hivue
Posts: 1945
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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: 2024
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: 3148
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: 2024
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.
 
speedking
Posts: 68
Joined: Thu Nov 15, 2018 3:00 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 11:24 pm

I agree this is a training problem in the end. Physical training specifically. If the pilots were strong enough, they could have saved the plane by using the manual trim wheels as they are supposed to do as final backup when all the automation and electrical systems have failed.
 
dakota123
Posts: 233
Joined: Wed Aug 30, 2006 11:03 pm

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 11:38 pm

kalvado wrote:
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.


Certifying authorities absolutely do allow "just a little bit over, officer!" from time to time, and it seems to be up to the "officer" on duty to some degree. Have a listen to interviews with D.P. Davies, CAA's longtime Chief Test Pilot.

And seriously, why are you being such an ass? I really don't get it.
“And If I claim to be a wise man, well surely it means that I don’t know”
 
WPIAeroGuy
Posts: 312
Joined: Tue Aug 21, 2007 11:52 pm

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 11:39 pm

kalvado wrote:
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.


I couldn't find a formal definition in Part 25, but I think the difference that people are trying to get across is that a "stall prevention" system will not allow even intentional entry into a stall. MCAS does not do that. All MCAS does is make sure the control feel is appropriate up to the stall. I know the point you're trying to make is that "well if the pilot accidentally pulls to hard, the plane will stall, therefore MCAS prevents that!" And that's true, but it is vastly different to say a system that reduces the chance of an inadvertent stall is the same as a system that prevents intentional stalls.
-WPIAeroGuy
 
kalvado
Posts: 2024
Joined: Wed Mar 01, 2006 4:29 am

Re: B737MAX Grounded Worldwide

Mon Apr 22, 2019 11:50 pm

WPIAeroGuy wrote:
kalvado wrote:
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.


I couldn't find a formal definition in Part 25, but I think the difference that people are trying to get across is that a "stall prevention" system will not allow even intentional entry into a stall. MCAS does not do that. All MCAS does is make sure the control feel is appropriate up to the stall. I know the point you're trying to make is that "well if the pilot accidentally pulls to hard, the plane will stall, therefore MCAS prevents that!" And that's true, but it is vastly different to say a system that reduces the chance of an inadvertent stall is the same as a system that prevents intentional stalls.

It seems that a term is defined by some people to suit their needs of this particular discussion. Word "prevention" doesn't have that absolute meaning in common or legal English.
 
kalvado
Posts: 2024
Joined: Wed Mar 01, 2006 4:29 am

Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:11 am

dakota123 wrote:
kalvado wrote:
OldAeroGuy wrote:

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.


Certifying authorities absolutely do allow "just a little bit over, officer!" from time to time, and it seems to be up to the "officer" on duty to some degree. Have a listen to interviews with D.P. Davies, CAA's longtime Chief Test Pilot.

And seriously, why are you being such an ass? I really don't get it.

First of all, "why";
"it is stable!", "just a bit stick lightening", "need to meet some corner case certification requirements" narration is used to create an impression that there is nothing wrong here, just a bit of some funny stuff.
I just want to call things by their names: not meeting stability requirements. Which causes a lot of argument on the other side using some non-aviation speak. "stick lightening" is not a term, it is called reversal of stick force and is explicitly unacceptable for FAA. Once this is recognized, we may start discussing exemptions.
Next question is about how much regulations need to be bent. I hear "just a little bit" - but somehow that means 20% of trim range authority for MCAS. This really doesn't add up.
 
WPIAeroGuy
Posts: 312
Joined: Tue Aug 21, 2007 11:52 pm

Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:37 am

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


I couldn't find a formal definition in Part 25, but I think the difference that people are trying to get across is that a "stall prevention" system will not allow even intentional entry into a stall. MCAS does not do that. All MCAS does is make sure the control feel is appropriate up to the stall. I know the point you're trying to make is that "well if the pilot accidentally pulls to hard, the plane will stall, therefore MCAS prevents that!" And that's true, but it is vastly different to say a system that reduces the chance of an inadvertent stall is the same as a system that prevents intentional stalls.

It seems that a term is defined by some people to suit their needs of this particular discussion. Word "prevention" doesn't have that absolute meaning in common or legal English.


Call it whatever you want. MCAS is fundamentally different from a system that will not allow intentional stalls.
-WPIAeroGuy
 
OldAeroGuy
Posts: 3886
Joined: Sun Dec 05, 2004 6:50 am

Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:58 am

kalvado wrote:

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.


Did you look at the plot on page 119 of AC 25-7C?

The example the FAA uses, Case B, has an average stability of 1 lb per 6 kts but is neutrally stable at each end of the curve. The FAA describes this as being acceptable. FAR 25.173 says an average of 1 lb per 6 kts is acceptable.

