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Stitch
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 5:14 pm

marcelh wrote:
Question remains why this wasn’t figured out before. The fuselage-wingbox interface is an essential structural part and I would presume it was designed with great care. It will be corrected and the 77X will be flying asap, but why haven’t they designed it right in the first place?


"Unknown unknowns" are by their very nature, unknown.

As SEPilot noted up-thread, if the OEMs could perfectly model everything in a computer using Finite Element Analysis, there would be no need for a flight test or certification program. The first frame would receive it's Type Certificate pro forma as it is being assembled and after it's first OEM and customer acceptance flights, be delivered directly into service.

But the OEMs can't model that accurately as of yet, so they're required to "show their work" via testing and when they fail, they are required to fix the issue and show the fix corrected the issue. Only then do they get their certification.
 
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747classic
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 5:20 pm

The grandfathering on the 777X is limited compared to the 747-8 and 737MAX, because the wing structure and load paths are different compared to the previous 777 series.

For that reason new 777X static and fatigue testframes are built ,

At the 747-8 and 737MAX the wingbox and center wingbox are only strengthend but the load paths are identical and NO new static and fatigue testing was needed.
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SEPilot
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 6:46 pm

marcelh wrote:
SEPilot wrote:
It is way too early for doom and gloom predictions, as we have no information as to exactly what went wrong. This is why they do this testing. If the engineers could accurately predict all the time exactly how the structure would react to the loads to which it was subject, the testing would be unnecessary. Be assured they will figure out exactly what went wrong and strengthen whatever proved to be inadequate. It may be something very minor, and then again it may not be. Seeing as how 777s have been flying since the mid 90s with, I expect, exactly the same cargo door and none has ever popped open in flight, I cannot imagine the problem is serious. Since the door is near the wingbox, which is new, it seems likely it has to do with the fuselage-wingbox interface. My suspicion is that the CFRP wingbox flexes more under load than the previous aluminum one did, and allowed more distortion of the cargo door frame than before. If that is the case it can be corrected in a number of ways. But it will be corrected.

Question remains why this wasn’t figured out before. The fuselage-wingbox interface is an essential structural part and I would presume it was designed with great care. It will be corrected and the 77X will be flying asap, but why haven’t they designed it right in the first place?

Small changes can sometimes have unexpected results. Using previously tested and certified components along with newly designed ones can have effects that nobody has considered. Which is precisely why they do this testing.
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Ertro
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 7:03 pm

There was an article earlier this summer which claims Boeing is targeting to avoid building and testing large and complex physical models and instead use computer simulations as "new technology and decades of testing experience have rendered some physical tests redundant for demonstrating safety".

https://www.reuters.com/article/us-fran ... SKCN1TH0A3

Just wondering how this new issue with the cargo door jives with the plan to shift to computer simulations. Amateurs like me could think that computer simulations catch only those kind of failures which engineers specifically look for and program the model to analyse in detail and all unpredictable failure modes which the engineers cannot even imagine being a problem are left unchecked. This kind of cargo door blowing open could belong to the latter category.

If Boeing is going along on this path they hopefully had already built the computer simulation model for this exact test scenario to check whether it the results from it correlate with reality. Now the question is whether the cargo door blowing open was predicted already in computer simulations. Probably not. So just wondering what implications this has to the plan towards computer simulations. And whether the reuters story is true at all and there is such a shift towards simulations at all.
 
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crimsonchin
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 7:45 pm

Seeing on Reuters that Boeing is suspending testing?
 
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Revelation
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 8:15 pm

crimsonchin wrote:
Seeing on Reuters that Boeing is suspending testing?

https://simpleflying.com/boeing-777x-st ... l-testing/ quotes a Boeing spokesman:

During final load testing on the 777X static test airplane, the team encountered an issue that required suspension of the test. The testing conditions were well beyond any load expected in commercial service. The event is under review and the team is working to understand the root cause. Final load testing is the last in a series of tests that Boeing has been conducting on this full-scale test airplane over the past several months.

So final load testing is suspended, nothing else.

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JoergAtADN
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 8:27 pm

What does such explosive depressurization mean for the hull stability? Will the test aircraft remain the full structural strenght, or will the strenght be weakened by some percent?

What's the check and repair procedure for aircraft, where this occurs in normal operation?
 
