Wing Bending

Sat Apr 10, 1999 6:55 am

I noticed when an A340, 744, or a MD-11 takes off or lands, the wings and winglets bends. It does not bend greatly, but it does bend. furthermore, the wingtips and winglets bends downwards slightly.

Why does this happening?
Posts: 389
Joined: Sat Aug 27, 2005 8:23 am

RE: Wing Bending

Sat Apr 10, 1999 7:42 am

This is the lift acting on the wings. We all know how a plane flies more or less.
High pressure under the wing and low pressure above. On the top of the wing the net pullng force will pull the wing up. Because the plane is heavy the wings tend to start flying before the plane fuselage. This is why you'll get the upwards bending of the wing. This bending of the wing is natural in all wing and is only more noticable on larger planes.
Wing bending is an essential part of it's total strength. You should look at a 777 taking off at maximum takeoff. It's even more noticable then on a 747.
On wing strength tests the 777 wing tip rose more then 24 feet from where it is supposed to be before finally breaking the wing.......

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Joined: Tue May 18, 1999 11:10 am

RE: Wing Bending

Sat Apr 10, 1999 7:43 am

Well, if you are thinking of what I am, that bending is related to the production of lift. While on the ground, wings droop because of their weight. When the aircraft takes off, the wings produce lift and are then bent upwards. Then when the aircraft lands, the wings stop making lift and they bend down again, but not as much, because of their lighter weight (less fuel).

If you don't understand, take a 2x4, put a weight in the middle, and lift up on both ends. The 2x4 (wing) now has lift (made by you), and because of the weight of the fuselage (weight in middle), the ends bend up.
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RE: Wing Bending

Sat Apr 10, 1999 9:24 am

Aren't the wings lighter? I'm no aircraft expert but I did read an article about Boeing using a lighter alloy metal when they were first building the 747-400 to reduce drag.

The latter aircraft 777rules mentioned are newer aircraft, so I suspect that this does not occur on older aircraft.
Posts: 389
Joined: Sat Aug 27, 2005 8:23 am

RE: Wing Bending

Sat Apr 10, 1999 10:06 am

All jetliner and even commuters have to bend to make the wing stronger.
A flexible wing is much better at heavy weights and in any kind of turbulence.
If the whole wing is made of a lighter material it wont make any difference.
It will bend when airborne and also when laden with fuel. You should look at a C-5 full of fuel and how the wing start flying in TO. If they were stiff, the wing spars will break very easily. This is how they're made.


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