Opus99
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 3:13 pm

Will we see the 777X at the Dubai Airshow (17-21 November)?
 
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Stitch
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 3:18 pm

Folks, the door failed at ~149% of a load the airframe will never, ever see in flight test, much less revenue service.

All this talk about flying the frame unpressurized is, frankly, ridiculous.

Boeing will need to prove the door can hold at 150% to meet the certification requirements, but the door is already more than capable of handling any load it will encounter during the flight test regimen.
 
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Polot
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 3:25 pm

WIederling wrote:
bikerthai wrote:
Which is exactly the reason why you do not need to delay flight tests due to the decompression.


Remember the posters explaining why Boeing should begin with 787 test flights
even if the wing had broken below final limits ?
"They'll never reach those limits" :-))))))))))

Both Boeing and Airbus begin test flights before the ultimate wing load test, it is not done prior to first flight. The A380 did just fine despite first flying about 9 months before it failed the ultimate load test.
 
Scotron12
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 4:16 pm

Stitch wrote:
Folks, the door failed at ~149% of a load the airframe will never, ever see in flight test, much less revenue service.

All this talk about flying the frame unpressurized is, frankly, ridiculous.

Boeing will need to prove the door can hold at 150% to meet the certification requirements, but the door is already more than capable of handling any load it will encounter during the flight test regimen.


Hopefully that will " open the door" for first flight. :D
 
WIederling
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 4:27 pm

Polot wrote:
WIederling wrote:
bikerthai wrote:
Which is exactly the reason why you do not need to delay flight tests due to the decompression.


Remember the posters explaining why Boeing should begin with 787 test flights
even if the wing had broken below final limits ?
"They'll never reach those limits" :-))))))))))

Both Boeing and Airbus begin test flights before the ultimate wing load test, it is not done prior to first flight. The A380 did just fine despite first flying about 9 months before it failed the ultimate load test.


The wing initially failed early ( June 2009):
https://www.seattletimes.com/business/b ... ide-plane/

imminent First flight was held back and happened later that year. Long discussion here that Boeing should start flying anyway. :-)
Amusingly any mention of the failure has been deleted from pages like Wikipedia.
( mentioned in Sept. 2009 and removed during the next year. no longer present in Oct. 2010 version and after.)
Murphy is an optimist
 
VV
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 4:33 pm

I think at this point we should just wait and see.
 
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Stitch
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 4:58 pm

The 787-8 wing to body join failed at below Limit Load - the maximum load the airframe should ever expect to see in revenue service. Boeing could have flown the frame, but they could not perform the full flight test and certification regimen.

The 777X cargo door failed well beyond Limit Load so there would be no limits on how hard they flew it and therefore they can perform the entire flight test and certification regimen.
 
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kanban
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 6:22 pm

keesje wrote:

"Yesterday the 777-9 completed it's first flight. The aircraft has around 300 on order and is not allowed to fly above 20k ft, due a door explosion during ground testing a few weeks ago. The test pilot said the first flight was uneventfull and it's really a great aircraft to fly."

Hurray :expressionless:


what's your source?? .. there's nothing in the financial pages.... or is this put on???
 
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bikerthai
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 8:43 pm

kanban wrote:
keesje wrote:

"Yesterday the 777-9 completed it's first flight. The aircraft has around 300 on order and is not allowed to fly above 20k ft, due a door explosion during ground testing a few weeks ago. The test pilot said the first flight was uneventfull and it's really a great aircraft to fly."

Hurray :expressionless:


what's your source?? .. there's nothing in the financial pages.... or is this put on???


Nah, the press release would just say, they completed an uneventful first flight. All test parameters were satisfactory completed. Its just that first flight test parameters will not include those issues in question. :wink2:

I don't recall Boeing taking those plane to significant elevation on the first flight anyway. Anyone have the track of the first 787 flight?

bt
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bikerthai
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 8:46 pm

Found it:

https://boeing.mediaroom.com/2009-12-15 ... rst-Flight

After takeoff from Everett, the airplane followed a route over the east end of the Strait of Juan de Fuca. Capts. Carriker and Neville took the airplane to an altitude of 13,200 feet (4,023 meters) and an air speed of 180 knots, or about 207 miles (333 kilometers) per hour, customary on a first flight.