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VirginFlyer
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 8:37 pm

jagraham wrote:
RickNRoll wrote:
jagraham wrote:

Especially with that 789 in front of it . . the 789 is not a small airplane!
That would be a MAX in front of it. They must be parking those things anywhere they can jam them in.



it's a 787! Look at the wing tips

Indeed, Scotron12’s post which jagraham was replying to was in response to this one:
qf789 wrote:
Some photos from ground tests of 779 N779XW (6 Aug)

Image

https://twitter.com/JenSchuld/status/11 ... 77344?s=20



The one with the 737 in front came later in the thread:

qf789 wrote:
There are now 5 777-9's on the flightline at PAE (26 Aug)

Image

Image

https://twitter.com/mattcawby/status/11 ... 83776?s=20


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ikramerica
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 8:43 pm

Revelation wrote:
crimsonchin wrote:
Seeing on Reuters that Boeing is suspending testing?

https://simpleflying.com/boeing-777x-st ... l-testing/ quotes a Boeing spokesman:

During final load testing on the 777X static test airplane, the team encountered an issue that required suspension of the test. The testing conditions were well beyond any load expected in commercial service. The event is under review and the team is working to understand the root cause. Final load testing is the last in a series of tests that Boeing has been conducting on this full-scale test airplane over the past several months.

So final load testing is suspended, nothing else.

Damn mediots.

Part of the analysis will involve whether it even matters, and if it does, how much or little. I remember the A380 had some kind of testing failure about max operating condition and they were allowed to design and model the fix without retesting the full frame. At most the failed part would be retested on a jig applying the same loads.

The reasoning behind not fully re-testing a fix is simple engineering. If something fails at 147% and it was meant to reach 150, and you have all the data leading up to the point of failure and a full understanding of the materials involved, adjusting the design for 3% more strength is a mere matter of calculations. There are no hidden surprises that will pop up elsewhere between 147 and 150. Its all already in the data.

This kind of thing is no worse than the original 777 being way too strong. Sure they could brag about it, but it really meant the structure was heavier than it needed to be.
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stresskid
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 9:11 pm

Ertro wrote:
So just wondering what implications this has to the plan towards computer simulations. And whether the reuters story is true at all and there is such a shift towards simulations at all.


Without a doubt, full-scale testing is hugely expensive, so it's no surprise to hear that Boeing is trying to avoid it, especially given that structural integrity is generally considered a "solved problem" by the industry. I can tell you that the top management at Airbus are also seriously pursuing the elimination of static full-scale testing for new aircraft. However, IMO, and as this failure may show (depending on what the cause was), our ability to predict failures might not be where it needs to be to eliminate this testing. Hopefully, this is a wake-up call to the entire industry that we need to create a more robust method of predicting failure before we can start eliminating full-scale tests.

Don't get me wrong, computer simulations are very useful, and are being relied on more and more as time goes on, but we're still at a point that we need to validate these models against test, even at an aircraft-level.
 
JayinKitsap
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 9:34 pm

What isn't known is whether the test pressure when the door failed was below, at, or above the required test pressure. Often in structures the test continues to failure. It is a good way to find what margin remains, if only a few percent not worth mining. But if it is like 10% over, it can be used for a MTOW increase or similar.
 
iamlucky13
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 9:35 pm

JoergAtADN wrote:
What does such explosive depressurization mean for the hull stability? Will the test aircraft remain the full structural strenght, or will the strenght be weakened by some percent?

What's the check and repair procedure for aircraft, where this occurs in normal operation?


If the door frame remains intact, the hull should remain stable.

Even if the frame is damaged, there is still margin in both the frame and the rest of the fuselage, and while the door may fail under pressure loads, the fuselage is designed to take both pressure and bending loads, such as those that occur during landing in particular, so I think it is unlikely the door would fail while the surrounding fuselage is under its maximum combined load state.

Of course, this is academic, since unless this occurred above the ultimate load (likely 150%, depending on the component), it will be fixed, and the actual in-flight loads will be lower.
 
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 9:37 pm

Regarding differences between the 777X fuselage and the 777 fuselage, the newer aircraft has a higher cabin pressure.

That may have been a factor in this test failure.
 
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 11:22 pm

Guillaume787 wrote:
Stitch wrote:
It would be helpful to know which of the ten doors failed. As the fuselage and Type A doors are the same as used on the rest of the 777 family, I am strongly inclined to think it was not a design issue there. If it was one of them, my guess would be it was not properly latched/secured.

