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hivue
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Nov 12, 2019 10:13 pm

Revelation wrote:
The people "with an inside knowenledge about aerodynamical instability" have largely left the discussion due to all the grief they get when their explanations don't match other people's expectations.


In lieu of them, here is someone who sounds like he has inside knowledge on aerodynamic instability --

https://www.youtube.com/watch?v=VImEvFg3smQ

It's my understanding that commercial transport category airplanes are, by regulation, no less aerodynamically stable than GA airplanes.
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aerolimani
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Nov 12, 2019 10:18 pm

morrisond wrote:
XRAYretired wrote:
morrisond wrote:

From our own Ray. See above the relevant FAR's are 25.255 and 25.143 - it wasn't 25-203.

I'm sure he can tell us when and why they were revised.

'................certification that the pitch controls could not get lighter on the approach to stall…….' i.e. 25-203.

Do your own research.

Ray


I did I quoted you. 25.255 requires increasing stick force per g, which is the more stringent requirement than just not getting lighter under 25-203 - that is what came into place after NG certification.

And once again we go down into the black hole.

255.203 still applies. Nowhere, in any of the information I've found out there, is there any suggestion that anyone was wrong about 25.203 being applicable to the 737. The fact that other regulations came along later does not negate the fact that the MAX must still meet 25.203. Or, are you, Morissond, suggesting that the MAX (sans MCAS) meets 25.203?

My point in bringing this up is to show that statements to the effect of "MCAS is to make the MAX fly like an NG" are not untruthful, but are somewhat misleading. It might even be considered whitewashing, as it masks the true problem. It suggests that MCAS is there to avoid differences training, when in fact, MCAS is there to make an otherwise uncertifiable plane into a certifiable one. I felt that it was important to point this out.

You are the one leading us down a black hole about which reg's the MAX breaks, and when they were in place. The intention of my post rings true regardless of when the reg's were put in place.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Nov 12, 2019 10:31 pm

aerolimani wrote:
My point in bringing this up is to show that statements to the effect of "MCAS is to make the MAX fly like an NG" are not untruthful, but are somewhat misleading. It might even be considered whitewashing, as it masks the true problem. It suggests that MCAS is there to avoid differences training, when in fact, MCAS is there to make an otherwise uncertifiable plane into a certifiable one. I felt that it was important to point this out.

You are the one leading us down a black hole about which reg's the MAX breaks, and when they were in place. The intention of my post rings true regardless of when the reg's were put in place.

So does this also apply to those who say that MCAS is a stall prevention system, including folks in the JTAR report?
 
Cdydatzigs
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Tue Nov 12, 2019 11:31 pm

questions wrote:
Will Boeing and/or the airlines do any sort of marketing to build the public's confidence in the aircraft? If so, what could it look like?


Honestly, the easiest route would just be to "rename" them using the same naming convention as the other newer types in the family: 737-7, -8, -9, -10 and be done with it.
 
art
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 12:41 am

Revelation wrote:
art wrote:
And Boeing say they are going to resume deliveries in December?

You do understand there is a difference between delivery and return to service, right?

Don't you have to pay the outstanding on the sales contract when you accept delivery? So why accept delivery of a product you cannot use until FAA authorises RTS?

frmrCapCadet wrote:
Art - your "thens" implies it is entirely a series set of problems. I suspect it is more of a parallel set of problems, and teams are working on setting up all of them. Including final pilot training.


OK, you might be right in saying that steps to ungrounding will be taken in parallel or flightglobal might be right in saying that steps to ungrounding will be taken in series. I have no insight into which of those 2 opposites is correct. I just reported what flightglobal was saying.

My impression, however. is that the MAX won't be getting back into commercial service before 2020.
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 2:57 am

art wrote:
Revelation wrote:
art wrote:
And Boeing say they are going to resume deliveries in December?

You do understand there is a difference between delivery and return to service, right?

Don't you have to pay the outstanding on the sales contract when you accept delivery? So why accept delivery of a product you cannot use until FAA authorises RTS?

Customers understand that it will take Boeing more than a year to get through the backlog of stored MAXes and they'd rather take a plane a few weeks too early rather than a few months too late. Besides, most airlines have their own induction activities to perform and these can take some time to accomplish.
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 3:04 am

Revelation wrote:
Customers understand that it will take Boeing more than a year to get through the backlog of stored MAXes and they'd rather take a plane a few weeks too early rather than a few months too late. Besides, most airlines have their own induction activities to perform and these can take some time to accomplish.

True, and usually some flying is involved, so if the regulators do not give permission for those flights....no time will be saved.
The other question, would the FAA even allow the ferry delivery flights by the clients pilots to leave the USA, this is different from a ferry flight for storage.
My opinion is still that Boeing should simply reduce the production rate further to minimize the storage problem. Due to the almost 1 year worth of stored frames, the time it takes them to ramp the production rate up after RTS will be spent clearing the stored frames.
 
2175301
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 4:53 am

art wrote:
Revelation wrote:
art wrote:
And Boeing say they are going to resume deliveries in December?

You do understand there is a difference between delivery and return to service, right?

