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PixelFlight
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Re: B737MAX Grounded Worldwide

Mon Apr 29, 2019 11:19 pm

dakota123 wrote:
And yes, absolutely, similar failure modes exist on the NG,and literally every other plane with an electric trim system.

Explain why only the 737 MAX need a software patch on a system that don't exists in any others 737 model and that is cited in 2 deadly crash as well as an EAD ?
I am not talking about a general category of failure, but a very precise failure mode that is only possible with a MCAS as found in the 737 MAX. That precise mode only exists on 737 MAX. Every single official document published, even from Boeing itself agree on that fact.
 
BravoOne
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Re: B737MAX Grounded Worldwide

Mon Apr 29, 2019 11:31 pm

par13del wrote:
art wrote:
I heard a little of what the Boeing representative said. He maintained that the primary consideration was always safety. If that were true the company would have redesigned the wingbox (or whatever) to avoid pushing the engines forward and up on the successor to NG, Or gone for NSA.

Which was not done because Boeing's secondary consideration was safety. Their primary consideration was maintaining market share by producing an A320NEO competitor ASAP..

I agree, a class action suit should be filed against every airline who bought the MAX, they are the one's who told Boeing that they would not wait for the NSA which was being pushed at them for years, in their effort to chase market share and compete with other airlines flying NEO's they had Boeing continue the progression of the obsolete 737.
Hmmm.....


Your suggestion is absurd but stranger things have happened before.
 
Aviation737
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Re: B737MAX Grounded Worldwide

Mon Apr 29, 2019 11:31 pm

kalvado wrote:
par13del wrote:
kalvado wrote:
Boeing could turn down AA/WN request and proceed with a clean sheet design. Narrowbody orders are ongoing, so loss of even a big customer is not the end of the world. Cash flow could be difficult if NG orders would go down, but that is a whole different story.

Except, more 737's are deployed outside of the USA, AA and WN may be large users but they will not account for 50% or more of the installed base.
At present, they have more a/c deployed than anyone else, which is a result of preferential treatment, but if you check the order book.....

Which is irrelevant. I am talking about different thing.
There is an impression that AA pushed Boeing into MAX by saying "give us a new plane, or we order 320NEO", and WN pushed into a no-training commitment by writing a penalty into contract. As big customers, these airlines have a significant influence on Boeing's decisions, no question about that. .
What I am saying, that shouldn't mean Boeing was improperly influenced. They could, at any time, turn down AA and WN if they thought they were unable to deliver. Or make a counteroffer - wait longer for new design. In either case, I don't see any ethical or legal problems with hard-line business negotiations in competitive environment.

You are thinking like this is because u know what's gonna happen when Boeing pursue down this path. But at that time the MAX was the perfect and logical solution to the neo. If you can do a few upgrades to your current design and make it as good or even better than your competitors why wouldn't you? It was a good plan, just that they failed in executing it properly. But I have faith they will fix it.
 
kalvado
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Re: B737MAX Grounded Worldwide

Mon Apr 29, 2019 11:42 pm

Aviation737 wrote:
kalvado wrote:
par13del wrote:
Except, more 737's are deployed outside of the USA, AA and WN may be large users but they will not account for 50% or more of the installed base.
At present, they have more a/c deployed than anyone else, which is a result of preferential treatment, but if you check the order book.....

Which is irrelevant. I am talking about different thing.
There is an impression that AA pushed Boeing into MAX by saying "give us a new plane, or we order 320NEO", and WN pushed into a no-training commitment by writing a penalty into contract. As big customers, these airlines have a significant influence on Boeing's decisions, no question about that. .
What I am saying, that shouldn't mean Boeing was improperly influenced. They could, at any time, turn down AA and WN if they thought they were unable to deliver. Or make a counteroffer - wait longer for new design. In either case, I don't see any ethical or legal problems with hard-line business negotiations in competitive environment.

You are thinking like this is because u know what's gonna happen when Boeing pursue down this path. But at that time the MAX was the perfect and logical solution to the neo. If you can do a few upgrades to your current design and make it as good or even better than your competitors why wouldn't you? It was a good plan, just that they failed in executing it properly. But I have faith they will fix it.

