HaulSudson
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 7:31 am

Why did Boeing remove the well-known yoke system for cutting out the automatic stabiliser trim and only kept the switches?

The switches that pilots seems much less familiar with.

What was the benefit for the change?
 
smartplane
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 7:32 am

prebennorholm wrote:
[All FBW planes have three AoA sensors with voting out a bad guy.

ALL FBW planes have three AoA sensors, or all Airbus FBW aircraft? Do some have four?
 
ELBOB
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 7:33 am

Interested wrote:
Must be an incredibly tough software fix with the amount of resource they could put behind it?


Tricky software fixes don't come sooner with more people, that actually makes it worse. There are probably just a couple of senior devs working on this in Boeing, along with the hardware systems experts and a billion project 'stakeholders'.

Testing it is going to be the big issue, both in the sim and in the air.
 
LTC8K6
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 7:36 am

Investigators on the ground near the crash site of the Ethiopian Airlines 737 MAX found the plane’s jackscrew, a part that moves the horizontal tail of the aircraft, and it indicates that the tail was in an unusual position, according to an aviation safety consultant briefed on the findings.


This, along with evidence from a new satellite-based system that tracked the flight data and revealed similar trajectories on the two flights, is what finally led the Federal Aviation Administration (FAA) to ground the MAX on Wednesday, following regulators around the world.


The company said it will change the MCAS software to give the system input from more than one AOA sensor. It will limit how much MCAS can move the horizontal tail in response to an erroneous AOA signal. And when activated, the system will kick in only for one cycle, rather than multiple times.


https://www.seattletimes.com/business/b ... eings-fix/

So that's what they found and the fix they are doing.
 
ELBOB
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 7:39 am

smartplane wrote:
ALL FBW planes have three AoA sensors, or all Airbus FBW aircraft? Do some have four?


A320 three
A330 theee
A350 four
787 two
777 two
 
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Finn350
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 7:57 am

ELBOB wrote:
smartplane wrote:
ALL FBW planes have three AoA sensors, or all Airbus FBW aircraft? Do some have four?


787 two


Interesting tidbit about the 787 left hand AoA sensor placement (and how sensors can become damaged)

http://www.boeing.com/assets/pdf/commer ... sensor.pdf
 
smartplane
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 8:14 am

ELBOB wrote:
smartplane wrote:
ALL FBW planes have three AoA sensors, or all Airbus FBW aircraft? Do some have four?


A320 three
A330 theee
A350 four
787 two
777 two

Do some elements of MAX systems rely on grandfathering from 787? Do some elements of X systems rely on grandfathering from MAX and/or 787? Should the FAA undertake a review of 787 and X systems?

Grandfathering has been pushed over the decades, to the point we have inter-model grandfathering.

The baseline for all 737 grandfathering should be the 100/200, not continual creep, with the NG being the default for the MAX, and the Classic for the NG. After a certain number of years, grandfathering eligibility should cease.
 
NTLDaz
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 8:22 am

 
rheinwaldner
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 8:22 am

HaulSudson wrote:
Why did Boeing remove the well-known yoke system for cutting out the automatic stabiliser trim and only kept the switches?

The switches that pilots seems much less familiar with.

What was the benefit for the change?

Because MCAS is intended to apply a nose down moment in cases, when the yoke is pulled.
Many things are difficult, all things are possible!
 
LTC8K6
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 8:24 am

NTLDaz wrote:


That info has been posted a couple times.

It doesn't really tell us much, though.

Well, it tells us why Trump issued the grounding order.

Was MCAS the cause, or was it just a factor?
 
Virtual737
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 8:29 am

LTC8K6 wrote:
It doesn't really tell us much, though.


I think it tells quite a lot. It tells that the horizontal stabilizer trim was very likely a significant factor in the aircraft's crash. That in turn increases, but doesn't prove, the likelihood that MCAS was involved.

If MCAS was involved and MCAS is not able to act with flaps extended, it also shows that either the wings were clean (many here have stated that the flaps would still have been extended) or that MCAS has another fault as yet unmentioned.

It also lowers considerably the likelihood of an intentional act, terrorism and probably many other contributors.
 
