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Boeing's New 787 Wings — Amazingly Flexible
Posted by
ScuttleMonkey
on Wed Jun 27, 2007 03:27 PM
from the reed-in-the-wind dept.
from the reed-in-the-wind dept.
An anonymous reader writes "Boeing is making the wings of its new 787 out of carbon fiber instead of metal. That means the wings are so strong and flexible that they could bend upward and touch above the fuselage — or come close. The company is expected to deliver the first 787 to All Nippon Airlines in May 2008. 'Boeing has completed static testing of a three-quarter wingbox, but engineers are still considering whether to limit testing of the full wing to a 150% load limit held for 3 sec. or to continue bending it to see when it breaks. 'There's a raging debate within the engineering team to see if we should break it or not,' says [787 General Manager Mike] Bair.'" They have come a long way in wing flexibility.
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I hope they test it! (Score:5, Insightful)
No one's ever really tried that before, so testing is critical.
Since this seems like such a new concept (please correct me if I'm wrong; I don't follow plane technology too much), it would just seem prudent to try bending the wings until they break... how can they make accurate judgments and calculations without knowing exactly how much stress the wings can take before snapping?
Re:I hope they test it! (Score:5, Informative)
My doctorate is in Mechanical Engineering - Materials, in this case fracture mechanics. The fact that the wing is so strong suggests that it may be being over-designed. My graduate structures professor, who worked on the 747, point out that airplanes are designed for what might be called simultaneous mode failures -- there is no point in having the wings significantly stronger than the fuselage, as once the fuselage breaks the wings don't do you any good, you have just been carrying too much material in the wings. The same is true for all sub-systems. Hence, you have to do a very exhaustive analysis of the expected situations and make sure that all of them are appropriately covered, then you add a safety factor.
Typically, fatigue cracking has been the limiting factor in aircraft structures, and has caused numerous crashes. With the experience that has been gained in military programs, we should now know enough to use these composites properly.
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Re:I hope they test it! (Score:5, Informative)
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Re:I hope they test it! (Score:5, Funny)
Pfffft. Real slashdotters only need a headline.
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Re:I hope they test it! (Score:5, Informative)
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Re:I hope they test it! (Score:5, Funny)
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Re:I hope they test it! (Score:5, Interesting)
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Why (not)? (Score:5, Interesting)
Well... (Score:5, Interesting)
Unless otherwise specified, a factor of safety of 1.5 must be applied to the prescribed limit load which are considered external loads on the structure. When a loading condition is prescribed in terms of ultimate loads, a factor of safety need not be applied unless otherwise specified
The three second requirement comes out of paragraph 305(b):
(b) The structure must be able to support ultimate loads without failure for at least 3 seconds. However, when proof of strength is shown by dynamic tests simulating actual load conditions, the 3-second limit does not apply. Static tests conducted to ultimate load must include the ultimate deflections and ultimate deformation induced by the loading. When analytical methods are used to show compliance with the ultimate load strength requirements, it must be shown that--
(1) The effects of deformation are not significant;
(2) The deformations involved are fully accounted for in the analysis; or
(3) The methods and assumptions used are sufficient to cover the effects of these deformations.
If our intrepid engineers manage to test to 200% for 3 second, then somebody is going to come along and say, "let's see if we can make the wings lighter"
Good thing or bad thing?....depends upon your point of view I guess.
As it turns out, validating airframe structures with respect to FAA airworthiness requirements is kinda what I do for a living.
Parent
Must resist onomatopoeic humor... (Score:5, Funny)
Slashdot Poll (Score:5, Funny)
1. Chicken out and don't break 'em
2. See how far they go and post it to YouTube
3. Orinthop mode! Pull 'em back and let 'em flap!
4. Cowboy Neal
While its great they are so flexible (Score:5, Insightful)
What? (Score:5, Informative)
If the aircraft is experiencing extreme conditions which are bending the wing excessively, then you _want_ to lose lift, rather than stress the wing and airframe more. Kind of like how sailors change to smaller sails during storms.