I am just talking basic business logic - you don't chase customer until you expect to make money out of the deal. Maybe not on that transaction, maybe in a long run.
Going towards MAX was a business decision, and that decision could be different. Was it logical? Well, I hope engineering had a big say in it, and they were on board.

But again, this mini-discussion started with the claim that airlines which pushed Boeing into MAX should be held responsible. I don't believe that. Airlines requested a competitive product or they would buy from a competitor. It was up to Boeing to commit or reject the request.
 
OldAeroGuy
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Re: B737MAX Grounded Worldwide

Mon Apr 29, 2019 11:44 pm

kalvado wrote:
I may be missing something, but I don't see them getting a problem cleaning up and going up to sort out the situation in a failsafe config - well, problem without MCAS at play.


I've it explained it previously on this thread but here it goes again.

When the stick shaker goes on at liftoff, the crew does not know why it did so. It could be for a number of reasons:

1) AoA signal could be faulty. This will cause other apparent failures such "Airspeed Unreliable" and "Altitude Unreliable". This is what happened for JT043, JT610 and ET302.
2) Airspeed could be totally inaccurate due to dual problems on both the left and right systems. It has happened before. The airplane could be dangerously slow. The AoA vane could be telling you the truth and you're teetering on the brink of a low speed, low altitude stall. Retracting Flaps could instantly stall the airplane with little chance of recovery.
3) One of the slat panels could be badly skewed or missing. Look at 7BOEING7's logo picture to see what a skewed slat looks like. Every 737 since the NG has a system that detects skewed or missing slats. If a skewed or missing slat is detected, the stick shaker defaults to the Flaps up schedule. As in Case 2, the crew doesn't know the airplane's actual condition. Retracting the Flaps could instantly stall the airplane due to a missing or skewed slat panel.

For Case 1, you can get away with retracting the Flaps.

For Case 2 & 3, retracting the Flaps could stall the airplane at low altitude with no chance of recovery.

The best course of action is to set pitch and power and climb to a safe altitude while monitoring airplane performance. Once at a safe altitude, sort out the airplane by running the "Unreliable Airspeed" procedure. There is little point in retracting Flaps now as you need to prepare to return to land at the origin airport. When the stick shaker went off, the mission should be aborted. Boeing procedures do not call for turning the stick shaker off by throwing the overhead panel circuit breaker. Do you think it's a good idea to complete the mission with the stick shaker going?

I know JT043 completed their planned flight with continuous stick shaker. Although that crew showed good airmanship skills for correct actions after the erroneous MCAS activation, those skills departed when they elected to complete their flight.

For Cases 1, 2 & 3, the airplane is alerting the crew that something is wrong. The crew needs to take actions to safeguard the airplane. These do not include retracting the Flaps and trying to complete the mission.
Last edited by OldAeroGuy on Tue Apr 30, 2019 12:08 am, edited 1 time in total.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
flybucky
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Re: B737MAX Grounded Worldwide

Mon Apr 29, 2019 11:54 pm

PW100 wrote:
Does the procedure mention anything about one or both stick shakers going off? Is a crew at liberty to determine that such procedure may not be appropriate when only one single shaker is active? For instance, when they have diagnosed the single stick shaker as false?

That's a good question. The 737 NG QRH does not mention anything about different procedures if one or both stick shakers. (screenshot)

"Immediately do the following at the first indication of stall (buffet or stick shaker)."

My guess is that a potential stall is critical, so there's no time to troubleshoot first. Immediately follow the procedure assuming it is a real warning. Then after the flight is stable, then troubleshoot whether it's a false stick shaker.

There was a flight where the pilots had a single stick shaker. Not sure if it was procedure, but they just pulled the stick shaker circuit breaker and continued with the rest of the flight. (March 2016. NASA ASRS Report # 1337942)
Last edited by flybucky on Tue Apr 30, 2019 12:06 am, edited 1 time in total.
 
OldAeroGuy
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 12:02 am

PW100 wrote:
Does the procedure mention anything about one or both stick shakers going off? Is a crew at liberty to determine that such procedure may not be appropriate when only one single shaker is active? For instance, when they have diagnosed the single stick shaker as false?


