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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 12:23 am

maint123 wrote:
In auto mode, mcas is off but is the AOA sensor still giving feedback to the controls.?

Depend of what you define by "control".
If you are talking about the "autopilot control system", yes the AoA sensors give feedback to it.
If you are talking about the "manual control yoke" while in autopilot, no directly.
Note: The autopilot control mode will changes to CWS (Control wheel Steering) as soon as the pilot use the manual control.
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 12:37 am

rheinwaldner wrote:
morrisond wrote:
You just proved my point - yes the Lionair pilots had no idea - but by the time of ET they sure should have.

That's wrong. Boeings official memo is so thin, that they would have to rely on newspaper articles to get the crucial information that you mean. I have experienced personally how a MAX pilot made a fool of herself even after the ET crash because she resisted to accept news from the newspaper and strictly relied on Boeings information.


More evidence of a failure in the Worldwide training system as I assume your friend flies for a western airline.

Boeing issued a lot of clarifications to its operators - I would assume they (the operators) didn't pass them on to there pilots like they should have.
 
Aviation737
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 4:48 am

Can someone tell me why the MAX was a bad idea? I mean to me it makes perfect sense for them to developed it.
 
prebennorholm
Posts: 7008
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 6:02 am

phollingsworth wrote:
... The point still remains that if you could solve, totally, the 2 to 3 problem via pilot training, you would not need to solve the 1 to 2...

Absolutely wrong. Even imagining that improved crew training could guarantee 100% success rate for MCAS misfires, then we would still have the problem that an MCAS misfire would send unbuckled pax, FAs and catering carts into the ceiling and down again breaking bones and crashing sculls even on buckled pax. This is no way to do business in 21st century.

In that case - "100% success rate" - some MAXs will land with no injuries, and overall fatalities will certainly be reduced. But when the MAX becomes as common as the NG today, then there will statistically be an MCAS misfire every one or two weeks. Due to the low numbers our statistics may be way off, and one in 1 or 2 weeks could instead be one every month or one every other day. It doesn't matter. In any case it's totally unacceptable.

Nobody (I guess) denies that the accident crews had a chance to land their MAX in one piece, if only they had known what we know today, and that they had understood their situation a few hundred times faster than us. And that it would have been fabulous if 346 lives had been saved. But it is totally unrelated to the MAX being grounded today. The MAX shall be fixed to become safety wise comparable to other airliners before it shall fly again. Period.

Then we can always talk about quality of flight crew training for Boeing, Airbus, CRJ, Embraer, MDD, ATR, and Tupolev pilots around the world. There are theories enough. Some people insist that commercial pilots are system operators who shall understand every bit of their plane's function to counter any type of malfunction. Others promote that thousands of hours reading yesterday's newspaper at 30,000 feet gives the ultimate experience to solve all problems. I will leave that to the experts. As a passenger I only have a problem if pilots reach retirement before they gain hours enough to qualify as commercial pilot.
Always keep your number of landings equal to your number of take-offs
 
prebennorholm
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 6:30 am

Aviation737 wrote:
Can someone tell me why the MAX was a bad idea? I mean to me it makes perfect sense for them to developed it.

The MAX was in principle a good idea, and it makes perfect sense to develop it. Problem is that it hasn't been developed yet. And that development process became unnecessarily delayed and "expensive" (money, fatalities).

Seen in the clear view of the back mirror there is no doubt that Boeing would rather have spent a little more resources and made the MAX with naturally acceptable aerodynamic qualities instead of the MCAS band-aid. But that train has left the station. Now the issue is to develop MCAS to work properly.
Always keep your number of landings equal to your number of take-offs
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 6:31 am

morrisond wrote:
rheinwaldner wrote:
morrisond wrote:
You just proved my point - yes the Lionair pilots had no idea - but by the time of ET they sure should have.

That's wrong. Boeings official memo is so thin, that they would have to rely on newspaper articles to get the crucial information that you mean. I have experienced personally how a MAX pilot made a fool of herself even after the ET crash because she resisted to accept news from the newspaper and strictly relied on Boeings information.


More evidence of a failure in the Worldwide training system as I assume your friend flies for a western airline.

Boeing issued a lot of clarifications to its operators - I would assume they (the operators) didn't pass them on to there pilots like they should have.


What clarification? When did Boeing start to explain MCAS?

Did it completely bypass you, that Boeing sabotaged every possibility of training for MCAS? That Boeing purposefully castrated available MAX simulators, so they would not show those dangerous failure modes?

If Boeing did anything, than Boeing obstructed possible training, did hide the existing of MCAS still after the Lion Air crash and lied about the MAX being a safe airplane.
 
astuteman
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 9:05 am

Aviation737 wrote:
Can someone tell me why the MAX was a bad idea? I mean to me it makes perfect sense for them to developed it.


We have an ongoing debate at work about being able to differentiate between "bad strategy" and "bad execution".

For me, the MAX falls into the latter.
I don't think it was a bad idea as such. It appears that Boeing's sprint to the finish line was a bit too rushed.
It does appear that the larger models operate at a disadvantage to the A321NEO.
But at least until 2019 the MAX had secured c. 5000 orders and about 45% of the market from the time of its launch.
Not ideal, but a very solid return for a relatively small investment.

I do feel that the barriers to exit from these huge programmes (A320 and 737) are seriously underrated on here.
The sheer commoditisation of these 2 programmes means that the whole air travel infrastructure knows exactly what to do when one of these planes rocks up.
Rebuilding all that infrastructure with a new model will have to happen some day, but it will bring pain as well as reward.

Rgds
 
jmry888
Posts: 30
Joined: Mon Jun 03, 2019 2:39 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 10:28 am

My friends and myself still refuse to believe that mcas took control of those 2 737 max's just at take off and flew them unitl it got tired and then crashed them. Pilots were of no use at all is what we read on this thread. This is what is presented on this thread to us.

Now how come Sothwest and others have over 40,000 flights covering almost 90,000 hours and not one crash or emerengcy landing. Something is not right here. We realize that this is a foreign web site / forum so opionions are going to be against Boeing no matter what.

All we are asking all you experts posting on this thread please enlighten us about why the no crashes over here and the crashes over there. There is at least 6 times the flight hours over here compared to those 2. One would think this would happen everywhere if what this thread is saying is true.
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 11:06 am

prebennorholm wrote:
Aviation737 wrote:
Can someone tell me why the MAX was a bad idea? I mean to me it makes perfect sense for them to developed it.

The MAX was in principle a good idea, and it makes perfect sense to develop it. Problem is that it hasn't been developed yet. And that development process became unnecessarily delayed and "expensive" (money, fatalities).

Seen in the clear view of the back mirror there is no doubt that Boeing would rather have spent a little more resources and made the MAX with naturally acceptable aerodynamic qualities instead of the MCAS band-aid. But that train has left the station. Now the issue is to develop MCAS to work properly.


Of course the MAX was a good idea. Fast to market and staying in competition with the A320 family.

But the idea started to go wrong, when the no change grandfathering philosophy went several steps to far. The change from the NG to MAX was done with restriction in place. No change of type and no training necessary to move from NG to MAX, the "no training requirement" was sold to Southwest and possible to other airlines like Norwegian and RyanAir.
Those two requirements trump technical considerations and common sense. Add to that a haste to get the frame to market.

Instead of using the change of model to clean out old exemptions, the FAA allowed Boeing to keep 20 to over 30 years old exemptions from rules in place, the moment Boeing cried, that it would cost money to comply.
 
mjoelnir
Posts: 8945
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 11:33 am

jmry888 wrote:
My friends and myself still refuse to believe that mcas took control of those 2 737 max's just at take off and flew them unitl it got tired and then crashed them. Pilots were of no use at all is what we read on this thread. This is what is presented on this thread to us.

Now how come Sothwest and others have over 40,000 flights covering almost 90,000 hours and not one crash or emerengcy landing. Something is not right here. We realize that this is a foreign web site / forum so opionions are going to be against Boeing no matter what.

All we are asking all you experts posting on this thread please enlighten us about why the no crashes over here and the crashes over there. There is at least 6 times the flight hours over here compared to those 2. One would think this would happen everywhere if what this thread is saying is true.


As you post here on a US American site, with the majority of poster being US citizen, I am slightly astonished you feel to be on a,( what do you call it?), foreign site.

The frames crashed when an AoA sensor failed high. It just happened to the Lion Air and Ethiopian frames and not to the for example Southwest frames.

If you are further astonished about why those frames crashed, I would recommend to you to start reading the Lion Air crash report.

http://knkt.dephub.go.id/knkt/ntsc_home/ntsc.htm

and perhaps the preliminary report for the ET crash

http://www.ecaa.gov.et/Home/wp-content/ ... ET-AVJ.pdf

I would recommend reading those, before you bring more conspiracy theories, about the foreigners beating up on old poor Boeing.
 