N649DL
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 8:32 am

RickNRoll wrote:
cpd wrote:
oldannyboy wrote:

I hope not, but on the other hand we should de-stigmatize a "cautionary grounding". In this regard Boeing should have behaved much more maturely, and immediately propose themselves a grounding of the MAX variant. Thing is, at the end of the day, the MAX was going to end up grounded anyway [it was pretty evident from the onset], and they should/could have handled this a lot better. This is not only proving to be a technical nightmare (with seemingly financial and image repercussions), but also a PR disaster - which was ultimately not necessary.


Finally a couple of people who’ve not been drinking the Kool-Aid. This whole thing is a disaster for Boeing and they should have been more proactive in dealing with it. It’s looking like their version of VW/Audi dieselgate.

I hope they can recover. And with any luck the FDR will yield useful information- despite how smashed up it is.


Dieselgate is not a once off. It is a cultural disease affecting business globally.


IMHO, a long time coming. It's amazing to me they didn't get the heat they deserved over the 787 battery situation.

As much as it blows having a whole Boeing line banned, I hope they learn a lesson from these acts. That, and the MAX idea was a freaking horrible plot out of the gate.
 
HaulSudson
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 8:51 am

rheinwaldner wrote:
HaulSudson wrote:
Why did Boeing remove the well-known yoke system for cutting out the automatic stabiliser trim and only kept the switches?

The switches that pilots seems much less familiar with.

What was the benefit for the change?

Because MCAS is intended to apply a nose down moment in cases, when the yoke is pulled.


Thanks. That means the old solution isn't only not working, it moreover triggers more of problem if the software (mistakenly) kicks in.

Wow.
 
WIederling
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 9:16 am

cpd wrote:
Finally a couple of people who’ve not been drinking the Kool-Aid. This whole thing is a disaster for Boeing and they should have been more proactive in dealing with it. It’s looking like their version of VW/Audi dieselgate.

Not a valid comparison at all.

The emissions control software worked exactly as required, designed and executed.
Without fault.
Only the design objective was illegal.

This is not the case here. problems seem to start with what is required
continue into the design and finish with bad execution. over all a "round" product.
Murphy is an optimist
 
Interested
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 9:56 am

ELBOB wrote:
Interested wrote:
Must be an incredibly tough software fix with the amount of resource they could put behind it?


Tricky software fixes don't come sooner with more people, that actually makes it worse. There are probably just a couple of senior devs working on this in Boeing, along with the hardware systems experts and a billion project 'stakeholders'.

Testing it is going to be the big issue, both in the sim and in the air.


I take that on board

I'm going to suggest that with no pressure of time they would ideally need years rather than months to be confident in what they have created?
 
cpd
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 9:57 am

WIederling wrote:
cpd wrote:
Finally a couple of people who’ve not been drinking the Kool-Aid. This whole thing is a disaster for Boeing and they should have been more proactive in dealing with it. It’s looking like their version of VW/Audi dieselgate.

Not a valid comparison at all.

The emissions control software worked exactly as required, designed and executed.
Without fault.
Only the design objective was illegal.

This is not the case here. problems seem to start with what is required
continue into the design and finish with bad execution. over all a "round" product.


You've misunderstood - it's the public relations fall out that is the same.
 
LTC8K6
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 10:05 am

Virtual737 wrote:
LTC8K6 wrote:
It doesn't really tell us much, though.


I think it tells quite a lot. It tells that the horizontal stabilizer trim was very likely a significant factor in the aircraft's crash. That in turn increases, but doesn't prove, the likelihood that MCAS was involved.

If MCAS was involved and MCAS is not able to act with flaps extended, it also shows that either the wings were clean (many here have stated that the flaps would still have been extended) or that MCAS has another fault as yet unmentioned.

It also lowers considerably the likelihood of an intentional act, terrorism and probably many other contributors.


The trim was already pretty much the suspect, though.
 
Forgedias
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 10:16 am

Putting up a link from Hindustan Times. Original article was from Bloomberg but if people are hitting the paywall, the full article is in this one.

https://www.hindustantimes.com/world-ne ... 5kq2J.html

This article is in reference to what Canada was reporting on Satellite information they received.
 
