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Comment by capableweb | Hacker News Reader

Absolutely. I think Boeing has proven with these statements that they no longer care about safety or engineering standards. They should have continued to run tests to prove that they meet 150%, make a video of it and continue to run, in order to regain the trust of the public. But they seem unwilling to get back the trust.

Also, I think this also shows that the interaction that Boeing have with the FAA and vice-versa, has been heavily corrupted by something (money?) and FAA is no longer trying to keep Boeing in check. They are trying to make sure that Boeing passes whatever certification even if they might miss some details.

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Airbus A380 failed a similar test at 3% less load and Airbus responded in a similar fashion. Boeing has problems, but this is practically a pass.

Airbus A380 failed A similar test at 3% less load and Airbus responded in a similar fashion. Boeing has problems, but this is practically a pass.

Airbus was testing a new (higher MTOW) variant of the A380. It's likely Airbus was expecting the premature failure as the fix was quickly deployed. I'm pretty sure you can't say the same about the 777X.

Note that wing spar cracks were later found in pretty much every early build A380 in service. Airbus then spent around 500,000,000 EUR to remedy the problem.

I'm sure Boeing can make the 777X safe, but it's likely a matter of motivation.

The 100% already factors in a large safety margin.

that's not how safety margin work, is not a budget leftover set aside for known unknowns, it's there for unknown unknowns.

e: downvoters might want to read Feynman again

"If a bridge is designed to withstand a certain load … it may be designed for the materials used to actually stand up under three times the load … But if the expected load comes on to the new bridge and a crack appears in a beam, this is a failure of the design. The O-rings of the solid rocket boosters were not designed to erode. Erosion was a clue that something was wrong. Erosion was not something from which safety could be inferred"

if you fail a test before your margin you haven't established that your safe up to 90% margin, you've established that the hypothetical on which your design was based are wrong and no further inference might be warranted, regardless of whether you fail at 99% or 60% of where you expected to fail

You aren't paying attention to the phrase "expected load".

If, in the bridge scenario, it cracks under 2.95x the normal load, vs. 3.0x or 3.05x, that is not what Feynman was describing. He was explicitly talking about a partial failure under about 1.0x. Which based on other comments is not what happened here.

except 3.75g here is the expected load°, the certification requirement. the design is engineered to reach that 3.75g°, the safety margin is what lies beyond.

°with the disclaimer that the plane might be not airworthy after landing

That doesn't apply in this case. Modeling will never be a perfect representation of reality. IE you're never going to have tested failure at 100.00% of the expected failure load. If it had failed at 90% I would agree that they should take another look at the design, but at 99% it's within expectations. And you still maintain essentially all of the designed safety margin for the unknown unknowns.

They didn't get a pass at 99%.

I didn't address my reply to FAA either

Back in March, the FAA was still insisting the 737 MAX was airworthy, even after it had been grounded by other countries. It seems like at the very least, the FAA is worried about the business interests of manufacturers.

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