ADIRU --> FCC --> MCAS ---> STAB TRIM MOTOR --> STAB POSITION ---\|
|                                \---------------------------------------\|
\------> SMYD -----------------------------------------------------------\|
            \-----> STICK SHAKER ----------------------------------------\|
                                                                           \--> FADU --> FDR

I understand that the AoA vane could not be the only common failure mode that can still keep a coherency between so much recorded data. A power supply issue or a cross wires electromagnetic perturbation for example could possibly do the same. But the AoA vane is still on the very top of the list until a published analysis of the AoA vane can suggest something else. To add to this, existing AoA fault analysis on others events have show mechanical issues that exhibit a common mode erratic value on the two links.


There is multiple ways for the same or similar symptoms to occur. For example a blocked or bad static pressure input will also cause undue stick shaker, incorrect airspeed, incorrect altitude.

Also if there is s bad AOA value in the system, ie the AOA is 8 to 11 degrees more than thermal anti-ice (TAI) biased stick shaker AOA, the Elevator Feel Shift Module will add up to 4 times higher normal control column pressure.

There are far too many conclusions being drawn from an incomplete preliminary factual report.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
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zeke
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 4:38 pm

Interested wrote:
NOBODY ever answers the question as to what went wrong to result in an initial plan/design of 0.6 nose down to be changed to 2.5 behind closed doors?

Why?


I get accused on here many times of being an Airbus fanboy, when many times I make comments or corrections regarding incorrect information being posted.

I have posted on these max threads not as a supporter of Boeing, or the 737. I am a supporter of the process. If I could use an analogy of the legal system, I am not trying to say someone is innocent or guilty, I am supporting the underlying concept of the law.

Now many reasons could explain the change, anything from expanding the cg envelope, changes required after flight testing etc. There is nothing sinister about this, it is the normal process.

Interested wrote:
What went wrong to make that happen? Why so extreme?
What is it preventing for all of us to stay safe in these planes?


We don’t know, lots of people guessing they know. Truth is they have not released any analysis of the facts they have presented in the preliminary factual report.

Interested wrote:
What is the big problem it had to fix?


Are you asking why MCAS was required in the MAX and not earlier 737s?

If that is your question the MAX is certified to a later standard of the FAR 25 requirements than earlier models. Numerous changes were made to meet the later certification standards.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
morrisond
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 5:16 pm

seahawk wrote:
You can not train the failure of a function that is not even documented (Lion Air) and also not for the MCAS fault scenario encountered by the ET crew as in the end they also did the normal procedure for unreliable airspeed indications.

In the end the whole case is not so much a problem of the aircraft or the pilots but a problem of money winning over safety and a whole new system being hidden in the documentation and in the cockpit.



Why wouldn't Lionair assume it was something to do with the trim system and turn off - the pilot knew it was doing weird things - if the autopilot kept turning you 90 degrees to the left - would you continue the flight with it engaged or turn it off?

ET did not do the normal procedure for unreliable airspeed as they failed to set N1 at 80% and establish a 5(or 10% I can't remember which) AOA.

Yes money is winning over safety - Training has been cut too far.
Last edited by morrisond on Mon Apr 22, 2019 5:32 pm, edited 1 time in total.
 
morrisond
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 5:26 pm

SomebodyInTLS wrote:
ArgentoSystems wrote:
rheinwaldner wrote:
Answer this question: why is it not allowed to lighten during stall entry? What would be the risk if it does lighten? Do you see why many are saying, it is ultimately to prevent stalls?


Was going to ask the same.


I keep making this point and it keeps getting ignored...


Quoting from OLDAEROGUY on the previous page

"For the benefit of all participants of this forum, here is the requirement the 737 MAX can't meet without MCAS:

From AC 25-7C: https://www.faa.gov/documentLibrary/med ... -7C%20.pdf

Stall Characteristics

Procedures
3(c) During the approach to the stall, the longitudinal control pull force should
increase continuously as speed is reduced from the trimmed speed to the onset of stall warning.
Below that speed some reduction in longitudinal control force is acceptable, provided it is not
sudden or excessive.

See Page 136"
 
morrisond
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 5:31 pm

PW100 wrote:
morrisond wrote:
Lionair was very unfortunate as no one knew what MCAS was however they failed to miss that maybe they have effectively runaway trim 22 times and did not follow the runaway trim procedures. Plus they were possibly dispatched with faulty equipment and the preceding flight should have done a lot more to warn the next flight.


They can be excused for not interpreting an intermittent moving trim as continuously moving trim (which is what the runaway trim checklist calls for].

That it may have been dispatched with possibly faulty equipment, became only apparent once airborne. The AoA sensor was replaced before flight, but that did not seem to have fixed the problem. But that was only clear once airborne. Apparently Boeing did not provide instructions for an end-to-end ground test of the AoA system.


