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scbriml
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 4:29 pm

Revelation wrote:
I thought I read in one of the analysis that $900M was spent on various MAX related activities, presumably things like developing and testing the fixes along with costs of flying MAXes to storage and putting them in mothballs, but it was being funded out of cash flows.

There's no way around the fact that this tragedy is costly in many different ways to many different entities.


I see that Leeham is reporting that DM has now said that while the majority of undelivered planes will be delivered in 2020, it's clear that deliveries will spill into 2021 (but he was not specific on numbers). Some members here naively expected Boeing to have some "mega month" where they'd deliver all the stored planes and enjoy a massive pay day, but that was never going to happen. Given how long it took Boeing to 'catch up' after 787 deliveries were halted, it's not surprising it will take a long time to deliver an extra, what, 350 planes? While the cost of storage, rework and deliveries will diminish with time, I wonder if another charge might be required by mid 2020?
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ikramerica
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 4:33 pm

scbriml wrote:
Revelation wrote:
I thought I read in one of the analysis that $900M was spent on various MAX related activities, presumably things like developing and testing the fixes along with costs of flying MAXes to storage and putting them in mothballs, but it was being funded out of cash flows.

There's no way around the fact that this tragedy is costly in many different ways to many different entities.


I see that Leeham is reporting that DM has now said that while the majority of undelivered planes will be delivered in 2020, it's clear that deliveries will spill into 2021 (but he was not specific on numbers). Some members here naively expected Boeing to have some "mega month" where they'd deliver all the stored planes and enjoy a massive pay day, but that was never going to happen. Given how long it took Boeing to 'catch up' after 787 deliveries were halted, it's not surprising it will take a long time to deliver an extra, what, 350 planes? While the cost of storage, rework and deliveries will diminish with time, I wonder if another charge might be required by mid 2020?

They have to do mods, tests, deliver shake out, etc. and paperwork. Lots of paperwork. And they aren’t about to hire 100% more staff for that. Overtime, canceled vacations, a few temps, sure.
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MrBretz
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 4:34 pm

sgrow787 wrote:

Software solution only. This isn't a PC upgrade where you can just replace the motherboard. Any hardware change to the FCC would take 2 years or more to get designed and tested.

Software only, and yes, the time to inplement the MCAS fix is taking so long because theyre tweaking the software that is already running at 95% capacity of the hardware. Worse case scenario, every tweak has the outcome of a halted FCC until they find the right one.

EDIT: Added "worse case scenario" since Im not working on the Max project and therefore not privy to the details.


You are right about one thing: you not working on it so you don’t know. I have no idea if the machine is running at 95% capacity. And since the fixes I have heard about are all logic and not computation, I would say you are adding little load to the CPU. The logic could be tricky and more complex than has been alluded to in the media or here.

I do agree about the all software and what you said about any hardware changes. Maybe someday we will all get a deeper view of the changes.
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 4:45 pm

mrbots wrote:
DenverTed wrote:
What's the cost inflection point between scrapping the MAX and getting it flying again? Probably 50 billion in aircraft already built, another 5 billion in penalties for those 5,000 cancelled orders, loss of 40 billion in production a year for the next ten years. Plus if every dollar has a 10x multiplier to the U.S. economy, then "scrapping the MAX" might be a 50 billion a year cost to Boeing and a 500 billion a year cost to the U.S. economy, times ten years is 5 trillion. Not a trivial amount, so even if it meant designing a larger horizontal stabilizer, it is still an easy economic case to make.

It's not necessarily the cost of scrapping the MAX but the loss of cash flow. The 737 generally accounts for about 40% of Boeing's overall profit. Boeing would go bankrupt (without an inevitable bailout) without the cashflow from the 737 sales before a new model could be designed, parts sourced, tested, delayed, certified, and production ramped up. Right now it's "all hands on deck" to get it back in the air ASAP so they can continue to pay their bills and payroll. It be like Ford not being able to sell the F150 or Apple the iPhone. They sell other things but not enough to bankroll the company.

Not to mention dealing with the angry customers. They too have $billions invested in the aircraft, the spare parts, the training of mechanics/aircrew, sims, etc.

How do you tell them you are going to kill off the 737 and to just wait five years or so while they come up with a replacement?

Do you think they'll even trust you to build a new airplane if the reason you're killing 737 is because you botched its design and implementation?

I get it, people are upset by the MAX tragedy, but they just aren't thinking very well when they suggest Boeing would scrap the MAX without doing everything in its power to get it back into service first.
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hilram
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 4:52 pm

I am getting increasingly hungry for details about Boeing's fix. Any leaks, inside information, anoyne?
Flown on: A319, 320, 321, 332, 333, 343 | B732, 734, 735, 736, 73G, 738, 743, 744, 772, 77W | CRJ9 | BAe-146 | DHC-6, 7, 8 | F50 | E195 | MD DC-9 41, MD-82, MD-87
 
lowbank
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 5:01 pm

Revelation wrote:
mrbots wrote:
DenverTed wrote:
What's the cost inflection point between scrapping the MAX and getting it flying again? Probably 50 billion in aircraft already built, another 5 billion in penalties for those 5,000 cancelled orders, loss of 40 billion in production a year for the next ten years. Plus if every dollar has a 10x multiplier to the U.S. economy, then "scrapping the MAX" might be a 50 billion a year cost to Boeing and a 500 billion a year cost to the U.S. economy, times ten years is 5 trillion. Not a trivial amount, so even if it meant designing a larger horizontal stabilizer, it is still an easy economic case to make.

It's not necessarily the cost of scrapping the MAX but the loss of cash flow. The 737 generally accounts for about 40% of Boeing's overall profit. Boeing would go bankrupt (without an inevitable bailout) without the cashflow from the 737 sales before a new model could be designed, parts sourced, tested, delayed, certified, and production ramped up. Right now it's "all hands on deck" to get it back in the air ASAP so they can continue to pay their bills and payroll. It be like Ford not being able to sell the F150 or Apple the iPhone. They sell other things but not enough to bankroll the company.

Not to mention dealing with the angry customers. They too have $billions invested in the aircraft, the spare parts, the training of mechanics/aircrew, sims, etc.

How do you tell them you are going to kill off the 737 and to just wait five years or so while they come up with a replacement?

Do you think they'll even trust you to build a new airplane if the reason you're killing 737 is because you botched its design and implementation?

I get it, people are upset by the MAX tragedy, but they just aren't thinking very well when they suggest Boeing would scrap the MAX without doing everything in its power to get it back into service first.



I know it’s a different time and different reason, but please consider the power of the travelling public.

