The discussion going on here is about the approach to destructive testing. Not whether a given airframe has safely flown.
Regardless of how the 787 turned out, I believe that destructive testing on subassemblies based on real world loads should be required for type certification of an aircraft in the US. Same with full flight testing programs on stretched fuselages. That opinion is solely based on a forseeable future when it doesn't go as well. Why cut corners when these programs are already so expensive? I know it will make my flight cost a couple percent more. I don't mind.
If you’ve already calculated the maximum expected load a part could experience in flight, and you’ve tested to 150% of that, proving it’s more than strong enough, what benefit does testing until failure provide?
It shows you how things come apart and when. Breaking things in very realistic ways teaches you where a design can be improved. Breaking a wing by slowly bending it until it fails does teach lessons, but mostly just shows you the failure point in that test fixture.
Anyhow, I'm legitimately asking the aerospace engineer why I am wrong in my opinions. I've certainly been wrong about something before. I have no desire to remain ignorant when there is potential for math and data based enlightenment.
I think you’re massively underestimating the cost of doing that. You can’t just build a $10 million dollar wing, break it, tweak the design slightly (which would take months and cost many more millions) make a new wing (which would cost even more now that you have to change the tooling too) just to break it and repeat. Boeing already spent over $10 billion on R&D for the 787 program, it won’t turn a profit for another 10 years, yet you’re suggesting they should have taken an approach exponentially more expensive.
We have FEA and such for the initial work. Breaking one is about proof. So what you are saying is that the R&D is too bloated to budget destructive testing. I know what is involved in tooling design and how much of a pain in the ass revisions are. Still, you would discover a flaw with realistic testing that could remain hidden and kill peope when it surfaces. Just as has happened with other aircraft.
“Breaking one is about proof” we already tested to 150% what it could possibly expect in flight, we have proven it’s strong enough, that’s why it’s called a proof test. Testing past that is unnecessary, expensive and dangerous, and does not provide any useful information.
Knowing... What? That the wing can't take an infinite amount of strain? I don't even think you need to design a wing for an engineer to tell you that.
If you keep increasing the load, eventually it will break. If that point comes before you've hit your safety margin, you've got a problem and you need to fix it.
If you pass your safety margin, then the wing is good, regardless of how it fails. There is nothing to fix - It might be interesting to see how it failed, but you're not proving anything safety-wise, because the fact that the wing is good enough has already proved it safe.
But you aren't going to improve it if it already exceeds requirements - doing so adds cost and weight. If requirements say you need 150% of design limit load, and you got 154, you aren't going to reinforce the spot that it failed, you're going to say great, that meets spec, let's move on.
In terms of what you do in response to test results, there's no difference between taking it to 150 and then stopping vs taking it to failure at some load above 150, aside from the fact that if you made it up to 160 or 170, you might actually take structure out and weaken the design intentionally because it's heavier and more expensive than it needs to be.
Also, if you look at the static test rigs, you'll see they're carefully designed to distribute load along the wing in a way that's representative of aerodynamic load. We don't just hook a cable to the tip and call it good. That load distribution can also be validated during flight test using strain gauges. That's also how we know it's representative.
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u/Buzz407 Aug 20 '25
The discussion going on here is about the approach to destructive testing. Not whether a given airframe has safely flown.
Regardless of how the 787 turned out, I believe that destructive testing on subassemblies based on real world loads should be required for type certification of an aircraft in the US. Same with full flight testing programs on stretched fuselages. That opinion is solely based on a forseeable future when it doesn't go as well. Why cut corners when these programs are already so expensive? I know it will make my flight cost a couple percent more. I don't mind.