I don't know of any Boeing approved flight crew procedure that differentiates crew actions for activation of only one stick shaker. One or both, the actions are the same, reduce pitch, apply power and don't retract Flaps. In a potentially high workload situation such as stall recovery, the crew shouldn't be trying to diagnose if the stick shaker is erroneous and if only or both are going off.

There is advisory material that talks about what may be impacted if one stick shaker is suspected to be erroneous.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
morrisond
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 12:03 am

OldAeroGuy wrote:
kalvado wrote:
I may be missing something, but I don't see them getting a problem cleaning up and going up to sort out the situation in a failsafe config - well, problem without MCAS at play.


I've it explained it previously on this thread but here it goes again.

When the stick shaker goes on at liftoff, the crew does not know why it did so. It could be for a number of reasons:

1) AoA signal could be faulty. This will cause other apparent failures such "Airspeed Unreliable" and "Altitude Unreliable". This is what happened for JT043, JT610 and ET302.
2) Airspeed could be totally inaccurate due to dual problems on both the left and right systems. It has happened before. The airplane could be dangerously slow. The AoA vane could be telling you the truth and you're teetering on the brink of a low speed, low altitude stall. Retracting Flaps could instantly stall the airplane with little chance of recovery.
3) One of the slat panels could be badly skewed or missing. Look at 7Boeing7's logo picture to see what a skewed slat looks like. Every 737 since the NG has a system that detects skewed or missing slats. If a skewed or missing slat is detected, the stick shaker defaults to the Flaps up schedule. As in Case 2, the crew does know the airplane's actual condition. Retracting the Flaps could instantly stall the airplane due to a missing or skewed slat panel.

For Case 1, you can get away with retracting the Flaps.

For Case 2 & 3, retracting the Flaps could stall the airplane at low altitude with no chance of recovery.

The best course of action is to set pitch and power and climb to a safe altitude while monitoring airplane performance. Once at a safe altitude, sort out the airplane by running the "Unreliable Airspeed" procedure. There is little point in retracting Flaps now as you need to prepare to return to land at the origin airport. When the stick shaker went off, the mission should be aborted. Boeing procedures do not call for turning the stick shaker off by throwing the overhead panel circuit breaker. Do you think it's a good idea to complete the mission with the stick shaker going?

I know JT043 completed their planned flight with continuous stick shaker. Although that crew showed good airmanship skills for correct actions after the erroneous MCAS activation, those skills departed when they elected to complete their flight.

For Cases 1, 2 & 3, the airplane is alerting the crew that something is wrong. The crew needs to take actions to safeguard the airplane. These do not include retracting the Flaps and trying to complete the mission.


Great write up.
 
kalvado
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 12:06 am

OldAeroGuy wrote:
kalvado wrote:
I may be missing something, but I don't see them getting a problem cleaning up and going up to sort out the situation in a failsafe config - well, problem without MCAS at play.


I've it explained it previously on this thread but here it goes again.

When the stick shaker goes on at liftoff, the crew does not know why it did so. It could be for a number of reasons:

1) AoA signal could be faulty. This will cause other apparent failures such "Airspeed Unreliable" and "Altitude Unreliable". This is what happened for JT043, JT610 and ET302.
2) Airspeed could be totally inaccurate due to dual problems on both the left and right systems. It has happened before. The airplane could be dangerously slow. The AoA vane could be telling you the truth and you're teetering on the brink of a low speed, low altitude stall. Retracting Flaps could instantly stall the airplane with little chance of recovery.
3) One of the slat panels could be badly skewed or missing. Look at 7Boeing7's logo picture to see what a skewed slat looks like. Every 737 since the NG has a system that detects skewed or missing slats. If a skewed or missing slat is detected, the stick shaker defaults to the Flaps up schedule. As in Case 2, the crew does know the airplane's actual condition. Retracting the Flaps could instantly stall the airplane due to a missing or skewed slat panel.

For Case 1, you can get away with retracting the Flaps.