GmvAfcs
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 10:33 am

smartplane wrote:
prebennorholm wrote:
[All FBW planes have three AoA sensors with voting out a bad guy.

ALL FBW planes have three AoA sensors, or all Airbus FBW aircraft? Do some have four?


E-Jets have four Smart Probes, which provides 4 independent AOA, without vanes.
 
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ExperimentalFTE
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 10:46 am

Very sorry for tragic loss of life and folks onboard both aircraft.

But I cant help myself with impression that this feels like the worst CSeries karma on Boeing...

Gravity of this situation will have tremendous impact on Boeing, industry, cert authorities, airlines and travelers....
 
dtw2hyd
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 10:51 am

More sensors are not going to help if the system cannot figure out a real stall (and a level flight??)
 
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anfromme
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 10:54 am

WIederling wrote:
cpd wrote:
Finally a couple of people who’ve not been drinking the Kool-Aid. This whole thing is a disaster for Boeing and they should have been more proactive in dealing with it. It’s looking like their version of VW/Audi dieselgate.

Not a valid comparison at all.

The emissions control software worked exactly as required, designed and executed.
Without fault.
Only the design objective was illegal.

This is not the case here. problems seem to start with what is required
continue into the design and finish with bad execution. over all a "round" product.


In fairness, I think cpd was liking dieselgate and the MAX grounding more at a PR level, not the technical level that you talk about.
VW and Audi were not really that forthcoming initially, and there is still reluctance on their part to transparently investigate and collaborate with authorities to find out who knew what when and why this illegal software even found its way into the cars to begin with, through various internal and external quality and sanity checks.
Similar story with MCAS - Boeing has not been all that transparent about it, and one does again wonder how the system as currently in place made it through internal audits and external certification procedures.
42
 
Amiga500
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 10:58 am

dtw2hyd wrote:
More sensors are not going to help if the system cannot figure out a real stall (and a level flight??)


If you have one AoA sensor and it goes wonky - you've no idea what flight state you are in.

If you have 2 AoA sensors and one goes wonky - you've no idea which one is good and which is bad - so you've still no idea what flight state you are in.

If you have 3 AoA sensors and one goes wonky - you've 2 sensors still reading the same values - so they are considered valid and the other disregarded - thus you do know what flight state you are in.


I've seen reports MCAS uses 1 sensor, I've seen reports MCAS uses 2 sensors. Either way, no redundancy.
 
dtw2hyd
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 11:28 am

Amiga500 wrote:
I've seen reports MCAS uses 1 sensor, I've seen reports MCAS uses 2 sensors. Either way, no redundancy.


There is a lot of conflicting information but one thing is sure only one active sensor.

The one on the side who is flying the plane.
The one on the side systems were powered up.

Adding redundancy to such primitive design needs an extensive redesign and physical changes. It could take a long time.

The best option is to find the logic which is interpreting climb profile as stall and correct it.
 
Babyshark
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 11:33 am

ExperimentalFTE wrote:
Very sorry for tragic loss of life and folks onboard both aircraft.

But I cant help myself with impression that this feels like the worst CSeries karma on Boeing...

Gravity of this situation will have tremendous impact on Boeing, industry, cert authorities, airlines and travelers....


It's a cut throat business and Boeing management was blunt but not crafty. If Boeing management was smart they would have bought it... Then killed it.
 
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ExperimentalFTE
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 11:36 am

anfromme wrote:
Amiga500 wrote:
ELBOB wrote:

Tricky software fixes don't come sooner with more people, that actually makes it worse. There are probably just a couple of senior devs working on this in Boeing, along with the hardware systems experts and a billion project 'stakeholders'.

Testing it is going to be the big issue, both in the sim and in the air.


But its not just a "software fix" folks.

They need to be able to have at least 3 input sources to the MCAS to provide at least one layer of redundancy. The systems architecture needs to change to accommodate that.