ET302 who should have know the proper procedures to deal with an MCAS fault by the time of the crash apparently forgot the procedures and failed to keep the plane in the proper speed range.


They DID follow uptrim instructions, and they DID use the cut-out switches. So the pretty much DID follow proper procedures.

We don't know if it was crew intervention which cut the uptrim short prior to cut-off switches. Uptrim stopped at 2.3 degrees elevator angle. In fact, all four up trim actions stopped at 2.3 degrees stabilizer angle. Coincidence . . . ? Perhaps. Fact that it was crew action that stopped uptrim premature and thus did not follow procedure? No.

Yes, they did turn it back on. But that could be an action of desperation. If they felt they were going to crash because of heavy out-of-trim condition, and they were unable to move the manual wheel by hand, then they can be excused for turning it back on.


I'm at total loss why one does not keep an open mind and try to understand why the crew decided for such actions. Instead, the crew is thrown under the bus without sufficient data. And Lionair Maintenance crew is also thrown under the same bus.

Again, I'm not claiming the cockpit/maintenance crew did not make any mistakes. Perhaps the main responsibility does lay with them. But we don't have conclusive evidence for such. Until such time, it is heartbreaking that they are put under the bus, when they can't defend for themselves having paid the ultimate price for not being able to control the plane.


They did what they could with the knowledge they had and I do feel terrible for them.

However I highly doubt that the final will show they did everything they could. Close doesn't count in Aviation - only in Horseshoes and Hand Grenades.

I feel terrible for them - but think a really detailed look at the training system that produced them should be done. It obviously was not good enough. They may have done everything they were taught 100% - it's just whether or not that training was comprehensive enough.
 
kalvado
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 5:52 pm

morrisond wrote:
PW100 wrote:
morrisond wrote:
Lionair was very unfortunate as no one knew what MCAS was however they failed to miss that maybe they have effectively runaway trim 22 times and did not follow the runaway trim procedures. Plus they were possibly dispatched with faulty equipment and the preceding flight should have done a lot more to warn the next flight.


They can be excused for not interpreting an intermittent moving trim as continuously moving trim (which is what the runaway trim checklist calls for].

That it may have been dispatched with possibly faulty equipment, became only apparent once airborne. The AoA sensor was replaced before flight, but that did not seem to have fixed the problem. But that was only clear once airborne. Apparently Boeing did not provide instructions for an end-to-end ground test of the AoA system.


ET302 who should have know the proper procedures to deal with an MCAS fault by the time of the crash apparently forgot the procedures and failed to keep the plane in the proper speed range.


They DID follow uptrim instructions, and they DID use the cut-out switches. So the pretty much DID follow proper procedures.

We don't know if it was crew intervention which cut the uptrim short prior to cut-off switches. Uptrim stopped at 2.3 degrees elevator angle. In fact, all four up trim actions stopped at 2.3 degrees stabilizer angle. Coincidence . . . ? Perhaps. Fact that it was crew action that stopped uptrim premature and thus did not follow procedure? No.

Yes, they did turn it back on. But that could be an action of desperation. If they felt they were going to crash because of heavy out-of-trim condition, and they were unable to move the manual wheel by hand, then they can be excused for turning it back on.


I'm at total loss why one does not keep an open mind and try to understand why the crew decided for such actions. Instead, the crew is thrown under the bus without sufficient data. And Lionair Maintenance crew is also thrown under the same bus.

Again, I'm not claiming the cockpit/maintenance crew did not make any mistakes. Perhaps the main responsibility does lay with them. But we don't have conclusive evidence for such. Until such time, it is heartbreaking that they are put under the bus, when they can't defend for themselves having paid the ultimate price for not being able to control the plane.


They did what they could with the knowledge they had and I do feel terrible for them.

However I highly doubt that the final will show they did everything they could. Close doesn't count in Aviation - only in Horseshoes and Hand Grenades.

I feel terrible for them - but think a really detailed look at the training system that produced them should be done. It obviously was not good enough. They may have done everything they were taught 100% - it's just whether or not that training was comprehensive enough.

Thinking about it.. It was a third pilot who saved the day for the first Lion flight. And high workload prevented ET crew from operating properly..
Maybe MAX need to be re-certified to a minimum of 3 or 4 person crew as a return to service condition? Unions will sure love that! Can cockpit bulkhead be moved to accommodate 5 or 6 people?
 
ArgentoSystems
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 6:13 pm

morrisond wrote:
Stall Characteristics

Procedures
3(c) During the approach to the stall, the longitudinal control pull force should
increase continuously as speed is reduced from the trimmed speed to the onset of stall warning.
Below that speed some reduction in longitudinal control force is acceptable, provided it is not
sudden or excessive.

See Page 136"

Carry on with that thought. Why that requirement exists in the FAR?
 