The Type C "Mid Emergency Exit" door is new to the family, but again...and on the test frame was it a full door or just a plug?


According to this Seattle Times article, it was a cargo door that exploded outward:

https://www.seattletimes.com/business/b ... -777x-jet/

On one hand having a cargo door bust open is bad.

Anyone else amused? This is a retest. But not as bad as the 747 having a door frame split during the same test. This won't delay 1st flight or EIS.

Lightsaber
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Max Q
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 11:24 pm

I believe this happened to a 747 freighter where the forward cargo
door blew off the aircraft during pressure testing ?
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kalvado
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 11:26 pm

lightsaber wrote:
Guillaume787 wrote:
Stitch wrote:
It would be helpful to know which of the ten doors failed. As the fuselage and Type A doors are the same as used on the rest of the 777 family, I am strongly inclined to think it was not a design issue there. If it was one of them, my guess would be it was not properly latched/secured.

The Type C "Mid Emergency Exit" door is new to the family, but again...and on the test frame was it a full door or just a plug?


According to this Seattle Times article, it was a cargo door that exploded outward:

https://www.seattletimes.com/business/b ... -777x-jet/

On one hand having a cargo door bust open is bad.

Anyone else amused? This is a retest. But not as bad as the 747 having a door frame split during the same test. This won't delay 1st flight or EIS.

Lightsaber

Do you have any information on what exact failure mode was it? So far what I heard is "door flying out" - which can mean anything from improperly closed latch failure to stringers holding the frame being ripped out.
 
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Stitch
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Re: Boeing 777X Testing Thread - 2019

Sat Sep 07, 2019 11:30 pm

Ertro wrote:
If Boeing is going along on this path they hopefully had already built the computer simulation model for this exact test scenario to check whether it the results from it correlate with reality. Now the question is whether the cargo door blowing open was predicted already in computer simulations. Probably not. So just wondering what implications this has to the plan towards computer simulations. And whether the reuters story is true at all and there is such a shift towards simulations at all.


The physical test probably was required by FAA regulations, which is why it was done. And Boeing would have certainly used the data from that test (as well as all other required tests) to help validate the computer model's accuracy.

Depending on where it failed, Boeing might be able to validate the design to the FAA's satisfaction by strengthening the part(s) that failed via computer simulation, as Airbus did with the A380's wing when it failed before Ultimate Load during it's test.
 
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 1:24 am

finnishway wrote:
I know that folding wingtips were added so 777X doesn't take so much space at the gate. What is the case with 777X, does it need "A380 cabable gate" or can it basically fly every airport that recieves another large widebody aircraft like 777-300ER?


With working folding wingtips the B777X will fit in Code E gates and taxiways.

If the wingtip folding mechanism in inoperative with the wingtips folded down it then becomes a Code F aircraft.

So in normal revenue operation it'll be no different to an existing B777.

If operating at an airport with no Code F gates or taxiways they'll just have to have special procedures in place in the off chance they need to move a B777X with wingtips down.
 
danj555
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 1:27 am

par13del wrote:
danj555 wrote:
Why is this an issue? Isn’t it supposed to be a nearly identical fuselage as the current 777? Why would this certified design suddenly fail?

I think the testing is part of the certification process, so now that there was a failure, Boeing has to investigate, make necessary repairs / corrections then retest.


Haha, no I get that. The point I was making was this isn't something new. The 777X fuselage is *nearly* the exact same as the currently flying 777. If it were a wing load test I might understand. It's just strange that the old stuff failed and the new stuff passed.
 
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 9:00 am

danj555 wrote:
par13del wrote:
danj555 wrote:
Why is this an issue? Isn’t it supposed to be a nearly identical fuselage as the current 777? Why would this certified design suddenly fail?

I think the testing is part of the certification process, so now that there was a failure, Boeing has to investigate, make necessary repairs / corrections then retest.


Haha, no I get that. The point I was making was this isn't something new. The 777X fuselage is *nearly* the exact same as the currently flying 777. If it were a wing load test I might understand. It's just strange that the old stuff failed and the new stuff passed.


The issue with grandfathering.

This is a door certified in scope of the classic 777.
The old door in the new frame leaves that scope.