P1aneMad
Posts: 393
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 11:42 am

jmry888 wrote:
My friends and myself still refuse to believe that mcas took control of those 2 737 max's just at take off and flew them unitl it got tired and then crashed them. Pilots were of no use at all is what we read on this thread. This is what is presented on this thread to us.

Now how come Sothwest and others have over 40,000 flights covering almost 90,000 hours and not one crash or emerengcy landing. Something is not right here. We realize that this is a foreign web site / forum so opionions are going to be against Boeing no matter what.

All we are asking all you experts posting on this thread please enlighten us about why the no crashes over here and the crashes over there. There is at least 6 times the flight hours over here compared to those 2. One would think this would happen everywhere if what this thread is saying is true.

Denial is not a river in Egypt.
Educate yourself!

My Letter to the Editor of New York Times Magazine

Letter to the Editor
Capt. “Sully” Sullenberger
New York Times Magazine
Published in print on October 13, 2019

In “What Really Brought Down the Boeing 737 MAX?” William Langewiesche draws the conclusion that the pilots are primarily to blame for the fatal crashes of Lion Air 610 and Ethiopian 302. In resurrecting this age-old aviation canard, Langewiesche minimizes the fatal design flaws and certification failures that precipitated those tragedies, and still pose a threat to the flying public. I have long stated, as he does note, that pilots must be capable of absolute mastery of the aircraft and the situation at all times, a concept pilots call airmanship. Inadequate pilot training and insufficient pilot experience are problems worldwide, but they do not excuse the fatally flawed design of the Maneuvering Characteristics Augmentation System (MCAS) that was a death trap.

As one of the few pilots who have lived to tell about being in the left seat of an airliner when things went horribly wrong, with seconds to react, I know a thing or two about overcoming an unimagined crisis. I am also one of the few who have flown a Boeing 737 MAX Level D full motion simulator, replicating both accident flights multiple times. I know firsthand the challenges the pilots on the doomed accident flights faced, and how wrong it is to blame them for not being able to compensate for such a pernicious and deadly design. These emergencies did not present as a classic runaway stabilizer problem, but initially as ambiguous unreliable airspeed and altitude situations, masking MCAS. The MCAS design should never have been approved, not by Boeing, and not by the Federal Aviation Administration (FAA).

The National Transportation Safety Board has found that Boeing made faulty assumptions both about the capability of the aircraft design to withstand damage or failure, and the level of human performance possible once the failures began to cascade. Where Boeing failed, the Federal Aviation Administration (FAA) should have stepped in to regulate but it failed to do so. Lessons from accidents are bought in blood and we must seek all the answers to prevent the next one. We need to fix all the flaws in the current system — corporate governance, regulatory oversight, aircraft maintenance, and yes, pilot training and experience. Only then can we ensure the safety of everyone who flies.

Capt. “Sully” Sullenberger

http://www.sullysullenberger.com/my-letter-to-the-editor-of-new-york-times-magazine/

Have a nice day.
 
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scbriml
Posts: 17817
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 12:02 pm

jmry888 wrote:
My friends and myself still refuse to believe that mcas took control of those 2 737 max's just at take off and flew them unitl it got tired and then crashed them. Pilots were of no use at all is what we read on this thread. This is what is presented on this thread to us.

Now how come Sothwest and others have over 40,000 flights covering almost 90,000 hours and not one crash or emerengcy landing. Something is not right here. We realize that this is a foreign web site / forum so opionions are going to be against Boeing no matter what.

All we are asking all you experts posting on this thread please enlighten us about why the no crashes over here and the crashes over there. There is at least 6 times the flight hours over here compared to those 2. One would think this would happen everywhere if what this thread is saying is true.


Do you and your friends know how many times US MAX pilots have faced the same issues that Lion and Ethiopian faced? It should be remembered that US MAX crews were less than impressed when they learned they’d been kept in the dark regarding MCAS. It also appears that one of those highly trained and vastly experienced American crews recently flew a perfectly serviceable 767 nose-first into the ground.

Despite any differences between pilots “over here” and “over there”, it’s the World’s aviation authorities that have unanimously grounded MAX and demanded that Boeing fix it. That the MAX is still grounded is an indication of how difficult (despite Boeing’s initial optimism) fixing MAX is proving to be.

Are you and your friends of the view there’s nothing wrong with MAX and it should never have been grounded?
Time flies like an arrow. Fruit flies like a banana!
There are 10 types of people in the World - those that understand binary and those that don't.
 
jmry888
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 12:25 pm

scbriml - Where are the crashes over here ? The shear number of flight hours should suggest at least 4 crashes / crash landings etc . But there are none so please explain . Our opionion is the 737 max should have been grounded where the 2 airlines were not all over the world. You said - Do you and your friends know how many times US MAX pilots have faced the same issues that Lion and Ethiopian faced? the difference is they are still walking and talking . In our opionion those 2 flights were 70 percent pilot error , 20 percent airline maintenance error aand 10 percent aircraft. What worlds aviation aurthorities ? Everyone on the 2 investigation boards worked for government agencies here and over there.

Well you still have not explained the huge i mean huge difference in flight hours with no crashes to the 2 over there. Those 2 airlines combined did not have even one third the flight hours on the 737 max that others have with no crashes.
 
maint123
Posts: 255
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 12:31 pm

PixelFlight wrote:
maint123 wrote:
In auto mode, mcas is off but is the AOA sensor still giving feedback to the controls.?

Depend of what you define by "control".
If you are talking about the "autopilot control system", yes the AoA sensors give feedback to it.
If you are talking about the "manual control yoke" while in autopilot, no directly.
Note: The autopilot control mode will changes to CWS (Control wheel Steering) as soon as the pilot use the manual control.

So in auto if the AOA sensor starts misbehaving, will the plane again start triming down ? And in the case of Max 1.0 , if the pilot notices that the plane is trimming down, and switches auto off, we are back to square one?
My point being even in auto, max would face the same situation.
Saving grace could be that auto is switched on at a much higher altitude and the pilots would have had much more time to recover
 
FluidFlow
Posts: 419
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 12:40 pm

jmry888 wrote:
scbriml - Where are the crashes over here ? The shear number of flight hours should suggest at least 4 crashes / crash landings etc . But there are none so please explain . Our opionion is the 737 max should have been grounded where the 2 airlines were not all over the world. You said - Do you and your friends know how many times US MAX pilots have faced the same issues that Lion and Ethiopian faced? the difference is they are still walking and talking . In our opionion those 2 flights were 70 percent pilot error , 20 percent airline maintenance error aand 10 percent aircraft. What worlds aviation aurthorities ? Everyone on the 2 investigation boards worked for government agencies here and over there.

Well you still have not explained the huge i mean huge difference in flight hours with no crashes to the 2 over there. Those 2 airlines combined did not have even one third the flight hours on the 737 max that others have with no crashes.


https://www.cbsnews.com/news/alaska-plane-crash-peninsula-airways-flight-crashes-unalaska-2-critically-injured-today-2019-10-18/
https://en.wikipedia.org/wiki/Miami_Air_Flight_293
https://en.wikipedia.org/wiki/Atlas_Air_Flight_3591
https://en.wikipedia.org/wiki/Taquan_Air_Flight_20

That are just the ones I have in my memory.
 
morrisond
Posts: 1816
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 12:45 pm

prebennorholm wrote:
phollingsworth wrote:
... The point still remains that if you could solve, totally, the 2 to 3 problem via pilot training, you would not need to solve the 1 to 2...

Absolutely wrong. Even imagining that improved crew training could guarantee 100% success rate for MCAS misfires, then we would still have the problem that an MCAS misfire would send unbuckled pax, FAs and catering carts into the ceiling and down again breaking bones and crashing sculls even on buckled pax. This is no way to do business in 21st century.


If that is what you think happens to the plane when MCAS is activated then you don't understand MCAS - it trims the Horizontal stabilizer at a rate barely more than electric trim.

Unless of course you think using electric trim would cause the same result. Wait a second - Eureka - you found they answer why 3 out of the 4 pilots were so reluctant to use Electric Trim - they thought it would break bones....
 
Ertro
Posts: 61
Joined: Thu Apr 04, 2019 9:28 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 12:45 pm

jmry888 wrote:
Where are the crashes over here ? The shear number of flight hours should suggest at least 4 crashes / crash landings etc . But there are none so please explain


Looking at wikipedia there are total of 423 MAXes delivered and from those 34 are with SW, 24 with AA and 12 with United.
16% of MAXes are in USA and 84% outside USA.
Tell me whether the fact that the 2 crashes occurred among those 84% of MAXes that are outside USA instead of the 16% of MAXes that are inside USA is some kind of strange anomaly?
Last edited by Ertro on Fri Nov 29, 2019 1:02 pm, edited 3 times in total.
 
morrisond
Posts: 1816
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 12:47 pm

P1aneMad wrote:
jmry888 wrote:
My friends and myself still refuse to believe that mcas took control of those 2 737 max's just at take off and flew them unitl it got tired and then crashed them. Pilots were of no use at all is what we read on this thread. This is what is presented on this thread to us.

