kalvado
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 1:37 pm

GalaxyFlyer wrote:
At 05:40:12, approximately three seconds after AND stabilizer motion ends, electric trim (from pilot activated switches on the yoke) in the Aircraft nose up (ANU) direction is recorded on the DFDR and the stabilizer moved in the ANU direction to 2.4 units. The Aircraft pitch attitude remained about the same as the back pressure on the column increased.
At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.


Why while increasing back pressure, did they not continue trimming? The switches worked. I think they weren’t trimming as every manually switch moved the stab. It lifted off with about 5 units up but never got back to anything 5 units. Take off trim is approximately V2.


Gf

Jammed jackscrew never happened in 737... Another nightmare scenario is if high loads caused issues with drive mechanism.
 
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N14AZ
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 1:42 pm

This is getting ridiculous: the German yellow press is now complaining that Boeing is using their employee’s parking spaces for storing B737Max’s including satellite picture:
Image
Source: https://www.bild.de/geld/wirtschaft/wir ... .bild.html

Note: I checked the last 48 hours of this thread and didn't see this having been already posted. If I am wrong, however, please delete.
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 1:48 pm

planecane wrote:
brindabella wrote:
planecane wrote:

1.1 from oxford allows for interruption.


Came in a little late; sorry if repetitive..

The trend of the posts above are trending that BA Tech assumed that any trained 737 pilot would recognise an inappropriate stab trim movement, however In a Court of Law the discontinuous movement may defeat this.

Expand please.



cheers Billy


In civil court Boeing will be found to have some percentage of liability anyway even if the procedure came with a video that showed MCAS failing.

In criminal court I doubt it would get near that far since I still can't find any federal law that could possibly be used to find Boeing guilty of the crashes as a homicide. Any criminal case will be mail fraud or wire fraud for lying to the FCC or something like that. Therefore, the semantics of the NNC condition will probably not come into play.


I am engineer. When I would do a negligent design and people get killed, I can end up in a criminal case. I can even end up in a criminal case when I know a design, that I did not do, is dangerous and I do nothing.
I know that everything depends on evidence and proof, but to declare categorically, that Boeing, or better certain people at Boeing are safe from criminal prosecution in regards to the people that have died in the crash, is a fantasy.
 
Etika
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 2:00 pm

Criminal liability is extremely hard to prove in cases like this. It would require that actions of a specific individual were linked to the outcome of the accident, and that it is shown that the person in question knew or should have known that his actions would place people in jeopardy. It is relatively easy to think a situation where this kind of thing could be proved to have happened to "someone in the engineering". But to do this on the level of specific individual is extremely difficult when the design process includes multiple large teams.

Civil cases, which have different standard of proof required, are far more likely than any criminal case. Regardless of what has happened, obtaining the level of proof on a specific individual to even prosecute a case is nearly impossible.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 2:34 pm

N14AZ wrote:
This is getting ridiculous: the German yellow press is now complaining that Boeing is using their employee’s parking spaces for storing B737Max’s including satellite picture:

Simple fixes to the problem.
1. Cease production of the MAX and send all staff home, just pay the vendors
2. Place a couple barges with ramps in the water behind the parking lot and let the staff park there.
3. Notify the staff that there is a grounding of the MAX a/c which is produced in mass quantities per month, so there is a problem to be addressed.

Seems pretty straight forward, thankfully, there is no I in team and no We either.
 
GalaxyFlyer
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 2:55 pm

kalvado wrote:
GalaxyFlyer wrote:
At 05:40:12, approximately three seconds after AND stabilizer motion ends, electric trim (from pilot activated switches on the yoke) in the Aircraft nose up (ANU) direction is recorded on the DFDR and the stabilizer moved in the ANU direction to 2.4 units. The Aircraft pitch attitude remained about the same as the back pressure on the column increased.
At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.


Why while increasing back pressure, did they not continue trimming? The switches worked. I think they weren’t trimming as every manually switch moved the stab. It lifted off with about 5 units up but never got back to anything 5 units. Take off trim is approximately V2.


Gf

Jammed jackscrew never happened in 737... Another nightmare scenario is if high loads caused issues with drive mechanism.


True, on jamming the jackscrew, but don’t let that happen!! That’s been a possibility since the 707, but by using trim correctly, not a risk in service.

GF
Last edited by GalaxyFlyer on Mon May 27, 2019 2:58 pm, edited 1 time in total.
 
AirFiero
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 2:57 pm

Interesting article from AvWeb, Max delayed again...

http://flash.avweb.com/eletter/4343-ful ... ail#232853
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 3:02 pm

GalaxyFlyer wrote:
At 05:40:12, approximately three seconds after AND stabilizer motion ends, electric trim (from pilot activated switches on the yoke) in the Aircraft nose up (ANU) direction is recorded on the DFDR and the stabilizer moved in the ANU direction to 2.4 units. The Aircraft pitch attitude remained about the same as the back pressure on the column increased.
At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.


Why while increasing back pressure, did they not continue trimming? The switches worked. I think they weren’t trimming as every manually switch moved the stab. It lifted off with about 5 units up but never got back to anything 5 units. Take off trim is approximately V2.


Gf


Perhaps the switches work but the trim does not go beyond 2.4/2.3. The data implies an external influence that is not the pilot.

Ray
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 3:04 pm

GalaxyFlyer wrote:
kalvado wrote:
GalaxyFlyer wrote:

Why while increasing back pressure, did they not continue trimming? The switches worked. I think they weren’t trimming as every manually switch moved the stab. It lifted off with about 5 units up but never got back to anything 5 units. Take off trim is approximately V2.


Gf

Jammed jackscrew never happened in 737... Another nightmare scenario is if high loads caused issues with drive mechanism.


True, on jamming the jackscrew, but don’t let that happen!!

GF

If you think about it in a different way: no flying machine has components with safety margin factor of way above minimum just because we can. So I expect the entire trim mechanism to be designed for about same force - motor, jackscrew, nuts, cables, cockpit wheel, levers, mounts. As we know, cockpit wheel forces can be very high in severe mistrim. So those forces can be above design threshold in any other part of the system as well.
Then there are many things which can happen: motor kicking off on overheat/overtorque/overcurrent; jackscrew nuts behaving funny, including backup nut becoming locknut; thread damage...
This is of course pure speculation - but not totally unfeasible. Trim not going past some value can be explained by a damage to screw drive, for example.
Investigating such scenario, though, is difficult without major Boeing cooperation, especially by small national authority - and I doubt Boeing is too willing to open a possible can of worms.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 3:05 pm

mjoelnir wrote:
planecane wrote:
brindabella wrote:

Came in a little late; sorry if repetitive..

The trend of the posts above are trending that BA Tech assumed that any trained 737 pilot would recognise an inappropriate stab trim movement, however In a Court of Law the discontinuous movement may defeat this.