You see the same "no longer the place it was certified for" fall out on the Jurassic -> Classic -> NG -> MAX line
of pushing things into the future. 757 and 767 never got so much BME to have these effects come up I'd guess.
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ACATROYAL
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 10:02 am

lightsaber wrote:
Guillaume787 wrote:
Stitch wrote:
It would be helpful to know which of the ten doors failed. As the fuselage and Type A doors are the same as used on the rest of the 777 family, I am strongly inclined to think it was not a design issue there. If it was one of them, my guess would be it was not properly latched/secured.

The Type C "Mid Emergency Exit" door is new to the family, but again...and on the test frame was it a full door or just a plug?


According to this Seattle Times article, it was a cargo door that exploded outward:

https://www.seattletimes.com/business/b ... -777x-jet/

On one hand having a cargo door bust open is bad.

Anyone else amused? This is a retest. But not as bad as the 747 having a door frame split during the same test. This won't delay 1st flight or EIS.

Lightsaber


How do you know with 100% certainty that this won't delay anything ?
 
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 11:06 am

JayinKitsap wrote:
What isn't known is whether the test pressure when the door failed was below, at, or above the required test pressure. Often in structures the test continues to failure. It is a good way to find what margin remains, if only a few percent not worth mining. But if it is like 10% over, it can be used for a MTOW increase or similar.


I think Boeing tests every production aircraft built beyond the normal maximum by increasing the internal pressure with the aircraft sealed.
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747classic
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 11:11 am

We don't know at what point in testing this cargo door issue came forward.
Was it before reaching the ultimate design load (150%)or after reaching that load ?

At the 747-100 ultimate load testing the following happened :
- On the first attempt on Jan 5, 1970, a failure of the aft body section at 107% of the ultimate design load terminated tests before the wing itself broke.
- Despite the fact that this failure occured above the certification limits, the damaged fuselage section was removed and the body was rebraced for the final test, wich occured in mid February.
- Final wing failure occured in the second test at 116,7 % of the ultimate design load, or 174 % of the maximum load expected in normal operation.
- The extra margin was used to increase the operating weights using the same structure.

Source : Boeing 747 - Design and development since 1969, page 45 &46, Guy Norris and Mark Wagner
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kalvado
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 11:22 am

747classic wrote:
We don't know at what point in testing this cargo door issue came forward?
Was it before reaching the ultimate design load (150%)or after reaching that load ?

At the 747-100 ultimate load testing the following happened :
- On the first attempt on Jan 5, 1970, a failure of the aft body section at 107% of the ultimate design load terminated tests before the wing itself broke.
- Despite the fact that this failure occured above the certification limits, the damaged fuselage section was removed and the body was rebraced for the final test, wich occured in mid February.
- Final wing failure occured in the second test at 116,7 % of the ultimate design load, or 174 % of the maximum load expected in normal operation.
- The extra margin was used to increase the operating weights using the same structure.


Wing breaking is a destructive test be design, and getting as much information as possible from the article that is already written off to test loss makes total sense. From description of what happened it doesn't sound like this was a destructive test. I am pretty sure that if failure was expected, there would be an appropriate statement by now, explicitly clarifying the nature of such test
 
morrisond
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 11:34 am

Isn't the 777X going to be flying with a lower Cabin Altitude? Aren't they setting it lower like the 787?

Wouldn't that require testing at a higher Pressure Differential than they did when they first certified the 777?

Is that why maybe the Cargo door failed?

That should be an easy fix.
 
RickNRoll
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 12:01 pm

danj555 wrote:
par13del wrote:
danj555 wrote:
Why is this an issue? Isn’t it supposed to be a nearly identical fuselage as the current 777? Why would this certified design suddenly fail?

I think the testing is part of the certification process, so now that there was a failure, Boeing has to investigate, make necessary repairs / corrections then retest.


Haha, no I get that. The point I was making was this isn't something new. The 777X fuselage is *nearly* the exact same as the currently flying 777. If it were a wing load test I might understand. It's just strange that the old stuff failed and the new stuff passed.
The frame has been changed. The interior is now wider.
 
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 12:01 pm

iamlucky13 wrote:
Regarding differences between the 777X fuselage and the 777 fuselage, the newer aircraft has a higher cabin pressure.

That may have been a factor in this test failure.