Now how come Sothwest and others have over 40,000 flights covering almost 90,000 hours and not one crash or emerengcy landing. Something is not right here. We realize that this is a foreign web site / forum so opionions are going to be against Boeing no matter what.

All we are asking all you experts posting on this thread please enlighten us about why the no crashes over here and the crashes over there. There is at least 6 times the flight hours over here compared to those 2. One would think this would happen everywhere if what this thread is saying is true.

Denial is not a river in Egypt.
Educate yourself!

My Letter to the Editor of New York Times Magazine

Letter to the Editor
Capt. “Sully” Sullenberger
New York Times Magazine
Published in print on October 13, 2019

In “What Really Brought Down the Boeing 737 MAX?” William Langewiesche draws the conclusion that the pilots are primarily to blame for the fatal crashes of Lion Air 610 and Ethiopian 302. In resurrecting this age-old aviation canard, Langewiesche minimizes the fatal design flaws and certification failures that precipitated those tragedies, and still pose a threat to the flying public. I have long stated, as he does note, that pilots must be capable of absolute mastery of the aircraft and the situation at all times, a concept pilots call airmanship. Inadequate pilot training and insufficient pilot experience are problems worldwide, but they do not excuse the fatally flawed design of the Maneuvering Characteristics Augmentation System (MCAS) that was a death trap.

As one of the few pilots who have lived to tell about being in the left seat of an airliner when things went horribly wrong, with seconds to react, I know a thing or two about overcoming an unimagined crisis. I am also one of the few who have flown a Boeing 737 MAX Level D full motion simulator, replicating both accident flights multiple times. I know firsthand the challenges the pilots on the doomed accident flights faced, and how wrong it is to blame them for not being able to compensate for such a pernicious and deadly design. These emergencies did not present as a classic runaway stabilizer problem, but initially as ambiguous unreliable airspeed and altitude situations, masking MCAS. The MCAS design should never have been approved, not by Boeing, and not by the Federal Aviation Administration (FAA).

The National Transportation Safety Board has found that Boeing made faulty assumptions both about the capability of the aircraft design to withstand damage or failure, and the level of human performance possible once the failures began to cascade. Where Boeing failed, the Federal Aviation Administration (FAA) should have stepped in to regulate but it failed to do so. Lessons from accidents are bought in blood and we must seek all the answers to prevent the next one. We need to fix all the flaws in the current system — corporate governance, regulatory oversight, aircraft maintenance, and yes, pilot training and experience. Only then can we ensure the safety of everyone who flies.

Capt. “Sully” Sullenberger

http://www.sullysullenberger.com/my-letter-to-the-editor-of-new-york-times-magazine/

Have a nice day.


Read the last two sentences of Sully's letter. I've been told those are always the most important and sum up the letter.
 
phollingsworth
Posts: 703
Joined: Sat Mar 06, 2004 6:05 am

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 12:54 pm

prebennorholm wrote:
phollingsworth wrote:
... The point still remains that if you could solve, totally, the 2 to 3 problem via pilot training, you would not need to solve the 1 to 2...

Absolutely wrong. Even imagining that improved crew training could guarantee 100% success rate for MCAS misfires, then we would still have the problem that an MCAS misfire would send unbuckled pax, FAs and catering carts into the ceiling and down again breaking bones and crashing sculls even on buckled pax. This is no way to do business in 21st century.

In that case - "100% success rate" - some MAXs will land with no injuries, and overall fatalities will certainly be reduced. But when the MAX becomes as common as the NG today, then there will statistically be an MCAS misfire every one or two weeks. Due to the low numbers our statistics may be way off, and one in 1 or 2 weeks could instead be one every month or one every other day. It doesn't matter. In any case it's totally unacceptable.

Nobody (I guess) denies that the accident crews had a chance to land their MAX in one piece, if only they had known what we know today, and that they had understood their situation a few hundred times faster than us. And that it would have been fabulous if 346 lives had been saved. But it is totally unrelated to the MAX being grounded today. The MAX shall be fixed to become safety wise comparable to other airliners before it shall fly again. Period.

Then we can always talk about quality of flight crew training for Boeing, Airbus, CRJ, Embraer, MDD, ATR, and Tupolev pilots around the world. There are theories enough. Some people insist that commercial pilots are system operators who shall understand every bit of their plane's function to counter any type of malfunction. Others promote that thousands of hours reading yesterday's newspaper at 30,000 feet gives the ultimate experience to solve all problems. I will leave that to the experts. As a passenger I only have a problem if pilots reach retirement before they gain hours enough to qualify as commercial pilot.


You missed my point, in safety you must be willing to discuss all aspects simultaneously. There are no magic bullets, but ignoring 2-3 in the case of the MAX is poor. One of the reasons is simply ignoring 2-3 is part of what creates 1-2. With aircraft it is almost never a purely hardware-software issue, it almost always involves the human being and how they react to emerging situations. If we could solve the human being reaction (unlikely to ever occur) then we could use much simpler hardware and lots of other issues go away.

The fact is you don't have to react 100s of times faster to MCAS1.0 to avoid a catastrophic accident or even a hazardous outcome. However, the allowable variation in reaction is quite small. This is what is critical to the safety analysis. How resilient is the system to variations in pilot response. If the answer is not very, then that greatly increases the likelihood of bad outcomes.

As for how often we would see these accidents. That is a Bayesian question, and not one that can be answered with solely the information contained on the graph. The observed failure rate can help us adjust our posterior estimate of likelihood, but it isn't the posterior likelihood. This is because we are not totally ignorant of the system. We know much about the MAX and the aircraft's behaviour over the vast majority of the flight envelope. These have been quite well explored, either directly or through analogy. We actually have very high confidence in the failure rate of AoA sensors. The reason for this is that the sensor is used on lots of other aircraft. Boeing assumes that the failure rate will be 1E-5 per flight hour. This is a bad assumption, though not for the reasons many people would think. The observed failure rate is approximately 1E-7 per flight hour (my understanding is this is the fail to a valid but incorrect reading rate vs signal disappearing). That is 100 times less often. The failure rates for the sensors on the MAX haven't really shifted this number as the installation is the same as on the NGs (the difference is in the additional use of the Captain's sensor). If the failure rate is 1E-5 and an average aircraft flies 120 hours/week. Then you need a fleet of about 400 aircraft to see the failure roughly every 2 weeks (it's actually a 1:417 chance that any aircraft would see the failure in a 2-week period). However, if the rate is closer to the actually observed 1E-7, you would need a fleet of over 40,000 to see the same rate (again it is actually a 1:41667 change that any one aircraft would see the failure in a 2-week period). The question that then needs to be asked, in both cases, is this acceptable? The answer would almost definitely be no for the first case, and probably not for the second. However, to answer that you would have to have more information, ie the information on what you believe the probabilities of different outcomes are given the failure. Again these are informed by the observed MAX information, but are not fully determined by it.

So what is the question we and the regulators must be asking before they sign off RTS of the MAX. It is not "Has the MAX demonstrated it is as safe as the existing overall fleet?" Which is what saying it has to get down to the number shown in the graph asks. Note: The metric use in the graph here is also inappropriate as it adds some external variables that, e.g. passengers per flight and distance of that flight, that don't really have any meaning to you or I choosing to fly. The question is "Do we believe that the MAX accident rate will be sufficiently low to make its RTS/my flight worth taking?" The answer to that question is, by definition, different for each individual and different for each regulator.
 
User avatar
PixelFlight
Posts: 795
Joined: Thu Nov 08, 2018 11:09 pm

Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 1:12 pm

maint123 wrote:
PixelFlight wrote:
maint123 wrote:
In auto mode, mcas is off but is the AOA sensor still giving feedback to the controls.?

Depend of what you define by "control".
If you are talking about the "autopilot control system", yes the AoA sensors give feedback to it.
If you are talking about the "manual control yoke" while in autopilot, no directly.
Note: The autopilot control mode will changes to CWS (Control wheel Steering) as soon as the pilot use the manual control.

So in auto if the AOA sensor starts misbehaving, will the plane again start triming down ? And in the case of Max 1.0 , if the pilot notices that the plane is trimming down, and switches auto off, we are back to square one?
My point being even in auto, max would face the same situation.
Saving grace could be that auto is switched on at a much higher altitude and the pilots would have had much more time to recover

The autopilot compare the two AoA sensors and will disengage itself if there is a disagreement.