Airbus works with 3, except for the A350, which has 4.
That said, 787 and 777 only have two. This gives you no real redundancy (once the two values disagree, you can't directly determine which signal is bad), but at least it enables you to determine a disagreement and act accordingly, e.g. by having automatic systems relying on the input switching off or at least throwing an explicit warning.
You could also then try and use secondary data to deduce the values you can't reliably measure directly any more (if any such secondary data is available), which in turn would allow you to cross-check against the directly measured values to determine which of your sensors is still producing valid data.
Again - no real redundancy, but at least it allows you to determine error states and act on them. Seems to work fine on the 787 and 777, too, as I'm not aware of issues cause by their lack of a 3rd sensor.

Amiga500 wrote:
[and there is also no f__king way the existing MCAS was ever at DAL A level assurance. Which is an absolute disgrace on the part of the FAA and actually is making me angry again even thinking about it. I step on a Boeing - I'm trusting the competence of the certifying authority to prevent the manufacturer taking one shortcut too many to save time/money. My confidence in the FAA has taken a real knock. This, along with the 787 battery debacle where ANA had to lead on the difficult decisions really makes me wonder about stepping onto either of the "new" Boeing programs. I am now further aware of how the FAA/Boeing have changed their certification approach over the past couple of decades - 777 was certified with FAA chosen authorisers/signatories. 787 and 737 was "certified" with Boeing chosen authorisers.]

Personally, I agree, based on how things look at the moment. A system as safety-critical/-relevant as MCAS and with as few built-in safeguards (basically: none) shouldn't have made it into the certified production version of a commercial airliner. It's been a while since I took that "Design of safety-critical real-time systems" lecture at university, but I remember that basically looking at the architecture and going through all inputs/outputs and all reasonably conceivable fault modes was an essential part of the exercise. Relying on a human to correct an error to avert disaster that would otherwise be caused or cntributed to by your system's behaviour should only ever be the very last resort. Ideally limited to cases where the human by the very nature or things has more information to make an intelligent decision than your system could ever possibly have.


Fully agree with you. Historically we have always required redundancy especially in flight control systems.

How did concept like this pass even through Critical Design Review and not to mention Certification and EIS is beyond me. Yes you can have single source failure but only if risk analysis (severity and probability) is very very low....which has never been the case for flight controls.

Based on what is known about MCAS so far and being familiar with issues arising from configuration, I would argue that Boeing couldnt pass certification handling quality wise (pitch up, power on stall, go-around, etc) and MCAS was needed to create "Apparent Stability" for HQ cert purposes and secondary match it up with previous version of the 737 handling to some extent.

Thought, what about windshear encounter either on takeoff or on landing? Will pilot applying power and commanding max nose up high result in MCAS pushing down and driving aircraft into the ground???

Being quick fix it appears that system wise MCAS fell through cracks, and how did it pass either ODA or FAA direct involvement I have no clue and I am very curious to learn.

Cheers
 
Babyshark
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 11:39 am

As to 3 AOAs. There have been instances where a A320 family member has 2 AOAs freeze in the same position which eventually set off the alpha protection in normal law. The 3 AOAs are not average, they vote, and 2 of 3 had identical information but bad information.

Hence Airbus pilots with that system have an abnormal alpha protection memory items which is a quick way to knock the airplane out of normal law and into Alternate which turns off the alpha protection. The specifics of the two incidents were a 330 and 321 where the vanes froze during climbout at 4 to 5 degrees, at the 20k to 30k range the FACs took it as the airplane was approaching a stall and acted a accordingly. There are indications something isn't right before it gets there but if missed the pilots have a plan.

Beauty there is there are 3 AOAs. Couldn't imagine just 2. I'd love 4.
Last edited by Babyshark on Fri Mar 15, 2019 11:46 am, edited 1 time in total.
 
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ExperimentalFTE
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 11:44 am

Babyshark wrote:
As to 3 AOAs. There have been instances where a A320 family member has 2 AOAs freeze in the same position which kicked off the alpha protection in normal law. The 3 AOAs are not average, they vote, and 2 of 3 had identical information but bad information.

Hence Airbus pilots with that system have an abnormal alpha protection memory items which is a quick way to knock the airplane out of normal law and into Alternate which turns off the alpha protection.