There are grey areas in grandfathering certification requirements and design. I promote a conservative approach here. When allowing to certify systems, structures based existing certification, defining which requirements & other systems are touched by changing loads, circumstances or requirements allows for interpretation, policies.

I think interfaces between systems, loads, procedures pose a risk of being overlooked, specially when time pressure, costs, customer demands and job security play a role.

https://www.google.com/amp/s/www.wsj.co ... 1398916634

The FAA has to seriously look at the chain of actions that let to this flying door. And it if it was an incident or more a standard process. Was there sufficient FAA oversight. Fixing the door is not enough.
"Never mistake motion for action." Ernest Hemingway
 
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DarkSnowyNight
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 12:33 pm

RickNRoll wrote:
danj555 wrote:
par13del wrote:
I think the testing is part of the certification process, so now that there was a failure, Boeing has to investigate, make necessary repairs / corrections then retest.


Haha, no I get that. The point I was making was this isn't something new. The 777X fuselage is *nearly* the exact same as the currently flying 777. If it were a wing load test I might understand. It's just strange that the old stuff failed and the new stuff passed.
The frame has been changed. The interior is now wider.


But did the frame actually change dimension or is this a function of interior wall modifications? It's worth mentioning that the wall paneling of the original 777 series do leave a lot of room for this on their own. And none of that is load bearing WRT pressurization.

I'll be interested to see what the findings here are.
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 12:36 pm

keesje wrote:
The FAA has to seriously look at the chain of actions that let to this flying door. And it if it was an incident or more a standard process. Was there sufficient FAA oversight. Fixing the door is not enough.

The same FAA that we state is not competent to work on another Boeing a/c going through grandfathering? Do we need to refer this to the JTAR committee to get their input earlier in the process, or even EASA? We already have post saying the FAA debacle on the MAX should also affect the 777X so....
 
mjoelnir
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 12:48 pm

keesje wrote:

The FAA has to seriously look at the chain of actions that let to this flying door. And it if it was an incident or more a standard process. Was there sufficient FAA oversight. Fixing the door is not enough.


We have here a FAA mandated test, supervised by the FAA, that revealed a fault in the design. Just like things should normally be. That is exactly what these tests are for. So I hardly see a reason for questioning the FAA oversight in this case.
 
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keesje
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 1:41 pm

mjoelnir wrote:
keesje wrote:

The FAA has to seriously look at the chain of actions that let to this flying door. And it if it was an incident or more a standard process. Was there sufficient FAA oversight. Fixing the door is not enough.


We have here a FAA mandated test, supervised by the FAA, that revealed a fault in the design. Just like things should normally be. That is exactly what these tests are for. So I hardly see a reason for questioning the FAA oversight in this case.


This was a final loading test on this aircraft. Before this simulations, grandfathering, design changes, strenght calculations and design freezes of the door, its sub assemblies were completed and approved by engineering, inspectors and authorities. And then it blew out. How come?
"Never mistake motion for action." Ernest Hemingway
 
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Finn350
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 2:27 pm

Just for comparison, here is a video from the A350 static ground testing including mechanical load and pressurization testing. On an A350, the pressurization is tested up to 1.3 bar according to the video.
https://youtu.be/B74_w3Ar9nI
 
marcelh
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 2:35 pm

morrisond wrote:
Isn't the 777X going to be flying with a lower Cabin Altitude? Aren't they setting it lower like the 787?

Wouldn't that require testing at a higher Pressure Differential than they did when they first certified the 777?

Is that why maybe the Cargo door failed?

That should be an easy fix.

This is a “known known”, so they should have done their homework.
 
mjoelnir
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 2:55 pm

keesje wrote:
mjoelnir wrote:
keesje wrote:

The FAA has to seriously look at the chain of actions that let to this flying door. And it if it was an incident or more a standard process. Was there sufficient FAA oversight. Fixing the door is not enough.


We have here a FAA mandated test, supervised by the FAA, that revealed a fault in the design. Just like things should normally be. That is exactly what these tests are for. So I hardly see a reason for questioning the FAA oversight in this case.


This was a final loading test on this aircraft. Before this simulations, grandfathering, design changes, strenght calculations and design freezes of the door, its sub assemblies were completed and approved by engineering, inspectors and authorities. And then it blew out. How come?