If the policeman says you're not speeding as you meet the definition of the 25.173, why do you dispute his judgement?
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
kalvado
Posts: 2024
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 1:29 am

OldAeroGuy wrote:
kalvado wrote:

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.


Did you look at the plot on page 119 of AC 25-7C?

The example the FAA uses, Case B, has an average stability of 1 lb per 6 kts but is neutrally stable at each end of the curve. The FAA describes this as being acceptable. FAR 25.173 says an average of 1 lb per 6 kts is acceptable.

If the policeman says you're not speeding as you meet the definition of the 25.173, why do you dispute his judgement?

"Stick lightening", which is "local reversal of the stick force gradient" if you prefer proper terminology, corresponds to curve C on the same chart. You're correct, it looks almost like curve B - but is unacceptable for FAA as it doesn't satisfy their definition of aircraft stability. So, to re-iterate, based on what we know, MAX does not meet CFR definition of a stable aircraft.
 
smartplane
Posts: 1024
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 1:55 am

dakota123 wrote:
kalvado wrote:
OldAeroGuy wrote:

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.


Certifying authorities absolutely do allow "just a little bit over, officer!" from time to time, and it seems to be up to the "officer" on duty to some degree. Have a listen to interviews with D.P. Davies, CAA's longtime Chief Test Pilot.

Even when the 'officer' is a Boeing employee making decisions on behalf of the FAA?

Before MCAS was named, Boeing often referred to it as 'pitch stability augmentation', but that is a common abbreviation for something else. PSA suggests a necessity to meet compliance with FAR, while MCAS has connotations of making a safe plane safer.

Might be 'just a little bit over' in a straight line, but in steep turns...................
 
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zeke
Posts: 13994
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 2:59 am

OldAeroGuy wrote:
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.


Well said OAG,

My only question to this is the design choice they made to develop MCAS if it’s only purpose is to have the required stick feel. With STS they used the Elevator Feel Shift Module to add control column pressure to the Elevator Feel “Computer” without an aerodynamic surface change.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
planecane
Posts: 1154
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 3:17 am

zeke wrote:
OldAeroGuy wrote:
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.


Well said OAG,

My only question to this is the design choice they made to develop MCAS if it’s only purpose is to have the required stick feel. With STS they used the Elevator Feel Shift Module to add control column pressure to the Elevator Feel “Computer” without an aerodynamic surface change.


I think from the block diagrams that it is simply because there is no AoA input to the eleveator feel computer so the EFC has no way to "know" that the force is getting light because it is AoA dependent. Either that or the elevator feel system can't add enough required force.
 
dakota123
Posts: 233
Joined: Wed Aug 30, 2006 11:03 pm

Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 3:37 am

smartplane wrote:
dakota123 wrote:
kalvado wrote:
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.


Certifying authorities absolutely do allow "just a little bit over, officer!" from time to time, and it seems to be up to the "officer" on duty to some degree. Have a listen to interviews with D.P. Davies, CAA's longtime Chief Test Pilot.

Even when the 'officer' is a Boeing employee making decisions on behalf of the FAA?

Before MCAS was named, Boeing often referred to it as 'pitch stability augmentation', but that is a common abbreviation for something else. PSA suggests a necessity to meet compliance with FAR, while MCAS has connotations of making a safe plane safer.

Might be 'just a little bit over' in a straight line, but in steep turns...................


They don’t make decisions of behalf of the FAA. They present their case, and the FAA (and CAA and EASA and...) accepts the argument or they don’t. Agree with it or not, same as it ever was. Anyway, this is a tangent since we don’t know that that even occurred.

As to your last point, yeah, don’t know. MCAS is an odd implementation, and I’m wondering as much as the next guy (at least) that there’s no proportional term, only integral. Maybe it specifically does have to do with the fact that it’s intended to come into play in steep turns, i.e. a turn takes time, and once a bank is established, ordinarily it wouldn’t be tightened further. Certainly a pusher would be startling in a turn, to have the column basically pulled out of your hand.
“And If I claim to be a wise man, well surely it means that I don’t know”
 
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seahawk
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 4:47 am

OldAeroGuy wrote:
seahawk wrote:
OldAeroGuy wrote:

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.


Which they could not, as the terrain is rising. But I agree that they did perform pitch and power not correctly, but if you look at the experience and training level of the crew, failure must be expected. This crash is 98% pilot error.
 
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zeke
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 4:49 am

planecane wrote:
I think from the block diagrams that it is simply because there is no AoA input to the eleveator feel computer so the EFC has no way to "know" that the force is getting light because it is AoA dependent. Either that or the elevator feel system can't add enough required force.


