An225
Topic Author
Posts: 257
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Why are they still medling with MCAS, and not looking for other options?

Thu Oct 03, 2019 3:59 pm

Hello all,
I hope that this is the right forum for my question...

The MAX is now grounded since March, and we are already in Q4 and nobody knows when will the aircraft be allowed to re-enter airlines' service. Boeing is still trying to rectify MCAS which is to blame in the 2 crashes. We can't be sure that these efforts would be successful and when will it get the ok by the regulators.

As far as I know, Boeing has developed the telescopic MLG for the MAX-10 due to the increase in length of this variant, which allows them to retain the original design of the wheelwells. Therefore, the aircraft is going to stand taller than any 737 ever designed, which means that new engines will have adequate ground clearance if they fit the engines as in the original placement of 737NG series.

If that is true, MCAS will not be needed anymore since the problem of placing the engines forward and upward is eliminated.
So why Boeing is not taking this path and continuing with efforts to fix a system that tarnished the reputation of the MAX and created so much disbelief in Boeing as a company and the MAX by regulators?

An225
 
flipdewaf
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Re: Why are they still medling with MCAS, and not looking for other options?

Thu Oct 03, 2019 4:32 pm

So the 737-10 does not stand taller on the ground, only on rotation would the landing gear extend. The 737 in any variant is not allowed to stand taller on the ramp than they currently do owing to grandfathering rules on the certification.

Fred


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abies111
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Re: Why are they still medling with MCAS, and not looking for other options?

Thu Oct 03, 2019 7:53 pm

Could the undesirable lift effect of the MAX nacelles at high AOA be fully compensated by aerodinamic ad-ons or a slight redesign of the nacelles, so no MCAS needed?
 
GalaxyFlyer
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Re: Why are they still medling with MCAS, and not looking for other options?

Thu Oct 03, 2019 9:54 pm

flipdewaf wrote:
So the 737-10 does not stand taller on the ground, only on rotation would the landing gear extend. The 737 in any variant is not allowed to stand taller on the ramp than they currently do owing to grandfathering rules on the certification.

Fred


Sent from my iPhone using Tapatalk


It’s an amended TC, not someone’s grandfather. The new G7500 stands a good bit taller than the G6000 and it’s on an amended TC, certified on the basis of the latest Part 25 amendments.

GF
 
WPvsMW
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Re: Why are they still medling with MCAS, and not looking for other options?

Fri Oct 04, 2019 8:37 am

An225 wrote:
So why Boeing is not taking this path and continuing with efforts to fix a system that tarnished the reputation of the MAX and created so much disbelief in Boeing as a company and the MAX by regulators? An225


Because the landing fix would have cost more and lengthened delivery times. Irony intended.
 
An225
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Re: Why are they still medling with MCAS, and not looking for other options?

Fri Oct 04, 2019 8:42 am

WPvsMW wrote:
An225 wrote:
So why Boeing is not taking this path and continuing with efforts to fix a system that tarnished the reputation of the MAX and created so much disbelief in Boeing as a company and the MAX by regulators? An225


Because the landing fix would have cost more and lengthened delivery times. Irony intended.


Good to know....
 
VSMUT
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Re: Why are they still medling with MCAS, and not looking for other options?

Fri Oct 04, 2019 9:00 am

GalaxyFlyer wrote:
flipdewaf wrote:
So the 737-10 does not stand taller on the ground, only on rotation would the landing gear extend. The 737 in any variant is not allowed to stand taller on the ramp than they currently do owing to grandfathering rules on the certification.

Fred


Sent from my iPhone using Tapatalk


It’s an amended TC, not someone’s grandfather. The new G7500 stands a good bit taller than the G6000 and it’s on an amended TC, certified on the basis of the latest Part 25 amendments.

GF


AFAIK, it is not the landing gear extension itself that is the issue, it is the lack of overwing emergency evacuation slides. It is already critical enough that the flaps must be extended and that passengers have to drop some 5 feet. Any further extension will make that method unworkable.
 
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Faro
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Re: Why are they still medling with MCAS, and not looking for other options?

Fri Oct 04, 2019 5:45 pm

The only other options are to fiddle with the landing gear and/or the frame’s center of gravity range...ie, a not insignificant or cheap undertaking...


Faro
The chalice not my son
 
flipdewaf
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Re: Why are they still medling with MCAS, and not looking for other options?

Mon Oct 07, 2019 4:57 am

GalaxyFlyer wrote:
flipdewaf wrote:
So the 737-10 does not stand taller on the ground, only on rotation would the landing gear extend. The 737 in any variant is not allowed to stand taller on the ramp than they currently do owing to grandfathering rules on the certification.

Fred


Sent from my iPhone using Tapatalk


It’s an amended TC, not someone’s grandfather. The new G7500 stands a good bit taller than the G6000 and it’s on an amended TC, certified on the basis of the latest Part 25 amendments.

GF

Lol, fair dos. The ‘rules’ set in place by the authorities that grant permissions for the legality of flying an aircraft, the semantics of the specific name applied by this authority or a general commonly used non industry specific term aside, mean they can’t make the gear longer on the ground for evacuation (is the correct term emergency egress in this instance?) reasons.