This is in fact exactly what happened to JT043, JT610 and ET302: The erratic high left AoA value was found in disagreement with the right AoA by the autopilot, so it disengaged itself forcing the manual flight mode, where the MCAS only use the single erratic high left AoA value to trim the horizontal stabilizer nose down with high authority. If the autopilot did have a third AoA input (a backup sensor or a synthetic sensor), the autopilot would have been able to stay engaged and the pilots would have just noticed a left AoA failure message, as long as there would have not enter in manual flight mode. Note: the erratic left AoA value also caused a speed disagree because the AoA value is used to correct the speed value, this explain why the pilots was focusing at the speed disagree message first, because there didn't have the AoA disagree message that Boeing have removed to make it a paying option. But the manual flight mode would still be highly risky with a MCAS v1 and an erratic high left AoA value, so the need of a proper solution to fix it.

This all show how fragile is the 737-8/9 MAX flight control system when it have to compete with FBW architecture on high end feature like maneuvering augmentation. The Ethiopian Airline CEO was probable right at saying that the 737-8/9 MAX flight control system have to be completely redesigned. And for sure this can be done with the Boeing internal competences that have designed the 777 and the 787. Would be a 737 FBW with a new type rating, but honestly I doubt this can be a serious idea right now.
Last edited by PixelFlight on Fri Nov 29, 2019 1:18 pm, edited 1 time in total.
 
P1aneMad
Posts: 393
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 1:12 pm

morrisond wrote:
P1aneMad wrote:
jmry888 wrote:
My friends and myself still refuse to believe that mcas took control of those 2 737 max's just at take off and flew them unitl it got tired and then crashed them. Pilots were of no use at all is what we read on this thread. This is what is presented on this thread to us.

Now how come Sothwest and others have over 40,000 flights covering almost 90,000 hours and not one crash or emerengcy landing. Something is not right here. We realize that this is a foreign web site / forum so opionions are going to be against Boeing no matter what.

All we are asking all you experts posting on this thread please enlighten us about why the no crashes over here and the crashes over there. There is at least 6 times the flight hours over here compared to those 2. One would think this would happen everywhere if what this thread is saying is true.

Denial is not a river in Egypt.
Educate yourself!

My Letter to the Editor of New York Times Magazine

Letter to the Editor
Capt. “Sully” Sullenberger
New York Times Magazine
Published in print on October 13, 2019

In “What Really Brought Down the Boeing 737 MAX?” William Langewiesche draws the conclusion that the pilots are primarily to blame for the fatal crashes of Lion Air 610 and Ethiopian 302. In resurrecting this age-old aviation canard, Langewiesche minimizes the fatal design flaws and certification failures that precipitated those tragedies, and still pose a threat to the flying public. I have long stated, as he does note, that pilots must be capable of absolute mastery of the aircraft and the situation at all times, a concept pilots call airmanship. Inadequate pilot training and insufficient pilot experience are problems worldwide, but they do not excuse the fatally flawed design of the Maneuvering Characteristics Augmentation System (MCAS) that was a death trap.

As one of the few pilots who have lived to tell about being in the left seat of an airliner when things went horribly wrong, with seconds to react, I know a thing or two about overcoming an unimagined crisis. I am also one of the few who have flown a Boeing 737 MAX Level D full motion simulator, replicating both accident flights multiple times. I know firsthand the challenges the pilots on the doomed accident flights faced, and how wrong it is to blame them for not being able to compensate for such a pernicious and deadly design. These emergencies did not present as a classic runaway stabilizer problem, but initially as ambiguous unreliable airspeed and altitude situations, masking MCAS. The MCAS design should never have been approved, not by Boeing, and not by the Federal Aviation Administration (FAA).

The National Transportation Safety Board has found that Boeing made faulty assumptions both about the capability of the aircraft design to withstand damage or failure, and the level of human performance possible once the failures began to cascade. Where Boeing failed, the Federal Aviation Administration (FAA) should have stepped in to regulate but it failed to do so. Lessons from accidents are bought in blood and we must seek all the answers to prevent the next one. We need to fix all the flaws in the current system — corporate governance, regulatory oversight, aircraft maintenance, and yes, pilot training and experience. Only then can we ensure the safety of everyone who flies.

Capt. “Sully” Sullenberger

http://www.sullysullenberger.com/my-letter-to-the-editor-of-new-york-times-magazine/

Have a nice day.


Read the last two sentences of Sully's letter. I've been told those are always the most important and sum up the letter.


The National Transportation Safety Board has found that Boeing made faulty assumptions both about the capability of the aircraft design to withstand damage or failure, and the level of human performance possible once the failures began to cascade. Where Boeing failed, the Federal Aviation Administration (FAA) should have stepped in to regulate but it failed to do so. Lessons from accidents are bought in blood and we must seek all the answers to prevent the next one. We need to fix all the flaws in the current system — corporate governance, regulatory oversight, aircraft maintenance, and yes, pilot training and experience. Only then can we ensure the safety of everyone who flies.

Yes, in addition to all others pilot training on issues not mentioned by the manufacturer is needed.
Especially when transitioning from the 737NG to the MAX was (deceptively and fraudulently) made out to be as simple as spending no more than two hours on an iPad "training" presentation....
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 1:14 pm

jmry888 wrote:
scbriml - Where are the crashes over here ? The shear number of flight hours should suggest at least 4 crashes / crash landings etc . But there are none so please explain . Our opionion is the 737 max should have been grounded where the 2 airlines were not all over the world. You said - Do you and your friends know how many times US MAX pilots have faced the same issues that Lion and Ethiopian faced? the difference is they are still walking and talking . In our opionion those 2 flights were 70 percent pilot error , 20 percent airline maintenance error aand 10 percent aircraft. What worlds aviation aurthorities ? Everyone on the 2 investigation boards worked for government agencies here and over there.

Well you still have not explained the huge i mean huge difference in flight hours with no crashes to the 2 over there. Those 2 airlines combined did not have even one third the flight hours on the 737 max that others have with no crashes.

There are no records of AoA High/MCAS activation except on those 2 aircraft where the resultant was a crash. This is the position of the FAA. This has been reported several times.

In case you are concerned, the FAA is a US regulation agency, not pesky foreigners.
 
phollingsworth
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 1:15 pm

FluidFlow wrote:
jmry888 wrote:
scbriml - Where are the crashes over here ? The shear number of flight hours should suggest at least 4 crashes / crash landings etc . But there are none so please explain . Our opionion is the 737 max should have been grounded where the 2 airlines were not all over the world. You said - Do you and your friends know how many times US MAX pilots have faced the same issues that Lion and Ethiopian faced? the difference is they are still walking and talking . In our opionion those 2 flights were 70 percent pilot error , 20 percent airline maintenance error aand 10 percent aircraft. What worlds aviation aurthorities ? Everyone on the 2 investigation boards worked for government agencies here and over there.

Well you still have not explained the huge i mean huge difference in flight hours with no crashes to the 2 over there. Those 2 airlines combined did not have even one third the flight hours on the 737 max that others have with no crashes.


https://www.cbsnews.com/news/alaska-plane-crash-peninsula-airways-flight-crashes-unalaska-2-critically-injured-today-2019-10-18/
https://en.wikipedia.org/wiki/Miami_Air_Flight_293
https://en.wikipedia.org/wiki/Atlas_Air_Flight_3591
https://en.wikipedia.org/wiki/Taquan_Air_Flight_20

That are just the ones I have in my memory.


Following on to FluidFlow's resposnse. There is no such thing as pilot error. Sorry, it does not exist, at least not in the sense that people think it does. Pilots react to situations based on a lot of different things, training being a large one. However, there is no guarantee, nor should there be too much of an expectation, that all pilots will react the "correct" way. One of the purposes of training is to minimise the variability in pilot reaction. Aircraft are human-machine systems, and the safety of these systems must be considered in the whole. Keep in mind the likelihood in any given flight hour that the Captain's AoA sensor will fail and fail high, is extremely low, ie ~1E-7 (Boeing uses 1E-5 as the blanket in their analysis). This is commensurate with likelihood of the Pitot System failing in a similar way. We could have gone years without seeing the Ethiopian accident, or we could have had two in near succession. The LionAir is a different kettle of fish as the maintenance programme failed to diagnose a "bad" sensor and fix it. This is no longer a random failure, it is built into each and every operation of that aircraft. As long as that issue was allowed to persist it greatly increased the likelihood of a catastrophic event occurring, even without MCAS. The issue with MCAS1.0 as implemented, including the Boeing designed training regime, is that the pilot response was way too variable to the failure mode and this variability greatly overlaps with chains that lead to a crash. Boeing, in their flawed FHA, and all that followed, put together a system that actually increased the likelihood that pilot actions in event of a failure would lead to a catastrophic outcome.

