> The relatively good news for Boeing is that because the test failed so explosively at just 1% shy of meeting federal requirements, it will almost certainly not have to do a retest. Regulators will likely allow it to prove by analysis that it’s enough to reinforce the fuselage in the localized area where it failed.<p>I don't understand this. So they did a test, and it failed at 99%. They reinforce that one area where it failed, and show by analysis that the reinforced area would have made it to at least 100%.<p>OK, but what about the rest of the fuselage? The rest was only tested to 99%. Couldn't there be another place that fails at, say, 99.5%, which wasn't detected in the first test because the place that fails at 99% stopped the test?<p>Edit: I would guess that during this kind of test they have the plane heavily instrumented with things like strain gauges so they can understand how it reacts and see if it is behaving according to spec. So maybe it is the case that the data from the rest of the fuselage showed that it would have made it to 100% if the test had continued, and only the area that failed was in trouble. That could explain why they aren't require to do another test.<p>That still leaves me unsatisfied, though. Presumably analysis of the design <i>before</i> the test said it would make it to 100%. If the failure was not due to a manufacturing defect in that particular fuselage, then it suggests that they analysis was not adequate. But then what assurance is there that their analysis that shows that the reinforcement would hold is good?
This sounds fine. It's a catastrophic failure test. They push until it breaks, then it broke, and they were very close to their designed target (within 1%). If they had gone 1% past their designed target, they would have been upset, as they could have made the plane lighter. They were 1% short of design limit, they are upset because they'll have to add reinforcement.<p>Have you seen the wing failure test? I worked for the company that did these tests (they did them before I worked there), and they still talk about how upset the engineers were that it went over spec in strength.<p><a href="https://www.youtube.com/watch?v=Ai2HmvAXcU0" rel="nofollow">https://www.youtube.com/watch?v=Ai2HmvAXcU0</a>
>And the interior of the plane was pressurized beyond normal levels to about 10 pounds per square inch — not typically a requirement for this test, but something Boeing chose to do.<p>Hmm. Does it lower structural integrity, or improves it?
Very impressive. They strengthened the fuselage to meet requirements almost exactly, and fell a tiny bit short. That's an incredible amount of optimization, that means there's hardly any excess material (weight). This keeps fuel costs low and airfares competitive.
This was in the related articles at the bottom. I wonder how the decision is related the test? I wonder how much say legal had. That is, if they end up in court is human-made easier to defend than robot-made?<p><a href="https://www.seattletimes.com/business/boeing-aerospace/boeing-abandons-its-failed-fuselage-robots-on-the-777x-handing-the-job-back-to-machinists/" rel="nofollow">https://www.seattletimes.com/business/boeing-aerospace/boein...</a>
Also a positive note, the carbon fiber wings bent 3x expected max<p>>bent the jet’s giant carbon composite wings upward more than 28 feet from their resting position. That’s far beyond the expected maximum deflection in normal flight of about 9 feet
>All this simulated the loads in a flight maneuver where a pilot would experience a force of 3.75 G, compared to the maximum of 1.3 G in normal flight<p>>All this simulated the loads in a flight maneuver where a pilot would experience a force of 3.75 G, compared to the maximum of 1.3 G in normal flight
It seems to me that if nothing ever fails short of the 100% test its probably overengineered, since the 100% already includes a significant safety margin.<p>Alternatively if nothing ever fails the test, then they could also just stop doing these tests, since the analysis would already be shown to be sufficient.
What gets me is what is the point of a limit to test to if you are not going to enforce it.<p>If 1% less is ok (Boeing) test to 1% less,<p>if 3% less is ok (Airbus) make the limit 3% less.<p>Not enforcing a limit smells bad and does not fill me with confidence.<p>Strengthening the failure area will change the failure modes to other areas and may well make it fail at an even lower limit as other areas will be bending more to make up for the reduced deflection of the area that is strengthened.<p>Not re-testing it after a design change like this worries me.
"we're not going to re-test. We failed the test but it was close enough"<p>Yeah that makes me feel safe Boeing, real safe. Specially given your history now.<p>Planes used to pass these tests with flying colors and they've been pretty safe. Have we forgotten already that planes used to break in half in the sky when there's heavy turbulence? 3.5G sounds like much, but it is also not that much. There's a reason why the test needs to be passed at a certain level, not just below.<p>Heck otherwise, how about I pay 99% of my taxes, mortgage, pass 99% of my exams, etc. What is this?<p>Note: before you read and trust the articles too much, airline planes have been WELL above 3.5G already in the real world. The fact that they're not supposed to go there does not mean they never do.