Expand please.



cheers Billy


In civil court Boeing will be found to have some percentage of liability anyway even if the procedure came with a video that showed MCAS failing.

In criminal court I doubt it would get near that far since I still can't find any federal law that could possibly be used to find Boeing guilty of the crashes as a homicide. Any criminal case will be mail fraud or wire fraud for lying to the FCC or something like that. Therefore, the semantics of the NNC condition will probably not come into play.


I am engineer. When I would do a negligent design and people get killed, I can end up in a criminal case. I can even end up in a criminal case when I know a design, that I did not do, is dangerous and I do nothing.
I know that everything depends on evidence and proof, but to declare categorically, that Boeing, or better certain people at Boeing are safe from criminal prosecution in regards to the people that have died in the crash, is a fantasy.

There is nothing I can find in the United States Code (federal statutes) that would allow for prosecution like that in this case. The deaths happened in foreign countries. Since there is no statute in the USC, there would be no provision in am extradition treaty because that crime wouldn't be punishable in the US under federal law.

If the crashes had occurred inside the US then State law would apply. Since most, of not all, states have criminal negligence statutes, the state where the crash occurred could likely prosecute.
 
SEU
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 3:07 pm

N14AZ wrote:
This is getting ridiculous: the German yellow press is now complaining that Boeing is using their employee’s parking spaces for storing B737Max’s including satellite picture:
Image
Source: https://www.bild.de/geld/wirtschaft/wir ... .bild.html

Note: I checked the last 48 hours of this thread and didn't see this having been already posted. If I am wrong, however, please delete.


Brilliant reporting hahaha.

Its a genius solution to park the planes there. Cars can be parked elsewhere, Planes can only use the airport space.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 3:08 pm

AirFiero wrote:
Interesting article from AvWeb, Max delayed again...

http://flash.avweb.com/eletter/4343-ful ... ail#232853

Again? This is the same news from a few days ago.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 3:22 pm

XRAYretired wrote:
GalaxyFlyer wrote:
At 05:40:12, approximately three seconds after AND stabilizer motion ends, electric trim (from pilot activated switches on the yoke) in the Aircraft nose up (ANU) direction is recorded on the DFDR and the stabilizer moved in the ANU direction to 2.4 units. The Aircraft pitch attitude remained about the same as the back pressure on the column increased.
At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.


Why while increasing back pressure, did they not continue trimming? The switches worked. I think they weren’t trimming as every manually switch moved the stab. It lifted off with about 5 units up but never got back to anything 5 units. Take off trim is approximately V2.


Gf


Perhaps the switches work but the trim does not go beyond 2.4/2.3. The data implies an external influence that is not the pilot.

Ray


I don't agree. Although it should certainly be investigated, the fact that the movement of the trim is linear right up to the moment that the command stopped leads me to believe this is unlikely. It's not like there is force feedback on the switch. I doubt the reaction time of the pilot would allow him to see the wheel stop moving and release the switch instantly even if that was something he thought he should do if the trim stopped moving. I also doubt the switch stopped working and opened for some reason at a specific trim setting and then started working again only to stop working at the same point again. If it was non-electric manual trim using the wheel that stopped at the same spot, then I would lean towards this being the case.
 
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 3:53 pm

GalaxyFlyer wrote:
At 05:40:12, approximately three seconds after AND stabilizer motion ends, electric trim (from pilot activated switches on the yoke) in the Aircraft nose up (ANU) direction is recorded on the DFDR and the stabilizer moved in the ANU direction to 2.4 units. The Aircraft pitch attitude remained about the same as the back pressure on the column increased.
At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.


Why while increasing back pressure, did they not continue trimming? The switches worked. I think they weren’t trimming as every manually switch moved the stab. It lifted off with about 5 units up but never got back to anything 5 units. Take off trim is approximately V2.
Gf


I think they were trimming, but somehow the system would not allow them to trim more than 2.4 units.
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
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NeBaNi
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 3:58 pm

SEU wrote:
N14AZ wrote:
This is getting ridiculous: the German yellow press is now complaining that Boeing is using their employee’s parking spaces for storing B737Max’s including satellite picture:
Image
Source: https://www.bild.de/geld/wirtschaft/wir ... .bild.html

Note: I checked the last 48 hours of this thread and didn't see this having been already posted. If I am wrong, however, please delete.


Brilliant reporting hahaha.

Its a genius solution to park the planes there. Cars can be parked elsewhere, Planes can only use the airport space.

But in the picture, there appears to be space for only 6 more MAXes to be parked. What happens in another month, as the MAX is still being produced at a rate of 42/mo?
 
DenverTed
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 4:05 pm

NeBaNi wrote:
SEU wrote:
N14AZ wrote:
This is getting ridiculous: the German yellow press is now complaining that Boeing is using their employee’s parking spaces for storing B737Max’s including satellite picture:
Image
Source: https://www.bild.de/geld/wirtschaft/wir ... .bild.html

Note: I checked the last 48 hours of this thread and didn't see this having been already posted. If I am wrong, however, please delete.


Brilliant reporting hahaha.

Its a genius solution to park the planes there. Cars can be parked elsewhere, Planes can only use the airport space.

But in the picture, there appears to be space for only 6 more MAXes to be parked. What happens in another month, as the MAX is still being produced at a rate of 42/mo?

Can't have that out in the open. They need to build a fake suburb roof on top of that, like the B-17 plant 2 factory.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 4:22 pm

NeBaNi wrote:
SEU wrote:
N14AZ wrote:
This is getting ridiculous: the German yellow press is now complaining that Boeing is using their employee’s parking spaces for storing B737Max’s including satellite picture:
Image
Source: https://www.bild.de/geld/wirtschaft/wir ... .bild.html

Note: I checked the last 48 hours of this thread and didn't see this having been already posted. If I am wrong, however, please delete.


Brilliant reporting hahaha.

Its a genius solution to park the planes there. Cars can be parked elsewhere, Planes can only use the airport space.

But in the picture, there appears to be space for only 6 more MAXes to be parked. What happens in another month, as the MAX is still being produced at a rate of 42/mo?


They'll fly them elsewhere for storage. The more they can fit on their property, the less they have to pay in storage fees.
 
AirFiero
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 4:50 pm

planecane wrote:
AirFiero wrote:
Interesting article from AvWeb, Max delayed again...

http://flash.avweb.com/eletter/4343-ful ... ail#232853

Again? This is the same news from a few days ago.


Sorry, I don’t read all ten pages of this thread per day, and the avweb article hit my email this morning.
 
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7BOEING7
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 7:08 pm

N14AZ wrote:
This is getting ridiculous: the German yellow press is now complaining that Boeing is using their employee’s parking spaces for storing B737Max’s including satellite picture:
Image
Source: https://www.bild.de/geld/wirtschaft/wir ... .bild.html


That area including the some of the parking you see used to be factory buildings. To my knowledge it was never used for employee parking.
 