Don't you have to pay the outstanding on the sales contract when you accept delivery? So why accept delivery of a product you cannot use until FAA authorises RTS?

frmrCapCadet wrote:
Art - your "thens" implies it is entirely a series set of problems. I suspect it is more of a parallel set of problems, and teams are working on setting up all of them. Including final pilot training.


OK, you might be right in saying that steps to ungrounding will be taken in parallel or flightglobal might be right in saying that steps to ungrounding will be taken in series. I have no insight into which of those 2 opposites is correct. I just reported what flightglobal was saying.

My impression, however. is that the MAX won't be getting back into commercial service before 2020.


I personally suspect the concept being explored is that the FAA will certify the 737Max's for RTS, with the caveat that the Pilot Training Package has not yet been finalized due to coordination with international agencies on a standard base training requirement (which is expected to be finalized in a few weeks). Specific "Delivery" Pilots will be able to ferry new aircraft to locations at least around the USA, and possibly other countries. The airlines can do their preps for the aircraft to enter service (commonly a month or more); and the new planes and pilots trained to the new standard will likely be available to fly in commercial service at about the same time.

That's my guess as to what is being discussed and hoped for.

Have a great day,
 
maint123
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 8:28 am

So I was reading that the A350 flew for 2600 hrs (5 test planes), before the Europeans and the FAA certified it. Means at an average, each plane flew for more than 500 hrs. At 8 hrs of flight per day, equals 62 days of flying per plane. Is using 5 planes to test fly a industry standard, as using too many planes would reduce the stress and compromise the results.
Wonder how much hours of testing will the Max have to undergo before its recertified for flight.?
 
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 8:44 am

maint123 wrote:
So I was reading that the A350 flew for 2600 hrs (5 test planes), before the Europeans and the FAA certified it. Means at an average, each plane flew for more than 500 hrs. At 8 hrs of flight per day, equals 62 days of flying per plane. Is using 5 planes to test fly a industry standard, as using too many planes would reduce the stress and compromise the results.


this are european standards
you can not expect that to happen in US
 
JayinKitsap
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 9:07 am

maint123 wrote:
So I was reading that the A350 flew for 2600 hrs (5 test planes), before the Europeans and the FAA certified it. Means at an average, each plane flew for more than 500 hrs. At 8 hrs of flight per day, equals 62 days of flying per plane. Is using 5 planes to test fly a industry standard, as using too many planes would reduce the stress and compromise the results.
Wonder how much hours of testing will the Max have to undergo before its recertified for flight.?


It has already complete a lot of test flights and flight hours.
Software Updates & Flight Testing: We updated the Maneuvering Characteristics Augmentation System (MCAS) on the MAX by adding three additional layers of protection that will prevent accidents like these from ever happening again. To date, we have conducted more than 800 test and production flights with the updated software, totaling more than 1,500 hours. The company is making steady progress on the second software update announced in June for additional flight control computer redundancy. Some 545 participants from more than 140 customers and regulators around the globe, including the FAA, have participated in simulator sessions to experience the proposed MCAS software update. Just last week the company successfully conducted a dry-run of a certification flight test.

https://boeing.mediaroom.com/news-relea ... tem=130536

I would certainly guess that FAA personnel have been on many a flight as observers, that the documents have been reviewed at a number of stages. This official certification steps now, are after the proof reading and every i is dotted and every t crossed. When the Technical Advisory Board signed off, the decision to accept has been made but some added steps to finalize the paperwork are done. But the official FAA certification flights must go well, but there have been many practice flights of this 'certification' flight.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 9:45 am

maint123 wrote:
So I was reading that the A350 flew for 2600 hrs (5 test planes), before the Europeans and the FAA certified it. Means at an average, each plane flew for more than 500 hrs. At 8 hrs of flight per day, equals 62 days of flying per plane. Is using 5 planes to test fly a industry standard, as using too many planes would reduce the stress and compromise the results.
Wonder how much hours of testing will the Max have to undergo before its recertified for flight.?

Just flying is't enough to certify an aircraft. There is a lot of specific tests to stress every aspects that need to be certified by verifying the compliance with the values expected by the design. Many tests are done on the ground, or even before integration. What's done in the air is just some parts of the certification process.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
benbeny
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 10:34 am

Why do we need to test fly a plane when we have immense computational power to simulate it?
 
asdf
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 10:42 am

benbeny wrote:
Why do we need to test fly a plane when we have immense computational power to simulate it?


because the simulators only simulates
- the planes behaevior in the air and
- the controls respondment
if you programm it into the simulator before

a SIM is not a computer simulating something
its a computer running pre programmed procedures if they are toggeled

if you "forget" to pre programm a crash into the SIM it will not crash

if you "forget" to pre programm MCAS into the SIM it will not crash, too
that is the reason why it was complete meaningless to demand SIM sessions pre MCAS 1.0
because MCAS and its reaction has`nt been programmed in the (very few) 737MAX SIMs
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 12:08 pm

asdf wrote:
maint123 wrote:
So I was reading that the A350 flew for 2600 hrs (5 test planes), before the Europeans and the FAA certified it. Means at an average, each plane flew for more than 500 hrs. At 8 hrs of flight per day, equals 62 days of flying per plane. Is using 5 planes to test fly a industry standard, as using too many planes would reduce the stress and compromise the results.


this are european standards
you can not expect that to happen in US

You totally expect that to be quite similar in US as standards are harmonized. As far as I remember, 787 had 5 flight test frames as well. It should be possible to look at MAX testing campaign story in some old thread here; but there were 15 months between first flight and first delivery. Guess what was going on during those months?
 