Keep in mind there have been a number of Speed Trim System (STS) runaways on 737NGs. None have been catastrophic. The likelihood of them happening is about the same as this type of MCAS failure. This is because the training adequately covers this and the system behaves differently when it fails.
 
astuteman
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 1:27 pm

jmry888 wrote:
scbriml - Where are the crashes over here ? The shear number of flight hours should suggest at least 4 crashes / crash landings etc . But there are none so please explain . Our opionion is the 737 max should have been grounded where the 2 airlines were not all over the world. You said - Do you and your friends know how many times US MAX pilots have faced the same issues that Lion and Ethiopian faced? the difference is they are still walking and talking . In our opionion those 2 flights were 70 percent pilot error , 20 percent airline maintenance error aand 10 percent aircraft. What worlds aviation aurthorities ? Everyone on the 2 investigation boards worked for government agencies here and over there.

Well you still have not explained the huge i mean huge difference in flight hours with no crashes to the 2 over there. Those 2 airlines combined did not have even one third the flight hours on the 737 max that others have with no crashes.


I'll try and explain the huge difference in flight hours if it will help. The Air safety databases say the MAX fleet made c. 650 000 flights worldwide before the grounding.

http://www.airsafe.com/events/models/rate_mod.htm

You think that 40 000 of those flights were in the USA - i.e. about 6% of flights.

Ertro posted where the delivered MAX's have gone - c. 16% of the delivered fleet going to US airlines

Either way, the HUGE difference in flight hours you refer to is biased the other way, i.e. outside the USA.
Can you point to a US case where the AOA sensor has failed as it did on the Lionair and Ethiopian flights?
It is entirely plausible that no such failure had occurred in the USA up to that point, so no US pilot has been exposed to it.

It is equally inevitable that at some point it would occur in the USA, given the failure rate stats for an AOA sensor.

And given that the STUPID architecture was not only dependent upon that single sensor, but was also INSANELY designed to ACTIVATE when the sensor failed - AGAIN AND AGAIN AND AGAIN…….
...it is entirely plausible that the outcome might have been exactly the same - US pilot or no US pilot.

That one bolded sentence above is why a lot of posters who are bigger fans of Boeing than I am are frustrated by what they have done.
No sane engineer alive today would consider that a rational solution for a safety system.

I might suggest that you and your friends might want to work your way past the defensive jingoism and take an objective look at the statistics, and the circumstances, before adopting the role of representatives of the "injured" party.

If it helps massage that nationalism somewhat, the thing that makes this really hurt is the world class safety record of every other Boeing model flying today - in the hands of the same pilots and maintenance teams, it has to be said.
Boeing DO know how to do this.
They just failed in this instance - with catastrophic consequences.

Rgds
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 1:36 pm

phollingsworth wrote:
Keep in mind there have been a number of Speed Trim System (STS) runaways on 737NGs. None have been catastrophic. The likelihood of them happening is about the same as this type of MCAS failure. This is because the training adequately covers this and the system behaves differently when it fails.

I disagree. The STS can't generate a nose down command input with the same rate, duration and schedule as the MCAS. This is proved by the JTAR:

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. The possibility of a pitch-up tendency during approach to stall was
identified for the flaps-up configuration prior to the implementation of MCAS.

In addition, the STS did not reset after 5 seconds of any manual electric stab trim, something that no pilots was ever formally trained for, worldwide. Not counting that the cockpit situation of the two 737-8/9 MAX crashes was far from a simple runaway.
 
phollingsworth
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 1:45 pm

PixelFlight wrote:
maint123 wrote:
PixelFlight wrote:
Depend of what you define by "control".
If you are talking about the "autopilot control system", yes the AoA sensors give feedback to it.
If you are talking about the "manual control yoke" while in autopilot, no directly.
Note: The autopilot control mode will changes to CWS (Control wheel Steering) as soon as the pilot use the manual control.

So in auto if the AOA sensor starts misbehaving, will the plane again start triming down ? And in the case of Max 1.0 , if the pilot notices that the plane is trimming down, and switches auto off, we are back to square one?
My point being even in auto, max would face the same situation.
Saving grace could be that auto is switched on at a much higher altitude and the pilots would have had much more time to recover

The autopilot compare the two AoA sensors and will disengage itself if there is a disagreement.

This is in fact exactly what happened to JT043, JT610 and ET302: The erratic high left AoA value was found in disagreement with the right AoA by the autopilot, so it disengaged itself forcing the manual flight mode, where the MCAS only use the single erratic high left AoA value to trim the horizontal stabilizer nose down with high authority. If the autopilot did have a third AoA input (a backup sensor or a synthetic sensor), the autopilot would have been able to stay engaged and the pilots would have just noticed a left AoA failure message, as long as there would have not enter in manual flight mode. Note: the erratic left AoA value also caused a speed disagree because the AoA value is used to correct the speed value, this explain why the pilots was focusing at the speed disagree message first, because there didn't have the AoA disagree message that Boeing have removed to make it a paying option. But the manual flight mode would still be highly risky with a MCAS v1 and an erratic high left AoA value, so the need of a proper solution to fix it.

This all show how fragile is the 737-8/9 MAX flight control system when it have to compete with FBW architecture on high end feature like maneuvering augmentation. The Ethiopian Airline CEO was probable right at saying that the 737-8/9 MAX flight control system have to be completely redesigned. And for sure this can be done with the Boeing internal competences that have designed the 777 and the 787. Would be a 737 FBW with a new type rating.


What about the 737MAX would require a complete redesign of the flight-control system (keep in mind parts of it were already redesigned)? This is separate from a complete redesign might be a reasonable idea. Some things we are pretty sure know about the 737MAX from the evidence in released reports:
  • The 737MAX naturally exhibits unacceptable stick lightening in wind-up turns. Such that there is too high of a likelihood that this will be exhibited on any given flight. This was not easily solved with aerodynamic modifications – Hence MCAS0.9
  • The 737MAX naturally exhibits poor unaugmented stall identification in wings-level flight. This is standard for all modern jetliner, including 757, A320, A330, and 737NG. They just tend to mush about. Hence the Speed Trim System on both the 757 and 737NG, and the envelope protection on the Airbus aircraft. The MAX is worse than the 737NG and could not quickly be made to behave the same way by tiny changes – Hence MCAS1.0
  • MCAS1.0 changed the failure mode and required response to what Boeing viewed as a run of the mill STS failure. Instead of being continuous trim it is intermittent, and the aftcutout no longer applies. Further, it keeps biting again and again – This is a function of the wind-up turn reason for existing in the first place

Some changes that could be made to the MAX that might solve the problem and not require significant redesign (combinations are possible and it looks like Boeing is doing some of them):
  • Return MCAS to its 0.9 use and add AoA functionality to STS. This would preserve the aft column cutout in the wings-level situation and the multiple firing issue, it would also create the continuous trim failure mode 737NG pilots are used to. Question here is would the increased authority required by STS be too much to react against. Keeping MCAS0.9 means that it only ever fires in the lower authority non 1g mode
  • Make MCAS (and possiblely STS) a duplex system. This reduces the errant firing of MCAS, but also reduces when it is available as now you have ~2E-5/-7 chances of a sensor failing. Is this acceptable risk for the approach to stall and wind-up turn cases originally identified.
  • Make MCAS fire only once if cutoff by counter trim. Probably ok for the wings-level case but what about the wind-up turn case
  • Remove the aft column cutout override. Same issues as above, but is more likely to cutout MCAS in wind-up turns
  • Change the Elevator Feel system to provide much increased nose down forcing well below expected stall (stick pusher/nudger). This would minimise STS requirement, but would have to be Duplex, again is it ok to be inoperative more often.

Also, let us suppose that the Boeing decided to completely redesign the flight control system. This does not necessitate a different type rating, as you could actually more easily make the 737MAX fly like the NG. However, if you are going to that extreme it might make sense to have your type rating align with other Boeing aircraft and not the 737. The biggest issue is that the MTC programmes for the two airframes would be completely different. People like WN would not be fans of that.

As for competing with FBW, it is really competing with fully irreversible controls where the pilot is only signalling the actual actuation system. The 737 is basically designed (though doesn't achieve) so that the pilot should be able to overcome any automated control system if they act appropriately. This is not, and cannot, be the case with FBW and similar systems as there is no physical link between the pilot and the control surface. The link is instead to the actuator system.
 
rheinwaldner
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 1:48 pm

phollingsworth wrote:
You missed my point, in safety you must be willing to discuss all aspects simultaneously. There are no magic bullets, but ignoring 2-3 in the case of the MAX is poor. One of the reasons is simply ignoring 2-3 is part of what creates 1-2.

You could not be more wrong.

Its not 2-3s fault that the MAX currently sits at 4550 fatalities per RPK. It is entirely the MAXs fault. Otherwise other aircraft would also deviate from point 2 strongly. Which is not the case.