Concorde had one accident, a fortune spent on making it safe.

It’s claimed it’s biggest customers were killed in the 9/11 rain towers.

But it finished off that airframe.

I linked a document about the public’s perception of travelling on the MAX.

If every MAX flight was only 20-30% full airlines would soon get fed up flying it.

If another one crashes in the 12 months following reintroduction, that could be the outcome.
Every days a school day.
 
frmrCapCadet
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 5:03 pm

An only little off topic post: I have often wondered why Boeing does not keep a reserve work force in existence from their recently retired personnel. But .... I have known a number of retired Boeing workers and have found it disturbing that they have a lack of loyalty after putting up with 30(?) years of being somewhat mistreated. My 'data base' is not all that large so I could be mistaken. But now, with all of those MAXs ready to go it really would be logical for a lot of former workers to put in a few months of heavy lifting and overtime. Buy a boat, go on a couple expensive vacations, pay off the mortgage. What ever. It could even be kind of fun.
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planecane
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 5:08 pm

kalvado wrote:
planecane wrote:
rheinwaldner wrote:
It looks like some more education is required about this topic:
14CFR §25.203 Stall characteristics.
(a) It must be possible to produce and to correct roll and yaw by unreversed use of the aileron and rudder controls, up to the time the airplane is stalled.

So the truth is the exact opposite of what you wrote.


No it isn't. It was a slight misstatement but the point isn't changed. MCAS and stall characteristics don't (based on available information) have anything to do with each other. The statement from the FAR that you quoted is stating that the airplane must remain controllable as long as it hasn't been stalled.

Such statement is very hard to believe. Remember, all that "stick force" argument completely ignores simulated nature of stick force in 737. Either airflow in MAX vs NG renders tail mounted Pitot inefficient - indicating significant change in aerodynamics; or airplane actually responds to control inputs in a different fashion. Given correction measures, it is totally fair to say there is a pitch up tendency corrected by MCAS; and since that occurs at stall entry past stick shaker onset... If you believe those don't have anything to do with each other, would you also be interested in acquiring couple of bridges in a major US megalopolis?


However, the stick force is simulated on the 737 using the stabilizer position and the stabilizer pitot system. A poster a few pages back said that the elevator feel computer is an analog hydraulic computer. If it were an electronic computer that runs software, the AoA could have been fed into it and the MCAS function could have been handled by it. Essentially, MCAS is tricking the elevator feel computer. Doing so requires the stabilizer trim to be changed.

That's why I say that MCAS and stall characteristics have nothing to do with each other. If the stick force gradient issue could have been solved by a software update to the EFC trim changes wouldn't have been necessary.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 5:14 pm

lowbank wrote:
Revelation wrote:
mrbots wrote:
It's not necessarily the cost of scrapping the MAX but the loss of cash flow. The 737 generally accounts for about 40% of Boeing's overall profit. Boeing would go bankrupt (without an inevitable bailout) without the cashflow from the 737 sales before a new model could be designed, parts sourced, tested, delayed, certified, and production ramped up. Right now it's "all hands on deck" to get it back in the air ASAP so they can continue to pay their bills and payroll. It be like Ford not being able to sell the F150 or Apple the iPhone. They sell other things but not enough to bankroll the company.

Not to mention dealing with the angry customers. They too have $billions invested in the aircraft, the spare parts, the training of mechanics/aircrew, sims, etc.

How do you tell them you are going to kill off the 737 and to just wait five years or so while they come up with a replacement?

Do you think they'll even trust you to build a new airplane if the reason you're killing 737 is because you botched its design and implementation?

I get it, people are upset by the MAX tragedy, but they just aren't thinking very well when they suggest Boeing would scrap the MAX without doing everything in its power to get it back into service first.



I know it’s a different time and different reason, but please consider the power of the travelling public.

Concorde had one accident, a fortune spent on making it safe.

It’s claimed it’s biggest customers were killed in the 9/11 rain towers.

But it finished off that airframe.

I linked a document about the public’s perception of travelling on the MAX.

If every MAX flight was only 20-30% full airlines would soon get fed up flying it.

If another one crashes in the 12 months following reintroduction, that could be the outcome.


I can guarantee that there will be some type of marketing plan after the approval. I expect some percentage of people to try and avoid the MAX for a little while. However, most of the avoidance will be in the first month or two after ungrounding. However, due to the time for the airlines to get them back into service, there aren't going to be that many flights a day on them. By the time large fleets are back in service, the perception will be that it has been flying for a couple of months without any incidents.

Now, if there is a crash of one then all bets are off. Even if it has absolutely nothing to do with the airframe.
 
oschkosch
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 5:30 pm

Revelation wrote:
The quote also spells out what many here have been suggesting all along: Once FAA signs off, it'll be harder for other regulators to not sign off.



Wait for CAAC / China. I have a feeling that the Chinese government will leave the max out of the skies a longer while than many others expect. After all, as the old saying goes "revenge is a dish best served cold", and China is surely waiting to give the US a lovely payback after all the sh*t that Trump has thrown their way.
 
MrBretz
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 5:37 pm

oschkosch wrote:
Revelation wrote:
The quote also spells out what many here have been suggesting all along: Once FAA signs off, it'll be harder for other regulators to not sign off.

I agree with you.

Wait for CAAC / China. I have a feeling that the Chinese government will leave the max out of the skies a longer while than many others expect. After all, as the old saying goes "revenge is a dish best served cold", and China is surely waiting to give the US a lovely payback after all the sh*t that Trump has thrown their way.
 
oschkosch
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 5:39 pm

planecane wrote:
I expect some percentage of people to try and avoid the MAX for a little while. However, most of the avoidance will be in the first month or two after ungrounding.


I work for a listed multinational company with a turnover of above 50 Billion US$ (much more actually). Our division has over 25K employees, total company workforce is above 200K people - I won't be precise on these figures in order to safeguard my employer. But let me tell you that since the initial groundings of the max outside of the US, we have a written memo in our corporate travel portal telling us not to fly on any max aircraft in any country. And I am very sure that my company is not the only one. We will not fly max aircraft until we feel it is safe to do so. Our internal requirements outweigh any un-grounding. The way our corporation works is such that we will not automatically allow our people to be on these planes immediately after RTS.

Are we now part of that 1% of people that will avoid the max as you, or was it someone that else posted that remark, have mentioned here on a.net?
 
lowbank
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 5:45 pm

planecane wrote:
lowbank wrote:
Revelation wrote:
Not to mention dealing with the angry customers. They too have $billions invested in the aircraft, the spare parts, the training of mechanics/aircrew, sims, etc.