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 12:18 pm

kalvado wrote:
You totally expect that to be quite similar in US as standards are harmonized. As far as I remember, 787 had 5 flight test frames as well. It should be possible to look at MAX testing campaign story in some old thread here; but there were 15 months between first flight and first delivery. Guess what was going on during those months?


you think so?
i am not convinced

in europe you never ever could expect a govermental facility to outsource primary check duties to the checked itself without a system of close monitoring what happens
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 1:03 pm

asdf wrote:
kalvado wrote:
You totally expect that to be quite similar in US as standards are harmonized. As far as I remember, 787 had 5 flight test frames as well. It should be possible to look at MAX testing campaign story in some old thread here; but there were 15 months between first flight and first delivery. Guess what was going on during those months?


you think so?
i am not convinced

in europe you never ever could expect a govermental facility to outsource primary check duties to the checked itself without a system of close monitoring what happens

Not sure if this would convince you, but here are some highlights from max test program: http://www.b737.org.uk/maxflttestprog.htm
As for outsourcing of check duties, you may read up on CE marking of consumer products in Europe vs NRTL program in US (personal opinion censored as those words are not permitted on a.net). Interestingly enough, results are similar, if not better, with less government involvement.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 1:19 pm

kalvado wrote:
As for outsourcing of check duties, you may read up on CE marking of consumer products in Europe vs NRTL program in US (personal opinion censored as those words are not permitted on a.net). Interestingly enough, results are similar, if not better, with less government involvement.

In the EU there is no direct government involvement outside of the rules to require notified body or not. https://ec.europa.eu/growth/single-market/ce-marking/manufacturers_en If the product do not require notified body, you can assess your product and issue a EU Declaration of Conformity (DoC) by yourself.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 1:23 pm

par13del wrote:
Revelation wrote:
Customers understand that it will take Boeing more than a year to get through the backlog of stored MAXes and they'd rather take a plane a few weeks too early rather than a few months too late. Besides, most airlines have their own induction activities to perform and these can take some time to accomplish.

True, and usually some flying is involved, so if the regulators do not give permission for those flights....no time will be saved.
The other question, would the FAA even allow the ferry delivery flights by the clients pilots to leave the USA, this is different from a ferry flight for storage.
My opinion is still that Boeing should simply reduce the production rate further to minimize the storage problem. Due to the almost 1 year worth of stored frames, the time it takes them to ramp the production rate up after RTS will be spent clearing the stored frames.

Storage is the least of Boeing's problems. If Moses Lake fills up there are plenty of other underutilized ex-SAC bases around to provide storage space.

A far bigger problem is that Boeing's customers were promised MAXes for delivery many months ago and have not been able to take delivery. A second problem is now they are afraid that Boeing may take many more months to deliver some aircraft ( ref: https://www.reuters.com/article/us-boei ... SKBN1XM2W2 ). Airlines don't want the aircraft they've been waiting for to be buried in the log jam of deliveries.

Yes, folks, companies do want their MAXes! They represent the very future of some airlines (WN, FR, etc) or at least a significant slice of it. MAX is far superior to the ageing NGs that they are flying right now. They have made significant financial investment in the MAXes in terms of pre-delivery payments if nothing else and they want to get their MAXes ASAP!

I'm not sure where the notion of cutting production rate is coming from, it will only make things worse rather than better. Boeing needs to secure the ability to deliver the planes then increase production rate rather than decrease it.

I read a few articles and all say the exact logistics of how the planes will be moved has not been disclosed, but it's clear Boeing has used company pilots to do delivery flights in the past and I don't see why this would be different. Company pilots now shuttle MAXes to Moses Lake, there's no reason they could not be flying them to wherever AA, WN or UA want them to be. Also it's fair to presume these will be flying with the software fixes approved and installed so the risk should be very low, it should fly like a NG as Boeing likes to say. I could see a path where customer instructor pilots / check airmen could be given a waiver after being trained with the initial proposed training regime.

I do feel international deliveries may be more difficult to arrange but where there is a will there is a way, and I'm sure AC, FR and other international MAX operators want their MAXes ASAP.
Last edited by Revelation on Wed Nov 13, 2019 1:31 pm, edited 2 times in total.
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mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 1:25 pm

asdf wrote:
benbeny wrote:
Why do we need to test fly a plane when we have immense computational power to simulate it?


because the simulators only simulates
- the planes behaevior in the air and
- the controls respondment
if you programm it into the simulator before

a SIM is not a computer simulating something
its a computer running pre programmed procedures if they are toggeled

if you "forget" to pre programm a crash into the SIM it will not crash

if you "forget" to pre programm MCAS into the SIM it will not crash, too
that is the reason why it was complete meaningless to demand SIM sessions pre MCAS 1.0
because MCAS and its reaction has`nt been programmed in the (very few) 737MAX SIMs


There is a big difference between a simulator build from the actual aircraft components running the actual used programs, usually used in the development of the aircraft, and the simulators sold for training of pilots build by the simulator guys.
 