The MAX was broken like no other aircraft since many decades and you will never be able to train every pilot worldwide to fly broken aircraft safely. That approach is hopeless.

phollingsworth wrote:
As for how often we would see these accidents. That is a Bayesian question, and not one that can be answered with solely the information contained on the graph. The observed failure rate can help us adjust our posterior estimate of likelihood, but it isn't the posterior likelihood. This is because we are not totally ignorant of the system. We know much about the MAX and the aircraft's behaviour over the vast majority of the flight envelope. These have been quite well explored, either directly or through analogy. We actually have very high confidence in the failure rate of AoA sensors. The reason for this is that the sensor is used on lots of other aircraft. Boeing assumes that the failure rate will be 1E-5 per flight hour. This is a bad assumption, though not for the reasons many people would think. The observed failure rate is approximately 1E-7 per flight hour (my understanding is this is the fail to a valid but incorrect reading rate vs signal disappearing).

The failure rate of the AoA sensor does not matter. The systems, which are fed with AoA data need to handle sensors outages gracefully no matter how often the sensors fail (because they fail anyway too often). That was the issue with MCAS V1 and that's what needs to be fixed with the MAX.
Many things are difficult, all things are possible!
 
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scbriml
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 1:51 pm

jmry888 wrote:
Where are the crashes over here ? The shear number of flight hours should suggest at least 4 crashes / crash landings etc . But there are none so please explain .


The question remains - It appears you don’t know if your “over here” pilots have ever faced the same circumstances that the “over there” ones did, therefore we cannot conclude one way or the other if they would have performed better or worse in the same circumstances.

jmry888 wrote:
What worlds aviation aurthorities ? Everyone on the 2 investigation boards worked for government agencies here and over there.


I’m talking about every aviation authority in the World that has grounded the MAX, including the “over here” FAA.

jmry888 wrote:
Well you still have not explained the huge i mean huge difference in flight hours with no crashes to the 2 over there. Those 2 airlines combined did not have even one third the flight hours on the 737 max that others have with no crashes.


See erto’s post. If the vast majority of delivered MAX are operated by airlines “over there”, where would you expect crashes to be more likely, “over here” or “over there”?
Time flies like an arrow. Fruit flies like a banana!
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phollingsworth
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 1:52 pm

PixelFlight wrote:
phollingsworth wrote:
Keep in mind there have been a number of Speed Trim System (STS) runaways on 737NGs. None have been catastrophic. The likelihood of them happening is about the same as this type of MCAS failure. This is because the training adequately covers this and the system behaves differently when it fails.

I disagree. The STS can't generate a nose down command input with the same rate, duration and schedule as the MCAS. This is proved by the JTAR:

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. The possibility of a pitch-up tendency during approach to stall was
identified for the flaps-up configuration prior to the implementation of MCAS.

In addition, the STS did not reset after 5 seconds of any manual electric stab trim, something that no pilots was ever formally trained for, worldwide. Not counting that the cockpit situation of the two 737-8/9 MAX crashes was far from a simple runaway.


Actually we are agreeing here, the failure rates are about the same, but the presentation is different. MCAS has a greater control input than STS, so when it fails the potential downsides are worse. This would still exist if we had extended STS to cover the MAX's aerodynamic case. It also presents as an intermittent failure and then resets – the reset comes from the wind-up turn. Finally, there is not aft column cutout to cancel. Whether or not revised training could have created a low enough catastrophic outcome likelihood is hard to say. However, not having a revised training to elaborate the differences definitely doesn't.

The sad thing is that Boeing could have added "intermittent" nose-down trim to the failure training for all 737 pilots before the MAX even flew. It would have added some additional items to 737NG training that would not come of use, but eliminated that aspect of differences training.
 
phollingsworth
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 2:10 pm

rheinwaldner wrote:
phollingsworth wrote:
You missed my point, in safety you must be willing to discuss all aspects simultaneously. There are no magic bullets, but ignoring 2-3 in the case of the MAX is poor. One of the reasons is simply ignoring 2-3 is part of what creates 1-2.

You could not be more wrong.

Its not 2-3s fault that the MAX currently sits at 4550 fatalities per RPK. It is entirely the MAXs fault. Otherwise other aircraft would also deviate from point 2 strongly. Which is not the case.

The MAX was broken like no other aircraft since many decades and you will never be able to train every pilot worldwide to fly broken aircraft safely. That approach is hopeless.

phollingsworth wrote:
As for how often we would see these accidents. That is a Bayesian question, and not one that can be answered with solely the information contained on the graph. The observed failure rate can help us adjust our posterior estimate of likelihood, but it isn't the posterior likelihood. This is because we are not totally ignorant of the system. We know much about the MAX and the aircraft's behaviour over the vast majority of the flight envelope. These have been quite well explored, either directly or through analogy. We actually have very high confidence in the failure rate of AoA sensors. The reason for this is that the sensor is used on lots of other aircraft. Boeing assumes that the failure rate will be 1E-5 per flight hour. This is a bad assumption, though not for the reasons many people would think. The observed failure rate is approximately 1E-7 per flight hour (my understanding is this is the fail to a valid but incorrect reading rate vs signal disappearing).

The failure rate of the AoA sensor does not matter. The systems, which are fed with AoA data need to handle sensors outages gracefully no matter how often the sensors fail (because they fail anyway too often). That was the issue with MCAS V1 and that's what needs to be fixed with the MAX.


Simply stating I am wrong does not make it so. MAXs accident rate sits where it is because of 1-3 not 1-2 separate from 1-3. The fact that it is where it is and the belief of where it will be without modification is a totally valid reason for developing. It isn't meaningful to compare MAX to the fleet, as there is no aircraft that is the fleet. Also, fatalities per 100 million RPK is the worst of the 3 common safety measures for making design decisions or the decision of an individual to fly on an aircraft. Accidents per flight hour and per flight are much more useful in these cases.

The failure rate of the sensor does matter, it always has and always will. The reason for this is the only way to guarantee no future aviation fatalities is to not have aviation. If we are to have aviaiton we need to know where to put our effort in to reduce the accident rate. Making the sensor more reliable is an option, making the system response to a sensor failure more graceful is another, making the flight crew response to the system response another still. All of these have to be considered. How do you answer if 1 in 10 million flight hours is too common, perfectly fine, or way less than would be a problem? You do this by figuring out where it is you want to be and how is the best way to get there. The fact is we accept that catastrophic aircraft accidents will happen at a rate higher than 1E-9 per flight hour. The regulators ask that we expect that no single failure pathway to catastrophic should occur at a rate more than 1E-9 per flight hour. Is this good enough?
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 2:45 pm

phollingsworth wrote:
PixelFlight wrote:
maint123 wrote:
So in auto if the AOA sensor starts misbehaving, will the plane again start triming down ? And in the case of Max 1.0 , if the pilot notices that the plane is trimming down, and switches auto off, we are back to square one?
My point being even in auto, max would face the same situation.
Saving grace could be that auto is switched on at a much higher altitude and the pilots would have had much more time to recover

The autopilot compare the two AoA sensors and will disengage itself if there is a disagreement.

This is in fact exactly what happened to JT043, JT610 and ET302: The erratic high left AoA value was found in disagreement with the right AoA by the autopilot, so it disengaged itself forcing the manual flight mode, where the MCAS only use the single erratic high left AoA value to trim the horizontal stabilizer nose down with high authority. If the autopilot did have a third AoA input (a backup sensor or a synthetic sensor), the autopilot would have been able to stay engaged and the pilots would have just noticed a left AoA failure message, as long as there would have not enter in manual flight mode. Note: the erratic left AoA value also caused a speed disagree because the AoA value is used to correct the speed value, this explain why the pilots was focusing at the speed disagree message first, because there didn't have the AoA disagree message that Boeing have removed to make it a paying option. But the manual flight mode would still be highly risky with a MCAS v1 and an erratic high left AoA value, so the need of a proper solution to fix it.

This all show how fragile is the 737-8/9 MAX flight control system when it have to compete with FBW architecture on high end feature like maneuvering augmentation. The Ethiopian Airline CEO was probable right at saying that the 737-8/9 MAX flight control system have to be completely redesigned. And for sure this can be done with the Boeing internal competences that have designed the 777 and the 787. Would be a 737 FBW with a new type rating.


