Demoose
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Cracks On Wings

Sat Oct 13, 2007 1:01 pm

Are cracks on wings common amonst aircraft?

I ask as yesterday i was onboard a 757-300 and half way through the flight noticed a pretty big crack on one part of the wing. At first I thought it was a dirty water mark, but looking closer i noticed they'd patched up some other areas near to it.

So what causes cracks such as this and does it affect the performance of the wing? I'm guessing its not a critical part of the wing hence it can fly fine with it?

http://i14.photobucket.com/albums/a317/ManchesterMark/753wing120CT07.jpg

Any input would be greatly appreciated

Thanks
Mark
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Starlionblue
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RE: Cracks On Wings

Sat Oct 13, 2007 1:04 pm

You mean the lines on the flap track fairing? Look more like scratches to me. I don't know if they would affect performance much.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
474218
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RE: Cracks On Wings

Sat Oct 13, 2007 2:16 pm

Cracks on the wings are fairly common. However, these cracks are so small special technique's such as X-Ray, Eddy Current and Ultra Sonic procedures are used to find them. If a crack is big enough for the untrained eye to see the aircraft should have been already repaired.
 
Accidentally
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RE: Cracks On Wings

Sat Oct 13, 2007 2:54 pm

Looks like grime to me...I bet you could go wipe that hydraulic fluid or whatever right off.
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jetmech
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RE: Cracks On Wings

Sat Oct 13, 2007 3:29 pm

Quoting Demoose (Thread starter):

If the "cracks" are what I think your talking about, I'd say that your photo is showing dirt streaks on the side of the canoe fairing that covers the flap track. The patched up area (light grey) is most probably the scuff resistant paint that is used due to the smaller section of flap rubbing up against the side of the canoe fairing.

Regards, JetMech
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Tristarsteve
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RE: Cracks On Wings

Sat Oct 13, 2007 4:13 pm

The flap track fairing is completely non-structural, in fact the aircraft can fly with it removed.
It is made of very thin fibregalss, and the paint quite often cracks as the fibreglass flexes.
No worries.
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tdscanuck
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RE: Cracks On Wings

Sat Oct 13, 2007 5:59 pm

Quoting Demoose (Thread starter):
Are cracks on wings common amonst aircraft?

Cracks of the primary wing structure (skin and spars) are uncommon. The flap fairing you're showing isn't really structural at all, just aerodynamic. Cracks there certainly happen, although you don't really want them. In this particular case, it's very difficult to tell if that's just a crack in the paint (zero impact), a crack in the resin (annoying but not a particularly huge deal), or a through crack (very unlikely for a composite part).

Quoting Demoose (Thread starter):
So what causes cracks such as this and does it affect the performance of the wing? I'm guessing its not a critical part of the wing hence it can fly fine with it?

Fatigue is the usual source of cracking. The flap fairings get a lot of vibration during takeoff and landing. The crack you are showing doesn't have any impact on the wing performance. You can't fly without it without getting permission from your regulator first (there are other parts that are pre-authorized to fly without).

Tom.
 
EMBQA
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RE: Cracks On Wings

Sat Oct 13, 2007 6:03 pm

Quoting Demoose (Thread starter):
At first I thought it was a dirty water mark, but looking closer i noticed they'd patched up some other areas near to it.

What you see in your photo is just dirt streaking. The 'patched up' area is just teflon paint used in the area that the flap moves. Teflon paint is used to protect the area from the rubbing of the flap seal runs. You will also see this on aircraft with movable horizontal stabs. Teflon paint is used there to protect the fuselage from the stabs seal.

[Edited 2007-10-13 11:10:32]
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Demoose
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RE: Cracks On Wings

Sat Oct 13, 2007 6:34 pm

it wasn't just dirt, i looked closely at it during the flight as i first thought it was just fluid marks, but noticed when we turned and the sunglight caugh it you could see it was a crack in the surface, it wasn't just a dirt mark.

Thanks for the replies guys, interesting to find it all out.
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Aaron747
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RE: Cracks On Wings

Sat Oct 13, 2007 6:59 pm

Don't look at dirt so closely anymore. Next time you'll be staring at a dirt or skydrol streak on an aileron for hours wondering when the thing is going to break off  Wink
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fr8mech
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RE: Cracks On Wings

Sat Oct 13, 2007 7:05 pm

Quoting Demoose (Reply 8):
it wasn't just dirt, i looked closely at it during the flight as i first thought it was just fluid marks, but noticed when we turned and the sunglight caugh it you could see it was a crack in the surface, it wasn't just a dirt mark

You looked at it from at least 10 feet away, through a thick pane of glass and a thin piece of plastic.

I can say, looking at the picture and relying on 20 years in maintenance, that the chances that the fairing is cracked are just about zero.

As many have said, it appears to be dirt/grime/grease.
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474218
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RE: Cracks On Wings

Sat Oct 13, 2007 10:06 pm

Quoting Fr8mech (Reply 10):
You looked at it from at least 10 feet away, through a thick pane of glass and a thin piece of plastic.

No glass in passenger windows, just plastic.
 
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Starlionblue
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RE: Cracks On Wings

Sun Oct 14, 2007 4:10 am

Quoting Aaron747 (Reply 9):
Next time you'll be staring at a dirt or skydrol streak on an aileron for hours wondering when the thing is going to break off

I thought the dirt and Skydrol were the only things that kept AF planes in one piece.  Wink
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
tdscanuck
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RE: Cracks On Wings

Sun Oct 14, 2007 5:49 am

Quoting Starlionblue (Reply 12):

I thought the dirt and Skydrol were the only things that kept AF planes in one piece.

Speed tape.

Tom.
 
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HAWK21M
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RE: Cracks On Wings

Sun Oct 14, 2007 10:41 am

Looks like dirt on the Flap track fairing.
regds
MEL
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boeing767mech
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RE: Cracks On Wings

Mon Oct 15, 2007 7:38 pm

That flap track in the pictures looks like the fairing that shares MLG trunion fairing. The fluid looks like everyones favorite skydrol, Or maybe deicing fluid.

David
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