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KC-135 Iced Wings

Sun May 09, 2004 8:03 pm

What do you think of this:

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Photo © Thomas Urbild

I know ice-related questions are brought up here often but I have never seen such massive icing under a wing of a plane...
Isn't there normally a heating system that prevents ice from building up? Or is this how it used to be on older planes? ? After all this KC-135 is about 44 years old... Would there also be a layer of ice on top of the wing surface
What about the aerodynamics, are they not influenced a lot but a thick layer of ice on the wings?
Thanks for any explanation you might have.

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RE: KC-135 Iced Wings

Sun May 09, 2004 8:23 pm

That appears to be massive icing, but is probably just a real thin layer of frost. Very common on aircraft that have just landed. You can tell that it is a very thin layer because you can clearly see the outline and impressions of the tanl access plates and other fasteners on the wing lower surface.

As to the aerodynamics: I believe that the there is an almost negligible affect on performance. If I remember my basic aerodymanics, frost on the upper surface causes a whole lot more problems than on the lower surface.
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RE: KC-135 Iced Wings

Sun May 09, 2004 9:52 pm

Thats normal.

Moisture in the air freezing to the supercooled fuel in the wing from altitude.

At one place I worked we where allowed 1/4 inch of buildup, at another airline the ops-specs allowed 3/8ths of an inch.
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RE: KC-135 Iced Wings

Sun May 09, 2004 10:24 pm

When an airplane flies for a few hours at altitude and you dump warmer fuel and the air is humid you get frost forming under the wings....That is normal....And as far as I know there really is no way to get rid of does not affect the wing when it is under like that.

the same thing can happen when you have a warm airplane (like in a hanger) and you take it out on a cold winter day and pour cold fuel into the tanks


Oh can happen to ANY airplane.....there is nothing that prevents it.....they do not even de-ice under the wing when they have to go for de-iceing

[Edited 2004-05-09 15:26:04]
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RE: KC-135 Iced Wings

Mon May 10, 2004 12:29 am

Ok, thanks for the replies. That was interesting. Never seen it before. You're right though, it's probably a rather thin layer.

 Smile/happy/getting dizzy PA
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RE: KC-135 Iced Wings

Mon May 10, 2004 10:37 am

If the ice isn't that thick and if it's fairly uniform, aerodynamics isn't a huge concern. As soon as it becomes quite thick or very irregular in its distribution, there can be problems in those terms...

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RE: KC-135 Iced Wings

Mon May 10, 2004 11:06 am

I remember touching the wing of a business jet that had just landed after a flight at high altitude. The wing was cold to the touch, and it was a rather warm day.
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RE: KC-135 Iced Wings

Mon May 10, 2004 4:49 pm

I see this everyday I work on the ramp. It isn't very thick and if I could reach the wings, I could wipe it off. It also melts quite quickly, at least here in Hawaii. I always get dripped on when I walk under the wings.
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RE: KC-135 Iced Wings

Mon May 10, 2004 9:11 pm

Just thought I’d confirm that ice on the underside of the wing isn’t a major concern. That’s not where the lift is generated and that’s not where you’ll get separated flow (stall). That’s also why you’ll have flap hinges and all that junk hanging below the wing rather than protruding out of the top surface.

The really bad ice is the kind that forms on the leading edges. If the LE de-ice/anti-ice is out of order, the buildup can take shocking proportions. The ice models used for certification flights are scary things. It is hard to imagine the aircraft flying with those mounted on the wings... but they do, which makes me feel better up there.  Smile

Then, you can have run back ice, when ice melts on the leading edge and flows back over the wing to freeze again on the top surface. Not good at all.

I thought I was doing good trying to avoid those airport hotels... and look at me now.
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RE: KC-135 Iced Wings

Wed May 19, 2004 10:21 am

About warm days and icing:

A couple of years ago a glider pilot was flying on Gotland (an island in the Baltic) in the middle of summer. In fact it turned out to be the hottest day of the year, so over 30 celsius. He had a close encounter with a thunderstorm and ended up way higher than he had intended.

On this hottest day, he had to be treated for frostbite. It can get that cold up there.

If you dig, there is an interesting article on Boeing's website about the calculations needed to fly over the Arctic. Quite a bit of fuel shuffling to keep the fuel (and thus the wings) "warm".
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