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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Aug 25, 2019 11:37 pm

mjoelnir wrote:
There is one real issue on the EASA list, that nobody mentions for quite a while. The manual trim. There is no software solution for that.

So since the same condition exist on the NG is EASA giving that a/c a waiver or they are going to propose grounding?
If an NG is in a high speed out of trim situation the wheel is just as hard to turn, the trigger does not change the fact that the wheel is hard to turn.

Now if EASA wants to ensure that the trigger event - MCAS - is as minimal as any type of issue on the NG then fine, but your comment is about the difficulty of moving the trim wheel, so what to do about the NG.
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Aug 25, 2019 11:45 pm

par13del wrote:
mjoelnir wrote:
There is one real issue on the EASA list, that nobody mentions for quite a while. The manual trim. There is no software solution for that.

So since the same condition exist on the NG is EASA giving that a/c a waiver or they are going to propose grounding?
If an NG is in a high speed out of trim situation the wheel is just as hard to turn, the trigger does not change the fact that the wheel is hard to turn.

Now if EASA wants to ensure that the trigger event - MCAS - is as minimal as any type of issue on the NG then fine, but your comment is about the difficulty of moving the trim wheel, so what to do about the NG.

Did the EASA ever officially confirm that they sent such a list? Or, is this only as "two people close to the situation confirmed"?
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Aug 25, 2019 11:54 pm

 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 12:42 am

aerolimani wrote:
I think you are correct. A “come to Jesus” moment will likely never come from Boeing and the FAA.

I think the best we can hope for is that US legislators will decide to adjust the role of the FAA in two ways. One would be to greatly reduce the amount of self-certification. The other would be to remove the role of the FAA as an encourager of innovation and development of the aviation industry. I wouldn’t go so far as to call it a definite conflict of interest, but I don’t think it aligns well with their role of ensuring safety. There’s a great potential for oversight to be seen as a hindrance to innovation.

However, with the state of American politics, I don’t think any such changes are likely to take place. I don’t think a change of government would increase the likelihood either. So… we will likely be disappointed.

I think the best we can actually hope for is that the financial cost of this major cockup will be enough for Boeing’s leaders to remember beyond the next fiscal quarter, and to take steps to ensure they don’t end up here ever again.

I agree with what you wrote, that a 'come to Jesus' moment is not likely, nor are legislative driven reforms.

Sadly, in the current US climate, the only real reform will be from lawyers grabbing Boeing by the short and curlies till they howl.

The only thing we have to rein in the excessive greed of capitalists is the excessive greed of lawyers.

It will be interesting to see what if anything comes from things like the JATR committee and/or the FBI/DoJ probes.
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 1:09 am

Revelation wrote:
It will be interesting to see what if anything comes from things like the JATR committee and/or the FBI/DoJ probes.

On the JATR I would expect agreement on the lifting on the grounding if the FAA says they are satisfied, with the USA going first and the others doing additional verification or just outright saying a phased lifting. I would have much preferred the JATR to be for the certification process versus MAX, it was a golden chance to have all regulators working on an item that has significant ramifications.

On the FBI / DOJ probe all I can say is wait and see or listen for leaks, there is more political input on the DOJ side, neither of them is immune, however the investigative powers of the FBI will or may bear fruit, if there are things hidden under rocks they will find them, what the DOJ does with the info is.....
 
foxtrotbravo21
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 2:33 am

FAA have already invited pilots from some airlines to use the simulator to test the upgraded software. Hope the 737 Max will be able to take to the skies by November.
 
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PITingres
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 4:39 am

JetBuddy wrote:
PITingres wrote:
keesje wrote:
:arrow: Show how the original MCAS solution got certified, how it passed all safety layers and double checks.
:arrow: Prove MCAS was an incident, no other, potentially faulty, design choices have followed the same approval process.
:arrow: Explain why Boeing and FAA were so late pulling the TC.
:arrow: How Boeing / FAA guarantee independent oversight, which can't be overruled by commercial, political interests
:arrow: Clarity on who was responsible for a faulty design entering service. What corrective actions have been taken.



What does any of that have to do with certification? You are describing investigative agency procedures (e.g. NTSB), not certificating steps. Determining who was at fault or what procedures were wrong has zero to do with verifying that the new solution is correct, as long as the new solution is analyzed without reliance on old solution data or assumptions.


It does have something to do with Boeing and FAA safety culture. Corporate interests over public safety. And so on. Personally I won't fly on a MAX until each of these questions are answered, even if the MAX is deemed safe again. It's a matter of building trust in both Boeing and FAA.


But nothing to do with certification or lifting of the grounding. Feel free to not fly on a MAX ever again, because I can pretty much guarantee that no certificating agency is going to make any attempt to answer those questions -- because they aren't certification relevant questions.

