How fast does the skin of the airplane cool to surrounding temperatures?

Mxsmanic wrote:
Danny Dot writes:

You might be better off to taxi out with 20 degree wings that will not have
the snow melt and attach.

The wings couldn't melt snow _and_ freeze it. They could freeze water
droplets, or melt ice particles, but not both.

Have you tried this with your simulator?

We have six airplanes here, and when we take them out of a warm
hangar into falling snow, the snow melts on the airplane, and then the
resultant water freezes as the structure cools off. Makes a mess. Works
better to open the hangar door and let the airplanes cool off first
before moving them outside.
Maybe you should take your computer outside in various weather
conditions and see frost form or snow melt and refreeze. Be sure it's
turned off, like the real airplane.

I bet you've never seen ice fog generated by an airplane
propeller. An aircraft on runup can trugger fog over the whole airport
in a minute or two under the right conditions. Maybe the fan on your
computer could be made to duplicate it?

Dan

Chris W writes:

How well aluminum conducts heat has nothing to do with it.

It has a great deal to do with it, because it determines how much heat
energy must be removed or added in order to reach a given temperature
at a given point. Since aluminum conducts heat well, as soon as the
skin of the plane cools, heat from within will flow into the skin and
further cooling will occur, and just about everything made of aluminum
will become cold very quickly.

If the skin were Styrofoam, it would cool almost instantly at the very
surface, but the remaining mass of foam and whatever was behind it
would stay warm much longer.

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writes:

Have you tried this with your simulator?

No. It depends on well-known principles of physics that I don't have
to simulate.

We have six airplanes here, and when we take them out of a warm
hangar into falling snow, the snow melts on the airplane, and then the
resultant water freezes as the structure cools off. Makes a mess. Works
better to open the hangar door and let the airplanes cool off first
before moving them outside.

That's what I would have suggested.

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Mxsmanic wrote:
Chris W writes:

How well aluminum conducts heat has nothing to do with it.

It has a great deal to do with it, because it determines how much heat
energy must be removed or added in order to reach a given temperature
at a given point. Since aluminum conducts heat well, as soon as the
skin of the plane cools, heat from within will flow into the skin and
further cooling will occur, and just about everything made of aluminum
will become cold very quickly.

If the skin were Styrofoam, it would cool almost instantly at the very
surface, but the remaining mass of foam and whatever was behind it
would stay warm much longer.

Sure. But it's the surface that ice forms upon, not the warmer
interior. A composite skin might cool off faster since it's insulated
from the rest of the structure.

Dan

writes:

Sure. But it's the surface that ice forms upon, not the warmer
interior. A composite skin might cool off faster since it's insulated
from the rest of the structure.

Yes, but this might not be the source of most problems.

Consider an aircraft that has been soaking in the cold for a long
time. If it's built of highly heat-conductive materials, it could
easily freeze any rain falling upon the wings when it is moved
outside. I recall at least one commercial jet that may have been
brought down by this effect, but I don't remember the details.

If the wings contain fuel (which has a high specific heat and thus can
store a lot of heat or cold) and highly conductive wings, it could
freeze water at ambient temperatures well above freezing after being
cold soaked, and develop a substantial layer of ice in no time.

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