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glideslope
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 6:19 pm

OldAeroGuy wrote:
PW100 wrote:
OldAeroGuy wrote:
Unfortunately, I'll probably now be tagged as part of the "Boeing PR" machine.
I really am more concerned about the AoA vane failure rate as it has the potential to impact many airplane fault trees and FMEA's.

The change from 0.6 to 2.5 may only represent flight test tuning. In normal operation at high AoA, it's probably not a major issue. With an AoA vane signal failure at low AoA, it becomes more important due to high dynamic pressure.

The important point is to have MCAS not activate at low AoA. That's why high AoA vane signal failure rate is a more important concern.


I agree completely. AoA failures have been the initial event in both accidents. There is a serious QC issue in the AoA supply chain IMO.
To know your Enemy, you must become your Enemy.” Sun Tzu
 
kalvado
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 6:24 pm

glideslope wrote:
OldAeroGuy wrote:
PW100 wrote:
I really am more concerned about the AoA vane failure rate as it has the potential to impact many airplane fault trees and FMEA's.

The change from 0.6 to 2.5 may only represent flight test tuning. In normal operation at high AoA, it's probably not a major issue. With an AoA vane signal failure at low AoA, it becomes more important due to high dynamic pressure.

The important point is to have MCAS not activate at low AoA. That's why high AoA vane signal failure rate is a more important concern.


I agree completely. AoA failures have been the initial event in both accidents. There is a serious QC issue in the AoA supply chain IMO.

I heavily doubt those sensors are guaranteed to anything like 1e9 cycles as required for flight safety. More likely failure rate is pretty much within the specs - there were posts about tens thousands hours MTBF. Try to look for another issue. Hint: it starts with B, and last letter is G...
 
OldAeroGuy
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 6:28 pm

ArgentoSystems wrote:
OldAeroGuy wrote:
By eliminating "stick lightening", MCAS makes inadvertent stalls less likely as required by certification regulations.

As I said above, MCAS is not a stall prevention device since the pilot can still stall the airplane with MCAS in operation.

LOL. Are you listening to yourself? It is like saying that collision avoidance system on my Subaru (that brakes automatically if I'm heading for an obstacle) is not really a collision avoidance system because I still can make a collision while driving this vehicle. Even when the system is activated.

Your statement does not make much sense.

The keyword here is inadvertent. Obviously MCAS won't work against deliberate attempt to stall, same as my CAS won't work against deliberate attempt to crash a vehicle. But that does not change the purpose of the system. If you deny that, you have to admit that MCAS serves no purpose whatsoever.


Let's keep the discussion to airplanes since that's the case at hand.

First we need at definition of stall.

From https://aviationglossary.com/stall/

Stall
At low angles of attack, the lift developed by an airfoil or wing will increase with an increase in angle of attack. However, there is a maximum angle of attack after which the lift will decrease instead of increase with increasing angle of attack.

The maximum angle of attack mentioned above is often referred to as the "Critical AoA". Let's use this short hand for this discussion.

Now let's describe various airplanes and discuss if they have stall prevention systems.

BAC 1-11 - The BAC 1-11 has a stick pusher. After a deep stall in flight test that caused a crash, production airplanes incorporated a stick pusher that prevented the airplane from reaching the "Critical AoA". Since "Critical AoA" can't be reached, the BAC 1-11 has a stall prevention system.

A320 - In "Normal" mode, the A320 flight control system limits AoA values to below "Critical AoA". Since "Critical AoA" can't be reached in "Normal" mode, the A320 has a stall prevention system.

777 - In "Normal" mode, as the airplane approaches stall warning, the flight control system increases column forces from 40-50lbs to over 100lbs to discourage the pilot from further AoA increases. The pilot can pull through this force increase and reach "Critical AoA" in all flight control modes. Because "Critical AoA" can be reached, the 777 does not have a stall protection system.

737 MAX - Above normal operating AoA's, MCAS activates to require increasing column forces for increasing AoA's. The pilot can pull through the increased forces to reach "Critical AoA". The 737 MAX does not have a stall protection system.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
kalvado
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 6:49 pm

OldAeroGuy wrote:
ArgentoSystems wrote:
OldAeroGuy wrote:
By eliminating "stick lightening", MCAS makes inadvertent stalls less likely as required by certification regulations.

As I said above, MCAS is not a stall prevention device since the pilot can still stall the airplane with MCAS in operation.

LOL. Are you listening to yourself? It is like saying that collision avoidance system on my Subaru (that brakes automatically if I'm heading for an obstacle) is not really a collision avoidance system because I still can make a collision while driving this vehicle. Even when the system is activated.

Your statement does not make much sense.

The keyword here is inadvertent. Obviously MCAS won't work against deliberate attempt to stall, same as my CAS won't work against deliberate attempt to crash a vehicle. But that does not change the purpose of the system. If you deny that, you have to admit that MCAS serves no purpose whatsoever.