Now, if you want an investigative body to go into those points, and then make safety recommendations based off the results of the investigation, that's fine and valid. But it's not a pre-requisite for lifting the grounding; that's simply not how any of this works.
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sgrow787
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 4:51 am

MrBretz wrote:
qf789 wrote:
737MAX could return to flight as early as October after both Boeing and the FAA give signs about returning the aircraft to service

https://www.seattletimes.com/business/b ... to-flight/


And it’s from Dominic Gates. I will have sleep on this one.


Yet Mr. Gates refers to the MCAS 1.0 events as "the original version of which went haywire in the two fatal MAX crashes". Didn't MCAS 1.0 behave exactly as it was designed? According to the manufacturer, Boeing, they depended on the pilots as backup for a failed AOA sensor. Why can't he just say "the original version of which was responsible for (or primarily responsible for) the two fatal MAX crashes"? Furthermore, there was no bug in MCAS 1.0. It was designed a certain way with certain assumptions. It behaved exactly the way it was designed. This isn't a bug. It's a redesign that needs recertification.
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sgrow787
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 5:09 am

PITingres wrote:

keesje wrote:
:arrow: Show how the original MCAS solution got certified, how it passed all safety layers and double checks.
:arrow: Prove MCAS was an incident, no other, potentially faulty, design choices have followed the same approval process.
:arrow: Explain why Boeing and FAA were so late pulling the TC.
:arrow: How Boeing / FAA guarantee independent oversight, which can't be overruled by commercial, political interests
:arrow: Clarity on who was responsible for a faulty design entering service. What corrective actions have been taken.

What does any of that have to do with certification?


Well it's still up to the FAA isn't it? It could be the day before the ungrounding and for whatever reason they decide something isn't right. Anything is fair game, especially for a regulatory body who needs to regain credibility.
Just one sensor,
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 10:43 am

sgrow787 wrote:
Well it's still up to the FAA isn't it? It could be the day before the ungrounding and for whatever reason they decide something isn't right. Anything is fair game, especially for a regulatory body who needs to regain credibility.

So the issue is now larger than the MAX, whether it is now safe is secondary to the FAA now showing the rest of the world that it has the authority to keep the MAX grounded until it feels it has regained some level of credibility?
 
sgrow787
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 10:53 am

par13del wrote:
sgrow787 wrote:
Well it's still up to the FAA isn't it? It could be the day before the ungrounding and for whatever reason they decide something isn't right. Anything is fair game, especially for a regulatory body who needs to regain credibility.

So the issue is now larger than the MAX, whether it is now safe is secondary to the FAA now showing the rest of the world that it has the authority to keep the MAX grounded until it feels it has regained some level of credibility?


Are you assuming we know everything there is to know about this plane?
Just one sensor,
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Just one sensor,
Ooh ooh oo-ooh
Oo-oo-ooh.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 11:16 am

Not assuming anything, just asking the question around your credibility statement. If the a/c is safe to fly it is safe to fly, that is the reason why it was grounded, not because of the FAA outsourcing loads of its certification authority.
The 777X is in the process of being certified, it is now behind schedule because of GE engines, do you hear any leaks about the FAA throwing additional resources at that a/c to regain credibility or are they going to wait until next year to start the process?
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 11:17 am

kalvado wrote:
mjoelnir wrote:
TTailedTiger wrote:

They could demand diamond encrusted thrust levers but that doesn't mean they will get them. Their issue has to be real. I have seen no evidence that their fetish over the trim wheel has any merit.


There is one real issue on the EASA list, that nobody mentions for quite a while. The manual trim. There is no software solution for that.

Can be a paperwork fix, though. In principle, Boeing may show that high-force manual trim from way out of trim position is no longer needed. Has to be a combination of past NG records for out of trim events, updated MCAS, possibly mandate roller coaster on a sim. But if they prove low enough crash probability, that is all they need.


Should the manual trim not be the last ditch defense also for an unknown problem? Is this attitude not part of what lead to the two crashes?
IMO one of the holes in the Swiss cheese.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 11:58 am

mjoelnir wrote:
Should the manual trim not be the last ditch defense also for an unknown problem? Is this attitude not part of what lead to the two crashes?
IMO one of the holes in the Swiss cheese.

I thought that was also the procedure for the NG?
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 12:08 pm

mjoelnir wrote:
kalvado wrote:
mjoelnir wrote:

There is one real issue on the EASA list, that nobody mentions for quite a while. The manual trim. There is no software solution for that.

Can be a paperwork fix, though. In principle, Boeing may show that high-force manual trim from way out of trim position is no longer needed. Has to be a combination of past NG records for out of trim events, updated MCAS, possibly mandate roller coaster on a sim. But if they prove low enough crash probability, that is all they need.


Should the manual trim not be the last ditch defense also for an unknown problem? Is this attitude not part of what lead to the two crashes?
IMO one of the holes in the Swiss cheese.

If it can be proved that things should never (i.e. 1 in billion or better) come to that last ditch scenario, then everything should be good even with suboptimal last ditch
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 12:09 pm

mjoelnir wrote:
kalvado wrote:
mjoelnir wrote:
There is one real issue on the EASA list, that nobody mentions for quite a while. The manual trim. There is no software solution for that.