OldAeroGuy
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 7:35 pm

ExperimentalFTE wrote:
-Cannot obtain meaningful voting on the validity of the data source, it is either OP or INOP.

-Cannot achieve failure rate (typ 10^-9) for critical flight control components and thus probability vs severity wrt stalling and departure from controlled flight.

-Without it aircraft is still uncertifiable wrt to 25.203 and it is still very shady wrt 25.1309 and single source failure.

-Ah and also, lets discuss bit a windsheer scenario, full power on application and pitch up.....

;)


Here's the text of 25.672.

§ 25.672 Stability augmentation and automatic and power-operated systems.
If the functioning of stability augmentation or other automatic or power-operated systems is necessary to show compliance with the flight characteristics requirements of this part, such systems must comply with § 25.671 and the following:

(a) A warning which is clearly distinguishable to the pilot under expected flight conditions without requiring his attention must be provided for any failure in the stability augmentation system or in any other automatic or power-operated system which could result in an unsafe condition if the pilot were not aware of the failure. Warning systems must not activate the control systems.

(b) The design of the stability augmentation system or of any other automatic or power-operated system must permit initial counteraction of failures of the type specified in § 25.671(c) without requiring exceptional pilot skill or strength, by either the deactivation of the system, or a failed portion thereof, or by overriding the failure by movement of the flight controls in the normal sense.

(c) It must be shown that after any single failure of the stability augmentation system or any other automatic or power-operated system -

(1) The airplane is safely controllable when the failure or malfunction occurs at any speed or altitude within the approved operating limitations that is critical for the type of failure being considered;

(2) The controllability and maneuverability requirements of this part are met within a practical operational flight envelope (for example, speed, altitude, normal acceleration, and airplane configurations) which is described in the Airplane Flight Manual; and

(3) The trim, stability, and stall characteristics are not impaired below a level needed to permit continued safe flight and landing.

[Amdt. 25-23, 35 FR 5675 Apr. 8, 1970]

I've bolded the relevant text. Paragraph (c) allows for single failures of MCAS sensors.

Note that (c)(1) requires that the airplane be safely controllable with the approved operating envelope. Operations near stall are not considered to be within the normal operating envelope.

As MCAS 2.0 will only normally activate outside the normal operating envelope, its failure to function after a single failure (eg a single AoA sensor with a subsequent MCAS shutdown) will not violate the requirements for (c)(3). MCAS 2.0 shutdown annunciation will provided by the "AoA Disagree" Alert

If two sensors fail to the same high AoA level, then MCAS could have one stabilizer cycle in the normal operating envelope. The single stabilizer cycle can be countered using the elevator and then trimmed out using stabilizer trim so full elevator functionality is regained.

25.1309 is not applicable as 25.672 allows for a single failure as long as continued safe flight and landing can be shown within the normal operating envelope.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
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ExperimentalFTE
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 8:08 pm

OldAeroGuy wrote:
ExperimentalFTE wrote:
-Cannot obtain meaningful voting on the validity of the data source, it is either OP or INOP.

-Cannot achieve failure rate (typ 10^-9) for critical flight control components and thus probability vs severity wrt stalling and departure from controlled flight.

-Without it aircraft is still uncertifiable wrt to 25.203 and it is still very shady wrt 25.1309 and single source failure.

-Ah and also, lets discuss bit a windsheer scenario, full power on application and pitch up.....

;)


Here's the text of 25.672.

§ 25.672 Stability augmentation and automatic and power-operated systems.
If the functioning of stability augmentation or other automatic or power-operated systems is necessary to show compliance with the flight characteristics requirements of this part, such systems must comply with § 25.671 and the following:

(a) A warning which is clearly distinguishable to the pilot under expected flight conditions without requiring his attention must be provided for any failure in the stability augmentation system or in any other automatic or power-operated system which could result in an unsafe condition if the pilot were not aware of the failure. Warning systems must not activate the control systems.

(b) The design of the stability augmentation system or of any other automatic or power-operated system must permit initial counteraction of failures of the type specified in § 25.671(c) without requiring exceptional pilot skill or strength, by either the deactivation of the system, or a failed portion thereof, or by overriding the failure by movement of the flight controls in the normal sense.

(c) It must be shown that after any single failure of the stability augmentation system or any other automatic or power-operated system -

(1) The airplane is safely controllable when the failure or malfunction occurs at any speed or altitude within the approved operating limitations that is critical for the type of failure being considered;

(2) The controllability and maneuverability requirements of this part are met within a practical operational flight envelope (for example, speed, altitude, normal acceleration, and airplane configurations) which is described in the Airplane Flight Manual; and

(3) The trim, stability, and stall characteristics are not impaired below a level needed to permit continued safe flight and landing.

[Amdt. 25-23, 35 FR 5675 Apr. 8, 1970]

I've bolded the relevant text. Paragraph (c) allows for single failures of MCAS sensors.

Note that (c)(1) requires that the airplane be safely controllable with the approved operating envelope. Operations near stall are not considered to be within the normal operating envelope.

As MCAS 2.0 will only normally activate outside the normal operating envelope, its failure to function after a single failure (eg a single AoA sensor with a subsequent MCAS shutdown) will not violate the requirements for (c)(3). MCAS 2.0 shutdown annunciation will provided by the "AoA Disagree" Alert

If two sensors fail to the same high AoA level, then MCAS could have one stabilizer cycle in the normal operating envelope. The single stabilizer cycle can be countered using the elevator and then trimmed out using stabilizer trim so full elevator functionality is regained.

25.1309 is not applicable as 25.672 allows for a single failure as long as continued safe flight and landing can be shown within the normal operating envelope.


Oh, we dont exactly know when we start having issues wrt pitch up close to stall and when "abnormal" stick force per G is starting to be experienced so unless we see concrete data that we are far away from stall and that MCAS is not engaging but as far as we can assume, aircraft can operate down to 1.13 Vsr0 in normal conditions and we have no idea where MCAS kicks in so no I cant disregard para c1 as non issue.

Para c2 same applies as we dont know when stick force per G start being affected and how classical wind-up-turn looks like say at 1.3Vsr0 trim.

Para c3 trim, stability and stall characteristics not impaired, well if you start having stick lightening after 1.3Vsr0 I would call that impaired.

I cant agree that complying with 671 will relieve anyone from complying with 1309....

Cheers
 
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7BOEING7
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 8:53 pm

ExperimentalFTE wrote:

Oh, we dont exactly know when we start having issues wrt pitch up close to stall and when "abnormal" stick force per G is starting to be experienced so unless we see concrete data that we are far away from stall and that MCAS is not engaging but as far as we can assume, aircraft can operate down to 1.13 Vsr0 in normal conditions and we have no idea where MCAS kicks in so no I cant disregard para c1 as non issue.

Para c2 same applies as we dont know when stick force per G start being affected and how classical wind-up-turn looks like say at 1.3Vsr0 trim.