Unknown unknowns, that is why they have this test.
 
trex8
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 3:01 pm

There was that CI 747-400F whose nose door blew open damaging the cockpit area during a pressurization test on an in production model. https://www.seattlepi.com/business/arti ... 197536.php
 
kalvado
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Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 3:05 pm

mjoelnir wrote:
keesje wrote:
mjoelnir wrote:

We have here a FAA mandated test, supervised by the FAA, that revealed a fault in the design. Just like things should normally be. That is exactly what these tests are for. So I hardly see a reason for questioning the FAA oversight in this case.


This was a final loading test on this aircraft. Before this simulations, grandfathering, design changes, strenght calculations and design freezes of the door, its sub assemblies were completed and approved by engineering, inspectors and authorities. And then it blew out. How come?


Unknown unknowns, that is why they have this test.

Problem is that if unknown unknowns are showing up on a final test to an extent of a catastrophic failure - not as 5% deviation from predicted values. That puts a huge question mark on all previous steps - is there a good understanding of design? Were all previous tests done so that weaknesses of a system were properly examined, or everything needs to start from scratch?
It better be an improperly closed latch, otherwise things are going beyond grim
 
T4thH
Posts: 296
Joined: Thu Jun 06, 2019 11:17 pm

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 3:11 pm

DarkSnowyNight wrote:
RickNRoll wrote:
danj555 wrote:

Haha, no I get that. The point I was making was this isn't something new. The 777X fuselage is *nearly* the exact same as the currently flying 777. If it were a wing load test I might understand. It's just strange that the old stuff failed and the new stuff passed.
The frame has been changed. The interior is now wider.


But did the frame actually change dimension or is this a function of interior wall modifications? It's worth mentioning that the wall paneling of the original 777 series do leave a lot of room for this on their own. And none of that is load bearing WRT pressurization.

I'll be interested to see what the findings here are.


I hope, I will use the correct words, basically the structure of the fuselage is the same, but the spars have been modified, they are narrow, so the inner walls can be thinner so there is now a little bit more space inside. Additional the position of the windows has been changed, they are bigger and located a little bit higher.
 
stresskid
Posts: 5
Joined: Sat Sep 07, 2019 8:32 pm

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 3:23 pm

T4thH wrote:
DarkSnowyNight wrote:
RickNRoll wrote:
The frame has been changed. The interior is now wider.


But did the frame actually change dimension or is this a function of interior wall modifications? It's worth mentioning that the wall paneling of the original 777 series do leave a lot of room for this on their own. And none of that is load bearing WRT pressurization.

I'll be interested to see what the findings here are.


I hope, I will use the correct words, basically the structure of the fuselage is the same, but the spars have been modified, they are narrow, so the inner walls can be thinner so there is now a little bit more space inside. Additional the position of the windows has been changed, they are bigger and located a little bit higher.


They're frames, but you're absolutely right, they've been narrowed out by 2" on both sides to give a wider cabin. However, I wouldn't expect this to have much impact on the cargo doors, since they are on the lower side of the fuselage, far from where the frames are narrowed.

Source: https://www.boeing.com/777x/reveal/face ... -fuselage/
Starting around 8:10
 
OldAeroGuy
Posts: 3877
Joined: Sun Dec 05, 2004 6:50 am

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 3:28 pm

kalvado wrote:
It better be an improperly closed latch, otherwise things are going beyond grim


Ahh.. How soon we forget.

https://www.flightglobal.com/news/artic ... ad-204716/

Which is the more difficult problem to solve, wing structure or a cargo door latch/structure?
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
kalvado
Posts: 1893
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 3:40 pm

OldAeroGuy wrote:
kalvado wrote:
It better be an improperly closed latch, otherwise things are going beyond grim


Ahh.. How soon we forget.

https://www.flightglobal.com/news/artic ... ad-204716/

Which is the more difficult problem to solve, wing structure or a cargo door latch/structure?

Let's see. A380 failed too early in an ultimate load test to destruction. Early failure is, of course, a problem, but it is a 2% error after all - and test artifact is a write-off either way
Is there any indication 777X was undergoing a destruction test to determine safety margin? I am pretty sure that would be explicitly mentioned a few times by now - but quazi-official "policy statement" above is pretty mum, and no official response from Boeing. Did they come to 2% within ultimate load during routine test, or this was a maximum load test - and that would mean whooping 50% error and no safety margin exists in the design?
This is a fatigue test frame; as far as I understand those are used for continuing test after the aircraft enters service - so destructive test is pretty doubtful to begin with.