Can be a paperwork fix, though. In principle, Boeing may show that high-force manual trim from way out of trim position is no longer needed. Has to be a combination of past NG records for out of trim events, updated MCAS, possibly mandate roller coaster on a sim. But if they prove low enough crash probability, that is all they need.

Should the manual trim not be the last ditch defense also for an unknown problem? Is this attitude not part of what lead to the two crashes?
IMO one of the holes in the Swiss cheese.

It's not clear that one can evaluate the probability of an unknown problem, and all these certification processes work by evaluating probabilities.
It'd be nice to have plans A-Z for every contingency, but that's not how things work in aviation.
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Asturias
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 1:59 pm

Revelation wrote:
It's not clear that one can evaluate the probability of an unknown problem, and all these certification processes work by evaluating probabilities.


The 737 design actually has no unknown problems, not any variant from the original to the NG, they have more than half a century of active operation - but the MAX does have problems, known and unknown, and these problems all stem from engine size and placement.

Revelation wrote:
It'd be nice to have plans A-Z for every contingency, but that's not how things work in aviation.


That's right, and because of that in civil aviation people do their darndest to design crafts to have as few contingencies as humanly possible.

It is a very conservative business, for that very reason. It's impossible to have plans for all contingencies, thus creating or engineering situations which present new contingencies is simply not encouraged. It's bad practice.

No matter how you look at it, the engine size and placement on the MAX is what created new contingencies, which simply did not exist before on the 737.

These were known contingencies, obviously, since steps were made to remedy them. These remedies were quite inadequate, which is why it's grounded worldwide.

Not because of "every contingency" wasn't accounted for, but as a result of a known contingency being addressed in an inadequate way. And addressing issues in an inadequate way is not how things work in aviation.
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 2:15 pm

Asturias wrote:
Not because of "every contingency" wasn't accounted for, but as a result of a known contingency being addressed in an inadequate way. And addressing issues in an inadequate way is not how things work in aviation.

Thanks for the retrospective view.

Now we find ourselves in a situation where the many faults of MCAS have been addressed, along with the 'cosmic ray' fix addressing even more classes of potential issues.

The industry has a history of using augmentation systems to deal with various adverse situations, such as Boeing's speed trim system going back to NG if not earlier.

MCAS 2.0 will now address a bit of adverse nacelle lift in a deep corner of the flight envelope.

Eventually in aviation we get to a point where even conservative people say all known issues have been addressed in an adequate way and it's time go fly.
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jollo
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 2:53 pm

Revelation wrote:
MCAS 2.0 will now address a bit of adverse nacelle lift in a deep corner of the flight envelope.


I would rephrase this more conservatively as:

MCAS 2.0 will now address in an technically adequate way a bit of adverse nacelle lift in a couple of deep corners of the flight envelope, without setting off critical control runaways in not-so-infrequent operational contingencies such as a single sensor failures.

Revelation wrote:
Eventually in aviation we get to a point where even conservative people say all known issues have been addressed in an adequate way and it's time go fly.


Now I can agree with your conclusion.
 
IADFCO
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 3:19 pm

I would rephrase this even more conservatively as:

jollo wrote:
Revelation wrote:
MCAS 2.0 will now address a bit of adverse nacelle lift in a deep corner of the flight envelope.


I would rephrase this more conservatively as:

MCAS 2.0 will now address in an technically adequate way a bit of adverse nacelle lift in a couple of deep corners of the flight envelope, without setting off critical control runaways in not-so-infrequent operational contingencies such as a single sensor failures.

Revelation wrote:
Eventually in aviation we get to a point where even conservative people say all known issues have been addressed in an adequate way and it's time go fly.


Now I can agree with your conclusion.


MCAS 2.0 now claims to address in a[n] technically adequate way a publicly undisclosed problem, presumed to be linked to nacelle-wing aerodynamic interaction in high-angle-of-attack portions of the flight envelope, without setting off critical control runaways in not-so-infrequent operational contingencies such as a single sensor failures.

Now I too can agree with your conclusions.
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 4:08 pm

I understand that a typical 737 in its entire life cycle never gets into the hazardous situation that MCAS was designed to operate. MCAS, and MCAS alone was what made two planes crash. (I am ignoring pilots and training here) Had MCAS not been installed no MAXs would have crashed. It is not the first time in the world that a 'safety' item caused fatalities. The other obvious one is poorly designed automobile inflatable safety bags.
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 4:24 pm

frmrCapCadet wrote:
It is not the first time in the world that a 'safety' item caused fatalities.

We sure it really was a "safety item" versus a certification check box, lighter feel on the stick is understood, but for the sections where MCAS was implemented, was it really needed?
Its a rhetorical question, but as good as any while we continue to wait for the September submission.
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 4:30 pm

par13del wrote:
mjoelnir wrote:
Should the manual trim not be the last ditch defense also for an unknown problem? Is this attitude not part of what lead to the two crashes?
IMO one of the holes in the Swiss cheese.

I thought that was also the procedure for the NG?