Whatever you want to call it, the 737 tain’t growing it’s legs because of rules.

Fred


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GalaxyFlyer
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Re: Why are they still medling with MCAS, and not looking for other options?

Mon Oct 07, 2019 12:20 pm

It’s not the rules in the 737’s case, longer gear would require a new wing center section. That’s the engineering involved and that’s a new plane. Boeing decided against that in 2011 or so.
 
patrickjp93
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Re: Why are they still medling with MCAS, and not looking for other options?

Mon Oct 07, 2019 12:48 pm

Because there has been a long-serving, more robust version of MCAS on military craft for over a decade. In other words, it's a fixable issue within engineering constraints to simply use the more robust version (which Boeing should have done from the start).
 
litzj
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Re: Why are they still medling with MCAS, and not looking for other options?

Mon Oct 07, 2019 12:53 pm

as far as I know, MCAS could save cost rather than a brand new system or training of a new characteristics
 
asdf
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Re: Why are they still medling with MCAS, and not looking for other options?

Mon Oct 07, 2019 7:36 pm

patrickjp93 wrote:
Because there has been a long-serving, more robust version of MCAS on military craft for over a decade. In other words, it's a fixable issue within engineering constraints to simply use the more robust version (which Boeing should have done from the start).


No

The KCs are basically already kinda fly-by-wire
In a fly by wire plane you can fit in automation of flight surfaces pretty easy

No fly-by- wire in the NG, nore the MAX

Not compareable at all
 
patrickjp93
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Re: Why are they still medling with MCAS, and not looking for other options?

Mon Oct 07, 2019 7:41 pm

asdf wrote:
patrickjp93 wrote:
Because there has been a long-serving, more robust version of MCAS on military craft for over a decade. In other words, it's a fixable issue within engineering constraints to simply use the more robust version (which Boeing should have done from the start).


No

The KCs are basically already kinda fly-by-wire
In a fly by wire plane you can fit in automation of flight surfaces pretty easy

No fly-by- wire in the NG, nore the MAX

Not compareable at all


You can't prove the system is inherently incompatible with non-fbw planes, so that's a red herring unless you've got something more conclusive.
 
asdf
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 8:40 am

patrickjp93 wrote:
asdf wrote:
patrickjp93 wrote:
Because there has been a long-serving, more robust version of MCAS on military craft for over a decade. In other words, it's a fixable issue within engineering constraints to simply use the more robust version (which Boeing should have done from the start).


No

The KCs are basically already kinda fly-by-wire
In a fly by wire plane you can fit in automation of flight surfaces pretty easy

No fly-by- wire in the NG, nore the MAX

Not compareable at all


You can't prove the system is inherently incompatible with non-fbw planes, so that's a red herring unless you've got something more conclusive.


i do not need to prove
we have two proves already
ya forgot?

and no, this is not ironic
 
mxaxai
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 9:06 am

VSMUT wrote:
AFAIK, it is not the landing gear extension itself that is the issue, it is the lack of overwing emergency evacuation slides. It is already critical enough that the flaps must be extended and that passengers have to drop some 5 feet. Any further extension will make that method unworkable.

Adding some slides, or larger slides, can't be that critical. Different variants already feature different exit configurations. How much does each slide weigh? 20 - 30 kg perhaps?
 
VSMUT
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 9:48 am

mxaxai wrote:
VSMUT wrote:
AFAIK, it is not the landing gear extension itself that is the issue, it is the lack of overwing emergency evacuation slides. It is already critical enough that the flaps must be extended and that passengers have to drop some 5 feet. Any further extension will make that method unworkable.

Adding some slides, or larger slides, can't be that critical. Different variants already feature different exit configurations. How much does each slide weigh? 20 - 30 kg perhaps?


Isn't it more like 50 kg? Slides are also awfully big, you need to find space for it - easier said than done in a 737. Then there is the whole thing about commonality and training, plus authorities might start asking some awkward questions and demand fixes to the other doors etc.

And all of that is on top of somehow extending the landing gear, which would be a major investment in itself.
 
asdf
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 10:20 am

mxaxai wrote:
VSMUT wrote:
AFAIK, it is not the landing gear extension itself that is the issue, it is the lack of overwing emergency evacuation slides. It is already critical enough that the flaps must be extended and that passengers have to drop some 5 feet. Any further extension will make that method unworkable.

Adding some slides, or larger slides, can't be that critical. Different variants already feature different exit configurations. How much does each slide weigh? 20 - 30 kg perhaps?


i would suspect that this does not work without changing parts of the hull

the 737 hull is certified from the 1950ties with 9G breakage
if you certifiy a hull today you need to prove 14G breakage

i think (but i do not know) you cant change the hull within grandfathering privilegs
 
patrickjp93
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 10:48 am

asdf wrote:
patrickjp93 wrote:
asdf wrote:

No

The KCs are basically already kinda fly-by-wire
In a fly by wire plane you can fit in automation of flight surfaces pretty easy

No fly-by- wire in the NG, nore the MAX

Not compareable at all


You can't prove the system is inherently incompatible with non-fbw planes, so that's a red herring unless you've got something more conclusive.


i do not need to prove
we have two proves already
ya forgot?

and no, this is not ironic


You don't need to prove it? It's your assertion. You HAVE to prove it. That's how debate works.