For Case 2 & 3, retracting the Flaps could stall the airplane at low altitude with no chance of recovery.

The best course of action is to set pitch and power and climb to a safe altitude while monitoring airplane performance. Once at a safe altitude, sort out the airplane by running the "Unreliable Airspeed" procedure. There is little point in retracting Flaps now as you need to prepare to return to land at the origin airport. When the stick shaker went off, the mission should be aborted. Boeing procedures do not call for turning the stick shaker off by throwing the overhead panel circuit breaker. Do you think it's a good idea to complete the mission with the stick shaker going?

I know JT043 completed their planned flight with continuous stick shaker. Although that crew showed good airmanship skills for correct actions after the erroneous MCAS activation, those skills departed when they elected to complete their flight.

For Cases 1, 2 & 3, the airplane is alerting the crew that something is wrong. The crew needs to take actions to safeguard the airplane. These do not include retracting the Flaps and trying to complete the mission.

(1) - expand that to any portion of air data system, I assume pitot damage will be similar. but otherwise, I am with you.
for (2) ET crew had a reference of recent rotation, so "way off" is quite unlikely. If anything, they could be above indicated speed and at risk of converting to (3) due to flaps/gear overspeed.
(3) Again, normal takeoff roll and no configuration change since rotation.

I understand the point of no retraction when you're slowing down, but this is about acceleration at almost full thrust, and overspeed could be an equal and bigger concern. Actually, they got into that - although not without many other events.

And I don't quite buy speculation about "complete the mission". for ET Not that I find it impossible, cavalier attitude sometimes is my problem as well. But If anything, they didn't have time to decide on that.

On a similar notice... we have a pilot in this thread, who suggested lowering flaps as a counter-MCAS measure. I believe I was the only one to dislike it. So even for exemplary trained gray-haired US pilots deviation from "no config change" is out of question...
 
morrisond
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 12:21 am

PixelFlight wrote:
dakota123 wrote:
And yes, absolutely, similar failure modes exist on the NG,and literally every other plane with an electric trim system.

Explain why only the 737 MAX need a software patch on a system that don't exists in any others 737 model and that is cited in 2 deadly crash as well as an EAD ?
I am not talking about a general category of failure, but a very precise failure mode that is only possible with a MCAS as found in the 737 MAX. That precise mode only exists on 737 MAX. Every single official document published, even from Boeing itself agree on that fact.


Because only the MAX controls barely get light at full AFT COG which was against the FAR's.

Even if the pilots had never heard of MCAS they need to be able to diagnose things and not rely on Memory.

If it had been a parts failure that led Speed Trim on an NG to cause the Plane to do similar things the procedure (which there probably isn't one for) would be the same - return the Trim to neutral using the electrics and hit the cutoff switches.

If the Trim switch was stuck in the down position on almost any plane - same procedure.

The Lionair flight might have been assuming that it was the Speed Trim System (as MCAS was not known existed at that point) - they failed to turn off the system that was causing them trouble 22 times. In no way shape or form is that good airmanship.

If it was the Autopilot turning them left 90 degrees with no pilot input 22 times at one point would you fault them for not turning it off?
 
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zeke
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 12:39 am

PixelFlight wrote:
Explain why only the 737 MAX need a software patch on a system that don't exists in any others 737 model and that is cited in 2 deadly crash as well as an EAD ?


The MAX is a newer aircraft, it is certified to a more recent amendment of the FARs. It needs to comply with new regulation amendments that earlier 737 did not. Anyone who does not understand that simple
concept is a fool. Newer regulations does not mean a safer aircraft, there can always be unintended outcomes like this MCAS abnormal behaviour.

OldAeroGuy wrote:
kalvado wrote:
I may be missing something, but I don't see them getting a problem cleaning up and going up to sort out the situation in a failsafe config - well, problem without MCAS at play.


I've it explained it previously on this thread but here it goes again.

