A door hatch from the aircraft was found 70 yards away.

[0] - https://theaviationgeekclub.com/time-kc-135-stratotanker-air...

I really hope you mean 154% of the max load, and I hope that max load is engineered to be far above what should be seen in actual service. 50% over the normal service load is not what I would consider extreme, and not something I would expect to be acceptable in an aircraft.

50% is indeed not a huge safety margin like you'd get with a bridge or something, which is why you need trained professionals flying it and regular inspections. If you fly into a big enough thunderstorm, the wings can definitely come off. Of course a bigger safety margin would be nice, but every pound of wing spar is a pound less payload. If the FAA required 200% of design limit, flying would be significantly more expensive.

Now that's also not to say that if you're going to add weight to an airplane in the name of safety that the best place to do it is the wing spar, but there is certainly a tradeoff between safety and weight.

Safety margins for bridges are like 25-50%.

* the loading on the bridge, which can be higher than the calculated amount.

* the resistance of the materials used, that can be lower than the requested amount.

* the quality of the soil,

* the lifespan of the bridge,

* ...

So the loading can be 25% percent higher, the materials can be 25% worse, the soil can be 25% worse, the lifespan can be 25% higher, ... and at the end you get a bridge that would still work if everything fails with a margin of 25%.

If the loads are 30% higher, the bridge might or might not fail. Who knows. Even though there are many other safety factors, and the bridge probably won't fail, it was not designed for that. There might be a critical part somewhere that has a resistance that's 25% worse than what it should be, and it therefore can only support a 25% overload, and with 30% that part might fail.

Bridges are designed to fail very slowly, loudly, and visibly, to avoid loss of functionality (e.g. when a bridge start to fail, this becomes obvious, and you still have months or years to sanitize the bridge).

I expect airplanes to have much tighter safety margins (<15% or <10%). The loads are more accurately known, the materials are higher quality, everything passes more extensive quality assurance tests, weight is much more important and companies are willing to pay prime prices on materials, manufacturing, etc. to reduce it, etc.

Safety margins aren't chosen arbitrarily. The job of a safety margin is to quantify an uncertainty, and with enough money thrown at each one, most of the uncertainties can be quite precisely quantified. Then it's the job of the designer to say "This plane should be in service for 50 years", and from the uncertainties and statistical analysis you can compute the highest load that the plane will receive in those 50 years with a certain quantified margin of error, and continue the design using that.

> This Boeing 777 wing was tested to destruction, finally breaking at one fifty four percent of the designed limit load.

The language is tricky, if you interpret it as I did, or 154% "more" than the design limit, then it is the design limit plus 1.54 more design limits. Like saying you salary is $100 and we're paying you 90% beyond your salary. Then you would expect to get $190.

If you interpret it to be 154% "of" the design limit, then I would agree it would be 1.54x the design limit.

Since other publications from Boeing, and Boeing staff at the "Future of Flight" museum in Everett have said that the planes are safer because they can withstand over twice their design limit, I read the 154% number as the amount "over" the limit.

Since folks from Boeing read Hackernews, it would be great for one of them to chime in here with some clarification :-).

[1] https://youtu.be/Ai2HmvAXcU0?t=45

Planes are safer because “they can withstand twice their design limit” is senseless. The 2x factor you are thinking of is the design limit. The design limit has all of the huge safety margins built in for the normal load limits.

The planes are designed to take at least 2x the max normal loads.

Edit: This is assuming the 'design level' is the level it was designed to withstand, which is how I would normally understand the term. Having watched the full video now though, it sounds like it actually exceeded the expected max force that could be expected in the real world by 1.54 times, and that the design anticipated about 1.5x. So indeed, it hit dead-on the design expectation, rather than vastly exceeding it—but that's fine, because the design included a 50% margin of error (and one would hope, a conservative worst-case estimate).

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf...

>Former Boeing Engineer Dr. Todd Curtis runs Airsafe.com and said this doesn't happen often. "I've never heard of a case where a door popped off like this during a stress test before," he said. "Doesn't mean it hasn't happened before, I'm just not aware of it."

Uh oh. Haven't we seen this story before with a different model (cough 737 cough)?

It's literally the first sentence of the article.

I doubt Boeing were pushing the envelopes further than the FAA required. And a door fell out.

>The test is meant to push the plane beyond its limits. Engineers had the plane pressurized and on the ground. They loaded it up well beyond capacity and bent its wings in an extreme manner, in a way almost certain to never happen in the real world.

and also further down, more "not necessarily a normal test" evidence:

>... The ultimate load test is the latest in a series of tests that Boeing has been conducting on this full-scale test airplane over the past several months."

Semantics.

https://www.seattletimes.com/business/boeing-aerospace/door-...

The Seattle Times explains it thusly:

During the ultimate load test, the wings are then pulled upward. To pass the test and be certified, the wings must bend without breaking until the load on them reaches at least 150 percent of the normally expected load.

…

Sometimes this final test is continued beyond the 150 percent load target until a wing actually breaks. But not always.

…

This time, however, though the wings did not give way; it was one of the doors that failed — an outcome that is definitely not supposed to happen.

https://en.wikipedia.org/wiki/Turkish_Airlines_Flight_981

The cargo hatch blew open and the cabin floor collapsed on account of differential pressure, disabling the rudder, elevator and rear engine controls.

This may well not happen on a 777X -- various other airplanes have lost part of their cabin structure without crashing -- but an unexpected event calls into doubt your design.

https://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243

If you're testing it up to the limit then no, it is not expected.

But if you're pushing it beyond the design limit then yes, it is expected to break.

Some wing tests are done beyond the limit, some are done below the limit (non-destructive tests cost less, that's why they're preferred, but for a new design they might just push it beyond the limit to see when does it effectively fail)

Given the stunned silence and halting of further testing I'm guessing this wasn't a stress it till breaking type 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...

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.

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

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.

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."

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.

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.

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

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

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

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

There is only one version of the A380, the A380-800.

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

I didn't mean "in service", I meant "in production". You're right that it wasn't in service at the time, but pieces of the plane had already been started to be produced, thus "in production".

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

There was/is no "newer, higher capacity A380". This was the certification for the original (and only) A380.

We're just arguing semantics and talking past each other. During the test, the wings 'failed', but this failure was intentional. I see where you're coming from in your statement that it was a "failure", but my point is that the test passed, because the test did exactly what was needed to provide data for the necessary certification, which was achieved based on the test.

edit: edited to be less inflammatory

https://www.ainonline.com/aviation-news/air-transport/2006-1...

QUOTE: Since manufacture of the initial wingset used in the tests, Airbus has refined the design, which will be slightly different on production rigs as a result of continued development, according to the European manufacturer. One factor may have been that earlier A380 weight-saving exercises had left no margin for error in the formal static load tests.

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.