Para c3 trim, stability and stall characteristics not impaired, well if you start having stick lightening after 1.3Vsr0 I would call that impaired.

I cant agree that complying with 671 will relieve anyone from complying with 1309....Cheers



Since the FAA agreed in principle with what MACS 1.0 was meant to do, probably flew some of the MCAS 1.0 flights and will do the same with MCAS 2.0, irrespective of the issues they presently have, I would defer to them relative to the interpretation of the FAR's -- this is sort of a mute discussion.
 
OldAeroGuy
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 9:53 pm

ExperimentalFTE wrote:
I cant agree that complying with 671 will relieve anyone from complying with 1309....

Cheers


To carry on with 7BOEING7's point about the FAA interpretation of MCAS 1.0, the single sensor failure with regard to MCAS operation was always present.

Under MCAS 1.0 certification, a single AoA vane signal failure at a low AoA would have disabled MCAS in a flight regime near stall where it was required to pass 25.203.

While not meeting 25.203, an MCAS failure to operate must not have created sufficient handling difficulties or stall propensity to endanger continued safe flight and landing.

If continued safe flight and landing is not in question, how is 25.1309 applicable?

OAG

PS it's 25.672, not 25.671 that speaks to single failure effects not in the normal operational envelope.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
ltbewr
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 10:27 pm

Boeing should consider speaking to Ken Fineberg who created structured settlement programs like done after 9/11 and with some other mass tort events to limit the payouts, minimize cuts to plaintiff's lawyers and their own lawyer's costs, assure fair and proper payments to victims families and airliners who's 737MAX's have been grounded.
 
smartplane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 11:34 pm

7BOEING7 wrote:
ExperimentalFTE wrote:

Oh, we dont exactly know when we start having issues wrt pitch up close to stall and when "abnormal" stick force per G is starting to be experienced so unless we see concrete data that we are far away from stall and that MCAS is not engaging but as far as we can assume, aircraft can operate down to 1.13 Vsr0 in normal conditions and we have no idea where MCAS kicks in so no I cant disregard para c1 as non issue.

Para c2 same applies as we dont know when stick force per G start being affected and how classical wind-up-turn looks like say at 1.3Vsr0 trim.

Para c3 trim, stability and stall characteristics not impaired, well if you start having stick lightening after 1.3Vsr0 I would call that impaired.

I cant agree that complying with 671 will relieve anyone from complying with 1309....Cheers


Since the FAA agreed in principle with what MACS 1.0 was meant to do, probably flew some of the MCAS 1.0 flights and will do the same with MCAS 2.0, irrespective of the issues they presently have, I would defer to them relative to the interpretation of the FAR's -- this is sort of a mute discussion.

In may posts, the term 'FAA' seems to be a catchall for FAA employees AND Boeing employees with FAA designated responsibilities (in many / most cases with no FAA employee oversight).

Airlines, crews and passengers can take ZERO comfort the FAA apparently agreed in principle with what MCAS 1.0 was mean't to do, (or why it was needed), nor subsequent undisclosed changes, and why they were made, because full disclosure is a precursor to a valid agreement.

Just as including MCAS references in maintenance documentation doesn't count as disclosure to flight crew and training staff.
 
IADFCO
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Mon May 27, 2019 11:54 pm

OldAeroGuy wrote:
IADFCO wrote:
furthermore, MCAS 2.0 will turn itself off *by design* after activating once. So, after the "protection" is needed once, it will not be available again (not clear for how long).


I think you're incorrect on how MCAS 2.0 will function.

- MCAS 2.0 will activate once when both AoA vanes exceed the trigger AoA. If AoA remains above the trigger AoA, it will not activate again.

- If both AoA's drop below the trigger AoA, MCAS 2.0 will re-activate if trigger AoA is again exceeded.

- If Left/Right AoA disagree by more than X deg, MCAS 2.0 will be shut down.

OAG


In fact, I was referring to the first item of your list. The hypothetical situation is a turn with increasing AoA, such as could be needed by some avoidance maneuver, with the pilot realizing that he/she needs to tighten the turn. This would be somewhat similar to a windup turn. So the chain of events of concern is:
1 - The aircraft find itself in the flight conditions for which MCAS has been designed (still not exactly known publicly, but presumably a steep turn with aft CG)
2 - Trigger AoA, correctly measured by both sensor, is exceeded, and MCAS kicks in with a nose down input.
3 - The pilot counteracts the MCAS input because he/she needs the AoA, and keeps increasing the force on the yoke to increase AoA. Since AoA has remained above the trigger value, MCAS 2.0 does not activate (MCAS 1.0 would have).
4 - What happens now?

Some questions:
(i) assume that the MAX pilot applies the same forces as in an NG, out of habit, muscle memory, whatever. These, presumably, will be higher than needed in an NG to achieve the same AoA: does the MAX under these higher forces go quickly into stall?
(ii) If the MAX enters stall, are the recovery characteristics different from the NG, and if so, how, and by how much?

All of this is driven by the uncertainty about the effects on the flow field of the larger engine in its higher and more forward position. It may very well be that these concerns are overblown, and the differences between MAX and NG are small to an experienced 737 pilot. But as an engineer, I would want experimental verification through flight tests.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 3:32 am

IADFCO wrote:
OldAeroGuy wrote:
IADFCO wrote:
furthermore, MCAS 2.0 will turn itself off *by design* after activating once. So, after the "protection" is needed once, it will not be available again (not clear for how long).


I think you're incorrect on how MCAS 2.0 will function.

- MCAS 2.0 will activate once when both AoA vanes exceed the trigger AoA. If AoA remains above the trigger AoA, it will not activate again.

- If both AoA's drop below the trigger AoA, MCAS 2.0 will re-activate if trigger AoA is again exceeded.

- If Left/Right AoA disagree by more than X deg, MCAS 2.0 will be shut down.

OAG


In fact, I was referring to the first item of your list. The hypothetical situation is a turn with increasing AoA, such as could be needed by some avoidance maneuver, with the pilot realizing that he/she needs to tighten the turn. This would be somewhat similar to a windup turn. So the chain of events of concern is:
1 - The aircraft find itself in the flight conditions for which MCAS has been designed (still not exactly known publicly, but presumably a steep turn with aft CG)
2 - Trigger AoA, correctly measured by both sensor, is exceeded, and MCAS kicks in with a nose down input.
3 - The pilot counteracts the MCAS input because he/she needs the AoA, and keeps increasing the force on the yoke to increase AoA. Since AoA has remained above the trigger value, MCAS 2.0 does not activate (MCAS 1.0 would have).
4 - What happens now?

Some questions:
(i) assume that the MAX pilot applies the same forces as in an NG, out of habit, muscle memory, whatever. These, presumably, will be higher than needed in an NG to achieve the same AoA: does the MAX under these higher forces go quickly into stall?
(ii) If the MAX enters stall, are the recovery characteristics different from the NG, and if so, how, and by how much?