When the stick shaker goes on at liftoff, the crew does not know why it did so. It could be for a number of reasons:

1) AoA signal could be faulty. This will cause other apparent failures such "Airspeed Unreliable" and "Altitude Unreliable". This is what happened for JT043, JT610 and ET302.
2) Airspeed could be totally inaccurate due to dual problems on both the left and right systems. It has happened before. The airplane could be dangerously slow. The AoA vane could be telling you the truth and you're teetering on the brink of a low speed, low altitude stall. Retracting Flaps could instantly stall the airplane with little chance of recovery.
3) One of the slat panels could be badly skewed or missing. Look at 7BOEING7's logo picture to see what a skewed slat looks like. Every 737 since the NG has a system that detects skewed or missing slats. If a skewed or missing slat is detected, the stick shaker defaults to the Flaps up schedule. As in Case 2, the crew doesn't know the airplane's actual condition. Retracting the Flaps could instantly stall the airplane due to a missing or skewed slat panel.

For Case 1, you can get away with retracting the Flaps.

For Case 2 & 3, retracting the Flaps could stall the airplane at low altitude with no chance of recovery.

The best course of action is to set pitch and power and climb to a safe altitude while monitoring airplane performance. Once at a safe altitude, sort out the airplane by running the "Unreliable Airspeed" procedure. There is little point in retracting Flaps now as you need to prepare to return to land at the origin airport. When the stick shaker went off, the mission should be aborted. Boeing procedures do not call for turning the stick shaker off by throwing the overhead panel circuit breaker. Do you think it's a good idea to complete the mission with the stick shaker going?

I know JT043 completed their planned flight with continuous stick shaker. Although that crew showed good airmanship skills for correct actions after the erroneous MCAS activation, those skills departed when they elected to complete their flight.

For Cases 1, 2 & 3, the airplane is alerting the crew that something is wrong. The crew needs to take actions to safeguard the airplane. These do not include retracting the Flaps and trying to complete the mission.


OAG well said. Any time a safety critical warning like stick shaker goes off, the only prudent action in my view is to treat it as real and get the aircraft on the ground as soon as safely possible.

The idea of continuing flight with the stick shaker on, or pulling a CB to deactivate it is beyond comprehension to me.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
OldAeroGuy
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 12:42 am

kalvado wrote:
I understand the point of no retraction when you're slowing down, but this is about acceleration at almost full thrust, and overspeed could be an equal and bigger concern. Actually, they got into that - although not without many other events.


Procedures are generally written as a one size fits all. If you try to include all possible situations, you get too many variations to wade through.

So instead of saying "Do this if Accelerating vs Do that if Decelerating", you have one instruction for stick shaker: Pitch, Power, Hold Configuration

kalvado wrote:
And I don't quite buy speculation about "complete the mission". for ET Not that I find it impossible, cavalier attitude sometimes is my problem as well. But If anything, they didn't have time to decide on that.


Read the ET302 Voice Transcript excerpt. With the stick shaker activated, a request is made for clearance to FL320. If the crew was planning on returning to land, why would this request have been made?
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
ArgentoSystems
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 12:47 am

dakota123 wrote:

It's equally puzzling to me how folks who have never flown a plane in their lives are so sure they have all the answers (to the point of arrogance), and so willing to discount those that have years and even decades in the field.

Appeal to authority is a logical fallacy, you know. See, just because pigeon can fly and I can't does not mean it knows more about aerodynamics than I 8-)
 
prebennorholm
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 12:49 am

lhrnue wrote:
In case the Boeing CEO tried to convince people to fly with the MAX again ... well he failed me.

It is not needed that he convinces you. He only needs to convince the authorities and the airlines that he has solved the problem, and that doesn't happen at press conferences.

Boeing is at present in 100% economic damage control mode. The total costs of this grounding is astronomical, and it is the Boeing CEO job to minimize Boeing's exposure to that cost. Every word he says today has the potential to be used against him in a courtroom in six months time, two years, five years, or whenever the last 737MAX trial is settled.

At the same time millions are earned on this situation. Competitors having their capacity temporarily reduced make miracles on many airline revenue management system algorithms these days. Nothing is so bad that it isn't good for something. That money pile is, however, out of reach for Boeing.
Always keep your number of landings equal to your number of take-offs
 
morrisond
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 1:08 am

zeke wrote:
PixelFlight wrote:
Explain why only the 737 MAX need a software patch on a system that don't exists in any others 737 model and that is cited in 2 deadly crash as well as an EAD ?