How do you tell them you are going to kill off the 737 and to just wait five years or so while they come up with a replacement?

Do you think they'll even trust you to build a new airplane if the reason you're killing 737 is because you botched its design and implementation?

I get it, people are upset by the MAX tragedy, but they just aren't thinking very well when they suggest Boeing would scrap the MAX without doing everything in its power to get it back into service first.



I know it’s a different time and different reason, but please consider the power of the travelling public.

Concorde had one accident, a fortune spent on making it safe.

It’s claimed it’s biggest customers were killed in the 9/11 rain towers.

But it finished off that airframe.

I linked a document about the public’s perception of travelling on the MAX.

If every MAX flight was only 20-30% full airlines would soon get fed up flying it.

If another one crashes in the 12 months following reintroduction, that could be the outcome.


I can guarantee that there will be some type of marketing plan after the approval. I expect some percentage of people to try and avoid the MAX for a little while. However, most of the avoidance will be in the first month or two after ungrounding. However, due to the time for the airlines to get them back into service, there aren't going to be that many flights a day on them. By the time large fleets are back in service, the perception will be that it has been flying for a couple of months without any incidents.

Now, if there is a crash of one then all bets are off. Even if it has absolutely nothing to do with the airframe.



100% agree.

Just hope it flies for a few years with no crashes.

The world needs Boeing.
Every days a school day.
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 5:56 pm

planecane wrote:
kalvado wrote:
planecane wrote:

No it isn't. It was a slight misstatement but the point isn't changed. MCAS and stall characteristics don't (based on available information) have anything to do with each other. The statement from the FAR that you quoted is stating that the airplane must remain controllable as long as it hasn't been stalled.

Such statement is very hard to believe. Remember, all that "stick force" argument completely ignores simulated nature of stick force in 737. Either airflow in MAX vs NG renders tail mounted Pitot inefficient - indicating significant change in aerodynamics; or airplane actually responds to control inputs in a different fashion. Given correction measures, it is totally fair to say there is a pitch up tendency corrected by MCAS; and since that occurs at stall entry past stick shaker onset... If you believe those don't have anything to do with each other, would you also be interested in acquiring couple of bridges in a major US megalopolis?


However, the stick force is simulated on the 737 using the stabilizer position and the stabilizer pitot system. A poster a few pages back said that the elevator feel computer is an analog hydraulic computer. If it were an electronic computer that runs software, the AoA could have been fed into it and the MCAS function could have been handled by it. Essentially, MCAS is tricking the elevator feel computer. Doing so requires the stabilizer trim to be changed.

That's why I say that MCAS and stall characteristics have nothing to do with each other. If the stick force gradient issue could have been solved by a software update to the EFC trim changes wouldn't have been necessary.

Stick force is NOT changed by moving control surfaces as MCAS does, plane movement is. Basically this is not about force, this is about MAX being more responsive to controls than NG at high AoA, near stall. Which fits purr-fectly into "easier to accidentally exceed critical AoA and enter into stall as less control movement is required for that"
Any other reading is a game of words.
 
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aerolimani
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 6:12 pm

So… I thought that it was confirmed (from many months ago) that Boeing had not informed the FAA about the changes in the regime in which MCAS was designed to function. To me, that is the important part of this dialogue between the technical pilots. The red herring is all the discussion of the simulator itself; ECAB flying for documentation purposes versus certification of a commercial 3rd party sim.

So, did Boeing update the FAA, or did they not? In that one recent ST article, Boeing seems to be passing the buck to the FAA, claiming that they passed all the change info on to the FAA.

So… what is it? Did Boeing tell the FAA about the expanded role of MCAS, or did they not?

In any case, this thread has been successfully diverted away from this question; a question which I think is more important than the endless discussions of pilot fault, and undetermined aerodynamic issues of the MAX.
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 6:20 pm

aerolimani wrote:
So… I thought that it was confirmed (from many months ago) that Boeing had not informed the FAA about the changes in the regime in which MCAS was designed to function. To me, that is the important part of this dialogue between the technical pilots. The red herring is all the discussion of the simulator itself; ECAB flying for documentation purposes versus certification of a commercial 3rd party sim.

So, did Boeing update the FAA, or did they not? In that one recent ST article, Boeing seems to be passing the buck to the FAA, claiming that they passed all the change info on to the FAA.

So… what is it? Did Boeing tell the FAA about the expanded role of MCAS, or did they not?

In any case, this thread has been successfully diverted away from this question; a question which I think is more important than the endless discussions of pilot fault, and undetermined aerodynamic issues of the MAX.

Purely personal opinion: looks like Boeing and FAA internal operations are fragmented, with limited interaction between teams. It is entirely plausible that initial value was first communicated to FAA in broad context, then FAA agreed not to include MCAS into documentation; after MCAS authority was increased, it was communicated by one of teams to counterparts in FAA, but never reached those who approved pilot documentation.
 
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aerolimani
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 7:44 pm

kalvado wrote:
aerolimani wrote:
So… I thought that it was confirmed (from many months ago) that Boeing had not informed the FAA about the changes in the regime in which MCAS was designed to function. To me, that is the important part of this dialogue between the technical pilots. The red herring is all the discussion of the simulator itself; ECAB flying for documentation purposes versus certification of a commercial 3rd party sim.

So, did Boeing update the FAA, or did they not? In that one recent ST article, Boeing seems to be passing the buck to the FAA, claiming that they passed all the change info on to the FAA.

So… what is it? Did Boeing tell the FAA about the expanded role of MCAS, or did they not?

In any case, this thread has been successfully diverted away from this question; a question which I think is more important than the endless discussions of pilot fault, and undetermined aerodynamic issues of the MAX.

Purely personal opinion: looks like Boeing and FAA internal operations are fragmented, with limited interaction between teams. It is entirely plausible that initial value was first communicated to FAA in broad context, then FAA agreed not to include MCAS into documentation; after MCAS authority was increased, it was communicated by one of teams to counterparts in FAA, but never reached those who approved pilot documentation.

It does seem like the Boeing - FAA lines are made very blurry with all the Boeing-employed FAA representatives.
 
rheinwaldner
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 8:13 pm

lowbank wrote:
If every MAX flight was only 20-30% full airlines would soon get fed up flying it.

If another one crashes in the 12 months following reintroduction, that could be the outcome.

I agree. Especially if you consider, that applying the average global crash rate, the expectation would be only one MAX crash in the first 88 months of operation.