If it is insufficient on the NG too, should that be a reason to not change it on the MAX, while there are still a limited number of frames involved?
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 4:40 pm

par13del wrote:
We sure it really was a "safety item" versus a certification check box, lighter feel on the stick is understood, but for the sections where MCAS was implemented, was it really needed?
Its a rhetorical question, but as good as any while we continue to wait for the September submission.

That's where we fall back to "aviation is a conservative business".

mjoelnir wrote:
par13del wrote:
mjoelnir wrote:
Should the manual trim not be the last ditch defense also for an unknown problem? Is this attitude not part of what lead to the two crashes?
IMO one of the holes in the Swiss cheese.

I thought that was also the procedure for the NG?

If it is insufficient on the NG too, should that be a reason to not change it on the MAX, while there are still a limited number of frames involved?

We have 7,000 NGs build and 20+ years of NG flight ops to tell us their trim wheel is adequate.

It only became an issue when the airplane was severely mistrimmed when MCAS 1.0 was trimming the nose down repeatedly and the trim wheel being used to trim the nose up and no one understanding how to disable the trim motor or the MCAS function.

Now that MCAS 2.0 fixes the many issues with MCAS 1.0, it falls back to the same classification as NG.
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 4:58 pm

Revelation wrote:
We have 7,000 NGs build and 20+ years of NG flight ops to tell us their trim wheel is adequate.

It only became an issue when the airplane was severely mistrimmed when MCAS 1.0 was trimming the nose down repeatedly and the trim wheel being used to trim the nose up and no one understanding how to disable the trim motor or the MCAS function.

Now that MCAS 2.0 fixes the many issues with MCAS 1.0, it falls back to the same classification as NG.

An stab trim runaway (from any causes) can easily miss trim any 737, including the NG. The MCAS v1 only added a deadly cause of miss time on the MAX that will be removed with MCAS v2, but all others possibles causes of miss trim remains and must be addressed properly in the safety assessment of each 737 models now that this is know that the trim wheels could not be effective as expected in some situations. The safety assessment could conclude that the risk is low enough to not require additional action, or it could conclude that the risk is not low enough and that new action is required, for example a specific training. We will see...
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 5:12 pm

mjoelnir wrote:
If it is insufficient on the NG too, should that be a reason to not change it on the MAX, while there are still a limited number of frames involved?

How do you propose to fix it on the thousands of NG's deployed, its easy to look at the limited number of MAX frames, you pushing grandfathering for a son but not a grand son?
 
ACATROYAL
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 5:26 pm

Revelation wrote:
JetBuddy wrote:
It does have something to do with Boeing and FAA safety culture. Corporate interests over public safety. And so on. Personally I won't fly on a MAX until each of these questions are answered, even if the MAX is deemed safe again. It's a matter of building trust in both Boeing and FAA.

I guess you won't be flying a MAX ever again, nor any US certified aircraft either, and others will make their own minds up in their own ways. That's OK, I'll never fly Air France after AF447. I have no faith they've changed the approach to selecting and training pilots after that accident. IMO, they just gave it the Gallic shrug and moved on. Similar to one poster's expectations in the case of Boeing/FAA, I was waiting for AF to have a "come to Jesus" moment and it never happened, yet AF seems to be no worse off due to my personal distaste for their safety culture.

ACATROYAL wrote:
My god, it seems that in this thread every possible component of the 737 MAX has been dissected, scrutinized and debated. I can't believe that there's anything left to discuss but I suspect some people will always find something else to analyze. This thread is now on its 40th and still counting page, so I will now predict it will hit 100+ pages by the time it gets authorized to fly again. I don't know what more can be said but it will be interesting to see...

It looks like you're going to lose that bet. Seems we now have the end of the MAX saga in sight, a few posters vented a bit and then this thread went 12 hours with no posts, and even fell off a.net's page one over night. As one poster likes to write, it seems we have had a lot of recalculation going on and this saga no longer suits various agendas, so IMO it will go even more quiet over time.


If there is anything I have learned in life and that is...don't believe anything until you actually see it!! Boeing is notorious for blowing lots of smoke, especially lately so until I see all the world's aviation authorities clear it for flying this Max Mess remains grounded until further notice...
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 5:36 pm

PixelFlight wrote:
Revelation wrote:
We have 7,000 NGs build and 20+ years of NG flight ops to tell us their trim wheel is adequate.

It only became an issue when the airplane was severely mistrimmed when MCAS 1.0 was trimming the nose down repeatedly and the trim wheel being used to trim the nose up and no one understanding how to disable the trim motor or the MCAS function.

Now that MCAS 2.0 fixes the many issues with MCAS 1.0, it falls back to the same classification as NG.

An stab trim runaway (from any causes) can easily miss trim any 737, including the NG. The MCAS v1 only added a deadly cause of miss time on the MAX that will be removed with MCAS v2, but all others possibles causes of miss trim remains and must be addressed properly in the safety assessment of each 737 models now that this is know that the trim wheels could not be effective as expected in some situations. The safety assessment could conclude that the risk is low enough to not require additional action, or it could conclude that the risk is not low enough and that new action is required, for example a specific training. We will see...

