sleekjet
Posts: 2006
Joined: Sat Jul 28, 2001 1:35 am

Answer This Man's Question:

Wed Jun 09, 2004 10:32 am

Freshly appearing in the latest photos is this:


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Photo © Roel Kroes



Can someone answer the question he has posed in the caption?
II Cor. 4:17-18
 
airplay
Posts: 3369
Joined: Sat Oct 25, 2003 1:58 am

RE: Answer This Man's Question:

Wed Jun 09, 2004 10:49 am

Its hard to tell if those particular wrinkles are permanent or not, but many airframes (especially old battered ones like the subject 747) often have permanent ripples and wrinkles in the skins.
 
cdfmxtech
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: Answer This Man's Question:

Wed Jun 09, 2004 2:49 pm

The Wrinkles and Buckles have an unofficial name...I think it is "Oil Canning". They are permanent (Section 46 is especially susceptable to this condition), though more noticeable at times than others. They are normal as defined by Aircraft Structural Repait manuals as long as they do not contain cracks and go through fasteners. Couple of other things as well, but can't recall.

[Edited 2004-06-09 07:51:07]
 
Toni_
Posts: 261
Joined: Sat Apr 06, 2002 8:56 am

RE: Answer This Man's Question:

Wed Jun 09, 2004 8:01 pm

"Will these be permanent or just because of the pressure of the landing?"

These wrinkles are normal and not permanent. What you see is the rear end of the fuselage bending a bit downwards caused by the weight of the tail during that heavy landing. It shows how flexible these planes are. Same happens when a plane is on a tailjack during maintenance. These same wrinkles will appear on top of the plane.

Greetz Toni  Smile
 
BritPilot777
Posts: 998
Joined: Thu Apr 08, 2004 10:05 am

RE: Answer This Man's Question:

Wed Jun 09, 2004 8:05 pm

Just looks like heat haze to me from the engines
Forever Flight
 
FredT
Posts: 2166
Joined: Thu Feb 07, 2002 9:51 pm

RE: Answer This Man's Question:

Wed Jun 09, 2004 8:19 pm

Those diagonal wrinkles is the way the skin of a stressed skin aircraft takes up the stress. They will always be present when there is a load on the structure, to a larger or smaller degree. Structural engineers spend a lot of time analysing them. As time and cycles build up, they often become more apparent.

Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
A/c train
Posts: 674
Joined: Sun Jun 10, 2001 7:57 am

RE: Answer This Man's Question:

Thu Jun 10, 2004 12:49 am

Tonis explanation sounds good, were I work I always noted when I was on the fwd jack that the skin would wrinkle around the jacking point and then go away on lowering, therefore they are not permanent, there are .040" skin pockets in that area so it doesnt surprise me.
regards a/c
 
diezel
Posts: 622
Joined: Mon Oct 14, 2002 6:50 pm

RE: Answer This Man's Question:

Thu Jun 10, 2004 8:16 am

I took the picture, thanks for reacting !

I also got an email from somebody who says that the wrinkles are permanent but will disappear when the aircraft is pressurized.

Roel.
Never be afraid of what you like. (Miles Davis)
 
aloges
Posts: 14842
Joined: Tue Jan 17, 2006 3:38 am

RE: Answer This Man's Question:

Thu Jun 10, 2004 5:24 pm

Here's another fine example of wrinkles, also on a KLM 747:

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Photo © Stephan Curkowskyj

Don't cry because it's over, smile because it happened.
 
MD-90
Posts: 7835
Joined: Mon Jan 17, 2000 12:45 pm

RE: Answer This Man's Question:

Thu Jun 10, 2004 6:10 pm

Look at the wing of every strut-braced Cessna ever built and they will all exhibit oil canning. It tends to be less visible on airliners because they have thicker gauge skins.
 
liamksa
Posts: 301
Joined: Mon Oct 29, 2001 1:13 pm

RE: Answer This Man's Question:

Thu Jun 10, 2004 8:06 pm

It's fascinating to watch the ripples in a low-wing aircraft when pulling a few G's. Kind of startling / amazing how much the wings flex and how much slack you can get on the top surface wing-skin!  Wow!

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