So, if another one crashes within 12 month, the suggestion that the fix is not sufficiently fixing the issue would not be so far fetched.
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 8:13 pm

morrisond wrote:
I think the turn backs might have just been coincidental - when they were over 100 knots above Vmo the control surfaces could have been particularly ineffective.


100 kts over Vmo??
You mean when they were in full dive???
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 8:16 pm

morrisond wrote:
PW100 wrote:
morrisond wrote:

As they were flying at full thrust at over Vmo - well above normal operating speed and the speed limit below 10,000' - it's as bad as no thrust and below stall speed - the trim wheel isn't going to help much there either.


You keep being economical with the facts . . .
. . . .

The were over Vmo when they supposedly tried to use the Manual trim wheel.


You make it sound that it was their choice to go over Vmo, when it was infact MCAS induced. However your posts seem to miss this little thing every single time . . .
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 8:30 pm

planecane wrote:
rheinwaldner wrote:
planecane wrote:

No they didn't. Stick force lightening that potentially makes it easier to get to a stall attitude is not the same thing as stall characteristics. Stall characteristics are the way the aircraft behaves in a stall and how it is able to recover from a stall. MCAS does nothing to change stall characteristics.

It looks like some more education is required about this topic:
14CFR §25.203 Stall characteristics.
(a) It must be possible to produce and to correct roll and yaw by unreversed use of the aileron and rudder controls, up to the time the airplane is stalled.

So the truth is the exact opposite of what you wrote.


. . .. MCAS and stall characteristics don't (based on available information) have anything to do with each other. The .


Information publicly available states the opposite:
JATR Report wrote:
Observation O3.4-B: Extension of MCAS to the low-speed and 1g environment
during the flight program was due to unacceptable stall characteristics with STS
only.
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hivue
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 8:37 pm

oschkosch wrote:
But let me tell you that since the initial groundings of the max outside of the US, we have a written memo in our corporate travel portal telling us not to fly on any max aircraft in any country. And I am very sure that my company is not the only one. We will not fly max aircraft until we feel it is safe to do so. Our internal requirements outweigh any un-grounding. The way our corporation works is such that we will not automatically allow our people to be on these planes immediately after RTS.


Once the MAX was grounded in a few countries it was easy to see that it would eventually be grounded in the U.S. It's not too expensive to look out for employee safety by not letting them fly on an airplane that can't carry passengers anyway. And I'm sure that the corporate bean counters will let you fly the MAX when they feel that it is better for the bottom li... er, that it is safe to do so.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
airnorth
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 8:38 pm

oschkosch wrote:
planecane wrote:
I expect some percentage of people to try and avoid the MAX for a little while. However, most of the avoidance will be in the first month or two after ungrounding.


I work for a listed multinational company with a turnover of above 50 Billion US$ (much more actually). Our division has over 25K employees, total company workforce is above 200K people - I won't be precise on these figures in order to safeguard my employer. But let me tell you that since the initial groundings of the max outside of the US, we have a written memo in our corporate travel portal telling us not to fly on any max aircraft in any country. And I am very sure that my company is not the only one. We will not fly max aircraft until we feel it is safe to do so. Our internal requirements outweigh any un-grounding. The way our corporation works is such that we will not automatically allow our people to be on these planes immediately after RTS.

Are we now part of that 1% of people that will avoid the max as you, or was it someone that else posted that remark, have mentioned here on a.net?


I find that really interesting, though maybe a little over the top, there are so many more day to day travel threats that seem much riskier than a type of aircraft. Just curious what other travel restriction your firm might be in place? I would think that some geographical areas would be off limits regardless of the type of transportation. Maybe a ban on some of the sketchy cabs? We were in a cab last week in Chicago.....scared the crap out of me. I will be one of the 99% jumping back on the MAX but carefully scrutinizing my type of ground transportation!!
 
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gatibosgru
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 8:44 pm

This may be be the wrong place for this question, but other than the BA order, have there been any others for the MAX since the grounding?
@DadCelo
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 8:50 pm

PW100 wrote:
morrisond wrote:
PW100 wrote:

You keep being economical with the facts . . .
. . . .

The were over Vmo when they supposedly tried to use the Manual trim wheel.


You make it sound that it was their choice to go over Vmo, when it was infact MCAS induced. However your posts seem to miss this little thing every single time . . .


Yes - by leaving Autothrottle engaged it was there choice to fly at that speed.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 9:05 pm

PW100 wrote:
morrisond wrote:
I think the turn backs might have just been coincidental - when they were over 100 knots above Vmo the control surfaces could have been particularly ineffective.


100 kts over Vmo??
You mean when they were in full dive???


Yes - when they were in full dive approaching 500knots in the last few seconds - I think that is the period of time the previous poster was referencing.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 9:15 pm

morrisond wrote:
PW100 wrote:
morrisond wrote:
The were over Vmo when they supposedly tried to use the Manual trim wheel.


You make it sound that it was their choice to go over Vmo, when it was infact MCAS induced. However your posts seem to miss this little thing every single time . . .


Yes - by leaving Autothrottle engaged it was there choice to fly at that speed.
:bored: Still the same kind of loop out of safety arguments: "The 737 MAX is safe as long as there still exists a way for the pilots to survive".

Again, this is not how safety work in civil commercial aviation. Pilots are not rated infallible is safety assessment, especially in non-normal condition where as solution need to be found alone and quickly, under stress and workload. This is why safety is, by far, more a process in the design, where engineers can safely think, simulate and test any non-normal conditions, and have so much more time to found a collaborative solution under normal workload and low stress; if the company culture and objectives are set to make this possible.
 
Chemist
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 10:44 pm

morrisond wrote:
PW100 wrote:
morrisond wrote:
The were over Vmo when they supposedly tried to use the Manual trim wheel.


You make it sound that it was their choice to go over Vmo, when it was infact MCAS induced. However your posts seem to miss this little thing every single time . . .


Yes - by leaving Autothrottle engaged it was there choice to fly at that speed.


When I took spin training, one of the first basics is that when you end up facing steeply downward with speed rapidly increasing, you immediately retard the throttle, then you make the other necessary control inputs to correct the attitude.
 
jplatts
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Oct 23, 2019 11:00 pm

lowbank wrote:
I know it’s a different time and different reason, but please consider the power of the travelling public.

Concorde had one accident, a fortune spent on making it safe.

It’s claimed it’s biggest customers were killed in the 9/11 rain towers.


One big difference between the plane crashes of the 9/11 attacks and the 737 MAX crashes is that the 9/11 plane crashes were caused by hijackers taking control over the plane and not due to defective controls or sensors whereas JT 610 and ET 302 were caused by defects in the MCAS system, horizontal trim controls, and/or angle of attack sensors.