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One year ago? How about twelve? (Score:5, Informative)
The linked video may have been uploded about a year ago, but it cites as its source a PBS production from 1995. (Which, incidentally, is discussing an entirely different airplane, the 777.)
Old News: Flexible wings on the Boeing B-47 (Score:5, Interesting)
Don't break it (Score:5, Insightful)
The story was about one of the earlier Boeing's, they had stressed the wing to like 10 times any theoretical force that could be possibly placed on it during a rather publicized testing of its strength. They test folks were all about trying to break it.
During the process of doing this an exec asked them what they were doing. "Breaking the wing" they replied.
The exec said No, stop the testing.
Why? the testers asked.
Because the headline won't read ,
"Boeing wing breaks at 40 times the stress encountered during possible flight conditions",
Instead it will read
"New wing of new Boeing Jet Breaks".
Please note Its been awhile since I heard that story, but I think the point is pretty clear.
This is your captain... (Score:5, Funny)
787 is a revolution in design and manufacturing (Score:5, Informative)
1) Yes, it's almost completely carbon fiber. This means that the plane can (and is) lighter, so it will be more fuel efficient. Also, it's easy to make complex curved shapes, so the wings and fuselage are slightly more aerodynamic. Because carbon fiber structures are so strong, the windows can be larger, and the plane can be pressurized to a lower altitude (it will be pressurized to 6000' instead of the typical 8000' of today's fleet). There is no corrosion, and little worry about fatigue in composites.
2) The plane is not built in Seattle, although that's where the final assembly takes place. All of the building takes place in multiple facilities around the globe, each producing parts to Boeing's plans. These parts will "snap together" in the Everett plant. The first 787 is being assembled right now, and will roll out on 7/8/7 (just over a week from now.) Apparently the left wing was off by 2 thousands of an inch or so, the right wing was absolutely perfect. Boeing converted three 747's to be gigantic cargo transporters to move all the parts from around the world to Everett.
3) The plane has almost completely electric, without the high-pressure pneumatic systems that older planes had. In particular, the AC systems are electric. This will be somewhat more efficient, and safer.
4) The plan for certification of the plane is borderline insane. The final assembly started a couple of weeks ago, and the plane will be rolled out in a week, the first flight will be in a couple of months, and the first delivery will be in Q2 2008. This is a tiny fraction of the time this process required on previous airplanes -- maybe 1/4 the time of the 777 and even less than that of the latest Airbus. This would be remarkable, even if the plane wasn't revolutionary in every other way, too!
5) Aviation Week and Space Technology visited the final assembly line recently, and were surprised to find that it was almost an empty building. That's not because they weren't ready -- that's because there are almost no tools needed to assemble the plane. They snap together the pieces, install the landing gear, and roll it down the building on its gear installing the various subassemblies. Boeing intends to assemble a plane every three days once they get going, a remarkable and unprecedented schedule.
Anyway -- there are so many revolutions in this airplane that I would have thought it was a scam if it was any other company than Boeing. It remains to be seen if they can meet their goals, but so far things are going remarkably according to the plan they laid out a few years ago.
Thad
Re:missed the best part... (Score:5, Funny)
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YMCA (Score:5, Funny)
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Re:Nothing new (Score:5, Informative)
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Re:Nothing new (Score:5, Informative)
Yeah, it kind of reminds me of when Airbus called Boeing's composite barrel design "old fashioned" [nwsource.com]!
Bearing in mind that nobody has produced such a design yet, including Airbus. Until Boeing did it a couple of weeks ago, that is.
The A350 was designed in direct response to the 787, which surprised Airbus in the amount of interest it received (they had at the time placed their bets on the now-troubled A380 program, which may never break even). Saying the 787 copied any of the A350's design or construction methods is getting it completely backwards.
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Re:Nothing new (Score:5, Informative)
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Re:I really don't see the big deal (Score:5, Informative)
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Re:Design accommodations? (Score:5, Funny)
What? Give up slashdot? Never. I'll die first.
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