We do NOT have any proof to the contrary. MCAS as it stands right now relies on one AoA sensor. If it relied on 2 or more, and provided the sensor disagree warning light from the start, we wouldn't even know it exists.
 
VSMUT
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 11:08 am

asdf wrote:
mxaxai wrote:
VSMUT wrote:
AFAIK, it is not the landing gear extension itself that is the issue, it is the lack of overwing emergency evacuation slides. It is already critical enough that the flaps must be extended and that passengers have to drop some 5 feet. Any further extension will make that method unworkable.

Adding some slides, or larger slides, can't be that critical. Different variants already feature different exit configurations. How much does each slide weigh? 20 - 30 kg perhaps?


i would suspect that this does not work without changing parts of the hull

the 737 hull is certified from the 1950ties with 9G breakage
if you certifiy a hull today you need to prove 14G breakage

i think (but i do not know) you cant change the hull within grandfathering privilegs


And that as well, and likely a myriad of other things. Every time Boeing makes a modification, they run the risk of authorities saying enough and forcing them to certify it as a new plane.
 
asdf
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 11:15 am

patrickjp93 wrote:
We do NOT have any proof to the contrary. MCAS as it stands right now relies on one AoA sensor. If it relied on 2 or more, and provided the sensor disagree warning light from the start, we wouldn't even know it exists.


MCAS is an attempt to reduce the likelihood of a crash due to poor MAX flow characteristics.
These poor flight characteristics of the MAX compared to the NG are the result of the larger engines installed way up and far above.

One can try to obscure the flow characteristics with electronics, but MCAS does not improve by one jota the poor aerodynamic properties of the MAX, especially in certain up-and-down curves and other maneuvers within the flight envelope.

The control of aircraft with unusual aerodynamic properties is quite easily possible with fly-by-wire controls because then the pilot does not command the changes to the attitude control but the flight computer. The pilot basically gives only the desired result.

Only partial automatic control of individual flight surfaces to compensate for certain aerodynamic effects is always uncertain.

Because HAL controls a flight surface without being able to recognize in which position the remaining flight areas controlled by the pilot are and how high the thrust is.
Even the attitude of the aircraft is only recognizable for this partial control when the sensors are working.

A redundant sensor control of critical systems (such as the compensation of the poor aerodynamic properties of the MAX) would have to be based on at least two sensors that have a third sensor in the event of a deviation from each other to determine which of the sensors provides the correct value and the automatic control continue to be maintained.

Simply notifying the crew that MCAS is not working is insufficient because MCAS is necessary to achieve the flight characteristics that are relevant to certification
 
Elshad
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 11:34 am

What about a larger horizontal stabiliser?
 
asdf
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 12:02 pm

Elshad wrote:
What about a larger horizontal stabiliser?


this would probably work for the flight attitudes
but i guess it does not help in the trim wheel case ..

and it would be a major chance of the plane
18 months or so?

if they would have started after the lion air crash it would be finished soon ..
 
Zeke2517
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 12:12 pm

patrickjp93 wrote:
asdf wrote:
patrickjp93 wrote:
Because there has been a long-serving, more robust version of MCAS on military craft for over a decade. In other words, it's a fixable issue within engineering constraints to simply use the more robust version (which Boeing should have done from the start).


No

The KCs are basically already kinda fly-by-wire
In a fly by wire plane you can fit in automation of flight surfaces pretty easy

No fly-by- wire in the NG, nore the MAX

Not compareable at all


You can't prove the system is inherently incompatible with non-fbw planes, so that's a red herring unless you've got something more conclusive.


You’re right. You can’t prove a negative. Thanks. The onus here is on Boeing to figure out how to keep their planes from smashing hundreds of people into the ground because the aoa information is wonky.
 
patrickjp93
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 12:19 pm

asdf wrote:
patrickjp93 wrote:
We do NOT have any proof to the contrary. MCAS as it stands right now relies on one AoA sensor. If it relied on 2 or more, and provided the sensor disagree warning light from the start, we wouldn't even know it exists.


MCAS is an attempt to reduce the likelihood of a crash due to poor MAX flow characteristics.
These poor flight characteristics of the MAX compared to the NG are the result of the larger engines installed way up and far above.

One can try to obscure the flow characteristics with electronics, but MCAS does not improve by one jota the poor aerodynamic properties of the MAX, especially in certain up-and-down curves and other maneuvers within the flight envelope.

The control of aircraft with unusual aerodynamic properties is quite easily possible with fly-by-wire controls because then the pilot does not command the changes to the attitude control but the flight computer. The pilot basically gives only the desired result.

Only partial automatic control of individual flight surfaces to compensate for certain aerodynamic effects is always uncertain.

Because HAL controls a flight surface without being able to recognize in which position the remaining flight areas controlled by the pilot are and how high the thrust is.
Even the attitude of the aircraft is only recognizable for this partial control when the sensors are working.

A redundant sensor control of critical systems (such as the compensation of the poor aerodynamic properties of the MAX) would have to be based on at least two sensors that have a third sensor in the event of a deviation from each other to determine which of the sensors provides the correct value and the automatic control continue to be maintained.