Another big difference between 9/11 and the 737 MAX crashes is that the plane crashes involved Boeing 757 and Boeing 767 planes. The Boeing 757 and Boeing 767 planes had also been in service for over 18 years at the time of the 9/11 attacks, whereas the 737 MAX had been in service for only a year at the time of the JT 610 crash.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 12:14 am

Chemist wrote:
morrisond wrote:
PW100 wrote:

You make it sound that it was their choice to go over Vmo, when it was infact MCAS induced. However your posts seem to miss this little thing every single time . . .


Yes - by leaving Autothrottle engaged it was there choice to fly at that speed.


When I took spin training, one of the first basics is that when you end up facing steeply downward with speed rapidly increasing, you immediately retard the throttle, then you make the other necessary control inputs to correct the attitude.


Me too!
 
WPIAeroGuy
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 1:51 am

kalvado wrote:
planecane wrote:
kalvado wrote:
Such statement is very hard to believe. Remember, all that "stick force" argument completely ignores simulated nature of stick force in 737. Either airflow in MAX vs NG renders tail mounted Pitot inefficient - indicating significant change in aerodynamics; or airplane actually responds to control inputs in a different fashion. Given correction measures, it is totally fair to say there is a pitch up tendency corrected by MCAS; and since that occurs at stall entry past stick shaker onset... If you believe those don't have anything to do with each other, would you also be interested in acquiring couple of bridges in a major US megalopolis?


However, the stick force is simulated on the 737 using the stabilizer position and the stabilizer pitot system. A poster a few pages back said that the elevator feel computer is an analog hydraulic computer. If it were an electronic computer that runs software, the AoA could have been fed into it and the MCAS function could have been handled by it. Essentially, MCAS is tricking the elevator feel computer. Doing so requires the stabilizer trim to be changed.

That's why I say that MCAS and stall characteristics have nothing to do with each other. If the stick force gradient issue could have been solved by a software update to the EFC trim changes wouldn't have been necessary.

Stick force is NOT changed by moving control surfaces as MCAS does, plane movement is. Basically this is not about force, this is about MAX being more responsive to controls than NG at high AoA, near stall. Which fits purr-fectly into "easier to accidentally exceed critical AoA and enter into stall as less control movement is required for that"
Any other reading is a game of words.


You (and several posters here) really shouldn’t be commenting on aerodynamics if you have no formal understanding of it. Stabilizer AoA absolutely effects elevator load. In MCAS, the stabilizer essentially works in the opposite direction of the ANU elevator. The effect it creates is that it requires additional elevator deflection to maintain a given pitch. MCAS was intended to trim the stab down at the same time the elevator load was lightening. Thus the pilot would feel the elevator getting heavier. It’s not an artificial force, it’s due to increased load on the elevator. But it was not (from any document I’ve seen) intended to pitch the nose down.

If Boeing wanted to pitch the nose down they would have just put a stick pusher and used the elevator. The elevator can respond far quicker than the stab trim. My guess is that the increased MCAS speed was because in flight testing the pilots could pull back faster than MCAS could trim the stab.
-WPIAeroGuy
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 2:33 am

WPIAeroGuy wrote:
kalvado wrote:
planecane wrote:

However, the stick force is simulated on the 737 using the stabilizer position and the stabilizer pitot system. A poster a few pages back said that the elevator feel computer is an analog hydraulic computer. If it were an electronic computer that runs software, the AoA could have been fed into it and the MCAS function could have been handled by it. Essentially, MCAS is tricking the elevator feel computer. Doing so requires the stabilizer trim to be changed.

That's why I say that MCAS and stall characteristics have nothing to do with each other. If the stick force gradient issue could have been solved by a software update to the EFC trim changes wouldn't have been necessary.

Stick force is NOT changed by moving control surfaces as MCAS does, plane movement is. Basically this is not about force, this is about MAX being more responsive to controls than NG at high AoA, near stall. Which fits purr-fectly into "easier to accidentally exceed critical AoA and enter into stall as less control movement is required for that"
Any other reading is a game of words.


You (and several posters here) really shouldn’t be commenting on aerodynamics if you have no formal understanding of it. Stabilizer AoA absolutely effects elevator load. In MCAS, the stabilizer essentially works in the opposite direction of the ANU elevator. The effect it creates is that it requires additional elevator deflection to maintain a given pitch. MCAS was intended to trim the stab down at the same time the elevator load was lightening. Thus the pilot would feel the elevator getting heavier. It’s not an artificial force, it’s due to increased load on the elevator. But it was not (from any document I’ve seen) intended to pitch the nose down.

If Boeing wanted to pitch the nose down they would have just put a stick pusher and used the elevator. The elevator can respond far quicker than the stab trim. My guess is that the increased MCAS speed was because in flight testing the pilots could pull back faster than MCAS could trim the stab.


Thanks for saying it better than I could.
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 3:17 am

WPIAeroGuy wrote:
kalvado wrote:
planecane wrote:

However, the stick force is simulated on the 737 using the stabilizer position and the stabilizer pitot system. A poster a few pages back said that the elevator feel computer is an analog hydraulic computer. If it were an electronic computer that runs software, the AoA could have been fed into it and the MCAS function could have been handled by it. Essentially, MCAS is tricking the elevator feel computer. Doing so requires the stabilizer trim to be changed.

That's why I say that MCAS and stall characteristics have nothing to do with each other. If the stick force gradient issue could have been solved by a software update to the EFC trim changes wouldn't have been necessary.

Stick force is NOT changed by moving control surfaces as MCAS does, plane movement is. Basically this is not about force, this is about MAX being more responsive to controls than NG at high AoA, near stall. Which fits purr-fectly into "easier to accidentally exceed critical AoA and enter into stall as less control movement is required for that"
Any other reading is a game of words.


You (and several posters here) really shouldn’t be commenting on aerodynamics if you have no formal understanding of it. Stabilizer AoA absolutely effects elevator load. In MCAS, the stabilizer essentially works in the opposite direction of the ANU elevator. The effect it creates is that it requires additional elevator deflection to maintain a given pitch. MCAS was intended to trim the stab down at the same time the elevator load was lightening. Thus the pilot would feel the elevator getting heavier. It’s not an artificial force, it’s due to increased load on the elevator. But it was not (from any document I’ve seen) intended to pitch the nose down.

If Boeing wanted to pitch the nose down they would have just put a stick pusher and used the elevator. The elevator can respond far quicker than the stab trim. My guess is that the increased MCAS speed was because in flight testing the pilots could pull back faster than MCAS could trim the stab.