Let's keep the discussion to airplanes since that's the case at hand.

First we need at definition of stall.

From https://aviationglossary.com/stall/

Stall
At low angles of attack, the lift developed by an airfoil or wing will increase with an increase in angle of attack. However, there is a maximum angle of attack after which the lift will decrease instead of increase with increasing angle of attack.

The maximum angle of attack mentioned above is often referred to as the "Critical AoA". Let's use this short hand for this discussion.

Now let's describe various airplanes and discuss if they have stall prevention systems.

BAC 1-11 - The BAC 1-11 has a stick pusher. After a deep stall in flight test that caused a crash, production airplanes incorporated a stick pusher that prevented the airplane from reaching the "Critical AoA". Since "Critical AoA" can't be reached, the BAC 1-11 has a stall prevention system.

A320 - In "Normal" mode, the A320 flight control system limits AoA values to below "Critical AoA". Since "Critical AoA" can't be reached in "Normal" mode, the A320 has a stall prevention system.

777 - In "Normal" mode, as the airplane approaches stall warning, the flight control system increases column forces from 40-50lbs to over 100lbs to discourage the pilot from further AoA increases. The pilot can pull through this force increase and reach "Critical AoA" in all flight control modes. Because "Critical AoA" can be reached, the 777 does not have a stall protection system.

737 MAX - Above normal operating AoA's, MCAS activates to require increasing column forces for increasing AoA's. The pilot can pull through the increased forces to reach "Critical AoA". The 737 MAX does not have a stall protection system.

OK, lets call MCAS stall protection system and get done with this. Any issues with that term?
In a different world. CDC calls for use of immunisations to protect against certain diseases. While efficiency of vaccine is rarely 100%, vaccination is still recommended as a protective measure.
 
OldAeroGuy
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 6:50 pm

kalvado wrote:
glideslope wrote:
OldAeroGuy wrote:


I agree completely. AoA failures have been the initial event in both accidents. There is a serious QC issue in the AoA supply chain IMO.

I heavily doubt those sensors are guaranteed to anything like 1e9 cycles as required for flight safety. More likely failure rate is pretty much within the specs - there were posts about tens thousands hours MTBF. Try to look for another issue. Hint: it starts with B, and last letter is G...


My working experience with AoA vanes indicated failure rates on the order of 10-6. When combined with pilot actions like a pilot induced stall being on the order of 10-3, you were able to show that a stall without annunciation (ie no stick shaker) was on the order of 10-9.

That's probably the thought train lead to the MCAS.v1 software.

Probability of an erroneous MCAS activation due to an AoA vane signal failure on the order of 10-6.
Probability of a crew to fail to deal with an erroneous MCAS activation via the "STAB Runaway" procedures on the order of 10-3.

Unfortunately, if the above analysis is about right, the predicted failure rates have not been bourn out in service.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
BravoOne
Posts: 3419
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 6:53 pm

I believe the FBI has opened a formal investigation into the training component.
 
OldAeroGuy
Posts: 3870
Joined: Sun Dec 05, 2004 6:50 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 6:57 pm

kalvado wrote:
OK, lets call MCAS stall protection system and get done with this. Any issues with that term?
In a different world. CDC calls for use of immunisations to protect against certain diseases. While efficiency of vaccine is rarely 100%, vaccination is still recommended as a protective measure.


I have a huge problem with it because MCAS is not fitted as a stall protection system and it does not prevent stalls because it does not limit AoA in any manner.

A more proper term would be say what it is, a Stability Augmentation System (SAS).
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
kalvado
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 7:01 pm

OldAeroGuy wrote:
kalvado wrote:
OK, lets call MCAS stall protection system and get done with this. Any issues with that term?
In a different world. CDC calls for use of immunisations to protect against certain diseases. While efficiency of vaccine is rarely 100%, vaccination is still recommended as a protective measure.


I have a huge problem with it because MCAS is not fitted as a stall protection system and it does not prevent stalls because it does not limit AoA in any manner.

A more proper term would be say what it is, a Stability Augmentation System (SAS).

Nope. Protection does not assume prevention. For example, now from OSHA world:
https://www.osha.gov/OshDoc/data_Bloodb ... act03.html
Title: Personal Protective Equipment (PPE) Reduces Exposure to Bloodborne Pathogens
Are you having hard time understanding terminology?
 
GalaxyFlyer
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 7:27 pm

No, we’re having a hard time of posters bringing in non-aviation terms, standards, and ideas into an argument about an aviation engineering problem. OHSA terms have no application here, even if that’s your background.

Please keep the discussion in aviation terms.

GF
 
OldAeroGuy
Posts: 3870
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 7:33 pm

:thumbsup: :thumbsup:
GalaxyFlyer wrote:
No, we’re having a hard time of posters bringing in non-aviation terms, standards, and ideas into an argument about an aviation engineering problem. OHSA terms have no application here, even if that’s your background.