Beauty there is there are 3. Couldn't imagine just 2. I'd love 4.


And there is aircraft whos team learned from others mistakes and situations including AF447.

A220 has 4 smartprobes plus two independent stall aoa vanes so you could say 6 in total...
 
juliuswong
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 11:45 am

Forgedias wrote:
Putting up a link from Hindustan Times. Original article was from Bloomberg but if people are hitting the paywall, the full article is in this one.

https://www.hindustantimes.com/world-ne ... 5kq2J.html

This article is in reference to what Canada was reporting on Satellite information they received.

Holy smoke! Read the article with disbelief......
- Life is a journey, travel it well -
 
StTim
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 11:51 am

I think I read that MCAS was added during flight testing when they found the effect of the large nacelles at high angles of attack - pushing the nose even higher.

It strikes me that the fix was rushed in oreder to keep to the published schedule and in being rushed it was a poor implementation\solution. I suspect the fix to the fix is going to take a lot more though and testing to ensure it works well and fails safe!
 
AvroLanc
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 11:56 am

I see a lot of blame directed at the FAA for certifying this model. Do other agencies throughout the world do independent analysis, or just rubber stamp the other agencies recommendations? If so should they not be equally at fault?
707, 717, 727, 732, 734, 737 ,738, 7M8, 742, 744, 767, 773, 789.
DC8, 9,10, MD80 ,L1011 ,HSTrident, BAC111, DHComet.
DH8-100, 400, CRJ100,200,700, EM75,90, A310,319,320,321,333
 
Interested
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 11:59 am

juliuswong wrote:
Forgedias wrote:
Putting up a link from Hindustan Times. Original article was from Bloomberg but if people are hitting the paywall, the full article is in this one.


https://www.hindustantimes.com/world-ne ... 5kq2J.html

This article is in reference to what Canada was reporting on Satellite information they received.

Holy smoke! Read the article with disbelief......


As each day passes the worse it all looks
 
mjoelnir
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:04 pm

Regarding the grounding off the 737MAX. IMO the FAA and Boeing have made a huge mistake, not having being the lead to ground the frame after the accident in Ethiopia. In the case they would have lead, they would also lead when they want the grounding be removed after changes to the frame.

Now agencies like EASA and CAAC have grounded the frame on their own authority. They will only lift the grounding on their own authority again. It will be an uphill battle for the FAA and Boeing to accept the future changes in regards to the safety and certification for the 737MAX.
 
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Finn350
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:06 pm

Forgedias wrote:
Putting up a link from Hindustan Times. Original article was from Bloomberg but if people are hitting the paywall, the full article is in this one.

https://www.hindustantimes.com/world-ne ... 5kq2J.html

This article is in reference to what Canada was reporting on Satellite information they received.


Thanks for the linki! It is well written article about the satellite tracking of the accident flight and its implications.
 
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keesje
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:09 pm

mjoelnir wrote:
Regarding the grounding off the 737MAX. IMO the FAA and Boeing have made a huge mistake, not having being the lead to ground the frame after the accident in Ethiopia. In the case they would have lead, they would also lead when they want the grounding be removed after changes to the frame.

Now agencies like EASA and CAAC have grounded the frame on their own authority. They will only lift the grounding on their own authority again. It will be an uphill battle for the FAA and Boeing to accept the future changes in regards to the safety and certification for the 737MAX.


Traditionally FAA and EASA have followed each others certifications. I hope that mutual acceptance hasn't been damaged.
"Never mistake motion for action." Ernest Hemingway
 
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United_fan
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:09 pm

"Suspicion is a matter of opinion"
 
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kelvin933
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:13 pm

StTim wrote:
I think I read that MCAS was added during flight testing when they found the effect of the large nacelles at high angles of attack - pushing the nose even higher.

It strikes me that the fix was rushed in oreder to keep to the published schedule and in being rushed it was a poor implementation\solution. I suspect the fix to the fix is going to take a lot more though and testing to ensure it works well and fails safe!