All of this is driven by the uncertainty about the effects on the flow field of the larger engine in its higher and more forward position. It may very well be that these concerns are overblown, and the differences between MAX and NG are small to an experienced 737 pilot. But as an engineer, I would want experimental verification through flight tests.


MCAS (at least from what is public) is supposed to activate in part of the flight envelope that nobody should be flying in to start with. MCAS is needed because it is possible to get the 737 into that AoA/airspeed range, not because it is normal operation. If the pilot "needs the AoA" and counteracts a properly operating MCAS, I hope I am never on one of their flights. I don't want to ever get that close to a stall.

It is supposed to take a lot of force to keep pulling the nose up at that point. MCAS is there to prevent "slipping" into a stall. Think about trying to remove a tight bolt. You pull with all of your strength and it doesn't budge but the suddenly it "breaks" and your hand moves a lot and slips off the wrench and hits the guy next to you. MCAS for the wrench would make it so the force required to turn the bolt remains high.
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 4:55 am

Another article on the MAX NG issue with the trim wheel.

https://www.moonofalabama.org/2019/05/b ... 7-ngs.html

Just as many airlines apparenlty made sure everyone knew how to do a UAS procedure after AF447, everyone now wants to know if they can turn that manual trim wheel if they need to.
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 9:37 am

RickNRoll wrote:
Another article on the MAX NG issue with the trim wheel.

https://www.moonofalabama.org/2019/05/b ... 7-ngs.html

Just as many airlines apparenlty made sure everyone knew how to do a UAS procedure after AF447, everyone now wants to know if they can turn that manual trim wheel if they need to.


That article refutes the opinion of quite a few posters here, that it is easy-peasy to counter a trim runaway at low elevation, if you just remember and do the right procedure.

Trim runaway has always been a deadly situation at low elevations, very chancy to recover from. The saving grace has been, that the occurrence of such a fault has been so much reduced, that it is very unlikely that a 737NG pilot will ever encounter it.

The problem that MCAS added is, a much higher rate of occurrence and it behaving different to the original runaway trim situation pilots trained for, making it more difficult to diagnose it. The coming of STS also helps to confuse, because you expect automatic trim commands, separate from pilot commanded, to happen.

As I pointed out before, the resizing of the trim wheels has not helped. What I did not know is, that the change in stabilizer surface reduced the authority of the elevators in comparison.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 10:44 am

RickNRoll wrote:
Another article on the MAX NG issue with the trim wheel.

https://www.moonofalabama.org/2019/05/b ... 7-ngs.html

Just as many airlines apparenlty made sure everyone knew how to do a UAS procedure after AF447, everyone now wants to know if they can turn that manual trim wheel if they need to.

Many thanks for that link. :thumbsup:
Very well written article. :checkmark:
 
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ExperimentalFTE
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 10:44 am

@7BOEING7 @OldAeroGuy

Since the FAA agreed in principle with what MACS 1.0 was meant to do, probably flew some of the MCAS 1.0 flights and will do the same with MCAS 2.0, irrespective of the issues they presently have, I would defer to them relative to the interpretation of the FAR's -- this is sort of a mute discussion.


To carry on with 7BOEING7's point about the FAA interpretation of MCAS 1.0, the single sensor failure with regard to MCAS operation was always present.

Under MCAS 1.0 certification, a single AoA vane signal failure at a low AoA would have disabled MCAS in a flight regime near stall where it was required to pass 25.203.

While not meeting 25.203, an MCAS failure to operate must not have created sufficient handling difficulties or stall propensity to endanger continued safe flight and landing.

If continued safe flight and landing is not in question, how is 25.1309 applicable?

OAG

PS it's 25.672, not 25.671 that speaks to single failure effects not in the normal operational envelope.


Yes and that is one of the first unanswered questions for both of you. How the heck was this possible and how heck was it "agreed to" to begin with. You can rest assured that other cert authorities are asking this question. 7B7, your statement "probably flew" is inadequate.

You can rest assured that boys will now turn into microscopes and look for every bit of puzzle.

I would start with natural stall of the aircraft, straight and turning stall, idle and power on. WUTs, idle and power on up to max G. Once "pitch up" and "minor stick lightening" and "lower stick force per g"have been quantified and there is a number on the table which is clear and understood by the authorities then we can start talking importance of the MCAS, severity of the failure of the MCAS and failure probability for criticality.

OAG. Well we are yet to see that continued safe flight and landing is or is not in question in normal performance envelope......or if there is restriction, speed adder and perf penalty in order to figure out how 1309 is applicable so until we see that........it is...

671 vs 672....fat fingers, typing on cell phone...

As we say in flight test: In God we trust, ALL others bring data!

Cheers
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 2:44 pm

mjoelnir wrote:
RickNRoll wrote:
Another article on the MAX NG issue with the trim wheel.

https://www.moonofalabama.org/2019/05/b ... 7-ngs.html

Just as many airlines apparenlty made sure everyone knew how to do a UAS procedure after AF447, everyone now wants to know if they can turn that manual trim wheel if they need to.


That article refutes the opinion of quite a few posters here, that it is easy-peasy to counter a trim runaway at low elevation, if you just remember and do the right procedure.

Trim runaway has always been a deadly situation at low elevations, very chancy to recover from. The saving grace has been, that the occurrence of such a fault has been so much reduced, that it is very unlikely that a 737NG pilot will ever encounter it.

The problem that MCAS added is, a much higher rate of occurrence and it behaving different to the original runaway trim situation pilots trained for, making it more difficult to diagnose it. The coming of STS also helps to confuse, because you expect automatic trim commands, separate from pilot commanded, to happen.

As I pointed out before, the resizing of the trim wheels has not helped. What I did not know is, that the change in stabilizer surface reduced the authority of the elevators in comparison.


A runaway stabilizer where it doesn't respond to opposite electric trim would certainly not be easy to recover from. As long as the electric trim works to counteract it should not be very difficult.

As far as the manual wheel, to determine how much more difficult it is to use on the NG vs. the classic, we need to know exactly how much smaller the wheel is, where the fold out handle is attached along the radius, any gearing changes, the effect of the damper that some have said was added and the amount of force added by the larger stabilizer surface area.

I am surprised that the regulations don't require that the elevator be capable of counteracting full nose up and full nose down trim. Not so much for the (previously very rare) runaway stabilizer but in case the jackscrew is jammed at one extreme. I wouldn't be surprised if there are more aircraft than just the 737 where this is the case
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 3:28 pm

planecane wrote:
mjoelnir wrote:
RickNRoll wrote:
Another article on the MAX NG issue with the trim wheel.

https://www.moonofalabama.org/2019/05/b ... 7-ngs.html

Just as many airlines apparenlty made sure everyone knew how to do a UAS procedure after AF447, everyone now wants to know if they can turn that manual trim wheel if they need to.