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 1:36 pm

Revelation wrote:
Storage is the least of Boeing's problems. If Moses Lake fills up there are plenty of other underutilized ex-SAC bases around to provide storage space.


But wasn’t running out of storage space one of the reasons Boeing gave for wanting to deliver planes to customers before the grounding was lifted?
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Noshow
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 1:44 pm

Boeing must buy all those parts and pay for the work without handing these planes over and receiving it's own payment. After a year and several hundred aircraft enormous pressure will mount financially before the parking space runs out.
They still must avoid any impression that they try to cut short anything. Getting back the flying public's confidence will be the next very hard part.
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 1:47 pm

scbriml wrote:
Revelation wrote:
Storage is the least of Boeing's problems. If Moses Lake fills up there are plenty of other underutilized ex-SAC bases around to provide storage space.

But wasn’t running out of storage space one of the reasons Boeing gave for wanting to deliver planes to customers before the grounding was lifted?

I didn't read that in any of the earlier articles I read nor the one I just posted ( https://www.reuters.com/article/us-boei ... SKBN1XM2W2 ).

The article speaks of the "logjam" but that refers mostly to the fact that there are a lot of logistical elements involved in an airliner delivery ( inspections, legal and financial sign offs, etc) and a finite number of people qualified to perform such tasks.
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 1:48 pm

Revelation wrote:
I'm not sure where the notion of cutting production rate is coming from, it will only make things worse rather than better. Boeing needs to secure the ability to deliver the planes then increase production rate rather than decrease it.

For me it is coming from the fact that all the frames built by Boeing and not delivered and all those in the production line are all production that Boeing has to deliver. A years worth of a/c sitting to be delivered can be viewed as almost having another production line. Boeing wants to increase production to 52 per month when RTS is granted, in the short term they can accomplish that rate by clearing out the backlog that exist both in their completed frames as well as the production units presently stored at their suppliers, we have seen the completed frames, we have also seen production items stored at Spirit, my assumption is that other vendors have been doing the same since the rate only fell to 40+.
My assumption is that both Boeing and it suppliers will have to get their backlogs cleared before they can focus on raising the production rate. Yes it would have been a problem to lower the rate by a larger margin for a short grounding, unfortunately, hindsight is 20/20 but I honestly do not believe that Boeing expected the grounding to go on this long. I think the length of the grounding and the logistics of now getting those completed frames delivered to customers presents a challenge in itself, see the hires being done at Moses Lake, for the most part, these are not the new hires that would be required for the increased production rate at Boeing or its suppliers.

Technically we can also begin to look at the airlines, does it make any difference to them whether the a/c they receive is one that Boeing stored or one straight from the line? We know that there is a difference to those that the airlines stored, WN has already stated that they would put new frames from Boeing into service first as the airline has to expend additional of their own resources to get those frames back up to speed once on property, paper work is probably a huge factor.
 
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SomebodyInTLS
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 1:56 pm

benbeny wrote:
Why do we need to test fly a plane when we have immense computational power to simulate it?


The short answer is because we *don't* have the computational power... and never will.

All simulation is based on human interpretation of what actually tends to happen in nature in real life. Unless you can build a computer model 100% accurately describing every interaction of every atom within the aircraft and all the airspace it interacts with you will always find that some assumption about how things behave or how humans behave or how manufacturing processes work in real life, etc. was not quite the same as in the real world.

Science is only as accurate as humans can make it by testing theories against the real world. And those tests bring changes... Newton becomes Einstein, the flat Earth becomes a globe, witchcraft becomes medicine. And the same with technology... the MCAS debacle is a result of assumptions not matching the real world - hence tests can never completely be replaced by simulation. QED.
"As with most things related to aircraft design, it's all about the trade-offs and much more nuanced than A.net likes to make out."
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 2:14 pm

par13del wrote:
For me it is coming from the fact that all the frames built by Boeing and not delivered and all those in the production line are all production that Boeing has to deliver. A years worth of a/c sitting to be delivered can be viewed as almost having another production line. Boeing wants to increase production to 52 per month when RTS is granted, in the short term they can accomplish that rate by clearing out the backlog that exist both in their completed frames as well as the production units presently stored at their suppliers, we have seen the completed frames, we have also seen production items stored at Spirit, my assumption is that other vendors have been doing the same since the rate only fell to 40+.

My assumption is that both Boeing and it suppliers will have to get their backlogs cleared before they can focus on raising the production rate. Yes it would have been a problem to lower the rate by a larger margin for a short grounding, unfortunately, hindsight is 20/20 but I honestly do not believe that Boeing expected the grounding to go on this long. I think the length of the grounding and the logistics of now getting those completed frames delivered to customers presents a challenge in itself, see the hires being done at Moses Lake, for the most part, these are not the new hires that would be required for the increased production rate at Boeing or its suppliers.

Technically we can also begin to look at the airlines, does it make any difference to them whether the a/c they receive is one that Boeing stored or one straight from the line? We know that there is a difference to those that the airlines stored, WN has already stated that they would put new frames from Boeing into service first as the airline has to expend additional of their own resources to get those frames back up to speed once on property, paper work is probably a huge factor.