I can imagine the people inside EASA that have wanted to reject the grandfathering of the original 737-100 certificate for 737 versions after the 737Classic was certified to be telling their colleagues who approved this grandfathering that they where wrong to allow that grandfathering..
Just imagine the 737MAX has had the wingbox redisigned, the wings redisigned, the engine redisigned and has acquired a glass cockpit and now also has partial FBW functions bolted onto the manual flight controls originally designed in the mid 60s.
Just looking at the engines the original Pratt & Whitney JT8D-1 weighed 4,741 pounds and had a 49 inch diameter fan (14Klbs to 18klbs thrust), the CFM LEAP-1B used on the 737MAX weighs 6,130 pounds and has a 69.4 diamerter fan (24Klbs to 35klbs thrust) .
“Nations have no permanent friends or allies, they only have permanent interests.”
 
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kelvin933
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:17 pm

keesje wrote:
mjoelnir wrote:
Regarding the grounding off the 737MAX. IMO the FAA and Boeing have made a huge mistake, not having being the lead to ground the frame after the accident in Ethiopia. In the case they would have lead, they would also lead when they want the grounding be removed after changes to the frame.

Now agencies like EASA and CAAC have grounded the frame on their own authority. They will only lift the grounding on their own authority again. It will be an uphill battle for the FAA and Boeing to accept the future changes in regards to the safety and certification for the 737MAX.


Traditionally FAA and EASA have followed each others certifications. I hope that mutual acceptance hasn't been damaged.

It has been damaged, the acting management at the FAA has been incredibly compliant to Boeing wishes. They did not ground the aircraft when everyone else including their close partner Transport Canada had grounded the 737MAX.
“Nations have no permanent friends or allies, they only have permanent interests.”
 
ytz
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:19 pm

juliuswong wrote:
Forgedias wrote:
Putting up a link from Hindustan Times. Original article was from Bloomberg but if people are hitting the paywall, the full article is in this one.

https://www.hindustantimes.com/world-ne ... 5kq2J.html

This article is in reference to what Canada was reporting on Satellite information they received.

Holy smoke! Read the article with disbelief......


Altitude variations of several hundred feet. Panicked pilot asking to rtb. And still so many folks here thought a grounding wasn't warranted. People really need to reevaluate their attitude to safety.

You shouldn't need a pilot's license or an engineering degree to look at the contextual similarities between two incidents and see that a cautionary pause is necessary.

Any of these folks going to apologize now? I doubt it. They were all waiting for one of those 1500 hr ATPLs to take another 180 souls with him before they decided Boeing's shareholders should take a temporary hit.

The FAA and TC's decision to err on the side of Boeing and the airlines for days, looks absolutely terrible on them now.
Last edited by ytz on Fri Mar 15, 2019 12:34 pm, edited 1 time in total.
 
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DL717
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:28 pm

ExperimentalFTE wrote:
anfromme wrote:
Amiga500 wrote:

But its not just a "software fix" folks.

They need to be able to have at least 3 input sources to the MCAS to provide at least one layer of redundancy. The systems architecture needs to change to accommodate that.

Airbus works with 3, except for the A350, which has 4.
That said, 787 and 777 only have two. This gives you no real redundancy (once the two values disagree, you can't directly determine which signal is bad), but at least it enables you to determine a disagreement and act accordingly, e.g. by having automatic systems relying on the input switching off or at least throwing an explicit warning.
You could also then try and use secondary data to deduce the values you can't reliably measure directly any more (if any such secondary data is available), which in turn would allow you to cross-check against the directly measured values to determine which of your sensors is still producing valid data.
Again - no real redundancy, but at least it allows you to determine error states and act on them. Seems to work fine on the 787 and 777, too, as I'm not aware of issues cause by their lack of a 3rd sensor.

Amiga500 wrote:
[and there is also no f__king way the existing MCAS was ever at DAL A level assurance. Which is an absolute disgrace on the part of the FAA and actually is making me angry again even thinking about it. I step on a Boeing - I'm trusting the competence of the certifying authority to prevent the manufacturer taking one shortcut too many to save time/money. My confidence in the FAA has taken a real knock. This, along with the 787 battery debacle where ANA had to lead on the difficult decisions really makes me wonder about stepping onto either of the "new" Boeing programs. I am now further aware of how the FAA/Boeing have changed their certification approach over the past couple of decades - 777 was certified with FAA chosen authorisers/signatories. 787 and 737 was "certified" with Boeing chosen authorisers.]

