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Question About Wing Flex. Newer Aircraft Vs Old  
User currently offlineTrnsWrld From United States of America, joined May 1999, 948 posts, RR: 0
Posted (1 year 5 months 1 day 17 hours ago) and read 5943 times:

Sorry if this is a topic that has been talked about before, but in a brief search nothing came up that got into what im talking about.

So I have been wondering for some time now about some of the details regarding wing flex. Why did older aircraft not really experience this where as most newer large aircraft have in some cases extreme flexing of the wings? For example I do not recall seeing aircraft such as the DC-10, L1011, 707, A300, even the classic 747s with very large wings had minimal movement of the wings. Sure they bounce up and down in turbulence, but im more so talking about heavy takeoffs where you see those wings flexing and doing so much work lifting all that weight. It seems that the first large aircraft that had wings that really flexed was the 767. Nowadays aircraft like the 744/748, 787, A330 etc etc have wings that move significantly depending on the phase of flight and weight etc etc.
So with all that said what has changed in the materials and design of wings over the years that causes such significant movement of the wings and larger aircraft starting with the 767? I'm just taking a guess here, but were older aircraft over engineered or something along those lines? How can an airplane such as a DC-10 or a 747-100 with such large wings have such minimal flex even on max weight takeoffs?

Thanks for any information regarding this subject.

8 replies: All unread, jump to last
 
User currently offlineHH65MAN From Australia, joined Feb 2013, 106 posts, RR: 0
Reply 1, posted (1 year 5 months 1 day 16 hours ago) and read 5761 times:
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Ever seen the wing flex on a B-52? From the early to the current models. The B-52 has been been flying for as long as ive been alive. It's quite impressive.

User currently offlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 2, posted (1 year 5 months 1 day 6 hours ago) and read 5451 times:

Quoting TrnsWrld (Thread starter):
Why did older aircraft not really experience this where as most newer large aircraft have in some cases extreme flexing of the wings?

As HH65MAN says, it really depends on the aircraft. Certainly a stiffer wing needs to be stronger, and thus heavier. If you can get away with more flex without flutter and such, it may well allow a lighter structure.

The 747 classic did flex a lot!



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently onlineakiss20 From United States of America, joined Sep 2007, 627 posts, RR: 5
Reply 3, posted (1 year 5 months 16 hours ago) and read 5211 times:

The increasing use of composites will also result in next gen aircraft having a lot more wing flex than before. Composites enable aspect ratios we used to only dream about, resulting a lot "floppier" wings  


Change will not come if we wait for some other person or some other time. We are the ones we've been waiting for. We are
User currently offlineLH707330 From United States of America, joined Jun 2012, 810 posts, RR: 0
Reply 4, posted (1 year 4 months 4 weeks 1 day 22 hours ago) and read 4968 times:

Quoting akiss20 (Reply 3):
The increasing use of composites will also result in next gen aircraft having a lot more wing flex than before. Composites enable aspect ratios we used to only dream about, resulting a lot "floppier" wings

I would add CFD as a factor for higher aspect ratios. Since the first jets, aerodynamicists have been able to reduce sweep, thicken and lengthen the wing, and maintain a .83-.85 cruise. Don't the A330s have the highest aspect ratio (10.06 IIRC) out there with a metal wing?


User currently offlineflyingturtle From Switzerland, joined Oct 2011, 2442 posts, RR: 14
Reply 5, posted (1 year 4 months 4 weeks 1 day 20 hours ago) and read 4893 times:

Quoting LH707330 (Reply 4):

Vickie Pedia says the Dash 8 Q400 has 12.8.  


David



Keeping calm is terrorism against those who want to live in fear.
User currently offlineLH707330 From United States of America, joined Jun 2012, 810 posts, RR: 0
Reply 6, posted (1 year 4 months 4 weeks 1 day 19 hours ago) and read 4890 times:

Quoting flyingturtle (Reply 5):
Vickie Pedia says the Dash 8 Q400 has 12.8.

Fair point. Of widebody jets, I think the A330 is up on the podium though.


User currently offlineYQBexYHZBGM From Canada, joined May 2009, 204 posts, RR: 1
Reply 7, posted (1 year 1 month 3 days 17 hours ago) and read 3453 times:

I recall 727s having much more wing flex than any other aircraft I have flown on, including DC9 / MD80 variants which, like the 727, lack wing-mounted engines that would tend to dampen the flex effect. I've never noticed much flex at all on the CRJ or ERJ, which also have rear engines, but whose wings are much smaller and shorter than those of the 727.

Al
YQBexYHZBGM


User currently offlineCALTECH From Poland, joined May 2007, 2283 posts, RR: 26
Reply 8, posted (1 year 1 month 3 days 15 hours ago) and read 3387 times:

Quoting HH65MAN (Reply 1):
Ever seen the wing flex on a B-52? From the early to the current models. The B-52 has been been flying for as long as ive been alive. It's quite impressive.

IIRC, the B-52 had a wing flex of 17 feet at the tips. When they came in after a flight, if one wing had substantially less fuel than the other one, had to get a stand to put in the outrigger gear pins.

http://cdn-www.airliners.net/aviation-photos/photos/1/0/8/1400801.jpg



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