Yes, there is a paperwork hurdle for everyone involved ( financiers, contract specialists, government registrars, etc ) but that's mostly an issue with staffing that can be solved the old fashioned way, throw money at the problem.

The main issue with the lower production rate is opportunity cost, you never get time back, once it's gone it's gone. Boeing will make the most money by dealing with the headaches of sorting out the staffing issues and getting the production rate up as soon as partners can do so. As you say one reason they produced ahead of time is so that they could ramp up quicker once the airplane was ungrounded. There's only a certain amount of opportunity to sell MAXes and once that opportunity passes it isn't coming back.
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flipdewaf
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 2:16 pm

seahawk wrote:


You do not need a linear stick force, you need a linear correlation between stick position and pitch control movement.


Not sure if this is what you mean precisely but humans are much much better at determining and counteracting force than they are position. A control of any type can be held at a constant force quite easily by most people whilst encountering a significant amount of movement or indeed with incredible finesse at small amounts of movement but ask a person to hold something still whilst encountering changing forces it is very difficult and needs concentration.

When the systems are simple and linear movement = force (mostly) but as things get complex (like big engines hanging off the front) the linearity beteween control deflection and control force is lost and so additional systems are required. My understanding of the Airbus implementation of the control systems is that it effectively works in reverse and the required output (by virtue of the spring loaded joystick) is always a linear response because its filtered through the computers to achieve this.

I believe there are sticks out there that don't even move and use strain gauges on fixed sticks for control such is the lack of moment of the controls important (for an individual controller, I'm not starting that argument)

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JetBuddy
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 3:08 pm

benbeny wrote:
Why do we need to test fly a plane when we have immense computational power to simulate it?


Because the simulation only has so much data to run the simulation on.

Things like production quality defects, material defects and so on won't show up in a simulation. Things that look good on paper aren't always that good in the real world.

There's a reason all new cars are physically crash tested before being rated. A computer program might simulate it 100% correctly with the data it has, but it never has all the data and variables.
 
hivue
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 4:58 pm

benbeny wrote:
Why do we need to test fly a plane when we have immense computational power to simulate it?


This way of thinking has more similarities to the process by which Boeing got into its present mess than may at first be apparent. It's a unique malady of our times that the distinction between the real world and virtual worlds starts to get confused.
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 5:34 pm

Interesting write up on all the steps each MAX will need before it can be delivered to each customer:

https://www.forbes.com/sites/lorenthomp ... he-ground/

Seems FAA is going to be right in the middle of things yet again, since each airframe gets an individual airworthiness certificate.
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 6:53 pm

 
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SomebodyInTLS
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 6:54 pm

hivue wrote:
benbeny wrote:
Why do we need to test fly a plane when we have immense computational power to simulate it?


This way of thinking has more similarities to the process by which Boeing got into its present mess than may at first be apparent. It's a unique malady of our times that the distinction between the real world and virtual worlds starts to get confused.


Yeah, I tried to touch on that in my reply as well. Quite ironic that the response to fixing a system based on bad assumptions would be to prove the fix using a system based on more assumptions...

It is true that there are a number of people out there who believe that just because simulations exist that somehow makes them equal to nature. It really really doesn't!

And fluid dynamics (at the root of the MCAS issue, after all) remains one of the toughest things to simulate accurately. (I've mentioned it on the forum before, but one of the newer F1 teams reckoned it could do without windtunnel tests a few years ago "because of simulation"... that car tanked BADLY!)

I've just thought of a great point: literally the most powerful simulations on Earth outside of the military are employed to predict the weather... can they tell me exactly when it will start and stop raining in a month's time? Or next week Tuesday? Or even tomorrow?
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seahawk
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 7:03 pm

flipdewaf wrote:
seahawk wrote:


You do not need a linear stick force, you need a linear correlation between stick position and pitch control movement.


Not sure if this is what you mean precisely but humans are much much better at determining and counteracting force than they are position. A control of any type can be held at a constant force quite easily by most people whilst encountering a significant amount of movement or indeed with incredible finesse at small amounts of movement but ask a person to hold something still whilst encountering changing forces it is very difficult and needs concentration.

When the systems are simple and linear movement = force (mostly) but as things get complex (like big engines hanging off the front) the linearity beteween control deflection and control force is lost and so additional systems are required. My understanding of the Airbus implementation of the control systems is that it effectively works in reverse and the required output (by virtue of the spring loaded joystick) is always a linear response because its filtered through the computers to achieve this.

I believe there are sticks out there that don't even move and use strain gauges on fixed sticks for control such is the lack of moment of the controls important (for an individual controller, I'm not starting that argument)

Fred

But the force is artificial.

So there is a direct correlation between force, stick position and pitch movement. The 737 needs MCAS because there are situations where the same force and stick position creates different pitch control movements.
 
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sergegva
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 7:04 pm

asdf wrote:
in europe you never ever could expect a govermental facility to outsource primary check duties to the checked itself without a system of close monitoring what happens


Let's talk about EFSA with Monsanto...
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 7:20 pm

SomebodyInTLS wrote:
I've just thought of a great point: literally the most powerful simulations on Earth outside of the military are employed to predict the weather... can they tell me exactly when it will start and stop raining in a month's time? Or next week Tuesday? Or even tomorrow?