So they would never get the airplane high enough to cause any issue anyway.

bt
Intelligent seeks knowledge. Enlightened seeks wisdom.
 
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bikerthai
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 8:56 pm

Now, here is a curious question that only an Engineer would ask.

So if you consider max wing deflection at ultimate load. At what delta cabin pressure (internal cabin pressure - outside static pressure) will you required to test? It would not be at max elevation, say 40,000 ft, because the only time when you will get the max wing loading would be if you are coming out of a high speed dive (at a lower elevation). :confused:

bt
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kanban
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 9:15 pm

This deviates from the subject a little however on the first 747 flight, most of the push button switches overhead flipped open and dropped the bulbs the flight deck floor.. there was a mad scramble to gather them up and try to get the switches illuminated again.. the switch vendor lost the contract.

So what the heck is Kessje talking about????????
 
iamlucky13
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 9:15 pm

bikerthai wrote:
Now, here is a curious question that only an Engineer would ask.

So if you consider max wing deflection at ultimate load. At what delta cabin pressure (internal cabin pressure - outside static pressure) will you required to test? It would not be at max elevation, say 40,000 ft, because the only time when you will get the max wing loading would be if you are coming out of a high speed dive (at a lower elevation). :confused:

bt


I'm not certain, but from some of the recent discussion and reporting, I'm under the impression they do enveloped load cases with one case at ultimate at a time. For example:

100% wing load + 150% pressurization
150% wing load + 100% pressurization

I'd be interested if someone can confirm or correct this.
 
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Stitch
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 9:32 pm

kanban wrote:
So what the heck is Kessje talking about????????


It was a joke post.
 
WIederling
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 9:49 pm

Stitch wrote:
kanban wrote:
So what the heck is Kessje talking about????????


It was a joke post.

no. Satire.
Murphy is an optimist
 
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Revelation
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 10:29 pm

WIederling wrote:
Stitch wrote:
kanban wrote:
So what the heck is Kessje talking about????????

It was a joke post.

no. Satire.

And yet #961 confirms the 787 first flight was done at an altitude where pressurization is not needed, so the joke is on him.

As per #940 it seems this season features a bumper crop of red herring.

Repeating:

CHICAGO, September 10, 2019 – During final load testing of the 777X static test airplane, a test which involves bending the wings of the airplane up to a level far beyond anything expected in commercial service, an issue arose that required the team to suspend testing. The testing issue occurred during the final minutes of the test, at approximately 99 percent of the final test loads, and involved a depressurization of the aft fuselage.

The test team followed all safety protocols, and we are conducting a comprehensive root-cause assessment over the coming weeks. The static airplane has been successfully undergoing testing since June, and this was the final test for the static test article. While our root cause assessment continues, at this time we do not expect that this will have a significant impact on aircraft design or on our overall test program schedule. We remain fully focused on safety as our highest priority, as we subject the 777X to a rigorous test program prior to first flight.

Ref: https://boeing.mediaroom.com/news-relea ... tem=130500

The only authoritative statement we have is the static load test issue is not expected to have a significant impact on overall test program schedule.

To me that suggests they do not need to hit the 150% load before first flight, or they have a path to a solution that will be in place by the first flight without impacting the overall test program schedule.

The whole "can they fly the plane unpressurized" is a red herring, IMO, but as far as I know one certainly can fly a plane on an experimental certificate without the cabin being pressurized.
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Stitch
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 10:43 pm

keesje wrote:
Just illustrating that using a handycapped, restricted aircraft for a high profile first flight, with all customers and stake holders watching, is something to be avoided by all means.


Good thing there will be no restrictions, then.
 
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ER757
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 11:13 pm

keesje wrote:
Just illustrating that using a handycapped, restricted aircraft for a high profile first flight, with all customers and stake holders watching, is something to be avoided by all means.

Everybody is looking for maturity, not a band-aid look-it-can-fly vehicle.

What leads you to believe it would be restricted? Certainly not the cargo door failure - as noted numerous times that happen well beyond any condition it would experience in flight.
Haters gonna hate I guess
 
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keesje
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 11:26 pm

Starting flight test without the pressurization issue solved was discussed.

bikerthai wrote:
Revelation wrote:
Yes, it is a given that you cannot have "just the cargo hold unpressurized", but this is the 777x testing thread, and yes, you can find some worthwhile testing you can do if the cabin is unpressurized, the experimental certificate allows for this if you choose to do so.