Personally, I agree, based on how things look at the moment. A system as safety-critical/-relevant as MCAS and with as few built-in safeguards (basically: none) shouldn't have made it into the certified production version of a commercial airliner. It's been a while since I took that "Design of safety-critical real-time systems" lecture at university, but I remember that basically looking at the architecture and going through all inputs/outputs and all reasonably conceivable fault modes was an essential part of the exercise. Relying on a human to correct an error to avert disaster that would otherwise be caused or cntributed to by your system's behaviour should only ever be the very last resort. Ideally limited to cases where the human by the very nature or things has more information to make an intelligent decision than your system could ever possibly have.


Fully agree with you. Historically we have always required redundancy especially in flight control systems.

How did concept like this pass even through Critical Design Review and not to mention Certification and EIS is beyond me. Yes you can have single source failure but only if risk analysis (severity and probability) is very very low....which has never been the case for flight controls.

Based on what is known about MCAS so far and being familiar with issues arising from configuration, I would argue that Boeing couldnt pass certification handling quality wise (pitch up, power on stall, go-around, etc) and MCAS was needed to create "Apparent Stability" for HQ cert purposes and secondary match it up with previous version of the 737 handling to some extent.

Thought, what about windshear encounter either on takeoff or on landing? Will pilot applying power and commanding max nose up high result in MCAS pushing down and driving aircraft into the ground???

Being quick fix it appears that system wise MCAS fell through cracks, and how did it pass either ODA or FAA direct involvement I have no clue and I am very curious to learn.

Cheers


This is a big question. It’s not like they take off, land and get handed a cert. Certification is some of the most demanding flying an aircraft is ever going to see. Why didn’t this show up during the cert process?

https://www.faa.gov/documentLibrary/med ... _25-7D.pdf
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seahawk
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:35 pm

Because it is a paper decision. Do you believe the system is working correctly and safely with input from one sensor or not. You do not try with a defective AoA sensor much less without knowing.

It is one of the cases were pilot error and design fault are kind of mixed. A test pilot with deep knowledge of all systems would probably make the right decisions and draw the right conclusions, but it might not be that easy for an average pilot.
 
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:50 pm

seahawk wrote:
Because it is a paper decision. Do you believe the system is working correctly and safely with input from one sensor or not. You do not try with a defective AoA sensor much less without knowing.

It is one of the cases were pilot error and design fault are kind of mixed. A test pilot with deep knowledge of all systems would probably make the right decisions and draw the right conclusions, but it might not be that easy for an average pilot.


Fair enough, but one would think something like this would be observable and noted. Given the apparent low rate of occurance, it does make one wonder if it’s a bad batch of components vs. software.
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:50 pm

Interested wrote:
juliuswong wrote:
Forgedias wrote:
Putting up a link from Hindustan Times. Original article was from Bloomberg but if people are hitting the paywall, the full article is in this one.


https://www.hindustantimes.com/world-ne ... 5kq2J.html

This article is in reference to what Canada was reporting on Satellite information they received.

Holy smoke! Read the article with disbelief......


As each day passes the worse it all looks

Sadly it is. I can't fathom what the pilot of both crash went through as they battled to save their plane. No amount of training can help in this sudden situation. What will Boeing do now to rectify the grave situation is in everyone guess. Hundreds of aircraft are now grounded and require fixing. Not forgetting those already in production line.......They should have gone for clean sheet NB rather than plunk two big engines and called it a day. Too bad they needed to catch up with A320neo urgently and took the shortcut, ended up paying dearly. I just hope this second patch-up by Boeing works and this senseless death will cease.

Boeing is filled with good engineering talent, time to make full use of it.
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:58 pm

DL717 wrote:
seahawk wrote:
Because it is a paper decision. Do you believe the system is working correctly and safely with input from one sensor or not. You do not try with a defective AoA sensor much less without knowing.