That article refutes the opinion of quite a few posters here, that it is easy-peasy to counter a trim runaway at low elevation, if you just remember and do the right procedure.

Trim runaway has always been a deadly situation at low elevations, very chancy to recover from. The saving grace has been, that the occurrence of such a fault has been so much reduced, that it is very unlikely that a 737NG pilot will ever encounter it.

The problem that MCAS added is, a much higher rate of occurrence and it behaving different to the original runaway trim situation pilots trained for, making it more difficult to diagnose it. The coming of STS also helps to confuse, because you expect automatic trim commands, separate from pilot commanded, to happen.

As I pointed out before, the resizing of the trim wheels has not helped. What I did not know is, that the change in stabilizer surface reduced the authority of the elevators in comparison.


A runaway stabilizer where it doesn't respond to opposite electric trim would certainly not be easy to recover from. As long as the electric trim works to counteract it should not be very difficult.

As far as the manual wheel, to determine how much more difficult it is to use on the NG vs. the classic, we need to know exactly how much smaller the wheel is, where the fold out handle is attached along the radius, any gearing changes, the effect of the damper that some have said was added and the amount of force added by the larger stabilizer surface area.

I am surprised that the regulations don't require that the elevator be capable of counteracting full nose up and full nose down trim. Not so much for the (previously very rare) runaway stabilizer but in case the jackscrew is jammed at one extreme. I wouldn't be surprised if there are more aircraft than just the 737 where this is the case


And recovery from automatic trim failure, be it STS or MCAS or something else, would be really aided, by it being be possible to turn off automatic trim without needing to turn off manual electrical trim.
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 4:07 pm

planecane wrote:
I am surprised that the regulations don't require that the elevator be capable of counteracting full nose up and full nose down trim. Not so much for the (previously very rare) runaway stabilizer but in case the jackscrew is jammed at one extreme. I wouldn't be surprised if there are more aircraft than just the 737 where this is the case

Looks like problem is not only elevator authority, but also with sheer amount of force required for that. And amount of that force, in turn, is given by FAR requirements, (and to add insult to injury - force is actually simulated on 737 as elevator is driven by hydraulics - as opposed to direct feedback from surfaces through the cable on earlier aircraft). So the catch is that controls are designed - by regulation - for fine control with relatively strong feedback, not for fighting with much bigger surfaces.
 
planecane
Posts: 871
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 4:23 pm

mjoelnir wrote:
planecane wrote:
mjoelnir wrote:

That article refutes the opinion of quite a few posters here, that it is easy-peasy to counter a trim runaway at low elevation, if you just remember and do the right procedure.

Trim runaway has always been a deadly situation at low elevations, very chancy to recover from. The saving grace has been, that the occurrence of such a fault has been so much reduced, that it is very unlikely that a 737NG pilot will ever encounter it.

The problem that MCAS added is, a much higher rate of occurrence and it behaving different to the original runaway trim situation pilots trained for, making it more difficult to diagnose it. The coming of STS also helps to confuse, because you expect automatic trim commands, separate from pilot commanded, to happen.

As I pointed out before, the resizing of the trim wheels has not helped. What I did not know is, that the change in stabilizer surface reduced the authority of the elevators in comparison.


A runaway stabilizer where it doesn't respond to opposite electric trim would certainly not be easy to recover from. As long as the electric trim works to counteract it should not be very difficult.

As far as the manual wheel, to determine how much more difficult it is to use on the NG vs. the classic, we need to know exactly how much smaller the wheel is, where the fold out handle is attached along the radius, any gearing changes, the effect of the damper that some have said was added and the amount of force added by the larger stabilizer surface area.

I am surprised that the regulations don't require that the elevator be capable of counteracting full nose up and full nose down trim. Not so much for the (previously very rare) runaway stabilizer but in case the jackscrew is jammed at one extreme. I wouldn't be surprised if there are more aircraft than just the 737 where this is the case


And recovery from automatic trim failure, be it STS or MCAS or something else, would be really aided, by it being be possible to turn off automatic trim without needing to turn off manual electrical trim.


I agree and have no idea why they didn't wire it that way. Maybe to avoid confusion of 2 identical switches next to each other that each turn off something different?
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 8:34 pm

planecane wrote:
mjoelnir wrote:
planecane wrote:

A runaway stabilizer where it doesn't respond to opposite electric trim would certainly not be easy to recover from. As long as the electric trim works to counteract it should not be very difficult.

As far as the manual wheel, to determine how much more difficult it is to use on the NG vs. the classic, we need to know exactly how much smaller the wheel is, where the fold out handle is attached along the radius, any gearing changes, the effect of the damper that some have said was added and the amount of force added by the larger stabilizer surface area.

I am surprised that the regulations don't require that the elevator be capable of counteracting full nose up and full nose down trim. Not so much for the (previously very rare) runaway stabilizer but in case the jackscrew is jammed at one extreme. I wouldn't be surprised if there are more aircraft than just the 737 where this is the case


And recovery from automatic trim failure, be it STS or MCAS or something else, would be really aided, by it being be possible to turn off automatic trim without needing to turn off manual electrical trim.


I agree and have no idea why they didn't wire it that way. Maybe to avoid confusion of 2 identical switches next to each other that each turn off something different?

They did have different functions in NG of course (but MAX FSB just refers to a nomenclature change). I understand that the reason for introducing cut out switches and runaway NNC was related to failure protection for the thumb switches, so organising specific switches for specific functions and potentially having to have additional or more complicated NNCs to work out when the thumb switches could left active perhaps could have ruled it out.

Ray
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 8:59 pm

planecane wrote:
mjoelnir wrote:
planecane wrote:

A runaway stabilizer where it doesn't respond to opposite electric trim would certainly not be easy to recover from. As long as the electric trim works to counteract it should not be very difficult.

As far as the manual wheel, to determine how much more difficult it is to use on the NG vs. the classic, we need to know exactly how much smaller the wheel is, where the fold out handle is attached along the radius, any gearing changes, the effect of the damper that some have said was added and the amount of force added by the larger stabilizer surface area.

I am surprised that the regulations don't require that the elevator be capable of counteracting full nose up and full nose down trim. Not so much for the (previously very rare) runaway stabilizer but in case the jackscrew is jammed at one extreme. I wouldn't be surprised if there are more aircraft than just the 737 where this is the case


And recovery from automatic trim failure, be it STS or MCAS or something else, would be really aided, by it being be possible to turn off automatic trim without needing to turn off manual electrical trim.


I agree and have no idea why they didn't wire it that way. Maybe to avoid confusion of 2 identical switches next to each other that each turn off something different?
Because you can't have the ability to turn off MCAS by itself by design. If you could it would mean you would need training on MCAS as MCAS would no longer be this magical piece of software you no longer needed to know anything about.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 9:00 pm

XRAYretired wrote:
planecane wrote:
mjoelnir wrote:

And recovery from automatic trim failure, be it STS or MCAS or something else, would be really aided, by it being be possible to turn off automatic trim without needing to turn off manual electrical trim.