Simply notifying the crew that MCAS is not working is insufficient because MCAS is necessary to achieve the flight characteristics that are relevant to certification


Absolutely incorrect. Letting pilots take full control is a GOOD thing, as even FBW systems fail catastrophically (several A330 cases, most notably the Qantas incident).

And MCAS is a mitigation system for specific cases of flight when the flow characteristics of the MAX cause a pitch up, and it does not need to be on an few system to do so successfully. Further, you do not need a 3rd sensor to say which of the first two is suddenly wrong. Visual demonstration of data, which you can keep thousands of records of per second in very little memory. I'm using integers for simplicity


AoA 1 ---- AoA 2
8 ___________ 8
8 ___________ 8
8 ___________ 8
8 ___________ 8
8 ___________ 8
8 ___________ 4 <--- Disagreement detected, could be a fluke, such as a heavy drop of water ramming into the foil of the sensor
8 ___________ 4 <--- Disagreement continues, depending on polling rate, may still be fluke
8 ___________ 4 <--- Disagreement still continues, log as a sensor disagreement mid-flight and proceed to test
7 ___________ 4 <--- Vertical stabilizer manipulated, only one sensor changed, and in the expected direction
9 ___________ 4 <--- Vertical stabilizer manipulated, only one sensor changed, and in the expected direction, confirming AoA 2 defect. AoA 2 inputs to systems disabled
8 ___________ 4 <--- Vertical stabilizer manipulated, only one sensor changed, original flight angle restored, pilot control resumed.

And if you want the other 7 failure modes, I can go through those too.

Edits: manipulation of the spacing and underscores to get the data table to line up.
Last edited by patrickjp93 on Tue Oct 08, 2019 12:25 pm, edited 4 times in total.
 
patrickjp93
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 12:21 pm

Zeke2517 wrote:
You’re right. You can’t prove a negative. Thanks. The onus here is on Boeing to figure out how to keep their planes from smashing hundreds of people into the ground because the aoa information is wonky.


This isn't a case of proving a negative. You have to prove that MCAS is only safely usable in a FBW system. You can use a multi-case proof set of Proof By Contradiction and Proof By Contraposition for that. Tedious, but it covers all failure modes explicitly. Proof by construction and induction would be more succinct but obscures the details of individual cases for the less technically minded.
 
asdf
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 12:34 pm

patrickjp93 wrote:
And if you want the other 7 failure modes, I can go through those too.


on the end of every of those failure modes on a single sensor on a (only) two sensor system you end up with a plane in a not certifiable status

there is no such occurance on any other actual brand
if there is a failure on a sensor you have maybe reduced automatics but you still have a plane flying within a certified flight envelope
 
patrickjp93
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 12:43 pm

asdf wrote:
patrickjp93 wrote:
And if you want the other 7 failure modes, I can go through those too.


on the end of every of those failure modes on a single sensor on a (only) two sensor system you end up with a plane in a not certifiable status

there is no such occurance on any other actual brand
if there is a failure on a sensor you have maybe reduced automatics but you still have a plane flying within a certified flight envelope


It's still certifiable. All planes must be able to be flown manually. You can fly the MAX manually just fine and disable MCAS to do it. By your half-baked logic, you can damage 3/4 sensors on a 4 sensor system via a birdstrike, so there should not be ANY system based on any number of AoA sensors which can manipulate the control surfaces. That, of course, is moronic and would ground every Airbus fbw plane flying today.
 
asdf
Posts: 437
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 2:08 pm

patrickjp93 wrote:
asdf wrote:
patrickjp93 wrote:
And if you want the other 7 failure modes, I can go through those too.


on the end of every of those failure modes on a single sensor on a (only) two sensor system you end up with a plane in a not certifiable status

there is no such occurance on any other actual brand
if there is a failure on a sensor you have maybe reduced automatics but you still have a plane flying within a certified flight envelope


It's still certifiable. All planes must be able to be flown manually. You can fly the MAX manually just fine and disable MCAS to do it. By your half-baked logic, you can damage 3/4 sensors on a 4 sensor system via a birdstrike, so there should not be ANY system based on any number of AoA sensors which can manipulate the control surfaces. That, of course, is moronic and would ground every Airbus fbw plane flying today.


fact is that a single point of failure in the MAX leds to a flight attitude which is not certifiable without augmentation
even with two sensors
 
mxaxai
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 2:15 pm

asdf wrote:
patrickjp93 wrote:
And if you want the other 7 failure modes, I can go through those too.


on the end of every of those failure modes on a single sensor on a (only) two sensor system you end up with a plane in a not certifiable status

there is no such occurance on any other actual brand
if there is a failure on a sensor you have maybe reduced automatics but you still have a plane flying within a certified flight envelope

Two sensors are enough to prevent the out-of-control failure that resulted in the two crashes. You simply disable the system automatically if the sensors disagree by more than a specified delta. Of course you need to prevent common mode failures, e. g. freezing up with identical readings, but that applies to all sensors.
VSMUT wrote:
And that as well, and likely a myriad of other things. Every time Boeing makes a modification, they run the risk of authorities saying enough and forcing them to certify it as a new plane.

