Moderators: richierich, ua900, PanAm_DC10, hOMSaR

 
User avatar
propilot83
Topic Author
Posts: 625
Joined: Sat Jan 27, 2001 2:41 am

Wing Flexation

Mon Sep 28, 2009 7:39 am

I've noticed that on the Boeing 747-400 during take-off the wing of the 747 seems to flex upward towards the outer wingtip area. I know that wings and other parts of an airplane are designed to "flex" up and down due to the stress imposed on the plane as it expands and contracts like a balloon. However if you ever notice a 747-400 on the ground, the wings seem to be like an "arch" almost, and then when it becomes airborne, it tends to bend and flex like a "u" shape. I believed that this occurs because of stress as the plane becomes airborne, or is this also because fuel inside the wings move around and causes the wings to flex upwards towards the outer wingtip area? This wing bending is very noticeable on larger aircraft like the 747 and MD-11, I've seen it on the 737 also.
 
FlyDeltaJets
Posts: 1658
Joined: Thu Feb 02, 2006 4:24 pm

RE: Wing Flexation

Mon Sep 28, 2009 8:18 am

That flex is caused by the lift generated by the wings. The air is literally picking the plane up by the wings. The fuel in the wings somewhat attempt to prevent the wing from flexing too much. Most wings will flex some more than others.
The only valid opinions are those based in facts
 
User avatar
Starlionblue
Posts: 20700
Joined: Fri Feb 27, 2004 9:54 pm

RE: Wing Flexation

Mon Sep 28, 2009 9:15 am

On a 747 or 380, the wings droop noticeable while on the ground if they are full of fuel. As the wings start producing lift on the take-off roll, they bend up into the "flight" position. The wings are lifting themselves first if you will. The reason for the U shape is that the fuse is sitting in the middle.

You can model it with a long steel ruler. Get two bricks and suspend the ruler between the bricks with only the ends supported. Then get a weight and put in on top of the middle of the ruler. The bricks represent lift and the weight is your fuselage. (The ruler, obviously, is the wing). The ruler will bend into a U shape,

Quads tend to have more wing flex since the outer engines allow a weaker wing by counter-acting flex.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
AirframeAS
Posts: 9898
Joined: Thu Feb 05, 2004 3:56 pm

RE: Wing Flexation

Mon Sep 28, 2009 7:57 pm

The 777's have a really nice wing flex that is very much noticeable.... and it looks sexy, too!!!
A Safe Flight Begins With Quality Maintenance On The Ground.
 
User avatar
ATA L1011
Posts: 1320
Joined: Thu Mar 01, 2001 6:47 am

RE: Wing Flexation

Wed Sep 30, 2009 5:40 pm

747-400's, 767's,777's, A330 and 340's all have nice wing flex on takeoff and at cruise. The MD-11 does not have nearly as much flex as the above as its wing is sorta designed downwards as you get toward the wingtips, the rest are angled upwards toward you get toward the tips.
Treat others as you expect to be treated!
 
CosmicCruiser
Posts: 2510
Joined: Tue Feb 22, 2005 3:01 am

RE: Wing Flexation

Wed Sep 30, 2009 6:26 pm

Checkout any old pics of a B-52
 
411A
Posts: 1788
Joined: Mon Nov 12, 2001 10:34 am

RE: Wing Flexation

Thu Oct 01, 2009 1:56 am

Maximum designed wing flex (at the tip) for the B707....12 feet UP, 11 feet DOWN....prior to wing skin deformation, while airbourne.
 
ArmitageShanks
Posts: 3780
Joined: Tue Dec 30, 2003 5:30 am

RE: Wing Flexation

Thu Oct 01, 2009 2:01 am



Quoting ATA L1011 (Reply 4):
The MD-11 does not have nearly as much flex

I always thought it had more.
 
User avatar
ATA L1011
Posts: 1320
Joined: Thu Mar 01, 2001 6:47 am

RE: Wing Flexation

Thu Oct 01, 2009 2:04 am



Quoting ArmitageShanks (Reply 7):
I always thought it had more.

Go look at photo's of the for mentioned vs the MD-11 on takeoff and at cruise and you will clearly see that its wings do not flex nearly as much.
Treat others as you expect to be treated!
 
User avatar
Starlionblue
Posts: 20700
Joined: Fri Feb 27, 2004 9:54 pm

RE: Wing Flexation

Thu Oct 01, 2009 7:49 am



Quoting 411A (Reply 6):
Maximum designed wing flex (at the tip) for the B707....12 feet UP, 11 feet DOWN....prior to wing skin deformation, while airbourne.

Wobble. Big grin I'm sure Boeing learned a lot from the B-47 and B-52 wings.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
AirframeAS
Posts: 9898
Joined: Thu Feb 05, 2004 3:56 pm

RE: Wing Flexation

Thu Oct 01, 2009 9:23 am



Quoting ATA L1011 (Reply 4):
747-400's, 767's,777's, A330 and 340's all have nice wing flex on takeoff and at cruise. The MD-11 does not have nearly as much flex as the above as its wing is sorta designed downwards as you get toward the wingtips, the rest are angled upwards toward you get toward the tips.

Don't forget the 737NG's have beautiful wingflex, too!
A Safe Flight Begins With Quality Maintenance On The Ground.
 
411A
Posts: 1788
Joined: Mon Nov 12, 2001 10:34 am

RE: Wing Flexation

Thu Oct 01, 2009 12:27 pm



Quoting Starlionblue (Reply 9):
I'm sure Boeing learned a lot from the B-47 and B-52 wings

They may well have, however....early aircraft suffered terribly from wing skin cracking, and many required extensive re-skining, to remain in extended revenue service.
Fuselage crown skin cracking was a very big issue, as well.
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE: Wing Flexation

Thu Oct 01, 2009 4:50 pm

Quoting Starlionblue (Reply 9):
I'm sure Boeing learned a lot from the B-47 and B-52 wings.

At one point, they were planning on using the very same configuration on the 707:

Big version: Width: 800 Height: 600 File size: 276kb


2H4

[Edited 2009-10-01 09:53:31]
Intentionally Left Blank
 
User avatar
ATA L1011
Posts: 1320
Joined: Thu Mar 01, 2001 6:47 am

RE: Wing Flexation

Thu Oct 01, 2009 8:18 pm



Quoting AirframeAS (Reply 10):

They do, but I was just referring to the big guys! For a smaller guy it's definately at the top of that league for flex!
Treat others as you expect to be treated!
 
MD11Engineer
Posts: 13899
Joined: Sun Oct 26, 2003 5:25 am

RE: Wing Flexation

Thu Oct 01, 2009 9:01 pm

A 737 wing is very "springy". If you walk on it towards the tip, you´ll feel it moving beneath you.

The biggest wing flex I have seen on older Tupolev aircraft. On ground the wings have a pronounced anhedral, while once airborne, the wings flex up into a dihedral configuration.

Jan
Je Suis Charlie et je suis Ahmet aussi

Who is online

Users browsing this forum: No registered users and 14 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos