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

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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The NASA online icing course addressed part of this question:

http://aircrafticing.grc.nasa.gov/courses.html


Peter R. wrote:
A question for those of you more adept at chemistry/physics than I: How
fast does the aluminum skin of the standard single engine GA aircraft take
to cool to surrounding air temperatures? For example, how long would it
take for the skin to cool from a heated hangar at 65 degrees F to outside
air at 20 degrees F?

This is my first winter where my airplane sits at my destination airport
(Buffalo, NY) all week in a heated hangar. The problem I just inherited
is that if I desire to depart during a lake effect snowfall event, falling
snow could melt on the wings and fuselage and then turn to ice.

--
Peter

M wrote:

The NASA online icing course addressed part of this question:

http://aircrafticing.grc.nasa.gov/courses.html

Thanks for the link.

--
Peter

In article ,
says...
A question for those of you more adept at chemistry/physics than I: How
fast does the aluminum skin of the standard single engine GA aircraft take
to cool to surrounding air temperatures? For example, how long would it
take for the skin to cool from a heated hangar at 65 degrees F to outside
air at 20 degrees F?

This is my first winter where my airplane sits at my destination airport
(Buffalo, NY) all week in a heated hangar. The problem I just inherited
is that if I desire to depart during a lake effect snowfall event, falling
snow could melt on the wings and fuselage and then turn to ice.

Put some fuel in them wings for the night. Take a while to bring all
that lot down to freezing level when you head out.

Indeed the reverse happenned to me a couple years ago, I was down in
Omarama in winter and stayed the night. Had to scrape the ice of the
wings in the morn, but they kept freezing up even though it was a lovely
sunny morning. Had to leave it for a couple of cups of coffee and let
the wing warm a bit (and all the fuel in the wing) before I was happy to
fly.

--
Duncan

Peter R. wrote:
A question for those of you more adept at chemistry/physics than I: How
fast does the aluminum skin of the standard single engine GA aircraft take
to cool to surrounding air temperatures? For example, how long would it
take for the skin to cool from a heated hangar at 65 degrees F to outside
air at 20 degrees F?

This is my first winter where my airplane sits at my destination airport
(Buffalo, NY) all week in a heated hangar. The problem I just inherited
is that if I desire to depart during a lake effect snowfall event, falling
snow could melt on the wings and fuselage and then turn to ice.

Buy ($80) or borrow an infrared remote thermometer and get some data.
NB: The laser only tells where the center of the cone is. It is not
involved in the measurement at all.

"Peter R." wrote in message
...
A question for those of you more adept at chemistry/physics than I: How
fast does the aluminum skin of the standard single engine GA aircraft take
to cool to surrounding air temperatures? For example, how long would it
take for the skin to cool from a heated hangar at 65 degrees F to outside
air at 20 degrees F?

This is my first winter where my airplane sits at my destination airport
(Buffalo, NY) all week in a heated hangar. The problem I just inherited
is that if I desire to depart during a lake effect snowfall event, falling
snow could melt on the wings and fuselage and then turn to ice.

--

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

Danny


Peter

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.

--
Transpose mxsmanic and gmail to reach me by e-mail.

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

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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The snow would most likely melt over the fuel tanks (if it's a wet
skinned tank) then flow aft and freeze again. I don't remember ever
having the problem, but the only time our Mooney saw the inside of a
heated hanger was when it needed to have snow and ice melted from it.
At least once I climbed aboard after it was hanger heat soaked then
took off in fairly light snow (vis at least a half mile.) I wasn't
smart enough to worry about snow melting and refreezing -- my concern
was braking, or lack of it! It couldn't have been too bad though, the
airplane didn't move during run up.

I think even with warm fuel tanks, the convective cooling would pretty
quickly get the wing surfaces cool enough to keep the white stuff
solid.





On Dec 10, 5:28 pm, "Danny Dot" wrote:
"Peter R." wrote in ...

A question for those of you more adept at chemistry/physics than I: How
fast does the aluminum skin of the standard single engine GA aircraft take
to cool to surrounding air temperatures? For example, how long would it
take for the skin to cool from a heated hangar at 65 degrees F to outside
air at 20 degrees F?

This is my first winter where my airplane sits at my destination airport
(Buffalo, NY) all week in a heated hangar. The problem I just inherited
is that if I desire to depart during a lake effect snowfall event, falling
snow could melt on the wings and fuselage and then turn to ice.

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

Danny



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