Besides, are you sure this is a latch failure - and not a catastrophic structural failure of primary load-bearing structures? We all hope for the best....
 
mysfit
Posts: 20
Joined: Tue Dec 27, 2016 7:16 pm

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 3:41 pm

Of course there are unknown unkowns.
A bit of hubris to think otherwise.

Complicated systems and interactions. Not to mention what we can measure and characterize is limited by current metrology. Unknown unknowns exist and we currently do not have the metrology to measure them.
 
stresskid
Posts: 5
Joined: Sat Sep 07, 2019 8:32 pm

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 3:51 pm

kalvado wrote:
OldAeroGuy wrote:
kalvado wrote:
It better be an improperly closed latch, otherwise things are going beyond grim


Ahh.. How soon we forget.

https://www.flightglobal.com/news/artic ... ad-204716/

Which is the more difficult problem to solve, wing structure or a cargo door latch/structure?

Let's see. A380 failed too early in an ultimate load test to destruction. Early failure is, of course, a problem, but it is a 2% error after all - and test artifact is a write-off either way
Is there any indication 777X was undergoing a destruction test to determine safety margin? I am pretty sure that would be explicitly mentioned a few times by now - but quazi-official "policy statement" above is pretty mum, and no official response from Boeing. Did they come to 2% within ultimate load during routine test, or this was a maximum load test - and that would mean whooping 50% error and no safety margin exists in the design?
This is a fatigue test frame; as far as I understand those are used for continuing test after the aircraft enters service - so destructive test is pretty doubtful to begin with.

Besides, are you sure this is a latch failure - and not a catastrophic structural failure of primary load-bearing structures? We all hope for the best....


While the A380 wing deserves every bit of criticism coming towards it for its cracking issues alone, kalvado is right that the static failure was very close to ultimate load, and is actually pretty impressive. The same thing may be true for this failure, we just don't have any details yet, and we probably won't get any until Boeing has done a thorough review of the failure itself. For all we know, the failure occurred a little above ultimate load, or maybe the test was set up incorrectly and they accidentally overpressurized it, or there was a one-off manufacturing flaw in the test place, etc, etc. Too bad a big failure like this is just too juicy to stop gossiping about!
 
Checklist787
Posts: 181
Joined: Sat Jun 01, 2019 2:37 am

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 4:10 pm

Finn350 wrote:
Just for comparison, here is a video from the A350 static ground testing including mechanical load and pressurization testing. On an A350, the pressurization is tested up to 1.3 bar according to the video.
https://youtu.be/B74_w3Ar9nI


There is no doubt they stopped at 1.3 bar to not suffer a break of the structure to 1.5 as on the A380!

https://www.flightglobal.com/news/artic ... ad-204716/
Last edited by Checklist787 on Sun Sep 08, 2019 4:11 pm, edited 1 time in total.
 
User avatar
ikolkyo
Posts: 2648
Joined: Tue Nov 05, 2013 8:43 pm

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 4:11 pm

OldAeroGuy wrote:
kalvado wrote:
It better be an improperly closed latch, otherwise things are going beyond grim


Ahh.. How soon we forget.

https://www.flightglobal.com/news/artic ... ad-204716/

Which is the more difficult problem to solve, wing structure or a cargo door latch/structure?


What do you mean? Airbus does no wrong, they are flawless in everything they do. :roll:
 
kalvado
Posts: 1893
Joined: Wed Mar 01, 2006 4:29 am

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 4:20 pm

ikolkyo wrote:
OldAeroGuy wrote:
kalvado wrote:
It better be an improperly closed latch, otherwise things are going beyond grim


Ahh.. How soon we forget.

https://www.flightglobal.com/news/artic ... ad-204716/

Which is the more difficult problem to solve, wing structure or a cargo door latch/structure?


What do you mean? Airbus does no wrong, they are flawless in everything they do. :roll:

Pressure at a ground level is 14.7 psi (760 torr), at FL400 2.72 psi (140 torr), and 11.77 psi (610 torr) at 6000 ft, which is the target altitude for modern design.
This gives about 9psi (470 torr, 0.62 barr) as a maximum in-flight pressure differential, and 1.3 bar overpressure is a 2x margin test at a QC stage for what can be a very serious failure. That margin is consumed to service fatigue and undetected defects - corrosion, etc - so 2x is about right in my book. Should be at least 10-20%, if not more, on top of that for the manufacturing defects...
 