The MAX is a newer aircraft, it is certified to a more recent amendment of the FARs. It needs to comply with new regulation amendments that earlier 737 did not. Anyone who does not understand that simple
concept is a fool. Newer regulations does not mean a safer aircraft, there can always be unintended outcomes like this MCAS abnormal behaviour.



It's been asked before - but would the NG need MCAS as well if it were certified today?
 
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zeke
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 1:14 am

morrisond wrote:
It's been asked before - but would the NG need MCAS as well if it were certified today?


Probably yes. The FAA certified the NG without STS also, however the JAA insisted it be installed to meet the requirements at the time.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
kalvado
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 1:22 am

OldAeroGuy wrote:
kalvado wrote:
I understand the point of no retraction when you're slowing down, but this is about acceleration at almost full thrust, and overspeed could be an equal and bigger concern. Actually, they got into that - although not without many other events.


Procedures are generally written as a one size fits all. If you try to include all possible situations, you get too many variations to wade through.

So instead of saying "Do this if Accelerating vs Do that if Decelerating", you have one instruction for stick shaker: Pitch, Power, Hold Configuration

kalvado wrote:
And I don't quite buy speculation about "complete the mission". for ET Not that I find it impossible, cavalier attitude sometimes is my problem as well. But If anything, they didn't have time to decide on that.


Read the ET302 Voice Transcript excerpt. With the stick shaker activated, a request is made for clearance to FL320. If the crew was planning on returning to land, why would this request have been made?

If you will, this is about looking at things at different angles. You're saying - "look what they did, they must be crazy!"; while I am saying "there should be a reason they did that, don't you think they were crazy?" Probably the truth is somewhere in between.
How about this: I don't really remember ET timeline; but climbing up to sort out a problem which sends the plane into a dive makes some sense. I would understand the push to proceed to the base from outstation, but return to base instead of getting stuck at outstation.... So I don't believe climb request is an intention to proceed.
As for procedures written in "one size fits all" - yes; and it is plainly impossible to write decision tree for any minuscule detail. The flip side of the coin is that the procedure is rarely ideal. I am trying to say that it may make sense to look for the reason they found going to the letter a bad idea.
Again, my background is different; I am not drilled to follow the procedure to the letter, rather look critically at each step (and I understand that pilot training is opposite of that)
 
dakota123
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 4:03 am

kalvado wrote:
OldAeroGuy wrote:
kalvado wrote:
I understand the point of no retraction when you're slowing down, but this is about acceleration at almost full thrust, and overspeed could be an equal and bigger concern. Actually, they got into that - although not without many other events.


Procedures are generally written as a one size fits all. If you try to include all possible situations, you get too many variations to wade through.

So instead of saying "Do this if Accelerating vs Do that if Decelerating", you have one instruction for stick shaker: Pitch, Power, Hold Configuration

kalvado wrote:
And I don't quite buy speculation about "complete the mission". for ET Not that I find it impossible, cavalier attitude sometimes is my problem as well. But If anything, they didn't have time to decide on that.


Read the ET302 Voice Transcript excerpt. With the stick shaker activated, a request is made for clearance to FL320. If the crew was planning on returning to land, why would this request have been made?

If you will, this is about looking at things at different angles. You're saying - "look what they did, they must be crazy!"; while I am saying "there should be a reason they did that, don't you think they were crazy?" Probably the truth is somewhere in between.
How about this: I don't really remember ET timeline; but climbing up to sort out a problem which sends the plane into a dive makes some sense. I would understand the push to proceed to the base from outstation, but return to base instead of getting stuck at outstation.... So I don't believe climb request is an intention to proceed.
As for procedures written in "one size fits all" - yes; and it is plainly impossible to write decision tree for any minuscule detail. The flip side of the coin is that the procedure is rarely ideal. I am trying to say that it may make sense to look for the reason they found going to the letter a bad idea.
Again, my background is different; I am not drilled to follow the procedure to the letter, rather look critically at each step (and I understand that pilot training is opposite of that)


Not to FL320 you wouldn’t, not to sort out a problem. (They were reportedly assigned FL340 but entered a Level Change of FL320.) At the least you’d stay out of RVSM airspace if you’re troubleshooting.