What about the 737MAX would require a complete redesign of the flight-control system (keep in mind parts of it were already redesigned)? This is separate from a complete redesign might be a reasonable idea. Some things we are pretty sure know about the 737MAX from the evidence in released reports:
  • The 737MAX naturally exhibits unacceptable stick lightening in wind-up turns. Such that there is too high of a likelihood that this will be exhibited on any given flight. This was not easily solved with aerodynamic modifications – Hence MCAS0.9
  • The 737MAX naturally exhibits poor unaugmented stall identification in wings-level flight. This is standard for all modern jetliner, including 757, A320, A330, and 737NG. They just tend to mush about. Hence the Speed Trim System on both the 757 and 737NG, and the envelope protection on the Airbus aircraft. The MAX is worse than the 737NG and could not quickly be made to behave the same way by tiny changes – Hence MCAS1.0
  • MCAS1.0 changed the failure mode and required response to what Boeing viewed as a run of the mill STS failure. Instead of being continuous trim it is intermittent, and the aftcutout no longer applies. Further, it keeps biting again and again – This is a function of the wind-up turn reason for existing in the first place

Some changes that could be made to the MAX that might solve the problem and not require significant redesign (combinations are possible and it looks like Boeing is doing some of them):
  • Return MCAS to its 0.9 use and add AoA functionality to STS. This would preserve the aft column cutout in the wings-level situation and the multiple firing issue, it would also create the continuous trim failure mode 737NG pilots are used to. Question here is would the increased authority required by STS be too much to react against. Keeping MCAS0.9 means that it only ever fires in the lower authority non 1g mode
  • Make MCAS (and possiblely STS) a duplex system. This reduces the errant firing of MCAS, but also reduces when it is available as now you have ~2E-5/-7 chances of a sensor failing. Is this acceptable risk for the approach to stall and wind-up turn cases originally identified.
  • Make MCAS fire only once if cutoff by counter trim. Probably ok for the wings-level case but what about the wind-up turn case
  • Remove the aft column cutout override. Same issues as above, but is more likely to cutout MCAS in wind-up turns
  • Change the Elevator Feel system to provide much increased nose down forcing well below expected stall (stick pusher/nudger). This would minimise STS requirement, but would have to be Duplex, again is it ok to be inoperative more often.

Also, let us suppose that the Boeing decided to completely redesign the flight control system. This does not necessitate a different type rating, as you could actually more easily make the 737MAX fly like the NG. However, if you are going to that extreme it might make sense to have your type rating align with other Boeing aircraft and not the 737. The biggest issue is that the MTC programmes for the two airframes would be completely different. People like WN would not be fans of that.

As for competing with FBW, it is really competing with fully irreversible controls where the pilot is only signalling the actual actuation system. The 737 is basically designed (though doesn't achieve) so that the pilot should be able to overcome any automated control system if they act appropriately. This is not, and cannot, be the case with FBW and similar systems as there is no physical link between the pilot and the control surface. The link is instead to the actuator system.

Good analysis. Yes a 737 FBW would be a project on it own with a timeline probably in years, so I don't think this is a realistic option for the existing 737-8/9 MAX. But the aircraft that will replace the 737-8/9 MAX in the future will certainly be FBW, regardless of if it would be a totally new design or not.
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 3:37 pm

morrisond wrote:
prebennorholm wrote:
phollingsworth wrote:
... The point still remains that if you could solve, totally, the 2 to 3 problem via pilot training, you would not need to solve the 1 to 2...

Absolutely wrong. Even imagining that improved crew training could guarantee 100% success rate for MCAS misfires, then we would still have the problem that an MCAS misfire would send unbuckled pax, FAs and catering carts into the ceiling and down again breaking bones and crashing sculls even on buckled pax. This is no way to do business in 21st century.


If that is what you think happens to the plane when MCAS is activated then you don't understand MCAS - it trims the Horizontal stabilizer at a rate barely more than electric trim.

Unless of course you think using electric trim would cause the same result. Wait a second - Eureka - you found they answer why 3 out of the 4 pilots were so reluctant to use Electric Trim - they thought it would break bones....


A pilot using the electrical trim will use it for a few seconds.

MCAS trims at a faster speed for 10 seconds and does it again and again until the frame crashes. It is an extreme action, not something benign.

The person who tries to confuse about the dangers of MCAS is you.You are defending a automation that makes a flying coffin out of a 737.
 
rheinwaldner
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 3:38 pm

phollingsworth wrote:
Simply stating I am wrong does not make it so.

There is a lot more that I posted. I have provided links, formula and explained the assumption.

phollingsworth wrote:
MAXs accident rate sits where it is because of 1-3 not 1-2 separate from 1-3. The fact that it is where it is and the belief of where it will be without modification is a totally valid reason for developing. It isn't meaningful to compare MAX to the fleet, as there is no aircraft that is the fleet. Also, fatalities per 100 million RPK is the worst of the 3 common safety measures for making design decisions or the decision of an individual to fly on an aircraft. Accidents per flight hour and per flight are much more useful in these cases.

Read my reply to MSPNWA. The calculation, that shows that 1 to 2 is caused by the MAX alone uses crashes per flight.

And, off course it is correct to consider the safety statistics achieved by the worldwide fleet as benchmark and compare the MAX against it.

And why on earth would RPK differ from crashes per flight? The variation between these is too small to change the conclusion in any way.
Many things are difficult, all things are possible!
 
morrisond
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 3:55 pm

mjoelnir wrote:
morrisond wrote:
prebennorholm wrote:
Absolutely wrong. Even imagining that improved crew training could guarantee 100% success rate for MCAS misfires, then we would still have the problem that an MCAS misfire would send unbuckled pax, FAs and catering carts into the ceiling and down again breaking bones and crashing sculls even on buckled pax. This is no way to do business in 21st century.


If that is what you think happens to the plane when MCAS is activated then you don't understand MCAS - it trims the Horizontal stabilizer at a rate barely more than electric trim.

Unless of course you think using electric trim would cause the same result. Wait a second - Eureka - you found they answer why 3 out of the 4 pilots were so reluctant to use Electric Trim - they thought it would break bones....


A pilot using the electrical trim will use it for a few seconds.

MCAS trims at a faster speed for 10 seconds and does it again and again until the frame crashes. It is an extreme action, not something benign.

The person who tries to confuse about the dangers of MCAS is you.You are defending a automation that makes a flying coffin out of a 737.


So it would break bones when it activates? It doesn't work that fast. Plus you know full well that it will only activate once on MAX 2.0 - if MCAS is even included on MAX 2.0.
 
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767333ER
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 4:22 pm

morrisond wrote:
mjoelnir wrote:
morrisond wrote:

If that is what you think happens to the plane when MCAS is activated then you don't understand MCAS - it trims the Horizontal stabilizer at a rate barely more than electric trim.

Unless of course you think using electric trim would cause the same result. Wait a second - Eureka - you found they answer why 3 out of the 4 pilots were so reluctant to use Electric Trim - they thought it would break bones....


A pilot using the electrical trim will use it for a few seconds.

MCAS trims at a faster speed for 10 seconds and does it again and again until the frame crashes. It is an extreme action, not something benign.

The person who tries to confuse about the dangers of MCAS is you.You are defending a automation that makes a flying coffin out of a 737.


So it would break bones when it activates? It doesn't work that fast. Plus you know full well that it will only activate once on MAX 2.0 - if MCAS is even included on MAX 2.0.

But it has already shown to be that dangerous which is why you have deflected to saying that it’s being fixed. Again this all begs a question. If MCAS needed this authority to be certified and now to fix it they are supposedly taking that authority away to make it safe, why did they need it like that in the first place? If they could make it effective while stopping after one activation why didn’t they to begin with? Is it because there’s something wrong with the flight characteristics or are they just making smoke and mirrors and the new version won’t be any safer?
Been on: 732 733 734 73G 738 752 763 A319 A320 A321 CRJ CR7 CRA/CR9 E145 E175 E190 F28 MD-82 MD-83 C172R C172S P2006T
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 4:22 pm

morrisond wrote:
mjoelnir wrote:
morrisond wrote:

If that is what you think happens to the plane when MCAS is activated then you don't understand MCAS - it trims the Horizontal stabilizer at a rate barely more than electric trim.

Unless of course you think using electric trim would cause the same result. Wait a second - Eureka - you found they answer why 3 out of the 4 pilots were so reluctant to use Electric Trim - they thought it would break bones....


A pilot using the electrical trim will use it for a few seconds.

MCAS trims at a faster speed for 10 seconds and does it again and again until the frame crashes. It is an extreme action, not something benign.

The person who tries to confuse about the dangers of MCAS is you.You are defending a automation that makes a flying coffin out of a 737.


So it would break bones when it activates? It doesn't work that fast. Plus you know full well that it will only activate once on MAX 2.0 - if MCAS is even included on MAX 2.0.


Yes, when a frame nosedives into the ground, bones will break. Has Boeing already brought out a technical description of MCAS 2.0? If yes, could you provide the reference?
 
milhaus
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 5:27 pm

To jrmy: 90000FH is nothing in terms of part reliability of aircraft parts, especially AOA sensors, in my 23 years experience as AMT on line mtce environment together with ten years at maintenance control center I can remember of only one AOA failure like this. I still can not get how it can fail on brand new aircrat.
 
Vladex
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 5:29 pm

Aviation737 wrote:
Can someone tell me why the MAX was a bad idea? I mean to me it makes perfect sense for them to developed it.


