Dreadnought From United States of America, joined Feb 2008, 7754 posts, RR: 22 Reply 2, posted (5 months 6 days 20 hours ago) and read 2965 times:
Quoting CM (Reply 1): No. But Boeing did break a static test wing (no fuselage attached). They released a video at the time. You may be able to find it on YouTube.
It looks from the video that the fuselage was attached. It broke at 154% of design load limit.
KC135Hydraulics From United States of America, joined Nov 2012, 164 posts, RR: 0 Reply 4, posted (5 months 6 days 18 hours ago) and read 2894 times:
Is 154% about standard for fail rates of wings during testing? I know some of those wings get bent quite high but how did the carbon fiber wing compare to say, the wing on the 777 when it broke?
CM From , joined Dec 1969, posts, RR: Reply 5, posted (5 months 6 days 18 hours ago) and read 2884 times:
Quoting KC135Hydraulics (Reply 4): Is 154% about standard for fail rates of wings during testing? I know some of those wings get bent quite high but how did the carbon fiber wing compare to say, the wing on the 777 when it broke?
Designers shoot for failure with a very small amount of margin above 150% of Limit Load. I doubt it is +4%, which means a great deal more margin than is needed. I would guess the goal is something closer to 151% or 152%. Just enough to remove the risk of failing the test.
You could argue the 787 failed well short of 150%, which was when the side-of-body issue was discovered. The second time around, the test exceeded 150% without breaking. I am unaware of Boeing making the test data public from the wing ultimate load test where they broke a solo 787 wing.
The only other wing where I know of the results from the static test is the A380. That wing broke at 147% of limit load.
dynamicsguy From Australia, joined Jul 2008, 762 posts, RR: 8 Reply 6, posted (5 months 6 days 18 hours ago) and read 2880 times:
Quoting CM (Reply 1): I believe Boeing stated some time ago the frame had passed 1xDSO. It will ultimately be tested to 3xDSO
I've read that it passed 1xDSO as well. For those not familiar with the jargon, DSO = design service objective and represents one lifetime. The certification requirement is 2xDSO, but in this case Boeing has set a higher standard of 3xDSO.
nomadd22 From United States of America, joined Feb 2008, 1561 posts, RR: 0 Reply 7, posted (5 months 6 days 9 hours ago) and read 2724 times:
Quoting CM (Reply 5): You could argue the 787 failed well short of 150%, which was when the side-of-body issue was discovered. The second time around, the test exceeded 150% without breaking. I am unaware of Boeing making the test data public from the wing ultimate load test where they broke a solo 787 wing.
Seems I remember it didn't fail, but showed unexpected damage at that point. It may have passed the break test if they'd kept going, but since it wasn't responding as predicted they needed to wring out the problem to certify the model.
Not trying to contradict the most knowlegable source of Boeing procedures in this asylum. Just meandering.
Stitch From United States of America, joined Jul 2005, 26679 posts, RR: 83 Reply 8, posted (5 months 6 days 6 hours ago) and read 2633 times:
Boeing chose not to push the 787 wing to the actual breaking point (once Ultimate Load had been achieved) due to the clean-up issues (CFRP shards and dust),
CM From , joined Dec 1969, posts, RR: Reply 9, posted (5 months 6 days 6 hours ago) and read 2626 times:
Quoting nomadd22 (Reply 7): Seems I remember it didn't fail, but showed unexpected damage at that point.
It probably depends on how we define the word "fail". The requirement of the ultimate load factor test is to achieve 150% of limit load factor without structural failure. Permenent deformation of the structure is permitted. By the standards of passing the test, the 787 wing failed. It was not, however, a spectacular failure in the sense of the wing breaking, as we've all seen from the 777 video.
Bit of a sidenote - Anyone remember the China Airlines flight where a 747SP went into an uncontrolled dive, went briefly supersonic, and recovered with a 5G pullout?
The plane continued service for many years and still exists today, and I remember reading that after the incident the wings always had a couple of degrees more dihedral than normal due to the wings having been bent up so hard.
Let's hear it for good old-fashioned 1960's over-engineering.
Bit of a sidenote - Anyone remember the China Airlines flight where a 747SP went into an uncontrolled dive, went briefly supersonic, and recovered with a 5G pullout?
I can't find any reference in the official NTSB accident report stating that the aircraft went supersonic. Where do you see that?
Dreadnought From United States of America, joined Feb 2008, 7754 posts, RR: 22 Reply 13, posted (5 months 5 days ago) and read 2197 times:
Quoting Viscount724 (Reply 12): I can't find any reference in the official NTSB accident report stating that the aircraft went supersonic. Where do you see that?
I can't find it either. I believe I recall reading it in one of MacArthur Job's Air Disaster books, but I don't have it in front of me. I could be wrong...
But in looking for it I found this page about the DC-8 that went over Mach 1 on a test flight, in a shallow dive.
amccann From United States of America, joined Mar 2008, 171 posts, RR: 0 Reply 14, posted (5 months 4 days 21 hours ago) and read 2144 times:
Quoting dynamicsguy (Reply 6): I've read that it passed 1xDSO as well. For those not familiar with the jargon, DSO = design service objective and represents one lifetime. The certification requirement is 2xDSO, but in this case Boeing has set a higher standard of 3xDSO.
If this is not public information please do NOT post it here. However, if it is public information, does anyone know how Boeing has been handling thermal fatigue on the 787 fatigue test frame? The interaction of two materials with different coefficients of thermal expansion across a wide temperature range, I would imagine, is tested somehow either large scale or small scale.
What one person receives without working for, another person must work for without receiving. - Ronald Reagan
bikerthai From United States of America, joined Apr 2010, 1588 posts, RR: 4 Reply 15, posted (5 months 2 days 7 hours ago) and read 1744 times:
Quoting amccann (Reply 14): Boeing has been handling thermal fatigue on the 787 fatigue test frame?
Thermal fatigue is a material dependent property that can be tested in larger batches at smaller scale. In fact, it would have been tested at the beginning of the program when they characterized the material to obtained material properties.
Usually, those testing will result in a "knock-down" factor at is included in the analysis to account for thermal stress/cycling.
FYI: typically, hot wet have more detrimental effect on composite than cold/freezing (unless when you have freezing water in honeycomb cell).
The test frame itself sees only the general environment impact of being out doors at the test facility just north of the main Everett factory. Right now it is seeing driving rain and 40mph wind gusts.
An no propriety information have been released in the above information.
amccann From United States of America, joined Mar 2008, 171 posts, RR: 0 Reply 16, posted (5 months 1 day 21 hours ago) and read 1561 times:
Quoting bikerthai (Reply 15): Thermal fatigue is a material dependent property that can be tested in larger batches at smaller scale. In fact, it would have been tested at the beginning of the program when they characterized the material to obtained material properties.
Usually, those testing will result in a "knock-down" factor at is included in the analysis to account for thermal stress/cycling.
Thanks for the information, I was very curious. I kind of assumed it was either a coupon test or small assembly test and resulted in an analytical knockdown.
I tried a quick Google search of the issue and found only the following article;
I think the issue in the article has more to do with the dissimilar coefficient of thermal expansion between the composite skin and the aluminum shear tie.
This thesis gives you a glimpse of what composite do at lower temperature.
Shear strength goes up. But I would bet brittleness would also go up which would result in more prone to impact damage. But I guess at 40,000 ft, you are not going to hit a ground cart or have a wrench drop on your wing.
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I kind of assumed it was either a coupon test or small assembly test and resulted in an analytical knockdown.
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