Crew do look at procedures critically as they’re following them. It’s not blind rote (or it sure as heck shouldn’t be). It’s just that most of the time the procedure should indeed be followed to the letter — but the pilot is (or should be) confirming each step is appropriate as it’s being implemented.
“And If I claim to be a wise man, well surely it means that I don’t know”
 
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seahawk
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 5:14 am

OldAeroGuy wrote:
kalvado wrote:
I may be missing something, but I don't see them getting a problem cleaning up and going up to sort out the situation in a failsafe config - well, problem without MCAS at play.


I've it explained it previously on this thread but here it goes again.

When the stick shaker goes on at liftoff, the crew does not know why it did so. It could be for a number of reasons:

1) AoA signal could be faulty. This will cause other apparent failures such "Airspeed Unreliable" and "Altitude Unreliable". This is what happened for JT043, JT610 and ET302.
2) Airspeed could be totally inaccurate due to dual problems on both the left and right systems. It has happened before. The airplane could be dangerously slow. The AoA vane could be telling you the truth and you're teetering on the brink of a low speed, low altitude stall. Retracting Flaps could instantly stall the airplane with little chance of recovery.
3) One of the slat panels could be badly skewed or missing. Look at 7BOEING7's logo picture to see what a skewed slat looks like. Every 737 since the NG has a system that detects skewed or missing slats. If a skewed or missing slat is detected, the stick shaker defaults to the Flaps up schedule. As in Case 2, the crew doesn't know the airplane's actual condition. Retracting the Flaps could instantly stall the airplane due to a missing or skewed slat panel.

For Case 1, you can get away with retracting the Flaps.

For Case 2 & 3, retracting the Flaps could stall the airplane at low altitude with no chance of recovery.

The best course of action is to set pitch and power and climb to a safe altitude while monitoring airplane performance. Once at a safe altitude, sort out the airplane by running the "Unreliable Airspeed" procedure. There is little point in retracting Flaps now as you need to prepare to return to land at the origin airport. When the stick shaker went off, the mission should be aborted. Boeing procedures do not call for turning the stick shaker off by throwing the overhead panel circuit breaker. Do you think it's a good idea to complete the mission with the stick shaker going?

I know JT043 completed their planned flight with continuous stick shaker. Although that crew showed good airmanship skills for correct actions after the erroneous MCAS activation, those skills departed when they elected to complete their flight.

For Cases 1, 2 & 3, the airplane is alerting the crew that something is wrong. The crew needs to take actions to safeguard the airplane. These do not include retracting the Flaps and trying to complete the mission.


Well said and it shows how pointless the grounding is.
 
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aerolimani
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 6:54 am

zeke wrote:
The MAX is a newer aircraft, it is certified to a more recent amendment of the FARs. It needs to comply with new regulation amendments that earlier 737 did not. Anyone who does not understand that simple concept is a fool. Newer regulations does not mean a safer aircraft, there can always be unintended outcomes like this MCAS abnormal behaviour.

Did you just try and blame FAA regulations for causing Boeing's poor implementation of MCAS?
 
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PW100
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 7:33 am

nikeherc wrote:
. . . Lion dispatched a non-airworthy plane . . .

Did you make that up, or did I miss that remark in the prelim report?
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
jollo
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 8:42 am

XRAYretired wrote:
OK. This is the published material, my notes in normal font to try and answer the question.

-Flight control system will now compare inputs from both AOA sensors. If the sensors disagree by 5.5 degrees or more with the flaps retracted, MCAS will not activate. The two sensor signals will be compared and if the difference is >5.5 deg, AOA DISAGREE Flag will be set. MCAS will check for the flag before it initiates and if present, it will not do so.
-An indicator on the flight deck display will alert the pilots to AoA Disagree. I would assume that an AOA Disagree QRH will be required
-If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. I understand the trigger will be the transition from below to above a set value, so if one or both the AOA signals is failed high above the set limit, it will only be triggered once
-There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
-MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column.
-The pilots will continue to always have the ability to override MCAS and manually control the airplane.