Boeing did not want to push the nose down with MCAS? Where than comes the aggressive action of MCAS? To change the feel a little bit? The arguments here are getting far out ridiculous.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 3:38 am

mjoelnir wrote:
WPIAeroGuy wrote:
kalvado wrote:
Stick force is NOT changed by moving control surfaces as MCAS does, plane movement is. Basically this is not about force, this is about MAX being more responsive to controls than NG at high AoA, near stall. Which fits purr-fectly into "easier to accidentally exceed critical AoA and enter into stall as less control movement is required for that"
Any other reading is a game of words.


You (and several posters here) really shouldn’t be commenting on aerodynamics if you have no formal understanding of it. Stabilizer AoA absolutely effects elevator load. In MCAS, the stabilizer essentially works in the opposite direction of the ANU elevator. The effect it creates is that it requires additional elevator deflection to maintain a given pitch. MCAS was intended to trim the stab down at the same time the elevator load was lightening. Thus the pilot would feel the elevator getting heavier. It’s not an artificial force, it’s due to increased load on the elevator. But it was not (from any document I’ve seen) intended to pitch the nose down.

If Boeing wanted to pitch the nose down they would have just put a stick pusher and used the elevator. The elevator can respond far quicker than the stab trim. My guess is that the increased MCAS speed was because in flight testing the pilots could pull back faster than MCAS could trim the stab.


Boeing did not want to push the nose down with MCAS? Where than comes the aggressive action of MCAS? To change the feel a little bit? The arguments here are getting far out ridiculous.

Well, even the JATR work was not conclusive on that point, so it's normal that this point continue to be debated to death in this forum. From the early information about the JT610 final report, this point will not be addressed, so the disagreement will continue, I guess for many many years...

That said, I found interesting the idea of thinking how the 737 MAX would have been tuned if it was a FBW system. I think that the obsolete flight control system, with multiple control systems connected to the barely minimal and without the level of redundancy expected for a new aircraft, have been pushed by the tuning in a near impossible corner from the safety point of view.
Last edited by PixelFlight on Thu Oct 24, 2019 3:40 am, edited 1 time in total.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 3:40 am

mjoelnir wrote:
WPIAeroGuy wrote:
kalvado wrote:
Stick force is NOT changed by moving control surfaces as MCAS does, plane movement is. Basically this is not about force, this is about MAX being more responsive to controls than NG at high AoA, near stall. Which fits purr-fectly into "easier to accidentally exceed critical AoA and enter into stall as less control movement is required for that"
Any other reading is a game of words.


You (and several posters here) really shouldn’t be commenting on aerodynamics if you have no formal understanding of it. Stabilizer AoA absolutely effects elevator load. In MCAS, the stabilizer essentially works in the opposite direction of the ANU elevator. The effect it creates is that it requires additional elevator deflection to maintain a given pitch. MCAS was intended to trim the stab down at the same time the elevator load was lightening. Thus the pilot would feel the elevator getting heavier. It’s not an artificial force, it’s due to increased load on the elevator. But it was not (from any document I’ve seen) intended to pitch the nose down.

If Boeing wanted to pitch the nose down they would have just put a stick pusher and used the elevator. The elevator can respond far quicker than the stab trim. My guess is that the increased MCAS speed was because in flight testing the pilots could pull back faster than MCAS could trim the stab.


Boeing did not want to push the nose down with MCAS? Where than comes the aggressive action of MCAS? To change the feel a little bit? The arguments here are getting far out ridiculous.

MCAS is not pushing the nose down. It is making it more difficult to pull the nose up. As stated by another poster if the goal was pushing the nose down they could have added a stick pusher. Only when it malfunctioned did it push the nose down.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 3:47 am

planecane wrote:
mjoelnir wrote:
WPIAeroGuy wrote:

You (and several posters here) really shouldn’t be commenting on aerodynamics if you have no formal understanding of it. Stabilizer AoA absolutely effects elevator load. In MCAS, the stabilizer essentially works in the opposite direction of the ANU elevator. The effect it creates is that it requires additional elevator deflection to maintain a given pitch. MCAS was intended to trim the stab down at the same time the elevator load was lightening. Thus the pilot would feel the elevator getting heavier. It’s not an artificial force, it’s due to increased load on the elevator. But it was not (from any document I’ve seen) intended to pitch the nose down.

If Boeing wanted to pitch the nose down they would have just put a stick pusher and used the elevator. The elevator can respond far quicker than the stab trim. My guess is that the increased MCAS speed was because in flight testing the pilots could pull back faster than MCAS could trim the stab.


Boeing did not want to push the nose down with MCAS? Where than comes the aggressive action of MCAS? To change the feel a little bit? The arguments here are getting far out ridiculous.

MCAS is not pushing the nose down. It is making it more difficult to pull the nose up. As stated by another poster if the goal was pushing the nose down they could have added a stick pusher. Only when it malfunctioned did it push the nose down.

From all the available description it's clear that the outputs of the MCAS system is an Automated Nose Down signal (with the related enable and trim speed signal) to the horizontal stabilized actuator. It's the only possible action it can physically do.

Guys, you are only debating the intent of that signal, but the signal itself out of the MCAS is clearly a nose down signal.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 4:06 am

PixelFlight wrote:
planecane wrote:
mjoelnir wrote:

Boeing did not want to push the nose down with MCAS? Where than comes the aggressive action of MCAS? To change the feel a little bit? The arguments here are getting far out ridiculous.

MCAS is not pushing the nose down. It is making it more difficult to pull the nose up. As stated by another poster if the goal was pushing the nose down they could have added a stick pusher. Only when it malfunctioned did it push the nose down.

From all the available description it's clear that the outputs of the MCAS system is an Automated Nose Down signal (with the related enable and trim speed signal) to the horizontal stabilized actuator. It's the only possible action it can physically do.

Guys, you are only debating the intent of that signal, but the signal itself out of the MCAS is clearly a nose down signal.

It is nose down TRIM. Neither a human pilot or the autopilot normally use trim to change pitch. Trim is to remove elevator force required normally. MCAS is using it to increase the elevator force required.
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 4:26 am

planecane wrote:
PixelFlight wrote:
planecane wrote:
MCAS is not pushing the nose down. It is making it more difficult to pull the nose up. As stated by another poster if the goal was pushing the nose down they could have added a stick pusher. Only when it malfunctioned did it push the nose down.