Please keep the discussion in aviation terms.

GF


:thumbsup: :thumbsup:
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
YYZatcboy
Posts: 1167
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 7:46 pm

kalvado wrote:
OldAeroGuy wrote:
kalvado wrote:
OK, lets call MCAS stall protection system and get done with this. Any issues with that term?
In a different world. CDC calls for use of immunisations to protect against certain diseases. While efficiency of vaccine is rarely 100%, vaccination is still recommended as a protective measure.


I have a huge problem with it because MCAS is not fitted as a stall protection system and it does not prevent stalls because it does not limit AoA in any manner.

A more proper term would be say what it is, a Stability Augmentation System (SAS).

Nope. Protection does not assume prevention. For example, now from OSHA world:
https://www.osha.gov/OshDoc/data_Bloodb ... act03.html
Title: Personal Protective Equipment (PPE) Reduces Exposure to Bloodborne Pathogens
Are you having hard time understanding terminology?


If it helps you, think of it as a stall discouragement system. It makes the forces heavier so that the pilots have to deliberately pull hard to achieve stall. There is no normal operation I can think of that would require 50-100lbs of back pressure, so that should be enough to let pilots know they are doing something wrong.

My question that is still unanswered, and might be unanswerable for the time being is: What are the chances that the fault lies in the computer, not the AOA sensor, and that is the other bug Boeing found when reviewing MCAS.

Apologies if that is already answered, I would appreciate a post number so I can go see it since this is a long thread and it's difficult to stay on top of it.
DH1/3/4 MD11/88 L1011 A319/20/21/30/50/80 717 727 735/6/7/8/9 744 762/3 77E/W E40/75/90 CRJ/700/705 CC150
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kalvado
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 7:47 pm

GalaxyFlyer wrote:
No, we’re having a hard time of posters bringing in non-aviation terms, standards, and ideas into an argument about an aviation engineering problem. OHSA terms have no application here, even if that’s your background.

Please keep the discussion in aviation terms.

GF

OK, great.
Do you have a link for definition of "protection" and "prevention" in 14CFR? 14CFR1.1 doesn't define either. Or you guys are using terminology you don't even know how to use properly?
 
Heinkel
Posts: 221
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:02 pm

GalaxyFlyer wrote:
No, we’re having a hard time of posters bringing in non-aviation terms, standards, and ideas into an argument about an aviation engineering problem. OHSA terms have no application here, even if that’s your background.

Please keep the discussion in aviation terms.

GF


And the first and most important worldwide accepted aviation term should be: "Safety first". Not "Profit first".
 
ArgentoSystems
Posts: 295
Joined: Sun Mar 24, 2019 12:05 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:09 pm

OldAeroGuy wrote:
Stability Augmentation System (SAS).

:lol:
Stability Augmentation System is a BS term which can mean a million of things. Or nothing. Explain in plain English, what it does and what purpose it serves. Just try avoiding mentioning FAR. FAR is not the end goal, it exists to serve some other purpose.
 
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WALmsp
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:11 pm

Forgive me if this has been asked already, but I don't want to read the previous 5800+ posts:

Has Boeing given an estimated time s to when they expect to resolve the problem and get the planes back in the air?
In memory of my Dad, Robert "Bob" Fenrich, WAL 1964-1979, MSP ONT LAX
 
ArgentoSystems
Posts: 295
Joined: Sun Mar 24, 2019 12:05 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:15 pm

WALmsp wrote:
Forgive me if this has been asked already, but I don't want to read the previous 5800+ posts:

Has Boeing given an estimated time s to when they expect to resolve the problem and get the planes back in the air?

Yes, according to the estimate the ban has been lifted 3 weeks ago.
 
GalaxyFlyer
Posts: 3363
Joined: Fri Jan 01, 2016 4:44 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:23 pm

Heinkel wrote:
GalaxyFlyer wrote:
No, we’re having a hard time of posters bringing in non-aviation terms, standards, and ideas into an argument about an aviation engineering problem. OHSA terms have no application here, even if that’s your background.

Please keep the discussion in aviation terms.

GF


And the first and most important worldwide accepted aviation term should be: "Safety first". Not "Profit first".


Based on aviation’s record over the last thirty years, aviation in all forms, has exactly that term—safety first. Even in the military, safety is paramount. Please stop with the dramatics and hysteria opposing the business.

GF
 
kalvado
Posts: 1809
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:23 pm

WALmsp wrote:
Forgive me if this has been asked already, but I don't want to read the previous 5800+ posts:

Has Boeing given an estimated time s to when they expect to resolve the problem and get the planes back in the air?

THis is not up to Boeing. Regulators are supposed to get an official submission of the fix from Boeing and start a review. THat is scheduled for next week:
https://www.reuters.com/article/us-ethi ... SKCN1RV19R
How long it will actually take, and if review panel would give a green light to MAX at all is not guaranteed. So far, 90 days is the initial projection. So if all goes well, it is beginning of August.
 