It was discussed upthread. Looks like stuck thumbswitches were a major reason for runaway in the early days. Once those were redesigned, runaway rate went well down, to the point that no actual events were brought up in the discussion. It is totally reasonable for Boeing to review the analysis of runaway scenarios (which was probably not changed since 737-100) and find,based on historical data to, that those are much less of an issue by now.
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 5:52 pm

Revelation wrote:
par13del wrote:
We sure it really was a "safety item" versus a certification check box, lighter feel on the stick is understood, but for the sections where MCAS was implemented, was it really needed?
Its a rhetorical question, but as good as any while we continue to wait for the September submission.

That's where we fall back to "aviation is a conservative business".

mjoelnir wrote:
par13del wrote:
I thought that was also the procedure for the NG?

If it is insufficient on the NG too, should that be a reason to not change it on the MAX, while there are still a limited number of frames involved?

We have 7,000 NGs build and 20+ years of NG flight ops to tell us their trim wheel is adequate.

It only became an issue when the airplane was severely mistrimmed when MCAS 1.0 was trimming the nose down repeatedly and the trim wheel being used to trim the nose up and no one understanding how to disable the trim motor or the MCAS function.

Now that MCAS 2.0 fixes the many issues with MCAS 1.0, it falls back to the same classification as NG.

Very poor characterisation of the events after two preliminary reports, a grounding and eight months of discussion. JT0- 43 cut out was employed and manual wheel used. JT610 - manual wheel did not come in to play. ET302 cut out was employed and manual wheel was at least attempted.

Ray
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 6:02 pm

PixelFlight wrote:
Revelation wrote:
We have 7,000 NGs build and 20+ years of NG flight ops to tell us their trim wheel is adequate.

It only became an issue when the airplane was severely mistrimmed when MCAS 1.0 was trimming the nose down repeatedly and the trim wheel being used to trim the nose up and no one understanding how to disable the trim motor or the MCAS function.

Now that MCAS 2.0 fixes the many issues with MCAS 1.0, it falls back to the same classification as NG.

An stab trim runaway (from any causes) can easily miss trim any 737, including the NG. The MCAS v1 only added a deadly cause of miss time on the MAX that will be removed with MCAS v2, but all others possibles causes of miss trim remains and must be addressed properly in the safety assessment of each 737 models now that this is know that the trim wheels could not be effective as expected in some situations. The safety assessment could conclude that the risk is low enough to not require additional action, or it could conclude that the risk is not low enough and that new action is required, for example a specific training. We will see...

Yes. I suspect that the suite of simulator tests being arranged to include newly MAX qualified pilots is most likely related to evaluation of revised operating procedures than anything else. It is quite possible that these include procedures related to runaway trim.

Ray
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 6:06 pm

XRAYretired wrote:
Very poor characterisation of the events after two preliminary reports, a grounding and eight months of discussion. JT0- 43 cut out was employed and manual wheel used. JT610 - manual wheel did not come in to play. ET302 cut out was employed and manual wheel was at least attempted.

Thank you for another interesting retroactive analysis.

The analysis we need is situations where mistrim is much less likely, namely NG with no MCAS and MAX with MCAS 2.0, 'cosmic ray' fix, and others.
Last edited by Revelation on Mon Aug 26, 2019 6:06 pm, edited 1 time in total.
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mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 6:06 pm

Revelation wrote:

We have 7,000 NGs build and 20+ years of NG flight ops to tell us their trim wheel is adequate.

It only became an issue when the airplane was severely mistrimmed when MCAS 1.0 was trimming the nose down repeatedly and the trim wheel being used to trim the nose up and no one understanding how to disable the trim motor or the MCAS function.

Now that MCAS 2.0 fixes the many issues with MCAS 1.0, it falls back to the same classification as NG.


Absolute nonsense. The manual trim wheel should be a back up under any circumstances. What the MCAS disaster showed us is, that you can not predict when you will need that backup and under what circumstances.
Furthermore the MAX is not a NG. Different flight characteristics,.that have to be compensated by computer action.
Last edited by mjoelnir on Mon Aug 26, 2019 6:32 pm, edited 2 times in total.
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 6:12 pm

kalvado wrote:
PixelFlight wrote:
Revelation wrote:
We have 7,000 NGs build and 20+ years of NG flight ops to tell us their trim wheel is adequate.

It only became an issue when the airplane was severely mistrimmed when MCAS 1.0 was trimming the nose down repeatedly and the trim wheel being used to trim the nose up and no one understanding how to disable the trim motor or the MCAS function.

Now that MCAS 2.0 fixes the many issues with MCAS 1.0, it falls back to the same classification as NG.

