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

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

Except for integral fuel tanks, where warm fuel is in
contact with the skin, the aluminum skin will be below
freezing in a matter of less than a minute. The warm hanger
will have the airplane ice free and all the weep holes
should drain, but if there is snow falling, spray it with
glycol with a rich enough mixture to keep the surface ice
free for the expected take-off delay.

Even better, don't take-off in the blizzard, wait for the
snow to stop and the taxi and runways to be plowed.



"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.
|
| --
| Peter

Jim Macklin wrote:

Thanks, Jim.

Even better, don't take-off in the blizzard, wait for the
snow to stop and the taxi and runways to be plowed.

Only when accompanied by winds of about 25mph or stronger would I consider
lake effect snowfall a blizzard-like condition. There are many of these
events where the winds are not so strong as to blow snow across the runways
and taxiways at a rate where the plows at these two commercial airports (my
home and my destination airports) cannot keep up.

--
Peter

On Fri, 8 Dec 2006 10:18:23 -0500, "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.

The wings and tail will very quickly go to ambient air temperature, I
would guess in 1-2 minutes.

I keep my plane in a 55deg heated hangar, and have pulled it outside,
and departed during a few light snows. I have not yet had a problem
with the 'warm' wings melting the snow and causing ice droplets.

Unless the flakes are very wet/heavy, I doubt you really need to worry
about this scenario. Of course, if the flakes are wet/heavy, then
perhaps it is not a good day for flying anyway...

Peter R. writes:

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?

Nor more than a couple of minutes. Aluminum is an excellent conductor
of heat.

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.

If the wings are cold enough to freeze water, falling snow won't melt
on them.

I suppose that if snow fell on the wing while it was still above
freezing, it might freeze into ice as the wing cooled, but since the
wing will cool so quickly and since ice is hard to melt, I don't know
that this would be much of a problem.

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

Mxsmanic wrote:
Peter R. writes:

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?

On a clear night the skin temperature can go BELOW the air
temperature due to the radiation losses into space. We regularly see
that here, and it's what causes frost to form so quickly.

Dan

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

Just remember the snow on the wing does not blow off during
take-off. Moderate snow is snow with the visibility reduced
to not less than 1/2 mile, which is low IFR.



"Peter R." wrote in message
...
| Jim Macklin wrote:
|
| Thanks, Jim.
|
| Even better, don't take-off in the blizzard, wait for
the
| snow to stop and the taxi and runways to be plowed.
|
| Only when accompanied by winds of about 25mph or stronger
would I consider
| lake effect snowfall a blizzard-like condition. There are
many of these
| events where the winds are not so strong as to blow snow
across the runways
| and taxiways at a rate where the plows at these two
commercial airports (my
| home and my destination airports) cannot keep up.
|
| --
| Peter

writes:

On a clear night the skin temperature can go BELOW the air
temperature due to the radiation losses into space.

The temperature of the aircraft won't drop below the temperature of
the ambient air, as long as the aircraft is dry.

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

Dan, it's not an important point, but from the physics/theromdynamics
side of the issue, the top surface of the wing is really at risk of
radiational cooling. The wing's leading edge's shape would allow
convective warming, as the warmer air in contact with the surface would
cool and flow downward.