There is via the elevator shift, that’s how control force is added for STS.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
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seahawk
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 4:54 am

morrisond wrote:
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.


Well I would not expect the training of the pilots to be sufficient to solve problems on their own. And in the Lion Air case the problem encountered did not match the checklist for unreliable trim. The fact that the previous Lion Air crew did not crash proofs that this too was a crash mostly caused by pilot error. the sad fact is that 2 pilot crews flew perfectly fine 737MAX into the ground and people blame the plane for it.
 
Interested
Posts: 647
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 5:33 am

speedking wrote:
I agree this is a training problem in the end. Physical training specifically. If the pilots were strong enough, they could have saved the plane by using the manual trim wheels as they are supposed to do as final backup when all the automation and electrical systems have failed.


It's so much not a training problem

It's a design problem where training is the last chance to prevent it becoming an accident

It's so wrong to focus on training

It's like saying cancer is all about the treatment rather than prevention in the first place

It's incredible how this thread has had so much focus on the pilots and training rather than the far bigger issues which is how we ended up with a plane design like this to start with

We are discussing training issues we now have to solve that need never have existed with a more safely designed plane
 
Interested
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 6:06 am

seahawk wrote:
morrisond wrote:
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.


Well I would not expect the training of the pilots to be sufficient to solve problems on their own. And in the Lion Air case the problem encountered did not match the checklist for unreliable trim. The fact that the previous Lion Air crew did not crash proofs that this too was a crash mostly caused by pilot error. the sad fact is that 2 pilot crews flew perfectly fine 737MAX into the ground and people blame the plane for it.


Yet the whole world knows this is a problem with the plane and not the pilots

All you have to do is Google Max 737 to see that

Even Boeing accept that
 
Interested
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 6:07 am

Interested wrote:
speedking wrote:
I agree this is a training problem in the end. Physical training specifically. If the pilots were strong enough, they could have saved the plane by using the manual trim wheels as they are supposed to do as final backup when all the automation and electrical systems have failed.


It's so much NOT a training problem

It's a design problem where training is the last chance to prevent it becoming an accident

It's so wrong to focus on training

It's like saying cancer is all about the treatment rather than prevention in the first place

It's incredible how this thread has had so much focus on the pilots and training rather than the far bigger issues which is how we ended up with a plane design like this to start with

We are discussing training issues we now have to solve that need never have existed with a more safely designed plane
 
zoom321
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 6:08 am

At the rate this is going, if B sells planes with parachutes thrown in, the wings fall off in flight and people die, B fans will blame the passengers for not knowing how to use parachute. I kid you not.
 
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seahawk
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 6:21 am

Interested wrote:
seahawk wrote:
morrisond wrote:


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.


Well I would not expect the training of the pilots to be sufficient to solve problems on their own. And in the Lion Air case the problem encountered did not match the checklist for unreliable trim. The fact that the previous Lion Air crew did not crash proofs that this too was a crash mostly caused by pilot error. the sad fact is that 2 pilot crews flew perfectly fine 737MAX into the ground and people blame the plane for it.


Yet the whole world knows this is a problem with the plane and not the pilots

All you have to do is Google Max 737 to see that

Even Boeing accept that


No, there was no problem flying the plane, there was no system or part not working that you need to fly the plane. They flew perfectly fine planes into the ground. It was missing training, missing documentation and missing experience, partly caused by failures made at Boeing.
 
Interested
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 6:31 am

seahawk wrote:
Interested wrote:
seahawk wrote:

Well I would not expect the training of the pilots to be sufficient to solve problems on their own. And in the Lion Air case the problem encountered did not match the checklist for unreliable trim. The fact that the previous Lion Air crew did not crash proofs that this too was a crash mostly caused by pilot error. the sad fact is that 2 pilot crews flew perfectly fine 737MAX into the ground and people blame the plane for it.


Yet the whole world knows this is a problem with the plane and not the pilots

All you have to do is Google Max 737 to see that

Even Boeing accept that


No, there was no problem flying the plane, there was no system or part not working that you need to fly the plane. They flew perfectly fine planes into the ground. It was missing training, missing documentation and missing experience, partly caused by failures made at Boeing.


Is this a wind up?

Are you just a troll?

You do Boeing no favours at all
 
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seahawk
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 6:49 am

Interested wrote:
seahawk wrote:
Interested wrote:

Yet the whole world knows this is a problem with the plane and not the pilots

All you have to do is Google Max 737 to see that

Even Boeing accept that


No, there was no problem flying the plane, there was no system or part not working that you need to fly the plane. They flew perfectly fine planes into the ground. It was missing training, missing documentation and missing experience, partly caused by failures made at Boeing.