Not really a good comparison. Stochastic process where small change in initial parameters develops into a major thing vs fairly consistent flow over the wing.
If airplane would work same way as weather, random loss of lift would be an every day thing. Complexity of navier-stokes comes a bit differently.
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 7:25 pm

par13del wrote:


TFA says:

Replacing Mills is Conrad Chun, who was vice president of communications for Boeing Global Services, the business unit formerly led by Deal.

Chun will continue to report to Deal and Anne Toulouse, Boeing's senior vice president of communications.

Seems Deal wanted to bring Chun along with him, at least that's what one tweet I read said.

I do feel sorry for Mills. "VP of communications for Boeing Commercial Airplanes during the MAX crisis" is not a good lede on a resume.

However a Boeing VP brings in good coin, she probably can go buy a vineyard somewhere and live a much happier life.
Wake up to find out that you are the eyes of the world
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smartplane
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 7:26 pm

Revelation wrote:
Interesting write up on all the steps each MAX will need before it can be delivered to each customer:

https://www.forbes.com/sites/lorenthomp ... he-ground/

Seems FAA is going to be right in the middle of things yet again, since each airframe gets an individual airworthiness certificate.

And marks the end of WN truncated / zero CAF's?
 
smartplane
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 7:32 pm

par13del wrote:

And increased emphasis / technology to identify leaks?
 
JayinKitsap
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 7:47 pm

SomebodyInTLS wrote:
benbeny wrote:
Why do we need to test fly a plane when we have immense computational power to simulate it?


The short answer is because we *don't* have the computational power... and never will.

All simulation is based on human interpretation of what actually tends to happen in nature in real life. Unless you can build a computer model 100% accurately describing every interaction of every atom within the aircraft and all the airspace it interacts with you will always find that some assumption about how things behave or how humans behave or how manufacturing processes work in real life, etc. was not quite the same as in the real world.

Science is only as accurate as humans can make it by testing theories against the real world. And those tests bring changes... Newton becomes Einstein, the flat Earth becomes a globe, witchcraft becomes medicine. And the same with technology... the MCAS debacle is a result of assumptions not matching the real world - hence tests can never completely be replaced by simulation. QED.


Yes, never will have the computational power. Each litre of air contains 2.15×10^22 molecules, each molecule has 6 freedoms of movement, just in the airplane's path it passes thru billions of litres every second at mach .75. Flat not possible to do. So each element in a finite element model uses classical physics.
 
flipdewaf
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 8:19 pm

seahawk wrote:
flipdewaf wrote:
seahawk wrote:


You do not need a linear stick force, you need a linear correlation between stick position and pitch control movement.


Not sure if this is what you mean precisely but humans are much much better at determining and counteracting force than they are position. A control of any type can be held at a constant force quite easily by most people whilst encountering a significant amount of movement or indeed with incredible finesse at small amounts of movement but ask a person to hold something still whilst encountering changing forces it is very difficult and needs concentration.

When the systems are simple and linear movement = force (mostly) but as things get complex (like big engines hanging off the front) the linearity beteween control deflection and control force is lost and so additional systems are required. My understanding of the Airbus implementation of the control systems is that it effectively works in reverse and the required output (by virtue of the spring loaded joystick) is always a linear response because its filtered through the computers to achieve this.

I believe there are sticks out there that don't even move and use strain gauges on fixed sticks for control such is the lack of moment of the controls important (for an individual controller, I'm not starting that argument)

Fred

But the force is artificial.

So there is a direct correlation between force, stick position and pitch movement. The 737 needs MCAS because there are situations where the same force and stick position creates different pitch control movements.

Kind of, the stick force and pitch control are way more correlated than control position. It’s the same as driving you car. The mechanical logical engineering brain says move the steering wheel 6degrees and you’ll get an a arc of x meters radius, you actually drive by feeling the force on the steering wheel and equating that back to the target of the control.

Watch a video of someone landing in a crosswind, those stick movements aren’t creating big pitch movements and it’s very intuitive.

Fred


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PW100
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 8:40 pm

kalvado wrote:
SomebodyInTLS wrote:
I've just thought of a great point: literally the most powerful simulations on Earth outside of the military are employed to predict the weather... can they tell me exactly when it will start and stop raining in a month's time? Or next week Tuesday? Or even tomorrow?

Not really a good comparison. Stochastic process where small change in initial parameters develops into a major thing vs fairly consistent flow over the wing.
If airplane would work same way as weather, random loss of lift would be an every day thing. Complexity of navier-stokes comes a bit differently.


If small changes have big effects, that just means your grid size is not small enough to fit the desired outcome accuracy.

With respect to weather, if you would have sensors every 10 meters, you will find that weather will be very predictable. I'm not sure if computational power or grid size sensoring is the limiting factor.
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kalvado
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 9:05 pm

PW100 wrote:
kalvado wrote:
SomebodyInTLS wrote:
I've just thought of a great point: literally the most powerful simulations on Earth outside of the military are employed to predict the weather... can they tell me exactly when it will start and stop raining in a month's time? Or next week Tuesday? Or even tomorrow?

Not really a good comparison. Stochastic process where small change in initial parameters develops into a major thing vs fairly consistent flow over the wing.
If airplane would work same way as weather, random loss of lift would be an every day thing. Complexity of navier-stokes comes a bit differently.