While there are limits to grandfathering, Boeing has made numerous changes to the 737. I doubt that the relatively small changes we're discussing here would really be an issue:
- added dorsal fin/extension of the vertical stabilizer for 737 Classic
- developed new wing for 737NG
- increased length and exit configuration for 737-900ER (and others)
- FBW for spoiler deployment on 737MAX
- removed eyebrow windows

If we look at the A320, large changes were made within the family too:
- 4-wheel bogeys in A320
- rearranged exits on A321NX
- new high-lift devices for A321, twice
- larger vertical stabilizer on A318
- welding instead of rivets on A318 parts
 
patrickjp93
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 2:40 pm

asdf wrote:
patrickjp93 wrote:
asdf wrote:

on the end of every of those failure modes on a single sensor on a (only) two sensor system you end up with a plane in a not certifiable status

there is no such occurance on any other actual brand
if there is a failure on a sensor you have maybe reduced automatics but you still have a plane flying within a certified flight envelope


It's still certifiable. All planes must be able to be flown manually. You can fly the MAX manually just fine and disable MCAS to do it. By your half-baked logic, you can damage 3/4 sensors on a 4 sensor system via a birdstrike, so there should not be ANY system based on any number of AoA sensors which can manipulate the control surfaces. That, of course, is moronic and would ground every Airbus fbw plane flying today.


fact is that a single point of failure in the MAX leds to a flight attitude which is not certifiable without augmentation
even with two sensors


You DO realize that same argument applies to Airbus' FBW system, right? That's what nearly made a Qantas A330 take a drink a few years ago. It's not a single point of failure and can be engineered to disable itself if the good sensor count falls to 1 or 0. Pilots are certainly capable of performing a nose down every few minutes or when conditions require.

MCAS in principle is perfectly safe even on a non-FBW craft. It simply needs to rely on 2+ sensors, be properly programmed to detect and handle the various failure modes of those sensors, and then take itself offline in the event of a sensor disagreement as I outlined above.
 
VSMUT
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 2:43 pm

mxaxai wrote:
- developed new wing for 737NG


It is a modified wing, not a new one. It still has design legacy from the 737-100 stuck in it, see how the inner part of the wing has a different sweep. You wouldn't design a wing like that today.

It is also worth noting that none of these changes have affected the wing box, which has remained unchanged apart from being built from composites today.


mxaxai wrote:
If we look at the A320, large changes were made within the family too:
- 4-wheel bogeys in A320
- rearranged exits on A321NX
- new high-lift devices for A321, twice
- larger vertical stabilizer on A318
- welding instead of rivets on A318 parts


Rearranged exits aren't an issue here, because Airbus never had to rely on half-arsed solutions such as sliding down the flaps.
Putting different trailing edge devices and larger tail fins is common practice since forever. The last one is mandatory to achieve a satisfactory level of longitudinal stability, as was the case on the 737-600, MD-87 and 747SP.

I'm not quite sure I get your point here? You forgot to mention that they changed the computers and put LED lights in. They didn't make significant structural changes.
 
mxaxai
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 3:04 pm

VSMUT wrote:
I'm not quite sure I get your point here?

I guess that we have differing views on what is a minor change and what would mandate a full new certification.
 
asdf
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Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 3:38 pm

patrickjp93 wrote:
asdf wrote:
patrickjp93 wrote:

It's still certifiable. All planes must be able to be flown manually. You can fly the MAX manually just fine and disable MCAS to do it. By your half-baked logic, you can damage 3/4 sensors on a 4 sensor system via a birdstrike, so there should not be ANY system based on any number of AoA sensors which can manipulate the control surfaces. That, of course, is moronic and would ground every Airbus fbw plane flying today.


fact is that a single point of failure in the MAX leds to a flight attitude which is not certifiable without augmentation
even with two sensors


You DO realize that same argument applies to Airbus' FBW system, right?....


i am not really a fan of that A versus B cases
and i dont like airbus as a company at all

but i think you are pretty wrong

if you have a reduced sensor set on the bus you get a reduced automation
you get clear infos what sensor is failing, what are the consequences, what do you expect from this point on
in the worst case you get a reduced envelope

in a real heavy events you get "direct law"
.. what is a lot better than "direct nosedive" on the MAX ;-)
 
patrickjp93
Posts: 384
Joined: Thu Aug 22, 2019 12:00 pm

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 5:19 pm

asdf wrote:
patrickjp93 wrote:
asdf wrote:

fact is that a single point of failure in the MAX leds to a flight attitude which is not certifiable without augmentation
even with two sensors


You DO realize that same argument applies to Airbus' FBW system, right?....


i am not really a fan of that A versus B cases
and i dont like airbus as a company at all

but i think you are pretty wrong

if you have a reduced sensor set on the bus you get a reduced automation
you get clear infos what sensor is failing, what are the consequences, what do you expect from this point on
in the worst case you get a reduced envelope

in a real heavy events you get "direct law"
.. what is a lot better than "direct nosedive" on the MAX ;-)


And if MCAS is disabled after finding a sensor disagreement fault, then we're in direct law anyway, so like I said, this is a very fixable issue.
 