An stab trim runaway (from any causes) can easily miss trim any 737, including the NG. The MCAS v1 only added a deadly cause of miss time on the MAX that will be removed with MCAS v2, but all others possibles causes of miss trim remains and must be addressed properly in the safety assessment of each 737 models now that this is know that the trim wheels could not be effective as expected in some situations. The safety assessment could conclude that the risk is low enough to not require additional action, or it could conclude that the risk is not low enough and that new action is required, for example a specific training. We will see...

It was discussed upthread. Looks like stuck thumbswitches were a major reason for runaway in the early days. Once those were redesigned, runaway rate went well down, to the point that no actual events were brought up in the discussion. It is totally reasonable for Boeing to review the analysis of runaway scenarios (which was probably not changed since 737-100) and find,based on historical data to, that those are much less of an issue by now.

SatCom guru has a rough analysis of trim related events in the 2000s. Events characterised as Runaway/jam seem to run at about E-8/Hr.

https://www.satcom.guru/2019/05/737-pit ... dents.html

Ray
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 6:19 pm

XRAYretired wrote:
ET302 cut out was employed and manual wheel was at least attempted.
Ray

Did we finally get confirmation on that, was he actually referring to trying the manual wheel, I recall there being some discussion based on the initial release of the conversations and the times involved, have any additional details been released?
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 6:22 pm

XRAYretired wrote:
kalvado wrote:
PixelFlight wrote:
An stab trim runaway (from any causes) can easily miss trim any 737, including the NG. The MCAS v1 only added a deadly cause of miss time on the MAX that will be removed with MCAS v2, but all others possibles causes of miss trim remains and must be addressed properly in the safety assessment of each 737 models now that this is know that the trim wheels could not be effective as expected in some situations. The safety assessment could conclude that the risk is low enough to not require additional action, or it could conclude that the risk is not low enough and that new action is required, for example a specific training. We will see...

It was discussed upthread. Looks like stuck thumbswitches were a major reason for runaway in the early days. Once those were redesigned, runaway rate went well down, to the point that no actual events were brought up in the discussion. It is totally reasonable for Boeing to review the analysis of runaway scenarios (which was probably not changed since 737-100) and find,based on historical data to, that those are much less of an issue by now.

SatCom guru has a rough analysis of trim related events in the 2000s. Events characterised as Runaway/jam seem to run at about E-8/Hr.

https://www.satcom.guru/2019/05/737-pit ... dents.html

Ray

And looks like there was no severe mistrim, beyond wheel control.
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 6:30 pm

XRAYretired wrote:
kalvado wrote:
It was discussed upthread. Looks like stuck thumbswitches were a major reason for runaway in the early days. Once those were redesigned, runaway rate went well down, to the point that no actual events were brought up in the discussion. It is totally reasonable for Boeing to review the analysis of runaway scenarios (which was probably not changed since 737-100) and find,based on historical data to, that those are much less of an issue by now.

SatCom guru has a rough analysis of trim related events in the 2000s. Events characterised as Runaway/jam seem to run at about E-8/Hr.

https://www.satcom.guru/2019/05/737-pit ... dents.html

Ray

It says:

There is no documented 737 accident as a result of stabilizer/pitch trim malfunction or failure (prior to JT610 and ET302).

Conclusion:

737 stabilizer trim has been very reliable. There are enough examples of runaway to assume at least one per year, with overall stab trim non-functional about one per month. There are enough examples to assume at least on jam per year.

It's hard to justify a continued grounding on this basis, IMO.
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 7:15 pm

mjoelnir wrote:
Absolute nonsense. The manual trim wheel should be a back up under any circumstances. What the MCAS disaster showed us is, that you can not predict when you will need that backup and under what circumstances.

Absolute nonsense.
Aviation standards do not require a back up for "any circumstances".
A300 flies to this day with a vertical stab you can rip off just by stomping on the rudder pedal above a certain speed.

mjoelnir wrote:
Furthermore the MAX is not a NG. Different flight characteristics,.that have to be compensated by computer action.

That compensation was analyzed when MAX was certified, and once MCAS is fixed, that analysis still holds.
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 7:50 pm

Revelation wrote:
mjoelnir wrote:
Absolute nonsense. The manual trim wheel should be a back up under any circumstances. What the MCAS disaster showed us is, that you can not predict when you will need that backup and under what circumstances.

Absolute nonsense.
Aviation standards do not require a back up for "any circumstances".
A300 flies to this day with a vertical stab you can rip off just by stomping on the rudder pedal above a certain speed.

mjoelnir wrote:
Furthermore the MAX is not a NG. Different flight characteristics,.that have to be compensated by computer action.

That compensation was analyzed when MAX was certified, and once MCAS is fixed, that analysis still holds.


If you would not be able to move the rudder in emergencies on the A300. you would have a point.

And in regards to the certification of the MAX, we have now seen how Boeing is trying to do short cuts when nobody watches. Anything certified on the MAX is in doubt after this certification disaster.
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 8:15 pm

mjoelnir wrote:
Revelation wrote:
mjoelnir wrote:
Absolute nonsense. The manual trim wheel should be a back up under any circumstances. What the MCAS disaster showed us is, that you can not predict when you will need that backup and under what circumstances.