Is this a wind up?

Are you just a troll?

You do Boeing no favours at all


Imagine all 737MAX would have the AoA disagree warning and would automatically disable MCAS in the case. There would be no problems at all flying the planes. It is a problem of the documentation of MCAS, how it is programmed, the man to machine interface and how crews were not trained to identify and handle the problem correctly.
 
Interested
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 8:59 am

seahawk wrote:
Interested wrote:
seahawk wrote:

No, there was no problem flying the plane, there was no system or part not working that you need to fly the plane. They flew perfectly fine planes into the ground. It was missing training, missing documentation and missing experience, partly caused by failures made at Boeing.


Is this a wind up?

Are you just a troll?

You do Boeing no favours at all


Imagine all 737MAX would have the AoA disagree warning and would automatically disable MCAS in the case. There would be no problems at all flying the planes. It is a problem of the documentation of MCAS, how it is programmed, the man to machine interface and how crews were not trained to identify and handle the problem correctly.


You think any member of the public wants to fly on a plane where their safety relies on pilots being able to turn those trim wheels at the right time

Boeing have designed planes that have software patches that make that more likely to be needed

No thank you. I would rather stay in the UK thanks.
 
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seahawk
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 9:01 am

Interested wrote:
seahawk wrote:
Interested wrote:

Is this a wind up?

Are you just a troll?

You do Boeing no favours at all


Imagine all 737MAX would have the AoA disagree warning and would automatically disable MCAS in the case. There would be no problems at all flying the planes. It is a problem of the documentation of MCAS, how it is programmed, the man to machine interface and how crews were not trained to identify and handle the problem correctly.


You think any member of the public wants to fly on a plane where their safety relies on pilots being able to turn those trim wheels at the right time

Boeing have designed planes that have software patches that make that more likely to be needed

No thank you. I would rather stay in the UK thanks.


Every 737 needs manual trim in certain fault scenarios - this has been the case since the 737-100.
 
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InsideMan
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 9:06 am

seahawk wrote:

Imagine all 737MAX would have the AoA disagree warning and would automatically disable MCAS in the case. There would be no problems at all flying the planes. It is a problem of the documentation of MCAS, how it is programmed, the man to machine interface and how crews were not trained to identify and handle the problem correctly.


Imagine a plane without engines too big to fit under the wings that doesn't need MCAS to fly stable on it's own. THERE would be no problem at all flying that plane.

Suddenly you shift from 98% pilot error to MCAS documentation, programming and MMI. Make up your mind!
 
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seahawk
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 9:20 am

InsideMan wrote:
seahawk wrote:

Imagine all 737MAX would have the AoA disagree warning and would automatically disable MCAS in the case. There would be no problems at all flying the planes. It is a problem of the documentation of MCAS, how it is programmed, the man to machine interface and how crews were not trained to identify and handle the problem correctly.


Imagine a plane without engines too big to fit under the wings that doesn't need MCAS to fly stable on it's own. THERE would be no problem at all flying that plane.

Suddenly you shift from 98% pilot error to MCAS documentation, programming and MMI. Make up your mind!


Could we cut the drama and stop pretending that a 737MAX would inevitably fall out of the sky with MCAS turned off. And regarding the ET crash it is mostly pilot error, as they were aware of the MCAS function and how a failure would be noticeably, yet failed to act correctly. Lion Air is a mix of pilot error (not recognizing the trim problem) and missing knowledge and documentation in addition to the sloppy implementation by Boeing.

I personally have a much bigger concern about Boeing´s lack of transparency when it comes to the system than anything else, because everybody makes errors and bad decisions but hiding such a system and its functions from the people flying the plane removes one important aspect of peer review between engineers and pilots in airplane development. This in addition to the bad implementation of the MCAS really put a dent into my opinion of Boeing.
 
CO953
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 9:45 am

SEPilot wrote:
77H wrote:
SEPilot wrote:
This is a gross exaggeration. Yes, two crashes occurred because Boeing engineers failed to understand how dense some pilots can be. That will be fixed. You obviously believe that situation will continue. It won’t. The 737 prior to the MAX accumulated an excellent safety record; once it gets cleared to fly again (which it will) the MAX will continue that record.


Are you seriously blaming the pilots for the MAX crashes ? Boeing’s rushed attempt to counter the NEO produced an aircraft that is inherently unstable. If it wasn’t, you wouldn’t need MCAS to begin with. Then, in an attempt to rush it through certification Boeing conceals certain aspects of MCAS or makes changes after certification all the while telling airlines it’s no different than the 73NG.

What Boeing did was extremely negligent. Blaming the pilots for this only serves expose a blind bias fanboy mentality.