SEPilot wrote:
Isn’t the 777X pressurized to 6,000 ft, while the old 777s were only pressurized to 8,000 ft? If that is the case then it is not all that surprising that a door popped.


Which is exactly the reason why you do not need to delay flight tests due to the decompression.

1) They can fly unpressurized if they maintain altitude of less than 14000 ft. (Not sure why would they do that, but I know you are allowed to do this by the regulations)

2) They can fly to 8000 ft. pressure altitude for many tests.

3) As long as they do not load the plane to max weight, the wing loading will never reach beyond the point where they decompressed during the test. The flight parameter will still meet the required regulations.

bt


Memory failure I guess.
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Re: Boeing 777X Testing Thread - 2019

Tue Oct 01, 2019 11:39 pm

keesje wrote:
Starting flight test without the pressurization issue solved was discussed.

Not being proposed by any authoritative source, so although possible, no actual proposal, except those made of straw then being thrashed.

Agenda failure, I guess.
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bikerthai
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 4:21 am

keesje wrote:
Starting flight test without the pressurization issue solved was discussed.


And the answer from evidence is that it is possible. Keesje would suggest that it would not be wise to do so in the current climate even though they have done so in the past. Recall that there were ECS issue with the 787 or was it the 777 during flight testing. Did they stop the whole test program until they got the issuse resolved? Or did they continue with the testing with restrictions?

Found an article about the original 777 first flight. They went to 19000ft which would still be well below the pressure differential where the doors depressurized. What stood out in the article was that they even did an engine out on that first flight. :hypnotized: Or did they experienced an engine failure and just reported as an engine restart test :rotfl:

https://www.thisdayinaviation.com/tag/boeing-777/

bt
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VV
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 5:31 am

Has the engine re-delivery been confirmed?
 
VV
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 6:36 am

Opus99 wrote:
Will we see the 777X at the Dubai Airshow (17-21 November)?


Is it necessary to fly it to Dubai?

I guess if the aircraft is flying, it is more useful to have it doing tests in Seattle than showing off at the show.
 
Scotron12
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 7:19 am

VV wrote:
Opus99 wrote:
Will we see the 777X at the Dubai Airshow (17-21 November)?


Is it necessary to fly it to Dubai?

I guess if the aircraft is flying, it is more useful to have it doing tests in Seattle than showing off at the show.


As an aside...guess we won't be seeing AAB there!
 
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FrenchPotatoEye
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 8:34 am

Stitch wrote:
The 787-8 wing to body join failed at below Limit Load - the maximum load the airframe should ever expect to see in revenue service. Boeing could have flown the frame, but they could not perform the full flight test and certification regimen.

The 777X cargo door failed well beyond Limit Load so there would be no limits on how hard they flew it and therefore they can perform the entire flight test and certification regimen.


Well said sticth. As ever, your the voice of reason.

It's also good to know 777X wing had no delamnation too.
 
VV
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 8:34 am

Scotron12 wrote:
VV wrote:
Opus99 wrote:
Will we see the 777X at the Dubai Airshow (17-21 November)?


Is it necessary to fly it to Dubai?

I guess if the aircraft is flying, it is more useful to have it doing tests in Seattle than showing off at the show.


As an aside...guess we won't be seeing AAB there!


Ah yes, the blockade.

Qatar won't be going, maybe.
 
Opus99
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 9:06 am

The engine re-installation has begun on WH002. The engines c-shells are on ground and ready for installation.
 
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FrenchPotatoEye
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 9:35 am

VV wrote:
Scotron12 wrote:
VV wrote:

Is it necessary to fly it to Dubai?

I guess if the aircraft is flying, it is more useful to have it doing tests in Seattle than showing off at the show.


As an aside...guess we won't be seeing AAB there!


Ah yes, the blockade.

Qatar won't be going, maybe.


The Qatar had no representations at air show in 2017 either. Black-ade started June's 2017
 
Opus99
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 9:41 am

Also if we see the 777x take off by the end of month/November when do we estimate certification to be granted? November 2020 at the earliest?
 