User avatar
WALmsp
Posts: 278
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:27 pm

ArgentoSystems wrote:
WALmsp wrote:
Forgive me if this has been asked already, but I don't want to read the previous 5800+ posts:

Has Boeing given an estimated time s to when they expect to resolve the problem and get the planes back in the air?

Yes, according to the estimate the ban has been lifted 3 weeks ago.


What a relief! :D

kalvado wrote:
WALmsp wrote:
Forgive me if this has been asked already, but I don't want to read the previous 5800+ posts:

Has Boeing given an estimated time s to when they expect to resolve the problem and get the planes back in the air?

THis is not up to Boeing. Regulators are supposed to get an official submission of the fix from Boeing and start a review. THat is scheduled for next week:
https://www.reuters.com/article/us-ethi ... SKCN1RV19R
How long it will actually take, and if review panel would give a green light to MAX at all is not guaranteed. So far, 90 days is the initial projection. So if all goes well, it is beginning of August.


That makes sense. Thanks.
In memory of my Dad, Robert "Bob" Fenrich, WAL 1964-1979, MSP ONT LAX
 
GalaxyFlyer
Posts: 3363
Joined: Fri Jan 01, 2016 4:44 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:31 pm

ArgentoSystems wrote:
OldAeroGuy wrote:
Stability Augmentation System (SAS).

:lol:
Stability Augmentation System is a BS term which can mean a million of things. Or nothing. Explain in plain English, what it does and what purpose it serves. Just try avoiding mentioning FAR. FAR is not the end goal, it exists to serve some other purpose.


It has been explained thoroughly. The FAR 25 standard is a continuous stick force applied as IAS decreases toward the stall, measured during a reduction in airspeed of 1 knot per second. Apparently, the 737 Max, as it the 1G stall, had a lessened amount of stick force. I believe the standard is 6# of aft per x amount of knots. The MAX reduced to a number a bit under the 6 pound figure, but did not go negative. By using the stab trim input, stick was increased to meet the 6# standard.

Since airspeed vs. stick force comes under “stability and control”; SAS is not a BS term, but maybe applied by different means. The C-5, A-10 and several other jets have SAS systems as did the MD-11. A yaw damper is a form of SAS.

GF
 
kalvado
Posts: 1809
Joined: Wed Mar 01, 2006 4:29 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:39 pm

GalaxyFlyer wrote:
ArgentoSystems wrote:
OldAeroGuy wrote:
Stability Augmentation System (SAS).

:lol:
Stability Augmentation System is a BS term which can mean a million of things. Or nothing. Explain in plain English, what it does and what purpose it serves. Just try avoiding mentioning FAR. FAR is not the end goal, it exists to serve some other purpose.


It has been explained thoroughly. The FAR 25 standard is a continuous stick force applied as IAS decreases toward the stall, measured during a reduction in airspeed of 1 knot per second. Apparently, the 737 Max, as it the 1G stall, had a lessened amount of stick force. I believe the standard is 6# of aft per x amount of knots. The MAX reduced to a number a bit under the 6 pound figure, but did not go negative. By using the stab trim input, stick was increased to meet the 6# standard.

Since airspeed vs. stick force comes under “stability and control”; SAS is not a BS term, but maybe applied by different means. The C-5, A-10 and several other jets have SAS systems as did the MD-11. A yaw damper is a form of SAS.

GF

So we're to square 1: MCAS is there for airframe stability reasons, right?
 
OldAeroGuy
Posts: 3870
Joined: Sun Dec 05, 2004 6:50 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:50 pm

kalvado wrote:
So we're to square 1: MCAS is there for airframe stability reasons, right?


Yes. As many of us have been saying all along, the 737 MAX Flaps Up is less stable than previous 737's but is not unstable.

It is very important to understand the nuance in the above sentence.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
kalvado
Posts: 1809
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 8:59 pm

OldAeroGuy wrote:
kalvado wrote:
So we're to square 1: MCAS is there for airframe stability reasons, right?


Yes. As many of us have been saying all along, the 737 MAX is less stable than previous 737's but is not unstable.

It is very important to understand the nuance in the above sentence.


Nope. 737MAX without MCAS is legally not stable. I am not using word "unstable", I am saying it is not stable.
It is very important to understand the nuance in the above sentence as well.

Definition of stability according to the law of United States:

14CFR25.171 General.
The airplane must be longitudinally, directionally, and laterally stable in accordance with the provisions of §§25.173 through 25.177
[..]
§25.173 Static longitudinal stability. [..]
(c) The average gradient of the stable slope of the stick force versus speed curve may not be less than 1 pound for each 6 knots.