77G

Yes, I am blaming the pilots. I am a pilot (although not an airline pilot) and I know enough that if I am getting uncommanded trim inputs to PULL THE BLEEPING BREAKER (or in this case flip the bleeping switch). A pilot who can’t figure that out has no business flying any plane.


Not in your perfect world, SEPilot, no.

Try doing what those pilots were subjected to at low altitude on climbout, and getting it right 99.999% of the time, instantaneously, so as not to crash,
I'm not a pilot, but I call BS. Those pilots had a dump-truck of manure dropped in their laps. It killed a lot of people
 
CO953
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 9:51 am

seahawk wrote:
morrisond wrote:
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.


Well I would not expect the training of the pilots to be sufficient to solve problems on their own. And in the Lion Air case the problem encountered did not match the checklist for unreliable trim. The fact that the previous Lion Air crew did not crash proofs that this too was a crash mostly caused by pilot error. the sad fact is that 2 pilot crews flew perfectly fine 737MAX into the ground and people blame the plane for it.


I thought that the MCAS was the system commanding nose-down, not the pilots?
 
lazyme
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 10:29 am

seahawk wrote:
Interested wrote:
seahawk wrote:

Imagine all 737MAX would have the AoA disagree warning and would automatically disable MCAS in the case. There would be no problems at all flying the planes. It is a problem of the documentation of MCAS, how it is programmed, the man to machine interface and how crews were not trained to identify and handle the problem correctly.


You think any member of the public wants to fly on a plane where their safety relies on pilots being able to turn those trim wheels at the right time

Boeing have designed planes that have software patches that make that more likely to be needed

No thank you. I would rather stay in the UK thanks.


Every 737 needs manual trim in certain fault scenarios - this has been the case since the 737-100.


Do you realize the 737 needs 250 full revolutions on the manual trim wheel from full down to full up ?

Flying nose down at low altitude, you will simply run out of time.
 
Interested
Posts: 647
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 10:32 am

seahawk wrote:
Interested wrote:
seahawk wrote:

Imagine all 737MAX would have the AoA disagree warning and would automatically disable MCAS in the case. There would be no problems at all flying the planes. It is a problem of the documentation of MCAS, how it is programmed, the man to machine interface and how crews were not trained to identify and handle the problem correctly.


You think any member of the public wants to fly on a plane where their safety relies on pilots being able to turn those trim wheels at the right time

Boeing have designed planes that have software patches that make that more likely to be needed

No thank you. I would rather stay in the UK thanks.


Every 737 needs manual trim in certain fault scenarios - this has been the case since the 737-100.


I know and the 2 crashes have shown how poor the manual trim system is and how difficult and dangerous it is

Yet weve designed planes that make the need for it to be used more likely
 
Interested
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 10:34 am

seahawk wrote:
InsideMan wrote:
seahawk wrote:

Imagine all 737MAX would have the AoA disagree warning and would automatically disable MCAS in the case. There would be no problems at all flying the planes. It is a problem of the documentation of MCAS, how it is programmed, the man to machine interface and how crews were not trained to identify and handle the problem correctly.


Imagine a plane without engines too big to fit under the wings that doesn't need MCAS to fly stable on it's own. THERE would be no problem at all flying that plane.

Suddenly you shift from 98% pilot error to MCAS documentation, programming and MMI. Make up your mind!


Could we cut the drama and stop pretending that a 737MAX would inevitably fall out of the sky with MCAS turned off. And regarding the ET crash it is mostly pilot error, as they were aware of the MCAS function and how a failure would be noticeably, yet failed to act correctly. Lion Air is a mix of pilot error (not recognizing the trim problem) and missing knowledge and documentation in addition to the sloppy implementation by Boeing.

I personally have a much bigger concern about Boeing´s lack of transparency when it comes to the system than anything else, because everybody makes errors and bad decisions but hiding such a system and its functions from the people flying the plane removes one important aspect of peer review between engineers and pilots in airplane development. This in addition to the bad implementation of the MCAS really put a dent into my opinion of Boeing.


Can we just cut the crap and stop blaming pilots for the death of 350 plus people

Its getting boring now
 
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PixelFlight
Posts: 653
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 10:47 am

zeke wrote:
PixelFlight wrote:
zeke wrote:

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.

No, a bad static pressure input will not generate a +20° erratic AoA value, nor a MCAS command. The scenario need to produce all the data recorded on the FDR to be valid.
Did you have the Elevator Feel Shift Module control column pressure data of ET610 and ET302 ?
 
flybucky
Posts: 175
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 11:14 am

morrisond wrote:
So if the Car was say a GM for example and GM sent you a note saying you can continue to use the car but if you are faced with runaway acceleration - ensure the wheel is pointed forward and hit the Stop button you can continue to use it. However when you are faced with that situation you don't ensure the wheels are pointed forward before you hit the switch - that is GM's fault?