If small changes have big effects, that just means your grid size is not small enough to fit the desired outcome accuracy.

With respect to weather, if you would have sensors every 10 meters, you will find that weather will be very predictable. I'm not sure if computational power or grid size sensoring is the limiting factor.

Not really, chaos theory has a different oppinion. Once you start hitting bifurcations, even high density of initial data quickly becomes useless
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 9:14 pm

JayinKitsap wrote:
SomebodyInTLS wrote:
benbeny wrote:
Why do we need to test fly a plane when we have immense computational power to simulate it?


The short answer is because we *don't* have the computational power... and never will.

All simulation is based on human interpretation of what actually tends to happen in nature in real life. Unless you can build a computer model 100% accurately describing every interaction of every atom within the aircraft and all the airspace it interacts with you will always find that some assumption about how things behave or how humans behave or how manufacturing processes work in real life, etc. was not quite the same as in the real world.

Science is only as accurate as humans can make it by testing theories against the real world. And those tests bring changes... Newton becomes Einstein, the flat Earth becomes a globe, witchcraft becomes medicine. And the same with technology... the MCAS debacle is a result of assumptions not matching the real world - hence tests can never completely be replaced by simulation. QED.


Yes, never will have the computational power. Each litre of air contains 2.15×10^22 molecules, each molecule has 6 freedoms of movement, just in the airplane's path it passes thru billions of litres every second at mach .75. Flat not possible to do. So each element in a finite element model uses classical physics.

And air is only gas: low density and relative uniformity. Now try to simulate fatigue of something as dense as the metal alloy at the atom level to take in account each phase grain boundary, with each possible force vectors, temperatures, imperfections, contamination, current flow, radiation, etc. Then try to do the same with even more complex composite materials...
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
Chemist
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Wed Nov 13, 2019 11:03 pm

§ 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. No abnormal nose-up pitching may occur. The longitudinal control force must be positive up to and throughout the stall. In addition, it must be possible to promptly prevent stalling and to recover from a stall by normal use of the controls.


25.203 requires that the plane remains controllable, the controls don't reverse, and there can't be abnormal nose-up pitching.

The reports I've read say that on the MAX the stick forces get lighter when approaching a stall without MCAS, in narrow ranges of the flight envelope and CG. That's not really the same as abnormally pitching up is it?

Contrary to the hyperbole we've read in these threads, there's never been any documented evidence that the MAX pitches up, or is unstable or uncontrollable. Only that the stick forces lighten in certain corners of the envelope when nearing stall. So that would seem to make the bolded text above something that the MAX passes without problem, even without MCAS.

If anybody has different data, please provide corrections.
 
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aerolimani
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Nov 14, 2019 12:06 am

Chemist wrote:
§ 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. No abnormal nose-up pitching may occur. The longitudinal control force must be positive up to and throughout the stall. In addition, it must be possible to promptly prevent stalling and to recover from a stall by normal use of the controls.


25.203 requires that the plane remains controllable, the controls don't reverse, and there can't be abnormal nose-up pitching.

The reports I've read say that on the MAX the stick forces get lighter when approaching a stall without MCAS, in narrow ranges of the flight envelope and CG. That's not really the same as abnormally pitching up is it?

Contrary to the hyperbole we've read in these threads, there's never been any documented evidence that the MAX pitches up, or is unstable or uncontrollable. Only that the stick forces lighten in certain corners of the envelope when nearing stall. So that would seem to make the bolded text above something that the MAX passes without problem, even without MCAS.

If anybody has different data, please provide corrections.

“Stick lightening” is a nice way of saying that the pressure is decreasing. In my books, a decrease in pressure is a movement in the negative direction. Thus, stick pressure is not remaining positive. I’m pretty sure stick lightening is not permissible under 25.203.

But hey, don’t take my word for 25.203 being applicable. Just google a few technical articles about MCAS, and you can read how 25.203 is cited in pretty much every single one. You guys seem to like Peter Lemme, so how about reviewing this in-depth article, where among others, he cites and bolds passages from 25.203: https://www.satcom.guru/2019/03/regulat ... s.html?m=1

Or, are they all wrong, these many sources citing 25.203? Are a few a.net members correct, and everyone else, including the authors of the Lion Air report, wrong?

My evidence may be a combination of my own logical surmising, combined with a whack of circumstantial evidence citing 25.203, but I feel that present a decent case. If anyone can prove me wrong, please do. I’m honestly happy to be corrected.

As to pitch-up tendency and instability, here’s R. John Hansman, an MIT professor of aeronautics, discussing the MAX:

As I understand it, at high angles of attack the Nacelles — which are the tube shaped structures around the fans — create aerodynamic lift. Because the engines are further forward, the lift tends to push the nose up — causing the angle of attack to increase further. This reinforces itself and results in a pitch-up tendency which if not corrected can result in a stall. This is called an unstable or divergent condition. It should be noted that many high performance aircraft have this tendency but it is not acceptable in transport category aircraft where there is a requirement that the aircraft is stable and returns to a steady condition if no forces are applied to the controls.