I agree and have no idea why they didn't wire it that way. Maybe to avoid confusion of 2 identical switches next to each other that each turn off something different?

They did have different functions in NG of course (but MAX FSB just refers to a nomenclature change). I understand that the reason for introducing cut out switches and runaway NNC was related to failure protection for the thumb switches, so organising specific switches for specific functions and potentially having to have additional or more complicated NNCs to work out when the thumb switches could left active perhaps could have ruled it out.

Ray


Also, the runaway stabilizer NNC on the NG said to move both switches to cutout anyway. If they were intended to always be used together then the way they did it on the MAX serves to add redundancy that a single cutoff switch doesn't fail in the short position and make it impossible to shut down electric trim.

Maybe they could have made the switches on the MAX (and even NG) only cut off the automatic trim functions since I'm 95% sure that the thumb switch is two switches that must be pressed simultaneously wired in series. Both would have to fail for the swtich to cause a runaway. I don't know if the captain and FO yokes are in series with eachother or not. If they are, 4 switches would have to fail simultaneously.
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 9:04 pm

kalvado wrote:
planecane wrote:
I am surprised that the regulations don't require that the elevator be capable of counteracting full nose up and full nose down trim. Not so much for the (previously very rare) runaway stabilizer but in case the jackscrew is jammed at one extreme. I wouldn't be surprised if there are more aircraft than just the 737 where this is the case

Looks like problem is not only elevator authority, but also with sheer amount of force required for that. And amount of that force, in turn, is given by FAR requirements, (and to add insult to injury - force is actually simulated on 737 as elevator is driven by hydraulics - as opposed to direct feedback from surfaces through the cable on earlier aircraft). So the catch is that controls are designed - by regulation - for fine control with relatively strong feedback, not for fighting with much bigger surfaces.
That is one thing that worries me. The amount of force required to deal with an out of control trim system. It's that all simulated? Because the amount of physical effort required from the pilot to his the column while the problem is diagnosed is ridiculous. All pilots are going to find out hard to deal with and most are going to find out impossible. Surely a force feedback system could be more humane.
 
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zckls04
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 9:49 pm

Revelation wrote:
One of many posts with absurd distortion of other people's positions, presumably because people are intensively triggered by investigation of the actions of the pilots. sigh.


No, it's intentional hyperbole to help you understand how you can say one thing, but mean another.

Let's cut to the chase.

Please vote:

    When the accident reports for JT610 and ET302 are issued:

    A) No criticism will be directed towards the pilots and all will be directed to Boeing, FAA, the airlines, etc.

    -- or --

    B) Some criticism for the accident will be directed towards the pilots and some will be directed to Boeing FAA, the airlines, etc.



I've got a better idea. Let's not do that, since everybody agrees the answer is B, as it has been in virtually every aviation incident since the dawn of time. Let's instead recognize that whilst there may be a consensus that Boeing is at fault, there is no consensus at all on exactly what they are at fault for, nor to what extent, even among those who are fiercely inclined to defend them. Thus an A or B answer doesn't really get to the root of the issue, since it conveniently negates any discussion of these nuances.

Remember there's a good reason many might be skeptical, and that's the reliability with which this scenario repeats itself across many industries. If you can find a human being to blame, it's the cheapest and easiest way to avoid addressing systemic failures in your organization. (side note- it's not by chance that we have a specific term for such an individual). Virtually every major corporate screwup in history has followed the same pattern. First, deny. If you can't deny, obfuscate. If you can't obfuscate, reframe.
Four Granavox Turbines!
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Tue May 28, 2019 11:37 pm

planecane wrote:
Maybe they could have made the switches on the MAX (and even NG) only cut off the automatic trim functions since I'm 95% sure that the thumb switch is two switches that must be pressed simultaneously wired in series. Both would have to fail for the swtich to cause a runaway. I don't know if the captain and FO yokes are in series with eachother or not. If they are, 4 switches would have to fail simultaneously.

Yes, the 2 thumb switches must be pressed simultaneously.
No, the 2 thumb switches are not wired in series.
* One of the switch can connect the "28V DC BUS 2 STAB TRIM CONTROL" either to the "NOSE UP" signal, to the "NOSE DN" signal, or to none of them.
* The other switch can connect the "28V DC BUS 2 STAB TRIM CONTROL" to the "MAIN TRIM ARM" signal or not.
The "MAIN TRIM ENABLE SPEED & DIRECTION" must have the "MAIN TRIM ARM" signal _AND_ either of the "NOSE UP" or "NOSE DN" signal to operate.
Note the side effect that the trim operate if one pilot operate only the "NOSE UP/DN" switch and the other pilot only operate the "TRIM ARM" switch.

The "CAPT COL CUTOUT SW MODULE" is in parallel of the "F/O COL CUTOFF SW MOD" for the "NOSE UP" and "NODE DN" signal. Only the "F/O COL CUTOFF SW MOD" cut signals from the "FCC".

Frankly, this is a incredibly old design. :old: There are so many connectors and switches contacts that can fail and no redundancy on many signals. No surprise that Aviation Herald list so many stab trim issues for the 737. I would not recommend anything like that on a new design.
Image
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Wed May 29, 2019 4:42 am

RickNRoll wrote:
kalvado wrote:
planecane wrote:
I am surprised that the regulations don't require that the elevator be capable of counteracting full nose up and full nose down trim. Not so much for the (previously very rare) runaway stabilizer but in case the jackscrew is jammed at one extreme. I wouldn't be surprised if there are more aircraft than just the 737 where this is the case

Looks like problem is not only elevator authority, but also with sheer amount of force required for that. And amount of that force, in turn, is given by FAR requirements, (and to add insult to injury - force is actually simulated on 737 as elevator is driven by hydraulics - as opposed to direct feedback from surfaces through the cable on earlier aircraft). So the catch is that controls are designed - by regulation - for fine control with relatively strong feedback, not for fighting with much bigger surfaces.
That is one thing that worries me. The amount of force required to deal with an out of control trim system. It's that all simulated? Because the amount of physical effort required from the pilot to his the column while the problem is diagnosed is ridiculous. All pilots are going to find out hard to deal with and most are going to find out impossible. Surely a force feedback system could be more humane.


However, if the electric trim is working, the pilot doesn't need to use that force on the column the whole time that the problem is diagnosed. Once the column starts getting very difficult to hold, the pilot can trim out the required force assuming the electric trim is working. This action does not require a checklist, it is just standard procedure. The troubleshooting/NNC is needed if the stabilizer keeps going back out of trim.