To make this analogy more accurate, it would be like GM sent a note saying:

If you are faced with runaway acceleration, hit the Stop button.

Note: You can point the wheel forward before hitting the Stop button. Or you can also steer the wheel after hitting the Stop button.

See this post that shows the differences in text between the Emergency Airworthiness Directive, which revises the Airplane Flight Manual (which flight crews do not deal with), compared to the Flight Crew Operations Manual bulletin update (which is what flight crews deal with).
 
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seahawk
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 11:31 am

Interested wrote:
seahawk wrote:
InsideMan wrote:

Imagine a plane without engines too big to fit under the wings that doesn't need MCAS to fly stable on it's own. THERE would be no problem at all flying that plane.

Suddenly you shift from 98% pilot error to MCAS documentation, programming and MMI. Make up your mind!


Could we cut the drama and stop pretending that a 737MAX would inevitably fall out of the sky with MCAS turned off. And regarding the ET crash it is mostly pilot error, as they were aware of the MCAS function and how a failure would be noticeably, yet failed to act correctly. Lion Air is a mix of pilot error (not recognizing the trim problem) and missing knowledge and documentation in addition to the sloppy implementation by Boeing.

I personally have a much bigger concern about Boeing´s lack of transparency when it comes to the system than anything else, because everybody makes errors and bad decisions but hiding such a system and its functions from the people flying the plane removes one important aspect of peer review between engineers and pilots in airplane development. This in addition to the bad implementation of the MCAS really put a dent into my opinion of Boeing.


Can we just cut the crap and stop blaming pilots for the death of 350 plus people

Its getting boring now


Pilot error, does not mean blaming the pilots. Pilot error can be caused by missing information, unsuitable man to machine interface, missing training, unclear instrument displays, wrong checklists, work overload and many more reasons. In both cases Boeing shoulders most of the blame for the crashes, not the pilots and to be honest also not the plane as the basic plane was fully functional.
 
XRAYretired
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 11:41 am

seahawk wrote:
Interested wrote:
seahawk wrote:

Could we cut the drama and stop pretending that a 737MAX would inevitably fall out of the sky with MCAS turned off. And regarding the ET crash it is mostly pilot error, as they were aware of the MCAS function and how a failure would be noticeably, yet failed to act correctly. Lion Air is a mix of pilot error (not recognizing the trim problem) and missing knowledge and documentation in addition to the sloppy implementation by Boeing.

I personally have a much bigger concern about Boeing´s lack of transparency when it comes to the system than anything else, because everybody makes errors and bad decisions but hiding such a system and its functions from the people flying the plane removes one important aspect of peer review between engineers and pilots in airplane development. This in addition to the bad implementation of the MCAS really put a dent into my opinion of Boeing.


Can we just cut the crap and stop blaming pilots for the death of 350 plus people

Its getting boring now


Pilot error, does not mean blaming the pilots. Pilot error can be caused by missing information, unsuitable man to machine interface, missing training, unclear instrument displays, wrong checklists, work overload and many more reasons. In both cases Boeing shoulders most of the blame for the crashes, not the pilots and to be honest also not the plane as the basic plane was fully functional.


I would suggest you stop digging. Not much credibility left to lose now.

Ray
 
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seahawk
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 11:43 am

XRAYretired wrote:
seahawk wrote:
Interested wrote:

Can we just cut the crap and stop blaming pilots for the death of 350 plus people

Its getting boring now


Pilot error, does not mean blaming the pilots. Pilot error can be caused by missing information, unsuitable man to machine interface, missing training, unclear instrument displays, wrong checklists, work overload and many more reasons. In both cases Boeing shoulders most of the blame for the crashes, not the pilots and to be honest also not the plane as the basic plane was fully functional.


I would suggest you stop digging. Not much credibility left to lose now.

Ray


I never had any credibility.
 
ArgentoSystems
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 11:58 am

seahawk wrote:
Pilot error, does not mean blaming the pilots. Pilot error can be caused by missing information, unsuitable man to machine interface, missing training, unclear instrument displays, wrong checklists, work overload and many more reasons. In both cases Boeing shoulders most of the blame for the crashes, not the pilots and to be honest also not the plane as the basic plane was fully functional.

Now you've gone completely off the rails. You are contradicting yourself, don't you see that?
 
morrisond
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:00 pm

seahawk wrote:
Interested wrote:
seahawk wrote:

Imagine all 737MAX would have the AoA disagree warning and would automatically disable MCAS in the case. There would be no problems at all flying the planes. It is a problem of the documentation of MCAS, how it is programmed, the man to machine interface and how crews were not trained to identify and handle the problem correctly.


