[jussij]

> You would expect things to break during a stress test.

Except, the whole point of the test is to stress the plane and to have nothing break.

The test is designed to make sure the aircraft has built-in safety (i.e. is over engineered).

When the A380 was attempting to earn it's certification it failed a similar static wing test:

http://www.airmech.co.uk/forums/showthread.php/5340-A380-Win...

[kbenson]

> Except, the whole point of the test is stress the plane and to have nothing break.

That depends on the type of stress test. Some stress tests are to confirm it acts as expected. Other stress tests are used to determine modes of failure. Good engineering isn't just building stuff to spec and assuming it works, just as good programming isn't just writing code and assuming it works as expected because the compiler doesn't throw any errors.

It's very useful to try to break something and see what happens. That's why engineers provide more stresses than systems are designed for to see what breaks, and that's why programmers sometimes run programs in environments constrained in ways it wasn't meant to run in (no disk space, out of memory, network drop, etc), and run fuzzers.

[agumonkey]

Also it depends on how far in the design process they are. Early failure is good. Late is bad, but mostly for them, they'll have to loopback.

[i_am_proteus]

Very importantly, this hasn't been described as a "test failure."

No indication of what the test criteria were, if any. Some tests, especially those past design limits, are just for informational data.

[inferiorhuman]

Very importantly, this hasn't been described as a "test failure."

That was heavily implied:

Sources tell KOMO there was a stunned silence after it happened.

…

an event occurred that forced the test team to halt testing. … The team is currently working to understand what happened and ensure the area is safe for work to continue.

Edit: You're not going to silence the crowd with a successful test and you don't temporarily halt testing because of a successful test.

Edit 2: Seattle Times says this explicitly: This ground test failure is another blow.

[i_am_proteus]

Yes, but this isn't the language they'd use if one of the test success criteria was "no door blows out" and then a door blows out.

This is evidenced by their plan to "analyze the door and run the test again." If this were actually a test failure, they'd be "analyzing the door, redesigning a bunch of stuff, and running the test again."

[txcwpalpha]

>Except, the whole point of the test is to stress the plane and to have nothing break.

What? No it's not. The entire point of these tests is specifically to break things. If nothing breaks, they did not perform the test correctly.

>When the A380 was attempting to earn it's certification it failed a similar static wing test:

No, it didn't. It passed the test handily. The wing broke well beyond the max load limit, which is what they were testing for.

edit for the sake of being less of an argumentative asshole: I see where you're coming from when you say that it was a 'failure'. However, what I mean to say is that while the wings failed in the test, the failure was intentional, and the data gathered during the test was exactly what was needed to prove that the A380's wings were strong enough for certification, and the A380 was certified based on the results of this test. In my mind, that means the test passed.

[inferiorhuman]

What? No it's not.

Yes, it is. The point is to check that the wings can take 150% of the rated load. The point of an ultimate load test is NOT to break things.

[jussij]

The first time the A380 tried the test it failed. Read the link.

And yes it did eventually pass that wing test only because if it had not it would not never have been certified.

[txcwpalpha]

>The first time the A380 tried the test it failed. Read the link.

I suggest you read it. The A380 did not fail. It says so in the link you provided.

[jussij]

"We'll be able to demonstrate" that the plane meets requirements, "maybe with some refinements needed for certification in time for first delivery at the end of the year," Kracht said in a telephone interview Thursday.

We'll is we will (i.e some time in the future).

[txcwpalpha]

The A380 was already in production at the time of the Feb 2006 test. No modifications to the wings were required because it did not fail it's structural stress test. The entire point of the test was to gather data on what load the test wings (which are weaker than the production wings) failed at, which is why they intentionally broke the wings. The engineers then used this data to calculate the load limit that the production wings (which are stronger than the test wings) failed at. The calculated load limit for the production wings was above the EASA certification requirement, meaning the wings passed their test.

[jussij]

> The A380 was already in production at the time of the Feb 2006 test.

There is more than one version of the A380.

But there was no A380 Airbus with a 550 seat capacity in service at that time.

The whole point of that wing testing was so this newer, higher capacity A380 could get certification.

http://www.modernairliners.com/airbus-a380/airbus-a380_histo...

25 October 2007 - The first commercial flight of the A380 took place from Singapore to Sydney. All seats were auctioned off for charity.

FYI that link also shows the certification wing test failed:

14 February 2006 - Stress testing of the wing revealed that the wing broke at 146% of the required level instead of 150%. Further strengthening was added which increased the weight by 30Kg

[jussij]

> The entire point of these tests is specifically to break things

When you do these types of tests you are testing for a expected outcome.

If you do a test and the outcome is un-expected (i.e. the fuselage fails prematurely) it means your engineering and the expectations built around that engineering are wrong.

[txcwpalpha]

This is incorrect. These tests are specifically done because they want to gather data on what the failure loads (which are previously unknown) are.

[inferiorhuman]

No, as the Seattle Times pointed out the intent of the test is to ensure the wings support 150% of their rated load. They may continue until things break, but the typical purpose is simply to ensure there's that 50% wiggle room.

[29_29]

I'd rather it break in a stress test - than when I'm on it.