It is one of the cases were pilot error and design fault are kind of mixed. A test pilot with deep knowledge of all systems would probably make the right decisions and draw the right conclusions, but it might not be that easy for an average pilot.


Fair enough, but one would think something like this would be observable and noted. Given the apparent low rate of occurance, it does make one wonder if it’s a bad batch of components vs. software.


My opinion based on experience in similar but not exactly same fields, is that today a critical automatic system using only one sensor is a no-go and should not have been certified. I can however see the reasoning why they did, as one can say that it is not that critical and a fault easy to recognize. But that takes us to the problems of grandfathering certifications and adding modern systems to an old one. Sometimes they brake the established man to machine interface. And to be honest I find it curios that the AP would disengage due to sensor errors, but the MCAS would not, there is a logical fault in the system in that case imho.

Same with MCAS not giving any hint of being active on the primary flight displays or warning panel.
 
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 12:58 pm

kelvin933 wrote:
...
It has been damaged, the acting management at the FAA has been incredibly compliant to Boeing wishes. They did not ground the aircraft when everyone else including their close partner Transport Canada had grounded the 737MAX.


EASA relationship shouldn't be a problem, they will come around. On the other hand, CAAC will milk this to the full extent. It will be a lot of fun if they ask the FAA to certify their planes.
 
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 1:26 pm

Photo of the mangled flight recorder:

Image

https://www.forbes.com/sites/kristykier ... 0856ed3377
 
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 1:34 pm

kelvin933 wrote:
keesje wrote:
mjoelnir wrote:
Regarding the grounding off the 737MAX. IMO the FAA and Boeing have made a huge mistake, not having being the lead to ground the frame after the accident in Ethiopia. In the case they would have lead, they would also lead when they want the grounding be removed after changes to the frame.

Now agencies like EASA and CAAC have grounded the frame on their own authority. They will only lift the grounding on their own authority again. It will be an uphill battle for the FAA and Boeing to accept the future changes in regards to the safety and certification for the 737MAX.


Traditionally FAA and EASA have followed each others certifications. I hope that mutual acceptance hasn't been damaged.

It has been damaged, the acting management at the FAA has been incredibly compliant to Boeing wishes. They did not ground the aircraft when everyone else including their close partner Transport Canada had grounded the 737MAX.

Seems the standard has shifted from "understand what the data is telling us" to "do what everyone else is doing"?

Personally, I prefer science and professional principals over peer pressure and emotion, but perhaps that's just me.
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 1:39 pm

Science and professional principals, should take in to account, statistics, and statistically we have a problem here.
 
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 1:41 pm

Once all of the aircraft are repositioned, AA is parking its 24 Boeing 737 MAX at the following airports:

Airport # Tail Numbers
Tulsa (TUL) 9 N350RV, N314RH, N342RX, N335RT, N303RE, N324RN, N326RP, N315RJ, N328RR
Orlando Melbourne (MLB) 3 N308RD, N310RF, N316RK
Mobile Downtown (BFM) 2 N303RG, N323RM
Boston (BOS) 2 N324RA, N321RL
Philadelphia (PHL) 2 N336RU, N338RS
Phoenix (PHX) 2 N304RB, N313SB
New York JFK 1 N306RC
Las Vegas (LAS) 1 N302SA
San Francisco (SFO) 1 N343RY
St. Louis (STL) 1 N341RW
The large number of aircraft being stored at Tulsa makes sense, as American Airlines has a massive maintenance base there. However, besides Boston — which typically has 4x scheduled 737 MAX flights a day — no other airports have scheduled AA 737 MAX flights. That means that AA will have to ferry these aircraft from these airports when the grounding is resolved. It seems the airline has calculated that the cost of parking these aircraft at these other airports would be cheaper than storing the planes at airports where it usually flies the MAX.
 
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Re: B737MAX Grounded Worldwide

Fri Mar 15, 2019 1:44 pm

Revelation wrote:
Personally, I prefer science and professional principals over peer pressure and emotion, but perhaps that's just me.


I absolutely do too. However I hope the events of the past few months teach is that the attitude of "it is never right to take action before all the facts are known" is both outdated and downright dangerous.

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