You think any member of the public wants to fly on a plane where their safety relies on pilots being able to turn those trim wheels at the right time

Boeing have designed planes that have software patches that make that more likely to be needed

No thank you. I would rather stay in the UK thanks.


Every 737 needs manual trim in certain fault scenarios - this has been the case since the 737-100.


Along with the A320 - it has a manual trim wheel as backup as well. If you are going to condemn the 737 for having one and demand a redesign - time to take it out of the A320 as well.
 
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SomebodyInTLS
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:00 pm

kalvado wrote:
OldAeroGuy wrote:
I have a huge problem with it because MCAS is not fitted as a stall protection system and it does not prevent stalls

Nope. Protection does not assume prevention.

[...]

Are you having hard time understanding terminology?


It does seem like people are mentally twisting to avoid having the word "stall" associated with MCAS, despite it being right there in the very regulations MCAS was created to address!
"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."
 
morrisond
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:02 pm

seahawk wrote:
InsideMan wrote:
seahawk wrote:

Imagine all 737MAX would have the AoA disagree warning and would automatically disable MCAS in the case. There would be no problems at all flying the planes. It is a problem of the documentation of MCAS, how it is programmed, the man to machine interface and how crews were not trained to identify and handle the problem correctly.


Imagine a plane without engines too big to fit under the wings that doesn't need MCAS to fly stable on it's own. THERE would be no problem at all flying that plane.

Suddenly you shift from 98% pilot error to MCAS documentation, programming and MMI. Make up your mind!


Could we cut the drama and stop pretending that a 737MAX would inevitably fall out of the sky with MCAS turned off. And regarding the ET crash it is mostly pilot error, as they were aware of the MCAS function and how a failure would be noticeably, yet failed to act correctly. Lion Air is a mix of pilot error (not recognizing the trim problem) and missing knowledge and documentation in addition to the sloppy implementation by Boeing.

I personally have a much bigger concern about Boeing´s lack of transparency when it comes to the system than anything else, because everybody makes errors and bad decisions but hiding such a system and its functions from the people flying the plane removes one important aspect of peer review between engineers and pilots in airplane development. This in addition to the bad implementation of the MCAS really put a dent into my opinion of Boeing.


The engineers and FAA knew about MCAS - Boeing (and their customers) just didn't want it in the training manuals as that would have required more training.
 
timh4000
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:06 pm

The two 737max aircraft which crashed were anything but a perfectly good plane. Normally I try not to get too involved with the crash threads, but out of curiosity was wondering what everyone was still talking about and I got my answer. While MOST 737max aircraft might have been ok, these two were anything but. It started with AOA sensors being off by huge margins. Then a system that supposedly was put in place to aid pilots with manual flight turned out to be this monster that overpowered pilot input. Pushing the nose down further and further. As the nose goes down the speed goes up... to the point with the ET crash they were in over speed conditions. Cutting out the computer trim system, disabling MCAS, losing altitude and now attempting to manually trim the aircraft by using the trim wheel itself which at high speeds becomes a very difficult task. I'm not saying there wasn't pilot error on either crash, but to say that they crashed a perfectly fine aircraft and slammed it into the earth is ridiculous. Especially when there was no specific training on how to deal with MCAS and in the case of lion air, not even aware of the system.

It sounds like Boeing has got fixed in place so in the same events, pilots won't be put into such difficulties and there will be adequate training on this. Now it's just a matter of getting these planes back in the air again but also not to rush it. Thorough checkouts of sensors, the revised MCAS system and proper pilot training, even if it means a type rating specific to the max. I won't mind getting on one so long as the same mistakes are not repeated in the case for quick profit. The max will likely be in the air for decades so a few more months or even longer if necessary will be beneficial long term. If the same rush for profit mistakes continues even if the results aren't so fatal, few will get on the plane including me and when that happens then Boeing truly will be in deep poo poo.
 
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zeke
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Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:06 pm

PixelFlight wrote:
No, a bad static pressure input will not generate a +20° erratic AoA value, nor a MCAS command. The scenario need to produce all the data recorded on the FDR to be valid.
Did you have the Elevator Feel Shift Module control column pressure data of ET610 and ET302 ?


A bad static source can result in inadvertent stick shaker, incorrect speed, incorrect altitude, and even windshear warnings.