If this requirement was not met, aircraft cannot be considered laterally stable in accordance with the provisions of §§25.173 through 25.177


Any further questions?
Please review applicable legislation if desired.
 
airnorth
Posts: 341
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 9:53 pm

OldAeroGuy and Galaxyflyer, thanks for all of you're patience. I'm sure there are many on here that read what you post, and try to learn from it. Others it seems , look for fault in your answers, and will continually ask over and over again, the same question looking for a different interpretation to suit their needs. It amazing the passion that some posters have, and language on here at times. Surprised that you keep responding, but happy you do!
Its fine to disagree, in fact it can promote interesting discussions, but its discouraging when it becomes argumentative and rude. Thanks for taking the high road!
 
GalaxyFlyer
Posts: 3363
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Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 10:06 pm

First, it’s the Code of Federal Regulations, not Public Law. It’s established thru administrative procedure, not Congressional law passed by Congress and signed into law by the President.

Second, it’s NOT unstable, it did not meet the required force gradient (thanks for the memory jog—1# per 6 knots) but remained stable. It is stable, the pilot would be required to apply aft pressure to continue toward the stall, but it would be less than 1# per 6 knots. Unstable, by definition, means the force gradient goes negative and the aircraft pitches vertically requiring a pilot nose down input. It’s a matter of degree of stability. In any case it would LONGITUDINALLY unstable, not laterally.

GF
 
dakota123
Posts: 233
Joined: Wed Aug 30, 2006 11:03 pm

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 10:14 pm

airnorth wrote:
OldAeroGuy and Galaxyflyer, thanks for all of you're patience. I'm sure there are many on here that read what you post, and try to learn from it. Others it seems , look for fault in your answers, and will continually ask over and over again, the same question looking for a different interpretation to suit their needs. It amazing the passion that some posters have, and language on here at times. Surprised that you keep responding, but happy you do!
Its fine to disagree, in fact it can promote interesting discussions, but its discouraging when it becomes argumentative and rude. Thanks for taking the high road!


Was typing something similar, but yours is much more "nuanced", lol.

Couldn't agree more.

In any case, 25.173(c) is specifically getting at pilot's interface with the plane, not necessarily stability of the plane itself. There is a difference; for example maybe a shorter column or a change in bellcrank radius or something allows the spec to be met. There are other subsections that deal directly with the airframe's stability.
“And If I claim to be a wise man, well surely it means that I don’t know”
 
OldAeroGuy
Posts: 3870
Joined: Sun Dec 05, 2004 6:50 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 10:24 pm

kalvado wrote:

Nope. 737MAX without MCAS is legally not stable. I am not using word "unstable", I am saying it is not stable.
It is very important to understand the nuance in the above sentence as well.

Definition of stability according to the law of United States:

14CFR25.171 General.
The airplane must be longitudinally, directionally, and laterally stable in accordance with the provisions of §§25.173 through 25.177
[..]
§25.173 Static longitudinal stability. [..]
(c) The average gradient of the stable slope of the stick force versus speed curve may not be less than 1 pound for each 6 knots.


If this requirement was not met, aircraft cannot be considered laterally stable in accordance with the provisions of §§25.173 through 25.177


Any further questions?
Please review applicable legislation if desired.


Now you're supposing things that you don't have basic knowledge and data to confirm.

Please do this:

- Go the AC 25-7C. https://www.faa.gov/documentLibrary/med ... -7C%20.pdf
- Go to page 119. Figure 26-2 on this page shows how to show compliance for 25.173(c). Look at Curve B on the diagram.
- 25.173(c) requires an average stick force of 1 lb per 6 kts. over the displacement from trim speed range. Curve B is satisfactory (ie stable) over the speed range because its average gradient is at least 1 lb per 6 kts. even though it shows "stick lightening" at the Push and Pull ends of the speed range.

You'd need to see these plots for the 737 MAX without MCAS to support your claim that it's not stable without MCAS.

It's quite rational that the MAX behaves like Curve B in the Figure 26-2. Stable overall but with "stick lightening" without MCAS at the "Pull" end. Since MCAS is not designed to be active at low AoA's, I think it's pretty clear that MCAS is not required for the MAX to meet FAR 25.173 and 25.175

See AC 25-7C page 136 paragraph (c) that gives the steady pull requirements for a Stall approach. This is where MCAS is needed to pass the Stall Handling requirements of FAR 25.203.
Last edited by OldAeroGuy on Mon Apr 22, 2019 10:39 pm, edited 1 time in total.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
WPIAeroGuy
Posts: 295
Joined: Tue Aug 21, 2007 11:52 pm

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 10:32 pm

airnorth wrote:
OldAeroGuy and Galaxyflyer, thanks for all of you're patience. I'm sure there are many on here that read what you post, and try to learn from it. Others it seems , look for fault in your answers, and will continually ask over and over again, the same question looking for a different interpretation to suit their needs. It amazing the passion that some posters have, and language on here at times. Surprised that you keep responding, but happy you do!
Its fine to disagree, in fact it can promote interesting discussions, but its discouraging when it becomes argumentative and rude. Thanks for taking the high road!