Ray


7BOEING7 wrote:
From what I have available it appears the AOA DISAGREE was standard on the NG, however it is an amber "Alert" (not warning) on the Mach Airspeed Indicator or the PFD (Primary Flight Display) and when you go to then QRH it only tells the pilots they may have an IAS DISAGREE or ALTIMETER DISAGREE alert -- there are no specific proceedures to carry out.

Whether it was installed or not would have made no difference to the outcome of the Ethiopian or Lion Air flights -- the flight crews knew they had "disagreements".


Thanks Ray and 7Boeing7, useful summary + relevant new info on the AOA DISAGREE alert on the NG and related NNC (a peculiar checklist with no actions). I would wrap it up by saying that the media focus is indeed on why the AOA DISAGREE alert disappeared from the current MAX, and I have a hunch it may be related to why Boeing needed to change the function of the STAB TRIM CUTOUT switches.

On a side note, I agree that just an additional AOA DISAGREE alert would not have given ET pilots an edge without specific knowledge of MCAS vulnerability to single AoA sensor failures (which was not available at the time).
 
SlashingAx
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 9:05 am

seahawk wrote:

Well said and it shows how pointless the grounding is.


I'm sorry but your comment is one of the most ridiculous things I've ever read. The grounding is the most justified response to this mess, and as much as I prefer the B737, it's safe to say that Boeing screwed the pooch on this one.
 
Paolo18
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 9:28 am

Boeing credibility has just left the room
What a shocking ceo they have.
 
Amiga500
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 9:35 am

zeke wrote:
Amiga500 wrote:
So you are trying to argue a FBW system could be assembled with single failure points all over the place - but that is fine as long as the physical connection between actuator and the control surface is redundant?


The software, wiring, and hydraulics are covered elsewhere. A FBW aircraft is certified the same way as a non FBW for that requirement, it needs to demonstrate that if a surface is jammed or failed the aircraft is still controlled.


Please point out the subsections - and point out where it says the requirements of §25.671 are superseded.

Indeed...

§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






zeke wrote:
You can return to land immediately for any emergency.


Yes you can. But you will have very unhappy bosses if you land the plane immediately and put it off the flight line for inspections.

zeke wrote:
You can return immediately for any emergency, no such thing as a “dire time-dependent emergency”.


There is no definition, yet consider:
(i) an aircraft that would appear to have two imminently failing engines.
(ii) a broken AoA indicator.

The former needs to get on the ground in a timely fashion, whilst the latter should be manageable for a considerable period of time.

The airline bosses will not thank you for plonking the latter down ASAP and having a needless overweight landing.


zeke wrote:
I am not aware of any C or D check required, we print out a Load 15 report, if the rate of descent on touchdown is within the zone nothing further is required.


In an Airbus. Which means unless you touch down like a feather (> -360 fpm sink rate and < 1.7g max), you are going in for a rather expensive inspection - which will be (locally) carried out at C or D check fidelity.

Boeing do it differently. Preliminary inspection, any damage found, big inspection. (I have to admit, I thought their preliminary inspection would be more detailed than I'm reading now - seems it could be turned around in a few hours if there are no findings.)
 
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zeke
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Re: B737MAX Grounded Worldwide

Tue Apr 30, 2019 9:45 am

aerolimani wrote:
Did you just try and blame FAA regulations for causing Boeing's poor implementation of MCAS?


I am not aware of any evidence that would suggest the MCAS implementation did not meet the required regulation. As far as I am aware no engineer, no mechanic, no test pilot, no airline, no regulator, and even the manufacturer had not anticipated this failure mode.

Think of the Comet, it met all the regulations at the time, that did not stop it from having failures which were not anticipated by anyone.

“It is easy to be wise after the event.” Arthur Doyle
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
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qf789
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Re: B737MAX Grounded Worldwide Q1 2019

Tue Apr 30, 2019 9:53 am

Please continue discussion in 737MAX grounding thread Q2 2019

viewtopic.php?f=3&t=1421471
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