VV
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 9:52 am

Opus99 wrote:
The engine re-installation has begun on WH002. The engines c-shells are on ground and ready for installation.


And on WH001?
 
Opus99
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 9:56 am

VV wrote:
Opus99 wrote:
The engine re-installation has begun on WH002. The engines c-shells are on ground and ready for installation.


And on WH001?

The source and the photo made no reference to WH001, but I would assume WH001 as well would be at the same stage
 
mjoelnir
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 10:39 am

Opus99 wrote:
VV wrote:
Opus99 wrote:
The engine re-installation has begun on WH002. The engines c-shells are on ground and ready for installation.


And on WH001?

The source and the photo made no reference to WH001, but I would assume WH001 as well would be at the same stage


It depends on how many sets of engines Boeing got from GE. As it is, I assume only one set for one frame.
 
RJMAZ
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 1:03 pm

Engines back already. That was fast.
 
Ronaldo747
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 1:05 pm

Opus99 wrote:
Will we see the 777X at the Dubai Airshow (17-21 November)?


Only if they managed first flight until end of October and fly at least WH002 early November as well and all goes well, then it is very much possible. They need the PR.
 
estorilm
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 1:13 pm

Random question - I guess I'm missing some information here.

This failure occurred during the wing stress test with the fuselage under pressure, correct?

How can they possibly perform this test again once the fixes are in place? Wouldn't the 149% of normal load have damaged the test article structurally (ie probably why it was the last test to ever be performed on it?)

I mean for the door to not blow out at normal pressurization numbers, stresses, etc implies it was latched and manufactured correctly according to design specs etc. Any failure at a number that high would obviously imply that the failure was structural in nature (somewhere - door frame, latches, hinges, whatever) - of course the worst case scenario would be that the wing box deformed to the point where door components failed and allowed the blow-out.

So again, if the latter was the case, and the structure's deformation caused the failure, how can they possibly perform the test again without using a different test article? Likewise, the wings can't be too "happy" about performing this test again.

Like I said, maybe a stupid question.. just curious.
 
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bikerthai
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 1:28 pm

estorilm wrote:
Like I said, maybe a stupid question..


Not really a stupid question, because the answers are somewhat complex.

estorilm wrote:
Likewise, the wings can't be too "happy" about performing this test again.


If this was a metal wing, then truly, the components on the wing would have gone past yield (metal deformed). But the thing is, that if you re-load the metal, the stress strain curve will go back up the same linear slope until it reaches yield and ultimate failure again, just at a different deflection point. As the regulation does not specify where in the deflection point you have to meet, just the actual load, then in theory, you can retest a metal wing. '

For a composite wing, not sure if there is any yield, it will break when it breaks. All you can do is check for delamination. If there is no delamination, then you can probably test it again. Note that even if the wing is composite, there are many metal parts. A thorough check with the stress notes must be done to see if the condition as noted above for the metal wing have been reached before you give a second try.

Now, if the decompression is caused by deformation of the fuselage, then it is a more complex problem to solve. They may decide to stiffen up the door frame . That may be done with a simple doubler patch for the test frames but may require a re-design. The re-design may not go into effect until later frames, so the first few frames will have to fly with flight restrictions, either weight limits, internal cabin pressure limits or both.

bt
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VV
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 3:22 pm

https://www.aerospacetestinginternation ... blems.html

QUOTE
While our root cause assessment continues, at this time we do not expect that this will have a significant impact on aircraft design or on our overall test program schedule.
UNQUOTE
 
patrickjp93
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 3:50 pm

VV wrote:
https://www.aerospacetestinginternational.com/news/structural-testing/boeing-confirms-investigation-into-777x-load-testing-problems.html

QUOTE
While our root cause assessment continues, at this time we do not expect that this will have a significant impact on aircraft design or on our overall test program schedule.
UNQUOTE


Excellent. Now if we can just get those engines back on the flight test frame and get to flight testing.

Perhaps a dumb question, but are the FAA pilots doing daily flights and tests? I can't really imagine it takes more than a month of 6 hours a day to actually run through the numerous flight scenarios if everything handles as expected (problems discovered by pilots in flight are, of course, going to halt the program). If they're pausing a week or more between tests to crunch data and analyze, rather than doing so in parallel, that's certainly one thing to reform about the certification process, especially given a lot of the basics of the data analysis are so well understood now that much of the basics can be automated (speaking as a computer scientist and physicist).
 