asdf
Posts: 437
Joined: Tue Mar 18, 2014 12:03 am

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 5:37 pm

patrickjp93 wrote:
And if MCAS is disabled after finding a sensor disagreement fault, then we're in direct law anyway, so like I said, this is a very fixable issue.


but you can not fix that the MAX has a aerodynamical behavior like a chicken without the MCAS augmentation

since there is no final report out we do not know how many % of the catastrophic outcome is put
A.) on the crew not following procedures
B.) on the automated MCAS influence
C.) on the unusual flight behavior of the MAX which prevented the crew from stabilizing the plane with manual control

till now we only know that A.) should get pretty low % because they pretty straight followed the checklists and the AD, (they only did not from the very beginning take into account a side note added at the end of the AD)

but we have no idea how much you have to weight on B.) or C.)

yes, B.) was firing in between, but why does it seem at the first look on the FDR data that the crew didnt want to get that nose up in the air again?
there is no reason to stop trimming if earth is going to bigger and bigger @ the frontwindow
there is no reason to stop pulling
they of course have not been suicidal
they wanted to survive
what stopped them from getting the nose back up?

if there is falling significant % on C.) we do have a complete other magnitude of problem than a redundance solution on the AoA sensor for "MCAS" ...
 
patrickjp93
Posts: 384
Joined: Thu Aug 22, 2019 12:00 pm

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 6:13 pm

asdf wrote:
patrickjp93 wrote:
And if MCAS is disabled after finding a sensor disagreement fault, then we're in direct law anyway, so like I said, this is a very fixable issue.


but you can not fix that the MAX has a aerodynamical behavior like a chicken without the MCAS augmentation

since there is no final report out we do not know how many % of the catastrophic outcome is put
A.) on the crew not following procedures
B.) on the automated MCAS influence
C.) on the unusual flight behavior of the MAX which prevented the crew from stabilizing the plane with manual control

till now we only know that A.) should get pretty low % because they pretty straight followed the checklists and the AD, (they only did not from the very beginning take into account a side note added at the end of the AD)

but we have no idea how much you have to weight on B.) or C.)

yes, B.) was firing in between, but why does it seem at the first look on the FDR data that the crew didnt want to get that nose up in the air again?
there is no reason to stop trimming if earth is going to bigger and bigger @ the frontwindow
there is no reason to stop pulling
they of course have not been suicidal
they wanted to survive
what stopped them from getting the nose back up?

if there is falling significant % on C.) we do have a complete other magnitude of problem than a redundance solution on the AoA sensor for "MCAS" ...


It can be manually flown safely just fine, so no, there is no ultra magnitude problem preventing recertification. By your logic, since an EMP can take out the flight controls o the A320, and because the family has a pitch problem similar to the MAX, it should be grounded too.
 
asdf
Posts: 437
Joined: Tue Mar 18, 2014 12:03 am

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 6:24 pm

patrickjp93 wrote:
It can be manually flown safely just fine, so no, there is no ultra magnitude problem preventing recertification. By your logic, since an EMP can take out the flight controls o the A320, and because the family has a pitch problem similar to the MAX, it should be grounded too.


stay serious

its not about a nuclear bomb
its about 350 death people and thousands of affected relatives

the pitch problem on the A320 (no idea why they dont call it a stall problem, maybe because "pitch" does not sound so dangerous?) is a load distribution problem, occuring only on the flex cabin variants and needs the operators now to block the last row in some circumstances
its annoying and it needs to get fixed
EASA is on that case and the busmakers have to fix that regardless of the cost of it

will you compare that to the MCAS drama?
you are serious?
 
patrickjp93
Posts: 384
Joined: Thu Aug 22, 2019 12:00 pm

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 6:36 pm

asdf wrote:
patrickjp93 wrote:
It can be manually flown safely just fine, so no, there is no ultra magnitude problem preventing recertification. By your logic, since an EMP can take out the flight controls o the A320, and because the family has a pitch problem similar to the MAX, it should be grounded too.


stay serious

its not about a nuclear bomb
its about 350 death people and thousands of affected relatives

the pitch problem on the A320 (no idea why they dont call it a stall problem, maybe because "pitch" does not sound so dangerous?) is a load distribution problem, occuring only on the flex cabin variants and needs the operators now to block the last row in some circumstances
its annoying and it needs to get fixed
EASA is on that case and the busmakers have to fix that regardless of the cost of it

will you compare that to the MCAS drama?
you are serious?

I think you're missing the point of my irony.