(emphasis is mine)
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Nov 14, 2019 12:54 am

Chemist wrote:
Contrary to the hyperbole we've read in these threads, there's never been any documented evidence that the MAX pitches up, or is unstable or uncontrollable.

The evidence is that MCAS commands nose down stabilizer to enhance pitch characteristics with flaps up during elevated angles of attack. (according to Boeing presentation to FAA).
Why do you think a nose down command is required, if this is not to fix a nose up pitch characteristics ?
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
DenverTed
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Nov 14, 2019 1:26 am

The pitch is too sensitive to small elevator movements or stick force at high AOA, due to whatever the curve of: upward force on the engines versus AOA looks like, probably not linear. To try to counter that, the burden of downward force on the tail was shifted more to the elevator and less to the stab by MCAS, which apparently decreased the sensitivity of elevator position to AOA in the realm in question.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Nov 14, 2019 1:39 am

PixelFlight wrote:
Why do you think a nose down command is required, if this is not to fix a nose up pitch characteristics ?

So in level flight with flaps up the autopilot is required to keep the aircraft level, so what happens if the AP is disengaged, will the pilots be able to use the electric trim or will MCAS kick in to keep the aircraft level?
How is it that so many MAX a/c were flying around and no one else encountered MCAS other than the two fatal crashes, I have to believe that there were times when pilots flew the a/c manually, if it is unstable, surely other pilots would have come forward after the crashes. Indeed a lot of the American pilots were angry that they did not know anything about MCAS. Is it taking liberties saying the MAX is unstable and MCAS is required, or the instability is only evident in certain sections of the flight envelope?
 
DenverTed
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Nov 14, 2019 1:56 am

On MCAS 1.0, were there two different trim speeds, for high speed and low speed approach to stall? Or was there just the faster trim speed for both?
 
WPIAeroGuy
Posts: 324
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Thu Nov 14, 2019 3:19 am

aerolimani wrote:
Chemist wrote:
§ 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. No abnormal nose-up pitching may occur. The longitudinal control force must be positive up to and throughout the stall. In addition, it must be possible to promptly prevent stalling and to recover from a stall by normal use of the controls.


25.203 requires that the plane remains controllable, the controls don't reverse, and there can't be abnormal nose-up pitching.

The reports I've read say that on the MAX the stick forces get lighter when approaching a stall without MCAS, in narrow ranges of the flight envelope and CG. That's not really the same as abnormally pitching up is it?

Contrary to the hyperbole we've read in these threads, there's never been any documented evidence that the MAX pitches up, or is unstable or uncontrollable. Only that the stick forces lighten in certain corners of the envelope when nearing stall. So that would seem to make the bolded text above something that the MAX passes without problem, even without MCAS.

If anybody has different data, please provide corrections.

“Stick lightening” is a nice way of saying that the pressure is decreasing. In my books, a decrease in pressure is a movement in the negative direction. Thus, stick pressure is not remaining positive. I’m pretty sure stick lightening is not permissible under 25.203.

But hey, don’t take my word for 25.203 being applicable. Just google a few technical articles about MCAS, and you can read how 25.203 is cited in pretty much every single one. You guys seem to like Peter Lemme, so how about reviewing this in-depth article, where among others, he cites and bolds passages from 25.203: https://www.satcom.guru/2019/03/regulat ... s.html?m=1

Or, are they all wrong, these many sources citing 25.203? Are a few a.net members correct, and everyone else, including the authors of the Lion Air report, wrong?

My evidence may be a combination of my own logical surmising, combined with a whack of circumstantial evidence citing 25.203, but I feel that present a decent case. If anyone can prove me wrong, please do. I’m honestly happy to be corrected.

As to pitch-up tendency and instability, here’s R. John Hansman, an MIT professor of aeronautics, discussing the MAX:

As I understand it, at high angles of attack the Nacelles — which are the tube shaped structures around the fans — create aerodynamic lift. Because the engines are further forward, the lift tends to push the nose up — causing the angle of attack to increase further. This reinforces itself and results in a pitch-up tendency which if not corrected can result in a stall. This is called an unstable or divergent condition. It should be noted that many high performance aircraft have this tendency but it is not acceptable in transport category aircraft where there is a requirement that the aircraft is stable and returns to a steady condition if no forces are applied to the controls.

(emphasis is mine)


That MIT professor is correct about the definition of longitudinal stability. However, based on my understanding as discussed in these threads, MCAS was required solely to meet the stick force gradient requirements (average gradient and no stick lightening) in the approach to stall.

The fact that the stick forces do not meet gradient requirements or get lighter at the edges of the flight envelope not necessarily mean the aircraft is unstable. It is likely that stability is reduced. A very nice explanation of stick force gradient versus longitudinal stability is discussed in this report. Note that a decrease in pressure is not the same as control reversal.

https://bura.brunel.ac.uk/bitstream/243 ... Thesis.pdf

While there is a relationship between longitudinal stability and stick force, you CANNOT say that an aircraft that doesn't meet the stick force gradient requirement is unstable. As discussed in this paper, the Cessna 150 doesn't mean the stick force gradient of 1 lbf per 6 knots specified in Part 25 (even though its a CAR3/Part 23 airplane) in several flight regimes tested, yet it would not be considered unstable.
-WPIAeroGuy

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