Yes the elevator shift can raise control forces four times higher than normal.
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morrisond
Posts: 1401
Joined: Thu Jan 07, 2010 12:22 am

Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:10 pm

flybucky wrote:
morrisond wrote:
So if the Car was say a GM for example and GM sent you a note saying you can continue to use the car but if you are faced with runaway acceleration - ensure the wheel is pointed forward and hit the Stop button you can continue to use it. However when you are faced with that situation you don't ensure the wheels are pointed forward before you hit the switch - that is GM's fault?

To make this analogy more accurate, it would be like GM sent a note saying:

If you are faced with runaway acceleration, hit the Stop button.

Note: You can point the wheel forward before hitting the Stop button. Or you can also steer the wheel after hitting the Stop button.

See this post that shows the differences in text between the Emergency Airworthiness Directive, which revises the Airplane Flight Manual (which flight crews do not deal with), compared to the Flight Crew Operations Manual bulletin update (which is what flight crews deal with).


I get it - and that is one of the possible scenarios on the ET flight - they might have thought that Manual Stabilizer Trim meant - Manually operating the electric trim. Although it should have been clear as the FCOM talks about electric trim right above.

No way to know until the full cockpit CVR is released.

In any case it's pretty clear they probably did not know there plane that well.
 
Jamie514
Posts: 148
Joined: Thu May 18, 2017 4:36 pm

Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:35 pm

morrisond wrote:
Along with the A320 - it has a manual trim wheel as backup as well. If you are going to condemn the 737 for having one and demand a redesign - time to take it out of the A320 as well.


Apples to oranges.

A320 doesn't have anything in the control systems that will randomly cut in with moving the stab half its total travel distance acting on one unverified data input alone like MCAS.

If you're going to implement automated flight control systems, better demand triple redundancy of the ones you don't disclose too, even the ones that allegedly serve no stability function and are merely "control column feel systems".

edited to add: also, just because 737 manual trim wheel becomes hard or nearly impossible to adjust manually when thrown against the end stop by MCAS, does not mean there are (many?) other h-stab trim system failure modes that might leave it disabled closer to aerodynamic neutral position meaning this backup tool is still useful in nearly every other case.
Last edited by Jamie514 on Tue Apr 23, 2019 12:48 pm, edited 1 time in total.
 
User avatar
seahawk
Posts: 8736
Joined: Fri May 27, 2005 1:29 am

Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:36 pm

ArgentoSystems wrote:
seahawk wrote:
Pilot error, does not mean blaming the pilots. Pilot error can be caused by missing information, unsuitable man to machine interface, missing training, unclear instrument displays, wrong checklists, work overload and many more reasons. In both cases Boeing shoulders most of the blame for the crashes, not the pilots and to be honest also not the plane as the basic plane was fully functional.

Now you've gone completely off the rails. You are contradicting yourself, don't you see that?


I am not interested in finding out who is to blame, but why events played out like they did. If you look at the preliminary report on the ET flight, the raw data, it imho there are many things that stand out, that are very interesting, but not discussed.

1. the maintenance record of the plane. It has 3 events of the altimeter showing erratic behaviour and one event of an un-commanded roll with AP engaged.
2. the thrust setting of the engines remained at full thrust for the whole flight - even though they reached VMO quickly
3. the altitude displays showed different values
4. the difference in airspeed readings was small

This leaves me with more question that the pure MCAS activation inputs.
 
kalvado
Posts: 2024
Joined: Wed Mar 01, 2006 4:29 am

Re: B737MAX Grounded Worldwide

Tue Apr 23, 2019 12:39 pm

morrisond wrote:
flybucky wrote:
morrisond wrote:
So if the Car was say a GM for example and GM sent you a note saying you can continue to use the car but if you are faced with runaway acceleration - ensure the wheel is pointed forward and hit the Stop button you can continue to use it. However when you are faced with that situation you don't ensure the wheels are pointed forward before you hit the switch - that is GM's fault?

To make this analogy more accurate, it would be like GM sent a note saying:

If you are faced with runaway acceleration, hit the Stop button.

Note: You can point the wheel forward before hitting the Stop button. Or you can also steer the wheel after hitting the Stop button.

See this post that shows the differences in text between the Emergency Airworthiness Directive, which revises the Airplane Flight Manual (which flight crews do not deal with), compared to the Flight Crew Operations Manual bulletin update (which is what flight crews deal with).


I get it - and that is one of the possible scenarios on the ET flight - they might have thought that Manual Stabilizer Trim meant - Manually operating the electric trim. Although it should have been clear as the FCOM talks about electric trim right above.

No way to know until the full cockpit CVR is released.

In any case it's pretty clear they probably did not know there plane that well.

An interesting question is if Boeing folks knew their plane that well. Challenger experience has shown that small pieces of knowledge existing at low level dissipate on the way up - and the result is a total lack of understanding on all levels.

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