From all the available description it's clear that the outputs of the MCAS system is an Automated Nose Down signal (with the related enable and trim speed signal) to the horizontal stabilized actuator. It's the only possible action it can physically do.

Guys, you are only debating the intent of that signal, but the signal itself out of the MCAS is clearly a nose down signal.

It is nose down TRIM. Neither a human pilot or the autopilot normally use trim to change pitch. Trim is to remove elevator force required normally. MCAS is using it to increase the elevator force required.


So what? Trimming the stabilizer is more effective in pushing the nose down the any elevator action. The stabilizer has the far bigger area and therefor the bigger nose down effect than the elevator for every degree of application. It does not matter what you call something, it matters what it does.

That is actually one of the dangerous points with the 737MAX, nose down trim can override completely the elevator action by the pilot.
 
sgrow787
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 5:13 am

MrBretz wrote:
sgrow787 wrote:
EDIT: Added "worse case scenario" since Im not working on the Max project and therefore not privy to the details.


You are right about one thing: you not working on it so you don’t know.


And you are right about absolutely nothing, including what I know or don't know. I may not know the details, but I have the background and experience to know that a bit flip that halts the FCC points towards a resource allocation issue, most likely computational. Plus the fact that they have taken a year so far and counting to get the "logical" fix in points to this as well.
Just one sensor,
Oh just one se-en-sor,
Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.
 
MrBretz
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 5:44 am

sgrow787 wrote:
MrBretz wrote:
sgrow787 wrote:
EDIT: Added "worse case scenario" since Im not working on the Max project and therefore not privy to the details.


You are right about one thing: you not working on it so you don’t know.


And you are right about absolutely nothing, including what I know or don't know. I may not know the details, but I have the background and experience to know that a bit flip that halts the FCC points towards a resource allocation issue, most likely computational. Plus the fact that they have taken a year so far and counting to get the "logical" fix in points to this as well.


I wouldn’t be as impolite as you. You are entitled to your opinion. And I am entitled to mine. BTW, I have actually programmed a flight computer for a military airplane. Have you? And, I might add, I find most of your comments quite interesting and pretty good. But you really don’t know.
 
Chemist
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 5:52 am

sgrow787 wrote:
MrBretz wrote:
sgrow787 wrote:
EDIT: Added "worse case scenario" since Im not working on the Max project and therefore not privy to the details.


You are right about one thing: you not working on it so you don’t know.


And you are right about absolutely nothing, including what I know or don't know. I may not know the details, but I have the background and experience to know that a bit flip that halts the FCC points towards a resource allocation issue, most likely computational. Plus the fact that they have taken a year so far and counting to get the "logical" fix in points to this as well.


I thought the bit flip issue was only found ~late spring? Not nearly a year.
 
asdf
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 7:37 am

mrbots wrote:
asdf wrote:
DenverTed wrote:
....so even if it meant designing a larger horizontal stabilizer, it is still an easy economic case to make.


will not work
i guess you can not certify it within grandfathering rules

you would need to to a recertification of the complete 737 and the 737 would fail in a lot of requierements of 2019

its still a 1960 technologie base


What requirements affect the tail plane today that wouldn't have worked in 1984 when the tail plane was redesigned and upsized when the engines moved from underneath to ahead of the wing? Also, pretty sure you don't have to recertify the whole plane, just what changes. The NG got a heavily revised wing in the 90s and didn't require full recertification and for a more recent example, the 777X has an entirely new wing and doesn't require (as yet determined) a full recertification.


with a larger stabilizer you have an even higher manual trim load than now
and now you cant turn it if you are out of trim because of aerodynamical forces

if you put a larger stabilizer on it you need to fix this
how would you do that under the rules of 1959 ?

and
btw:
what was able in the past with "grandfathering" does not has to be able now
maybe there have been taken some "shortcuts" here and there and no one saw it ...
 
AirBoat
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 8:38 am

The larger stabilizer was never going to happen.
The implication is that the structural design of the rear half of the aircraft would have to be redone, due to larger stabilizer forces, and possibly the structure strengthened. That late in the process, this was not going to happen.
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 8:49 am

AirBoat wrote:
The larger stabilizer was never going to happen.
The implication is that the structural design of the rear half of the aircraft would have to be redone, due to larger stabilizer forces, and possibly the structure strengthened. That late in the process, this was not going to happen.


Due to the age of the 737 design and the initial requirements (which it met very successfully), there were constraints everywhere in attempts to modernise it which resulted in compromises.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 9:32 am

mjoelnir wrote:
planecane wrote:
PixelFlight wrote:
From all the available description it's clear that the outputs of the MCAS system is an Automated Nose Down signal (with the related enable and trim speed signal) to the horizontal stabilized actuator. It's the only possible action it can physically do.

Guys, you are only debating the intent of that signal, but the signal itself out of the MCAS is clearly a nose down signal.

It is nose down TRIM. Neither a human pilot or the autopilot normally use trim to change pitch. Trim is to remove elevator force required normally. MCAS is using it to increase the elevator force required.


So what? Trimming the stabilizer is more effective in pushing the nose down the any elevator action. The stabilizer has the far bigger area and therefor the bigger nose down effect than the elevator for every degree of application. It does not matter what you call something, it matters what it does.

That is actually one of the dangerous points with the 737MAX, nose down trim can override completely the elevator action by the pilot.

I was talking about when it is operating properly. The DESIGN INTENTION was not for it to override the elevator or push the nose down. The intention was for it to make it more difficult to pull the nose up when the nacelle interaction (or whatever is really happening aerodynamically) is making it easier to pull the nose up.
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 10:01 am

WPIAeroGuy wrote:
kalvado wrote:
planecane wrote:

However, the stick force is simulated on the 737 using the stabilizer position and the stabilizer pitot system. A poster a few pages back said that the elevator feel computer is an analog hydraulic computer. If it were an electronic computer that runs software, the AoA could have been fed into it and the MCAS function could have been handled by it. Essentially, MCAS is tricking the elevator feel computer. Doing so requires the stabilizer trim to be changed.

That's why I say that MCAS and stall characteristics have nothing to do with each other. If the stick force gradient issue could have been solved by a software update to the EFC trim changes wouldn't have been necessary.

Stick force is NOT changed by moving control surfaces as MCAS does, plane movement is. Basically this is not about force, this is about MAX being more responsive to controls than NG at high AoA, near stall. Which fits purr-fectly into "easier to accidentally exceed critical AoA and enter into stall as less control movement is required for that"
Any other reading is a game of words.