WIederling
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 4:04 pm

patrickjp93 wrote:
VV wrote:
https://www.aerospacetestinginternational.com/news/structural-testing/boeing-confirms-investigation-into-777x-load-testing-problems.html

QUOTE
While our root cause assessment continues, at this time we do not expect that this will have a significant impact on aircraft design or on our overall test program schedule.
UNQUOTE


Excellent. Now if we can just get those engines back on the flight test frame and get to flight testing.

Perhaps a dumb question, but are the FAA pilots doing daily flights and tests? I can't really imagine it takes more than a month of 6 hours a day to actually run through the numerous flight scenarios if everything handles as expected (problems discovered by pilots in flight are, of course, going to halt the program). If they're pausing a week or more between tests to crunch data and analyze, rather than doing so in parallel, that's certainly one thing to reform about the certification process, especially given a lot of the basics of the data analysis are so well understood now that much of the basics can be automated (speaking as a computer scientist and physicist).


"Minimal change" MAX testing/certification took 2000++ hours. At 6 per day that is 333 flight days.
Murphy is an optimist
 
VV
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 4:11 pm

12 months of flight test to certification is extremely tight.
I would say it is very unlikely, but who knows?
 
patrickjp93
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 4:12 pm

WIederling wrote:
patrickjp93 wrote:
VV wrote:
https://www.aerospacetestinginternational.com/news/structural-testing/boeing-confirms-investigation-into-777x-load-testing-problems.html

QUOTE
While our root cause assessment continues, at this time we do not expect that this will have a significant impact on aircraft design or on our overall test program schedule.
UNQUOTE


Excellent. Now if we can just get those engines back on the flight test frame and get to flight testing.

Perhaps a dumb question, but are the FAA pilots doing daily flights and tests? I can't really imagine it takes more than a month of 6 hours a day to actually run through the numerous flight scenarios if everything handles as expected (problems discovered by pilots in flight are, of course, going to halt the program). If they're pausing a week or more between tests to crunch data and analyze, rather than doing so in parallel, that's certainly one thing to reform about the certification process, especially given a lot of the basics of the data analysis are so well understood now that much of the basics can be automated (speaking as a computer scientist and physicist).


"Minimal change" MAX testing/certification took 2000++ hours. At 6 per day that is 333 flight days.


2000 hours actually in the air? I realize it would take some in-depth analysis of real data, but my instincts tell me there's got to be plenty of overlapping scenarios being redundantly flown in that amount of time without good reason.
Last edited by patrickjp93 on Wed Oct 02, 2019 4:16 pm, edited 1 time in total.
 
musman9853
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 4:14 pm

RJMAZ wrote:
Engines back already. That was fast.


that was what, like 5 weeks? so much for everyone claiming that the 77x would be months behind the schedule.
Welcome to the City Beautiful.
 
VV
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 4:19 pm

musman9853 wrote:
RJMAZ wrote:
Engines back already. That was fast.


that was what, like 5 weeks? so much for everyone claiming that the 77x would be months behind the schedule.


I just wish to say that the first flight is now about 9 months behind the initially expected date.

I think it is fair to say that it is today behind schedule.

It is still unclear whether there was a schedule buffer and how much of this buffer had been eaten so far.
 
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kanban
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 4:37 pm

aren't the 2000 estimated test hours divided by the number of test airplanes (not equally because the planes to not perform the same tests) and then there is the down time for evaluating test results and setting the equipment for the next series. aren't 3 planes scheduled for the test fleet and maybe a 4th for evacuation testing and other interior related items. Then since there will be a few planes available a 5th may do route proving and ETOPS testing.
Also the FAA does not fly the test program, Boeing does. However the results are reviewed with the FAA who sometimes ask for further tests. FAA pilots only fly after the tests are complete.
 
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Stitch
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 4:37 pm

bikerthai wrote:
Now, if the decompression is caused by deformation of the fuselage, then it is a more complex problem to solve. They may decide to stiffen up the door frame . That may be done with a simple doubler patch for the test frames but may require a re-design. The re-design may not go into effect until later frames, so the first few frames will have to fly with flight restrictions, either weight limits, internal cabin pressure limits or both.