I second this, the two of you have been putting out solid answers for this whole thread and I certainly appreciate it and have learned a lot.
-WPIAeroGuy
 
OldAeroGuy
Posts: 3870
Joined: Sun Dec 05, 2004 6:50 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 10:32 pm

:thumbsup: :thumbsup: :thumbsup: Thanks airnorth, GF and dakota123

:thumbsup: WPIAeroguy as well.

My intent when I got on this forum was to hear other opinions and share what knowledge I had.

Hasn't always worked out that way as I have my opinions and view points. Let's all try to be nice, even that can be difficult at times.

OAG :)
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
hivue
Posts: 1903
Joined: Tue Feb 26, 2013 2:26 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 10:56 pm

ArgentoSystems wrote:
LOL. Are you listening to yourself? It is like saying that collision avoidance system on my Subaru (that brakes automatically if I'm heading for an obstacle) is not really a collision avoidance system because I still can make a collision while driving this vehicle. Even when the system is activated.


If Subaru had sold you a collision prevention system you would have been cheated. However, they sold you a collision avoidance system.

I continue to be dumbfounded at people having so much trouble with the concept that MCAS is not a stall prevention system because it doesn't prevent stalls. That's a grammatical tautology. It's perennially true.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
kalvado
Posts: 1809
Joined: Wed Mar 01, 2006 4:29 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 11:06 pm

OldAeroGuy wrote:
kalvado wrote:

Nope. 737MAX without MCAS is legally not stable. I am not using word "unstable", I am saying it is not stable.
It is very important to understand the nuance in the above sentence as well.

Definition of stability according to the law of United States:

14CFR25.171 General.
The airplane must be longitudinally, directionally, and laterally stable in accordance with the provisions of §§25.173 through 25.177
[..]
§25.173 Static longitudinal stability. [..]
(c) The average gradient of the stable slope of the stick force versus speed curve may not be less than 1 pound for each 6 knots.


If this requirement was not met, aircraft cannot be considered laterally stable in accordance with the provisions of §§25.173 through 25.177


Any further questions?
Please review applicable legislation if desired.


Now you're supposing things that you don't have basic knowledge and data to confirm.

Please do this:

- Go the AC 25-7C. https://www.faa.gov/documentLibrary/med ... -7C%20.pdf
- Go to page 119. Figure 26-2 on this page shows how to show compliance for 25.173(c). Look at Curve B on the diagram.
- 25.173(c) requires an average stick force of 1 lb per 6 kts. over the displacement from trim speed range. Curve B is satisfactory (ie stable) over the speed range because its average gradient is at least 1 lb per 6 kts. even though it shows "stick lightening" at the Push and Pull ends of the speed range.

You'd need to see these plots for the 737 MAX without MCAS to support your claim that it's not stable without MCAS.

It's quite rational that the MAX behaves like Curve B in the Figure 26-2. Stable overall but with "stick lightening" without MCAS at the "Pull" end. Since MCAS is not designed to be active at low AoA's, I think it's pretty clear that MCAS is not required for the MAX to meet FAR 25.173 and 25.175

See AC 25-7C page 136 paragraph (c) that gives the steady pull requirements for a Stall approach. This is where MCAS is needed to pass the Stall Handling requirements of FAR 25.203.

This is all great, but we're talking about something black and white, no went just a bit over, officer!"
You're showing advisory circular interpreting requirements set forth in CFR. Now you're saying that it ALMOST meets those requirements. We don't have the data, but it is reasonable - but just a tiny little bit... Which means that it doesn't satisfy certification requirements. ).999 is still less than 1. And it means aircraft is not stable per 14CFR25 requirements.

It is nice how you seem to be willing to bend regulations by saying "it is just a little bit". Were all certifications you're so proud of participating done the same way? You can bend it - but only that much, and someone bent it too much as evidenced by two crashes.
 
frmrCapCadet
Posts: 2991
Joined: Thu May 29, 2008 8:24 pm

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 11:16 pm

I think what people have been saying is "stall prevention systems" have a very specific definition. MCAS does not meet that definition. It is about stall prevention, but that is not quite the same. And the Red Queen says ..... LOL
Buffet: the airline business...has eaten up capital...like..no other (business)
 
kalvado
Posts: 1809
Joined: Wed Mar 01, 2006 4:29 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 11:21 pm

frmrCapCadet wrote:
I think what people have been saying is "stall prevention systems" have a very specific definition. MCAS does not meet that definition. It is about stall prevention, but that is not quite the same. And the Red Queen says ..... LOL

Can you show "stall prevention system" being defined in a real document? I cannot find any definition which would be relevant to certification issues.

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