User avatar
Finn350
Posts: 1564
Joined: Tue Jul 09, 2013 4:57 am

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 4:23 pm

Checklist787 wrote:
Finn350 wrote:
Just for comparison, here is a video from the A350 static ground testing including mechanical load and pressurization testing. On an A350, the pressurization is tested up to 1.3 bar according to the video.
https://youtu.be/B74_w3Ar9nI


There is no doubt they stopped at 1.3 bar to not suffer a break of the structure to 1.5 as on the A380!

https://www.flightglobal.com/news/artic ... ad-204716/


That is two different things: 1.3 bar is the cabin over-pressurization and 1.5 is the safety factor (multiplier) in the mechanical load testing.
 
User avatar
ikolkyo
Posts: 2648
Joined: Tue Nov 05, 2013 8:43 pm

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 4:31 pm

kalvado wrote:
ikolkyo wrote:


What do you mean? Airbus does no wrong, they are flawless in everything they do. :roll:

Pressure at a ground level is 14.7 psi (760 torr), at FL400 2.72 psi (140 torr), and 11.77 psi (610 torr) at 6000 ft, which is the target altitude for modern design.
This gives about 9psi (470 torr, 0.62 barr) as a maximum in-flight pressure differential, and 1.3 bar overpressure is a 2x margin test at a QC stage for what can be a very serious failure. That margin is consumed to service fatigue and undetected defects - corrosion, etc - so 2x is about right in my book. Should be at least 10-20%, if not more, on top of that for the manufacturing defects...


I believe you responded to the wrong comment.
 
OldAeroGuy
Posts: 3877
Joined: Sun Dec 05, 2004 6:50 am

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 4:43 pm

kalvado wrote:
OldAeroGuy wrote:
kalvado wrote:
It better be an improperly closed latch, otherwise things are going beyond grim


Ahh.. How soon we forget.

https://www.flightglobal.com/news/artic ... ad-204716/

Which is the more difficult problem to solve, wing structure or a cargo door latch/structure?

Let's see. A380 failed too early in an ultimate load test to destruction. Early failure is, of course, a problem, but it is a 2% error after all - and test artifact is a write-off either way
Is there any indication 777X was undergoing a destruction test to determine safety margin? I am pretty sure that would be explicitly mentioned a few times by now - but quazi-official "policy statement" above is pretty mum, and no official response from Boeing. Did they come to 2% within ultimate load during routine test, or this was a maximum load test - and that would mean whooping 50% error and no safety margin exists in the design?
This is a fatigue test frame; as far as I understand those are used for continuing test after the aircraft enters service - so destructive test is pretty doubtful to begin with.

Besides, are you sure this is a latch failure - and not a catastrophic structural failure of primary load-bearing structures? We all hope for the best....


Please read the referenced article.

ttps://simpleflying.com/boeing-777x-st ... l-testing/ quotes a Boeing spokesman:

"During final load testing on the 777X static test airplane, the team encountered an issue that required suspension of the test. The testing conditions were well beyond any load expected in commercial service. The event is under review and the team is working to understand the root cause. Final load testing is the last in a series of tests that Boeing has been conducting on this full-scale test airplane over the past several months."

- This was the static test airplane, not the fatigue airplane.
- Final load testing is to 150% of limit load, it doesn't need to be to destruction.
- The door failure could be due to a latching failure or structural failure. It's still easier to solve than a wing structural failure.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
WIederling
Posts: 8744
Joined: Sun Sep 13, 2015 2:15 pm

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 4:45 pm

OldAeroGuy wrote:
Which is the more difficult problem to solve, wing structure or a cargo door latch/structure?


"wings not coming off" has been mastered earlier than "doors not blowing out" afair.
Murphy is an optimist
 
OldAeroGuy
Posts: 3877
Joined: Sun Dec 05, 2004 6:50 am

Re: Boeing 777X Testing Thread - 2019

Sun Sep 08, 2019 4:50 pm

WIederling wrote:
OldAeroGuy wrote:
Which is the more difficult problem to solve, wing structure or a cargo door latch/structure?


"wings not coming off" has been mastered earlier than "doors not blowing out" afair.


While I'd prefer no failures, a cargo door failure is preferable to a wing failure.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis

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