Absolute nonsense.
Aviation standards do not require a back up for "any circumstances".
A300 flies to this day with a vertical stab you can rip off just by stomping on the rudder pedal above a certain speed.

mjoelnir wrote:
Furthermore the MAX is not a NG. Different flight characteristics,.that have to be compensated by computer action.

That compensation was analyzed when MAX was certified, and once MCAS is fixed, that analysis still holds.


If you would not be able to move the rudder in emergencies on the A300. you would have a point.

And in regards to the certification of the MAX, we have now seen how Boeing is trying to do short cuts when nobody watches. Anything certified on the MAX is in doubt after this certification disaster.



Thank you for your opinion --- and that is all it is -- your opinion.
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 8:25 pm

mjoelnir wrote:
Revelation wrote:
mjoelnir wrote:
Absolute nonsense. The manual trim wheel should be a back up under any circumstances. What the MCAS disaster showed us is, that you can not predict when you will need that backup and under what circumstances.

Absolute nonsense.
Aviation standards do not require a back up for "any circumstances".
A300 flies to this day with a vertical stab you can rip off just by stomping on the rudder pedal above a certain speed.

If you would not be able to move the rudder in emergencies on the A300. you would have a point.

You were the one who wrote "any circumstances", and that was absolute nonsense.
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kalvado
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 8:41 pm

Revelation wrote:
It's hard to justify a continued grounding on this basis, IMO.

Two options to think otherwise:
1. unlike NG, stab blowback was part of a crash, where multiple slices of cheese aligned. Fixing EVERY slice of cheese is a must in this situation, you cannot patch one hole and call that a day.
2. Bureaucratic thinking: ungrounding MAX (or grounding NG, if you want to argue "NG has to be treated the same) is an action, whoever takes that action, assumes responsibility. There has to be a good reason for that. Not ungrounding MAX (or keeping NG flying) doesn't require any additional action and thus no responsibility.

Not that I really like any of these arguments, it is objection to "hard to justify" statement, not truly pro-grounding argument. For the record, I am (like most people here) an observer with no say on the matter, I can afford to have no opinion one way or the other.
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 8:48 pm

TTailedTiger wrote:
keesje wrote:
EASA and CAAC will approve return to service when their explicit requirements have been met.

Additionally it might be wise of FAA and Boeing to demonstrate enhancement to the certification process.

Keeping in mind the upcoming Boeing 777-9 certification by FAA, where grand fathering of design and certification requirements seemingly entered new territory.


They could demand diamond encrusted thrust levers but that doesn't mean they will get them. Their issue has to be real. I have seen no evidence that their fetish over the trim wheel has any merit.


No, they could not demand that.
All their "dermands" are in reference to existing Certification Specifications (CS' for EASA, or FAR's for FAA). Of course there's always some layer of, shall we it call mist, in the interpretation of those specs, but that is still a far cry from diamond encrusted thrust levers.
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 8:50 pm

Revelation wrote:
XRAYretired wrote:
kalvado wrote:
It was discussed upthread. Looks like stuck thumbswitches were a major reason for runaway in the early days. Once those were redesigned, runaway rate went well down, to the point that no actual events were brought up in the discussion. It is totally reasonable for Boeing to review the analysis of runaway scenarios (which was probably not changed since 737-100) and find,based on historical data to, that those are much less of an issue by now.

SatCom guru has a rough analysis of trim related events in the 2000s. Events characterised as Runaway/jam seem to run at about E-8/Hr.

https://www.satcom.guru/2019/05/737-pit ... dents.html

Ray

It says:

There is no documented 737 accident as a result of stabilizer/pitch trim malfunction or failure (prior to JT610 and ET302).

Conclusion:

737 stabilizer trim has been very reliable. There are enough examples of runaway to assume at least one per year, with overall stab trim non-functional about one per month. There are enough examples to assume at least on jam per year.

It's hard to justify a continued grounding on this basis, IMO.

I was initially not talking about grounding but about safety assessment, exactly as SatCom guru did, and I explicitly listed the two possible outcomes. Now SatCom guru is not the FAA nor the EASA, so I am still waiting for there conclusions. While the historical record of the 737 (MAX excluded) did not show any concern regarding the trim wheels in extreme out of trim (because this did not seem to have happened to date), the discovery of this problem could still be a non conformity with some safety rules required by the certification.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 8:53 pm

mjoelnir wrote:
TTailedTiger wrote:
keesje wrote:
EASA and CAAC will approve return to service when their explicit requirements have been met.

Additionally it might be wise of FAA and Boeing to demonstrate enhancement to the certification process.

Keeping in mind the upcoming Boeing 777-9 certification by FAA, where grand fathering of design and certification requirements seemingly entered new territory.


They could demand diamond encrusted thrust levers but that doesn't mean they will get them. Their issue has to be real. I have seen no evidence that their fetish over the trim wheel has any merit.


There is one real issue on the EASA list, that nobody mentions for quite a while. The manual trim. There is no software solution for that.