If the blow-out was caused by fuselage deformation, that should have been detected during the test and I would have expected Boeing to have halted the test once they saw it.

And again, why are we speculating that Boeing will have to "restrict" the flight testing envelope? The failure occurred well beyond what the flight test articles will ever experience. There is no reason to restrict them in any way.
 
musman9853
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Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 4:39 pm

VV wrote:
musman9853 wrote:
RJMAZ wrote:
Engines back already. That was fast.


that was what, like 5 weeks? so much for everyone claiming that the 77x would be months behind the schedule.


I just wish to say that the first flight is now about 9 months behind the initially expected date.

I think it is fair to say that it is today behind schedule.

It is still unclear whether there was a schedule buffer and how much of this buffer had been eaten so far.


it is a bit behind schedule but people were claiming that this engine issue would take forever to get fixed and there would be absolutely no way it would fly anywhere near on time.
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StTim
Posts: 3446
Joined: Thu Aug 08, 2013 7:39 am

Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 5:21 pm

You have test cases, versions of test cases, test conditions happening individually, test conditions happening concurrently. Time taken to set up test cases.

Repeat test cases after fixes.

Finally certification flying.

12 months minimum.
 
VV
Posts: 947
Joined: Sat Feb 13, 2016 1:03 pm

Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 5:32 pm

musman9853 wrote:
VV wrote:
musman9853 wrote:

that was what, like 5 weeks? so much for everyone claiming that the 77x would be months behind the schedule.


I just wish to say that the first flight is now about 9 months behind the initially expected date.

I think it is fair to say that it is today behind schedule.

It is still unclear whether there was a schedule buffer and how much of this buffer had been eaten so far.


it is a bit behind schedule but people were claiming that this engine issue would take forever to get fixed and there would be absolutely no way it would fly anywhere near on time.


No, the engine hardware issue was not difficult to fix. I think it is related to the kinematics and the strength of the actuator arms of the variable pitch vanes. In addition those are relatively "cheap" parts although there are a lot of the just outside the casing.

My understanding is that the gas path is good enough, so there has not been any fundamental redesign.
 
patrickjp93
Posts: 389
Joined: Thu Aug 22, 2019 12:00 pm

Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 5:35 pm

StTim wrote:
You have test cases, versions of test cases, test conditions happening individually, test conditions happening concurrently. Time taken to set up test cases.

Repeat test cases after fixes.

Finally certification flying.

12 months minimum.

And I'm saying it's likely bogus that it takes 12 months MINIMUM by necessity rather than simply by poor management, especially if you have multiple test craft and enough test pilots on staff. Assuming the FAA isn't stalling between test flights to crunch data (because this CAN and SHOULD be done concurrently with the flying and is largely automatable), then if it takes 12 months with 1 craft, then 6 with 2, 4 with 3. And my job as a software tester was not just to create a comprehensive suite of tests, but make sure it was a minimal comprehensive suite, IE absolutely no redundant tests, because the improvements in processing seed needed to be in production ASAP or millions of dollars could be lost. Half the time I was writing proposals for removing test cases or otherwise consolidating them because they were orthogonal and combinable in entirely predictable ways. If you think there are zero such cases with the FAA's test regimen, I'd like to sell you the Verrazano Bridge.

There's really no point in testing overspeed tolerance at 2, 3, and 4% parameters individually. Just go right up to the edge before the predicted redline where turbulent and supersonic flow cause control loss, validate that you're still handling as normal, then go past your red line, validate that the control is lost in the EXPECTED manner, and move on to the next set of tests. Incremental tests like that are completely redundant and results highly predictable (can be interpolated with 8+ 9s of accuracy if you have the base and far tail cases in hard, reliable data).

We all know how inefficient government agencies are, and I'm not saying play fast and loose. I'm saying I'd be very interested to see how much of the testing is purely redundant, because that's your tax dollars at waste doing nothing useful. The stress test frame is a dedicated one performing all your longterm studies of wear and tear.
 
Opus99
Posts: 52
Joined: Thu May 30, 2019 10:51 pm

Re: Boeing 777X Testing Thread - 2019

Wed Oct 02, 2019 5:50 pm

The fact that there are 6 test aircrafts does that make the certification process any shorter?

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