You (and several posters here) really shouldn’t be commenting on aerodynamics if you have no formal understanding of it. Stabilizer AoA absolutely effects elevator load. In MCAS, the stabilizer essentially works in the opposite direction of the ANU elevator. The effect it creates is that it requires additional elevator deflection to maintain a given pitch. MCAS was intended to trim the stab down at the same time the elevator load was lightening. Thus the pilot would feel the elevator getting heavier. It’s not an artificial force, it’s due to increased load on the elevator. But it was not (from any document I’ve seen) intended to pitch the nose down.

If Boeing wanted to pitch the nose down they would have just put a stick pusher and used the elevator. The elevator can respond far quicker than the stab trim. My guess is that the increased MCAS speed was because in flight testing the pilots could pull back faster than MCAS could trim the stab.

Frankly speaking,this is not about aerodynamics. This is about control systems, control systems 101 or so. ANd by the way, I hope my PhD in physics allows to have a borader view of the problem, if we're talking about the formal understanding of things.
Stabilizer deflection (trim) changes lift generated by that stabilizer assuming wing AoA and airspeed are constant - would you argue with that? Thank you.
Any control stick forces are only secondary effects from there.
Yes, you can trade in the change of stabilizer lift for change of elevator deflection - and required stick force - to maintain the same pitch; that is normal "trim out of stick force" operation.
Or you can take that force at a face value and have a change of pitch at a given stick force - apparently, that is the way MCAS is using it. In this case, it is now up to the pilot to restore the pitch (into close-to-stall region for MCAS case) or accept a helping hand and enjoy safely reduced pitch/AoA at the same control input. Consider that as rudimentary envelope protection/stall avoidance action.
Are you still with me?

Why Boeing settled with a slower trim action instead of fast elevator action? Remember, timing is the same for either stick force or pitch change point of view. Extreme forces at high deflection come to mind. We're already in a situation, where higher mechanical leverage of the trim system is unable to overcome MCAS induced forces, overloading can be a problem here.
Second (slightly less realistic) explanation is that MCAS is slow to gradually compensate for entry into the hazardous region for same plane rotation speed - and it should be limited by the angular momentum of long body if nothing else. Again, you may interpret that as "plane requires more force to go to same pitch", or as "pitch response to fixed control force is cut back by the computer-generated movement", two sides of the same coin.
However, pilot input in an emergency - and MCAS is for abnormal situations! - should have relatively slow feedback, i.e. pulling controls starts with the same force; so my explanation of fixed control force which now produces reduced pitch is much more realistic.
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 10:01 am

planecane wrote:
mjoelnir wrote:
planecane wrote:
It is nose down TRIM. Neither a human pilot or the autopilot normally use trim to change pitch. Trim is to remove elevator force required normally. MCAS is using it to increase the elevator force required.


So what? Trimming the stabilizer is more effective in pushing the nose down the any elevator action. The stabilizer has the far bigger area and therefor the bigger nose down effect than the elevator for every degree of application. It does not matter what you call something, it matters what it does.

That is actually one of the dangerous points with the 737MAX, nose down trim can override completely the elevator action by the pilot.

I was talking about when it is operating properly. The DESIGN INTENTION was not for it to override the elevator or push the nose down. The intention was for it to make it more difficult to pull the nose up when the nacelle interaction (or whatever is really happening aerodynamically) is making it easier to pull the nose up.


How do you know what the design intention was? Did you design it? Do you have some information somewhere you can point to?

MCAS at low speeds pushes the nose aggressively down, even if it operates properly only once. When it quacks like a duck and walks like a duck and so on.
 
planecane
Posts: 1267
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 10:05 am

AirBoat wrote:
The larger stabilizer was never going to happen.
The implication is that the structural design of the rear half of the aircraft would have to be redone, due to larger stabilizer forces, and possibly the structure strengthened. That late in the process, this was not going to happen.

I still don't understand how a larger stabilizer would have helped with this issue. The issue is non linear. There is a different amount of lift induced by the engines at different speed and AoA combinations. A larger stabilizer would just add more force but I don't see how it would deal with the non linear aspect of the problem. Wouldn't you need to design a stabilizer that added more lift to the tail as AoA increased? Not only that but in specific amounts at specific AoA. I just don't see how simply making it larger would do anything.
 
planecane
Posts: 1267
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 10:09 am

mjoelnir wrote:
planecane wrote:
mjoelnir wrote:

So what? Trimming the stabilizer is more effective in pushing the nose down the any elevator action. The stabilizer has the far bigger area and therefor the bigger nose down effect than the elevator for every degree of application. It does not matter what you call something, it matters what it does.

That is actually one of the dangerous points with the 737MAX, nose down trim can override completely the elevator action by the pilot.

I was talking about when it is operating properly. The DESIGN INTENTION was not for it to override the elevator or push the nose down. The intention was for it to make it more difficult to pull the nose up when the nacelle interaction (or whatever is really happening aerodynamically) is making it easier to pull the nose up.


How do you know what the design intention was? Did you design it? Do you have some information somewhere you can point to?

MCAS at low speeds pushes the nose aggressively down, even if it operates properly only once. When it quacks like a duck and walks like a duck and so on.


Granted I'm going by what Boeing has stated but if they are being truthful (which at this point they have no reason not to be) then my description of the intention is correct.

You are just making things up like it pushes the nose aggressively down at low speed. What is your source for that fact? A simple understanding of physics would tell you that the lower the speed, the more stabilizer movement is necessary to produce the same force.
 
kalvado
Posts: 2178
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Oct 24, 2019 10:10 am

planecane wrote:
mjoelnir wrote:
planecane wrote:
It is nose down TRIM. Neither a human pilot or the autopilot normally use trim to change pitch. Trim is to remove elevator force required normally. MCAS is using it to increase the elevator force required.


So what? Trimming the stabilizer is more effective in pushing the nose down the any elevator action. The stabilizer has the far bigger area and therefor the bigger nose down effect than the elevator for every degree of application. It does not matter what you call something, it matters what it does.

That is actually one of the dangerous points with the 737MAX, nose down trim can override completely the elevator action by the pilot.

I was talking about when it is operating properly. The DESIGN INTENTION was not for it to override the elevator or push the nose down. The intention was for it to make it more difficult to pull the nose up when the nacelle interaction (or whatever is really happening aerodynamically) is making it easier to pull the nose up.

Officer, I stepped on the throttle to make sure my wheels are spinning faster, not to speed up!
Design intention is to eliminate (unsafe) nose-up movement wich would be caused by unaugmented control input. Since we're talking not about changing parameters within control path, but about the direct effect on the system under control, any "just change force" argument is halfhearted at best.

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