Not necessarily. If Boeing can demonstrate that the chances of getting into a severely out-of-trim state are sufficiently low, then it could still get accepted (and we are looking into 10E-9 territory). The report demonstrating such to convincing levels is by no means straight forward though. But the hundreds of millions of flight hours generated by the NG would provide a solid starting point. The devil is in the detailed differences between NG and MAX in this respect. Or in other words, the analysed reliability of MCAS 2.0.
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 8:55 pm

Revelation wrote:
A300 flies to this day with a vertical stab you can rip off just by stomping on the rudder pedal above a certain speed.

Anyone can crash any aircraft by doing inappropriately, no even need of any training for that. :tombstone:
As for the American Airlines Flight 587:
The vertical stabilizer's structural performance was determined to be consistent with design specifications and exceeded certification requirements.

https://en.wikipedia.org/wiki/American_Airlines_Flight_587#Findings
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 9:11 pm

PixelFlight wrote:
Revelation wrote:
A300 flies to this day with a vertical stab you can rip off just by stomping on the rudder pedal above a certain speed.

Anyone can crash any aircraft by doing inappropriately, no even need of any training for that. :tombstone:
As for the American Airlines Flight 587:
The vertical stabilizer's structural performance was determined to be consistent with design specifications and exceeded certification requirements.

https://en.wikipedia.org/wiki/American_Airlines_Flight_587#Findings


I smell hypocrisy. Some of you claimed Boeing was at fault for making planes too complicated for the average pilot. So why should Airbus be let off the hook for designing a plane that allowed the rudder to travel beyond design limits?
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 9:19 pm

TTailedTiger wrote:
I smell hypocrisy. Some of you claimed Boeing was at fault for making planes too complicated for the average pilot. So why should Airbus be let off the hook for designing a plane that allowed the rudder to travel beyond design limits?

Yes, in this thread one vendor is held to the standard "exceeded certification requirements", another needs to work under "any circumstances", must close all the holes in the Swiss cheese, etc.
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 9:29 pm

TTailedTiger wrote:
PixelFlight wrote:
Revelation wrote:
A300 flies to this day with a vertical stab you can rip off just by stomping on the rudder pedal above a certain speed.

Anyone can crash any aircraft by doing inappropriately, no even need of any training for that. :tombstone:
As for the American Airlines Flight 587:
The vertical stabilizer's structural performance was determined to be consistent with design specifications and exceeded certification requirements.

https://en.wikipedia.org/wiki/American_Airlines_Flight_587#Findings


I smell hypocrisy. Some of you claimed Boeing was at fault for making planes too complicated for the average pilot. So why should Airbus be let off the hook for designing a plane that allowed the rudder to travel beyond design limits?

The A300 was found in conformance with safety certification.
The 737-8/9 MAX was found non in conformance with safety certification.

From the safety point of view, the A300 should have trigger an update of the existing certification safety rules at that time (I don't know if this was the case), while the 737-8/9 MAX was below the existing certification safety rules at his design time. Be killed by one or the other did not change anything to the poor victims and relatives, but from, again, a safety point of view, the causes and correctives actions are not the same.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
mjoelnir
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 10:37 pm

TTailedTiger wrote:
PixelFlight wrote:
Revelation wrote:
A300 flies to this day with a vertical stab you can rip off just by stomping on the rudder pedal above a certain speed.

Anyone can crash any aircraft by doing inappropriately, no even need of any training for that. :tombstone:
As for the American Airlines Flight 587:
The vertical stabilizer's structural performance was determined to be consistent with design specifications and exceeded certification requirements.

https://en.wikipedia.org/wiki/American_Airlines_Flight_587#Findings


I smell hypocrisy. Some of you claimed Boeing was at fault for making planes too complicated for the average pilot. So why should Airbus be let off the hook for designing a plane that allowed the rudder to travel beyond design limits?


The rudder did not travel past design limits. The point was the pilot or copilot applied full rudder to one side followed by full rudder to the other side several times in quick succession. all the time the rudder answered to his commands. He ended up with over stressing the vertical fin. The simple solution was to avoid applying full rudder side to side, no sensible reason to do it.

How does that compare to not being able to use manual trim in part of the flight envelope of the 737MAX?

The rudder of the A300 answers to inputs of the pilot in all parts of the flight envelope. The A300 is an airplane without an FBW, so you can not expect protections against crazy pilot inputs, but you can expect the manual trim to work when you need it
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Aug 26, 2019 10:41 pm

Revelation wrote:
TTailedTiger wrote:
I smell hypocrisy. Some of you claimed Boeing was at fault for making planes too complicated for the average pilot. So why should Airbus be let off the hook for designing a plane that allowed the rudder to travel beyond design limits?

Yes, in this thread one vendor is held to the standard "exceeded certification requirements", another needs to work under "any circumstances", must close all the holes in the Swiss cheese, etc.

The two vendors are held to the certification requirements set by FAA and EASA, none of them need to work under "any circumstances" claimed in a forum message. :white:
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:

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