As far as the force feedback system, I'm curious what aircraft was used to make the elevator feel like. I'm sure the 737 was based on the 727 which was probably based on the 707 but what were they replicating the feel of with the 707?
 
sgrow787
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Wed May 29, 2019 6:14 am

https://www.ft.com/content/a7dd933a-7e5 ... 85092ab560

“It’s pointless to train for what is not going to happen anyway because of the software fix,” said another US pilots union representative.

Also, in relation to the re-examination of 737 NG runaway stabilizer procedures, is this a sign of the kind of training the FAA is seeking for the Max un-grounding scenario? More specifically, is the FAA (and Boeing) trying to get pilot training for the Max, but get it under the umbrella of its predecessor (in order to not show new training due to MCAS, they are going to say the additional training was needed for previous 737 generations, so it isn't per se specific to MCAS, and hence doesn't require a new type certificate... and/or doesn't require additional training for those pilots who can demonstrate they know the runaway stabilizer for the NG).
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Wed May 29, 2019 6:33 am

planecane wrote:
RickNRoll wrote:
kalvado wrote:
Looks like problem is not only elevator authority, but also with sheer amount of force required for that. And amount of that force, in turn, is given by FAR requirements, (and to add insult to injury - force is actually simulated on 737 as elevator is driven by hydraulics - as opposed to direct feedback from surfaces through the cable on earlier aircraft). So the catch is that controls are designed - by regulation - for fine control with relatively strong feedback, not for fighting with much bigger surfaces.
That is one thing that worries me. The amount of force required to deal with an out of control trim system. It's that all simulated? Because the amount of physical effort required from the pilot to his the column while the problem is diagnosed is ridiculous. All pilots are going to find out hard to deal with and most are going to find out impossible. Surely a force feedback system could be more humane.


However, if the electric trim is working, the pilot doesn't need to use that force on the column the whole time that the problem is diagnosed. Once the column starts getting very difficult to hold, the pilot can trim out the required force assuming the electric trim is working. This action does not require a checklist, it is just standard procedure. The troubleshooting/NNC is needed if the stabilizer keeps going back out of trim.

As far as the force feedback system, I'm curious what aircraft was used to make the elevator feel like. I'm sure the 737 was based on the 727 which was probably based on the 707 but what were they replicating the feel of with the 707?


When QF72 was nearly sent out of complete control due to a faulty sensor the pilot only had to deal with nudging his sidestick. The force generated by the 737 feedback system to the control column becomes a needless part of the problem when MCAS failed. The problem for Boeing now is what happens when a real runaway trim event occurs. It rapidly takes the plane out of trim. What happens next? You can't use electric trim because it has to be disabled since any electric trim is instantly going to move the trim all the way to the extremes, so it can't help you. The only option is the manual trim wheel. One pilot is physically struggling with the control column and one is physically struggling with the trim wheel. (See Mentour Pilot video for an example).
 
planecane
Posts: 871
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q2 2019

Wed May 29, 2019 6:37 am

sgrow787 wrote:
https://www.ft.com/content/a7dd933a-7e5c-11e9-81d2-f785092ab560

“It’s pointless to train for what is not going to happen anyway because of the software fix,” said another US pilots union representative.

Also, in relation to the re-examination of 737 NG runaway stabilizer procedures, is this a sign of the kind of training the FAA is seeking for the Max un-grounding scenario? More specifically, is the FAA (and Boeing) trying to get pilot training for the Max, but get it under the umbrella of its predecessor (in order to not show new training due to MCAS, they are going to say the additional training was needed for previous 737 generations, so it isn't per se specific to MCAS, and hence doesn't require a new type certificate... and/or doesn't require additional training for those pilots who can demonstrate they know the runaway stabilizer for the NG).


It's not a conspiracy. The crash investigations (especially ET) have opened questions related to pilots executing the runaway stabilizer NNC. The procedure is the same on the NG. If there is a training it documentation issue with the NNC on the max out also exists on the NG.
 
chiad
Posts: 1182
Joined: Tue May 16, 2006 4:24 pm

Re: Boeing 737MAX Grounded Worldwide Q2 2019

Wed May 29, 2019 7:31 am

I haven' read all the posts here so I don't know if anyone has linked this already about "Could US pilots have saved the 737 MAX8 ?"
https://www.youtube.com/watch?v=ZtHBz2-YpWE
 
asdf
Posts: 269
Joined: Tue Mar 18, 2014 12:03 am

Re: Boeing 737MAX Grounded Worldwide Q2 2019

Wed May 29, 2019 7:37 am

they do it the clever way

they move the MAX training requirement from the MAX to the old version NG

so there will be "...no special training requirement..." for the MAX
but there will be additional training requirement for the NG ( ...and the MAX)

so they do not need to give the one million discount per aircraft to the US companies


well
better this way (NG training) than the other way (no training)
 
User avatar
PixelFlight
Posts: 476
Joined: Thu Nov 08, 2018 11:09 pm

Re: Boeing 737MAX Grounded Worldwide Q2 2019

Wed May 29, 2019 9:12 am

RickNRoll wrote:
When QF72 was nearly sent out of complete control due to a faulty sensor the pilot only had to deal with nudging his sidestick.

QF72 issue was not a sensor but an insanely erratic ADIRU 1, undetected by any of his internal self check and integrity test, that send corrupted data spikes, and a software error in the EFCS that did not filter the corrupted data spikes if there where more than 1.2 seconds apart. The EFCS commanded elevator nose down. Note: the horizontal stabilizer was still able to be operated manually from the electrical trim switch and the trim wheels.

You are right in the fact that all the pilot have to do is to apply back pressure on his sidestick. From the final report:
First upset 8.4° nose down:
captain immediately applied back pressure on his sidestick to arrest the pitch-down movement. The aircraft’s flight control system did not initially respond to the captain’s sidestick input, but after about 2 seconds the aircraft responded normally and the captain commenced recovery to the assigned altitude. During this 2-second period the aircraft descended about 150 ft. Overall, the aircraft descended 690 ft over 23 seconds before returning to FL370.

Second upset: 3.5° nose down:
The flight crew described the event as being similar in nature to the first event but less severe. The captain promptly applied back pressure on his sidestick to arrest the pitch-down movement. He said that, consistent with the first event, this action initially had no effect, but soon after the aircraft responded normally. FDR data showed that the flight control system did not respond to flight crew inputs for at least 2 seconds, and that the aircraft descended 400 ft over 15 seconds before returning to FL370.
 
 
User avatar
Dutchy
Posts: 9133
Joined: Sat Nov 03, 2007 1:25 am

Re: Boeing 737MAX Grounded Worldwide Q2 2019

Wed May 29, 2019 10:43 am

FluidFlow wrote:


Still no timeline. Boeing might still be a bit optimistic for the return of the MAX. Will the authorities demand there will be a second AoA sensor on board? Or will it just be a software update, the latter is much easier to implement of course. And some extra training after this for the aircrew. If so, this will push the return into service to September / October at the earliest.
Many happy landings, greetings from The Netherlands!

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