Reductio. Ad. Absurdum. The 350 deaths are irrelevant from an engineering perspective. Facts do NOT care about your feelings about a tragedy involving a system that mathematically is not equivalent to what I'm proposing. All MCAS needs is 2-sensor input, with safe failure modes upon sensor disagreement (IE failure results in MCAS being disabled with audible pilot alerts and manual flying takes over). I just proved beyond all doubt that you can detect the faulty part in the pair without a third sensor (anyone wanting the other 7 failure modes' data flows, PM me). Just because the A320's pitch problem hasn't killed people YET doesn't mean it lacks a very serious potential to, so if you want to debate the engineering solutions' merit, take the deaths out of it. Stick to the facts of the engineering. The fact is Boeing has a perfectly reliable variant in use by the military, and putting aside some deeper integrations, can be placed on a non-FBW craft just fine, but Boeing cut corners on the end design. Fix that issue and we're all kosher. There is no reason to keep the 737 MAX grounded after MCAS is fixed.
 
asdf
Posts: 437
Joined: Tue Mar 18, 2014 12:03 am

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 7:19 pm

patrickjp93 wrote:
...All MCAS needs is 2-sensor input, with safe failure modes upon sensor disagreement ..... The fact is Boeing has a perfectly reliable variant in use by the military, and putting aside some deeper integrations, can be placed on a non-FBW craft just fine, but Boeing cut corners on the end design. Fix that issue and we're all kosher. There is no reason to keep the 737 MAX grounded after MCAS is fixed.


i think you are way to optimistic in predicting consequences
if even you are interested in the consequences of your estimates

it may be that a only-two-sensor solution may acceptable withing regulations

but with this additional sensor you - again - are simply cutting corners
this way the MAX will never be as safe as some would expect from a post-millenial transport category aircraft

and statistics will prove that
btw ... i think you know that, too

but i can see your mission ....
 
oschkosch
Posts: 289
Joined: Mon Oct 29, 2018 3:41 pm

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 7:44 pm

patrickjp93 wrote:
The 350 deaths are irrelevant from an engineering perspective.


wow, just wow!

Gesendet von meinem SM-G950F mit Tapatalk
 
patrickjp93
Posts: 384
Joined: Thu Aug 22, 2019 12:00 pm

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 8:03 pm

asdf wrote:
patrickjp93 wrote:
...All MCAS needs is 2-sensor input, with safe failure modes upon sensor disagreement ..... The fact is Boeing has a perfectly reliable variant in use by the military, and putting aside some deeper integrations, can be placed on a non-FBW craft just fine, but Boeing cut corners on the end design. Fix that issue and we're all kosher. There is no reason to keep the 737 MAX grounded after MCAS is fixed.


i think you are way to optimistic in predicting consequences
if even you are interested in the consequences of your estimates

it may be that a only-two-sensor solution may acceptable withing regulations

but with this additional sensor you - again - are simply cutting corners
this way the MAX will never be as safe as some would expect from a post-millenial transport category aircraft

and statistics will prove that
btw ... i think you know that, too

but i can see your mission ....


It's not cutting corners at all. I proved those corners don't exist in the first place. Now, if you think a plane under autopilot is safer than one being manually flown, then fine, but the fallback of the industry is human flight, so...

Now, if you want to ADD additional redundancy before human fallback is required, fine, but 2 is perfectly suitable, and then in-flight incidents largely are the fault of bad maintenance practices (Ethiopian and Lion Air both). And they're still safe incidents.
 
patrickjp93
Posts: 384
Joined: Thu Aug 22, 2019 12:00 pm

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 8:08 pm

oschkosch wrote:
patrickjp93 wrote:
The 350 deaths are irrelevant from an engineering perspective.


wow, just wow!

Gesendet von meinem SM-G950F mit Tapatalk


What's so "wow" about that statement? Boeing tossed faulty engineering out the door to the flying public. If these faults had been discovered before human deaths, people would STILL be up in arms against Boeing (and rightfully so), and Boeing would simply have dodged the wrongful termination lawsuits. The quality of Boeing's and Airbus' engineering has absolutely nothing to do with how many people die in each OEM's craft. If Lion Air and Ethiopian had properly maintained their AoA sensors, we likely still wouldn't know these faults exist, because the failsafe worked. Get it?

Engineering is a psychopathic field, but only to those people too attached to their emotions to stick to the facts.
 
flipdewaf
Posts: 2893
Joined: Thu Jul 20, 2006 6:28 am

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 8:17 pm

patrickjp93 wrote:
but the fallback of the industry is human flight, so...

Fallback? Human flight?

That’s Icarus mate, I don’t think it was real, more real than the place where you live.

Checklist787 wrote:

The quality of Boeing's and Airbus' engineering has absolutely nothing to do with how many people die in each OEM's craft.


Say what now?

Have fun everyone Patrick has taken yet another thread off track.

Fred




Sent from my iPhone using Tapatalk
Image
 
patrickjp93
Posts: 384
Joined: Thu Aug 22, 2019 12:00 pm

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 8:28 pm

flipdewaf wrote:
patrickjp93 wrote:
but the fallback of the industry is human flight, so...

Fallback? Human flight?

That’s Icarus mate, I don’t think it was real, more real than the place where you live.

Checklist787 wrote:

The quality of Boeing's and Airbus' engineering has absolutely nothing to do with how many people die in each OEM's craft.


Say what now?

Have fun everyone Patrick has taken yet another thread off track.