It was a bad idea because it's totally outdated design , it looks absurd and has misfitting parts like engines. It was just a financial short term decision and a purported cash grab at the expense and the risk against everyone else. It would never happen in a competitive non government regulated industry
 
smartplane
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Fri Nov 29, 2019 6:51 pm

Presumably MCAS 2.0 is proposed to be MCAS tamed or vanished. STS 2.0 will become the new MCAS. When fixes are published, check new with previous incarnations, and MCAS/STS and STS/SAS (or similar abbreviation) permitted interactions.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 1:37 am

smartplane wrote:
Presumably MCAS 2.0 is proposed to be MCAS tamed or vanished. STS 2.0 will become the new MCAS. When fixes are published, check new with previous incarnations, and MCAS/STS and STS/SAS (or similar abbreviation) permitted interactions.

The MCAS is in fact a function appended to the STS.
The JATR document find that the MCAS is implemented into the STS.
The NTSB document detail how the STS software evolved to include the different MCAS versions.
 
maint123
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 3:10 am

milhaus wrote:
To jrmy: 90000FH is nothing in terms of part reliability of aircraft parts, especially AOA sensors, in my 23 years experience as AMT on line mtce environment together with ten years at maintenance control center I can remember of only one AOA failure like this. I still can not get how it can fail on brand new aircrat.

Exactly. Everyone assumes that both crashes were due to AOA sensor failures but these sensors are being used in thousands of other Boeings and airbuses. Unless special sensors were made for max, the fault could be in some other aspect of the feedback loop. Boeing might be happily diverting attention from other issues. The probability of 2 max sensors damaged in such a short interval while 1000s of other models are not effected is very low.
 
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aerolimani
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 6:37 am

Vladex wrote:
Aviation737 wrote:
Can someone tell me why the MAX was a bad idea? I mean to me it makes perfect sense for them to developed it.


It was a bad idea because it's totally outdated design , it looks absurd and has misfitting parts like engines. It was just a financial short term decision and a purported cash grab at the expense and the risk against everyone else. It would never happen in a competitive non government regulated industry

To be fair to Boeing, it was also a move to cling to market share. Not moving quickly would have surrendered more share to Airbus and Bombardier. Getting that share back, further down the road, with a new design, would be a much slower process. While I'm sure an NSA (instead of the MAX) would have eventually paid off, it would likely be a decade or more before Boeing got itself back to something close to 50% share of the NB market, if that. As it is, the 737 is only at 45%.
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 8:32 am

maint123 wrote:
milhaus wrote:
To jrmy: 90000FH is nothing in terms of part reliability of aircraft parts, especially AOA sensors, in my 23 years experience as AMT on line mtce environment together with ten years at maintenance control center I can remember of only one AOA failure like this. I still can not get how it can fail on brand new aircrat.

Exactly. Everyone assumes that both crashes were due to AOA sensor failures but these sensors are being used in thousands of other Boeings and airbuses. Unless special sensors were made for max, the fault could be in some other aspect of the feedback loop. Boeing might be happily diverting attention from other issues. The probability of 2 max sensors damaged in such a short interval while 1000s of other models are not effected is very low.

Simply incorrect in all aspects. The difference is MCAS and that is why the aircraft type has been grounded for 9 months.

Ray
 
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Veigar
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 8:33 am

aerolimani wrote:
Vladex wrote:
Aviation737 wrote:
Can someone tell me why the MAX was a bad idea? I mean to me it makes perfect sense for them to developed it.


It was a bad idea because it's totally outdated design , it looks absurd and has misfitting parts like engines. It was just a financial short term decision and a purported cash grab at the expense and the risk against everyone else. It would never happen in a competitive non government regulated industry

To be fair to Boeing, it was also a move to cling to market share. Not moving quickly would have surrendered more share to Airbus and Bombardier. Getting that share back, further down the road, with a new design, would be a much slower process. While I'm sure an NSA (instead of the MAX) would have eventually paid off, it would likely be a decade or more before Boeing got itself back to something close to 50% share of the NB market, if that. As it is, the 737 is only at 45%.


To add to your point, the plane would have been fine if it was a bit more revised and redundant. I don't think these disasters are the result of an "outdated design", rather, a rushed update.
 
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seahawk
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 9:11 am

maint123 wrote:
milhaus wrote:
To jrmy: 90000FH is nothing in terms of part reliability of aircraft parts, especially AOA sensors, in my 23 years experience as AMT on line mtce environment together with ten years at maintenance control center I can remember of only one AOA failure like this. I still can not get how it can fail on brand new aircrat.

Exactly. Everyone assumes that both crashes were due to AOA sensor failures but these sensors are being used in thousands of other Boeings and airbuses. Unless special sensors were made for max, the fault could be in some other aspect of the feedback loop. Boeing might be happily diverting attention from other issues. The probability of 2 max sensors damaged in such a short interval while 1000s of other models are not effected is very low.


Well it seems like the Lion Air sensor was infact defective, while the second crash looks like a bird strike damaged the sensor.
 
mjoelnir
Posts: 8945
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 10:07 am

maint123 wrote:
milhaus wrote:
To jrmy: 90000FH is nothing in terms of part reliability of aircraft parts, especially AOA sensors, in my 23 years experience as AMT on line mtce environment together with ten years at maintenance control center I can remember of only one AOA failure like this. I still can not get how it can fail on brand new aircrat.

Exactly. Everyone assumes that both crashes were due to AOA sensor failures but these sensors are being used in thousands of other Boeings and airbuses. Unless special sensors were made for max, the fault could be in some other aspect of the feedback loop. Boeing might be happily diverting attention from other issues. The probability of 2 max sensors damaged in such a short interval while 1000s of other models are not effected is very low.


In other frames the failure of one AoA sensor does not lead to an automatic trying to ram the frame into the ground. In the MAX, one failed high AoA sensor will wake up the deadly failure mode of MCAS.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 10:41 am

milhaus wrote:
To jrmy: 90000FH is nothing in terms of part reliability of aircraft parts, especially AOA sensors, in my 23 years experience as AMT on line mtce environment together with ten years at maintenance control center I can remember of only one AOA failure like this. I still can not get how it can fail on brand new aircrat.

On all aircrafts others than the 737-8/9 MAX with MCAS v1, an erratic high value will be identified as a banal AoA sensors disagreement and/or failure.
You can you be certain that all the AoA sensors you see replaced did not expose an erratic high value ?
 
checklist350
Posts: 23
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 11:02 am

mjoelnir wrote:
maint123 wrote:
milhaus wrote:
To jrmy: 90000FH is nothing in terms of part reliability of aircraft parts, especially AOA sensors, in my 23 years experience as AMT on line mtce environment together with ten years at maintenance control center I can remember of only one AOA failure like this. I still can not get how it can fail on brand new aircrat.

Exactly. Everyone assumes that both crashes were due to AOA sensor failures but these sensors are being used in thousands of other Boeings and airbuses. Unless special sensors were made for max, the fault could be in some other aspect of the feedback loop. Boeing might be happily diverting attention from other issues. The probability of 2 max sensors damaged in such a short interval while 1000s of other models are not effected is very low.


In other frames the failure of one AoA sensor does not lead to an automatic trying to ram the frame into the ground. In the MAX, one failed high AoA sensor will wake up the deadly failure mode of MCAS.


I can't believe that after a year of publications online that explained to laymen why AoA sensor failure triggered a deadly chain of events on both airplanes and thousands of posts in this very thread there are enthusiasts that fail to understand that.
Dumbfounded really.
Last edited by checklist350 on Sat Nov 30, 2019 11:05 am, edited 3 times in total.
 
milhaus
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 11:03 am

AOA sensors value are also send to DFDR and are monitored and checked by flight safety department together wiht hundred of other parameters on each flight. Aditionally AOA outputs are used by ADC or ADIRU in Airbus to compute speed, so when AOA values between sensors are different You get indicated airspeed difference too. Most AOA are being removed due to heating failure, mechanical damage and for modifications
 
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seahawk
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Re: Boeing 737MAX Grounded Worldwide Q4 2019

Sat Nov 30, 2019 11:09 am

PixelFlight wrote:
milhaus wrote:
To jrmy: 90000FH is nothing in terms of part reliability of aircraft parts, especially AOA sensors, in my 23 years experience as AMT on line mtce environment together with ten years at maintenance control center I can remember of only one AOA failure like this. I still can not get how it can fail on brand new aircrat.

On all aircrafts others than the 737-8/9 MAX with MCAS v1, an erratic high value will be identified as a banal AoA sensors disagreement and/or failure.
You can you be certain that all the AoA sensors you see replaced did not expose an erratic high value ?


That is the actual amazing thing that they did not implement at least one cross check in the system. It would not even need to be the other sensor, it would have been enough to check the elevator / stick position and the engine setting.

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