Fred




Sent from my iPhone using Tapatalk


Keep things in context instead of attempting to score political points. Of COURSE the quality of the planes both put out has a direct EFFECT on how many people die in their craft if they're allowed to fly. HOWEVER, the quality of Boeing's and Airbus' engineering DOES NOT CARE about how many die beyond zero. The AIM is zero. The AIM is to be perfectly safe while beating the opponent on the business case. When Boeing and Airbus engineers lock themselves in a war room to design a plane, grandfathered or not, neither team cares how many die from their designs, because both are designing for zero death. The Boeing engineers right now addressing the 737 MAX MCAS' shortcomings should not under any circumstance care that 1, 350, or 350,000,000 people died because of the corners cut in the 737 MAX's MCAS 1.0. They should only care that the 2.0 design meets the requirement that, in the future, 0 people die.

Engineers should not and mostly do not care that people die as part of faulty designs under a company's banner. Engineers care about getting the product right, and nothing else matters, because as long as the product comes out right, the other parts of the equation don't come into play.
 
asdf
Posts: 437
Joined: Tue Mar 18, 2014 12:03 am

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 9:52 pm

patrickjp93 wrote:
...If Lion Air and Ethiopian had properly maintained their AoA sensors, we likely still wouldn't know these faults exist ....


please provide a source

all public sources point to a flawless maintainance (at least in case of those affected planes), perfectly according to boeings textbook
 
asdf
Posts: 437
Joined: Tue Mar 18, 2014 12:03 am

Re: Why are they still medling with MCAS, and not looking for other options?

Tue Oct 08, 2019 9:55 pm

patrickjp93 wrote:
....The Boeing engineers right now addressing the 737 MAX MCAS' shortcomings ..... should only care that the 2.0 design meets the requirement that, in the future, 0 people die.


its pretty showing that you FIRST mentioned the requierments, and after that the "0 people die"

if one would be a psychologist he/she could tell you a whole story where your premises really are ...
 
Armadillo1
Posts: 518
Joined: Thu Apr 20, 2017 5:14 pm

Re: Why are they still medling with MCAS, and not looking for other options?

Wed Oct 09, 2019 8:03 am

patrickjp93 wrote:

I'm using integers for simplicity


AoA 1 ---- AoA 2
8 ___________ 8
8 ___________ 8
8 ___________ 8
8 ___________ 8
8 ___________ 8
8 ___________ 4 <--- Disagreement detected, could be a fluke, such as a heavy drop of water ramming into the foil of the sensor
8 ___________ 4 <--- Disagreement continues, depending on polling rate, may still be fluke
8 ___________ 4 <--- Disagreement still continues, log as a sensor disagreement mid-flight and proceed to test
7 ___________ 4 <--- Vertical stabilizer manipulated, only one sensor changed, and in the expected direction
9 ___________ 4 <--- Vertical stabilizer manipulated, only one sensor changed, and in the expected direction, confirming AoA 2 defect. AoA 2 inputs to systems disabled
8 ___________ 4 <--- Vertical stabilizer manipulated, only one sensor changed, original flight angle restored, pilot control resumed.

And if you want the other 7 failure modes, I can go through those too.

Edits: manipulation of the spacing and underscores to get the data table to line up.

good try, but this will not work so good and simple in dynamic situation while AoA (and speed) still changing.
 
mxaxai
Posts: 1153
Joined: Sat Jun 18, 2016 7:29 am

Re: Why are they still medling with MCAS, and not looking for other options?

Wed Oct 09, 2019 9:48 am

Armadillo1 wrote:
patrickjp93 wrote:

I'm using integers for simplicity


AoA 1 ---- AoA 2
8 ___________ 8
8 ___________ 8
8 ___________ 8
8 ___________ 8
8 ___________ 8
8 ___________ 4 <--- Disagreement detected, could be a fluke, such as a heavy drop of water ramming into the foil of the sensor
8 ___________ 4 <--- Disagreement continues, depending on polling rate, may still be fluke
8 ___________ 4 <--- Disagreement still continues, log as a sensor disagreement mid-flight and proceed to test
7 ___________ 4 <--- Vertical stabilizer manipulated, only one sensor changed, and in the expected direction
9 ___________ 4 <--- Vertical stabilizer manipulated, only one sensor changed, and in the expected direction, confirming AoA 2 defect. AoA 2 inputs to systems disabled
8 ___________ 4 <--- Vertical stabilizer manipulated, only one sensor changed, original flight angle restored, pilot control resumed.

And if you want the other 7 failure modes, I can go through those too.

Edits: manipulation of the spacing and underscores to get the data table to line up.

good try, but this will not work so good and simple in dynamic situation while AoA (and speed) still changing.

True. You'd typically log a disagreement and not bother to determine which sensor is faulty, but isolate both sensors. This kind of analytical redundancy is usually only employed for actuators.
 
patrickjp93
Posts: 384
Joined: Thu Aug 22, 2019 12:00 pm

Re: Why are they still medling with MCAS, and not looking for other options?

Wed Oct 09, 2019 5:17 pm

asdf wrote:
patrickjp93 wrote:
...If Lion Air and Ethiopian had properly maintained their AoA sensors, we likely still wouldn't know these faults exist ....


please provide a source

all public sources point to a flawless maintainance (at least in case of those affected planes), perfectly according to boeings textbook


No they don't, and we have at least 1 Ethiopian employee claiming maintenance crews were often exhausted and beaten, which has been a long known problem in Ethiopia, so even the records claiming perfect compliance are highly suspect.

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