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Physics of frost


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This morning I had an extended experience with frost on my plane. My plane is hangared in a mostly enclosed T hangar. I got up to the airport at 6:30 this morning. The thermostat next to the plane said it was 27. There was no frost on the plane. I thought great we will be able to go fly. I pulled it out from under the covering and almost instantly I could see frost creeping along the wings. By the time I finished the preflight the plane was pretty well frosted over. I have only had to deal with frost on my plane once but it was warm enough by the time I got to the plane I was able to wipe the frost right off. But I knew I wasn’t flying this morning till this frost was gone. I didn’t have any deicer and first I sprayed just a little of the wash all stuff to see if it would take it off. Lol, it froze so fast....

 

After the sun finally coming out and using the space heater on all the leading edges and tops of the wings and tail feathers the plane was frost free and had a great flight to bend and back.

 

My question/s is what would of caused the frost to form on the plane even though it was below freezing in the hanger?

 

It would seem even if it was in a heated hangar it would have done the same? Or would the plane been warm enough it would have kept from frosting over?

 

Or was the plane below freezing and when I pulled it out, it was surrounded by air that was above freezing and had moisture in it that stuck to the plane?

 

Is it like the super freezing liquid scenario?

 

And what would be the best way to avoid this? I was thinking of putting some wool packing blankets over the wings while in the hanger, or could I rub a little deicer over the plane before I pulled it out of the hanger?

 

Or am I stuck with this situation?

 

 

 

 

 

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Just now, Hank said:

I never had that problem living along the Ohio River, but I always preflighted in the hangar; pull the plane out, get in and crank up.

Good luck with winter! I don't have those anymore . . . 

Never say never, forecast has a "wintery mix" headed to the south east

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This morning I had an extended experience with frost on my plane. My plane is hangared in a mostly enclosed T hangar. I got up to the airport at 6:30 this morning. The thermostat next to the plane said it was 27. There was no frost on the plane. I thought great we will be able to go fly. I pulled it out from under the covering and almost instantly I could see frost creeping along the wings. By the time I finished the preflight the plane was pretty well frosted over. I have only had to deal with frost on my plane once but it was warm enough by the time I got to the plane I was able to wipe the frost right off. But I knew I wasn’t flying this morning till this frost was gone. I didn’t have any deicer and first I sprayed just a little of the wash all stuff to see if it would take it off. Lol, it froze so fast....
 
After the sun finally coming out and using the space heater on all the leading edges and tops of the wings and tail feathers the plane was frost free and had a great flight to bend and back.
 
My question/s is what would of caused the frost to form on the plane even though it was below freezing in the hanger?
 
It would seem even if it was in a heated hangar it would have done the same? Or would the plane been warm enough it would have kept from frosting over?
 
Or was the plane below freezing and when I pulled it out, it was surrounded by air that was above freezing and had moisture in it that stuck to the plane?
 
Is it like the super freezing liquid scenario?
 
And what would be the best way to avoid this? I was thinking of putting some wool packing blankets over the wings while in the hanger, or could I rub a little deicer over the plane before I pulled it out of the hanger?
 
Or am I stuck with this situation?
 
 
 
 
 
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The sub freezing metal of the wings allows humid warmer air to reach the frost point and create frost on the wing surface. It will be hit or miss depending on the humidity in the air.

I would normally carry a small spray bottle (pump up kind) of a mixture of 50:50 isopropyl alcohol and water. When you buy it in the store, it is usually 91% with the rest water. I just dilute it down further.


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And if you had the plane in a heated hangar, it wouldn’t frost as long as the skin temp stayed above the frost point temp (and the humidity was right). In other words, as long as you get your butt moving fairly soon after pulling it out of the heated hangar, it won’t frost up in those conditions.


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The sub freezing metal of the wings allows humid warmer air to reach the frost point and create frost on the wing surface. It will be hit or miss depending on the humidity in the air.

I would normally carry a small spray bottle (pump up kind) of a mixture of 50:50 isopropyl alcohol and water. When you buy it in the store, it is usually 91% with the rest water. I just dilute it down further.


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Does it mess with paint?


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No hanger door?  Concrete or gravel floor?  I would think temp and humidity would be similar if the hanger is open to the elements. Unless the hanger floor was releasing some moisture during the seasonal change. Was the wing dry before you rolled it out?

Sorry, posted a pic of the hangar but didn’t tag it to your comment. The wing was dry while in the hangar. At least what I could tell.


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Quirky situation...

1) The plane was colder than freezing...

2) The air was carrying moisture...

3) The moisture condenses and freezes...

4) It can't do this very long, the plane warms up to match the temp of the air and moisture...

5) If the air is above freezing, spraying additional warmed water on it can remove it...  use caution, any extra moisture is sure to freeze with altitude.

6) A ziplock filled with warm water can be used as a heater for localized heating.  Like frozen fuel caps.  Put the warm bag right on the spot...

7) The flight school used a common solution of RV anti-freeze the colored stuff they put in the water tanks in winter...  used a Weed sprayer for distribution....

8) realistically, this only happens during the odd temperature inversion... colder in the hangar, warmer outside...

9) It may make sense to leave the plane outside on days like these...

10) Putting the plane out in the sun was my usual tactic... I didn't have any engine heat to go with those challenges... Frost was a constant challenge...

PP ideas only, not a CFI or weatherman....

Best regards,

-a-

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8 hours ago, carusoam said:

8) realistically, this only happens during the odd temperature inversion... colder in the hangar, warmer outside...

9) It may make sense to leave the plane outside on days like these...

The hanger looks almost completely open from the picture above.  Since he was trying to leave before the sun came up I would think it would be in equilibrium?

I was told in the past (OWT?) that RV antifreeze is corrosive to metal strainers so I wipe them down after getting the cottage ready for winter.  It would be a lot less expensive than tks fluid. 

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To those using isopropyl alcohol in a spray bottle, are you using it straight or diluting?  If the latter, what ratio are you mixing to?

Now that Signature has taken over my FBO, the days of a quick defrost in the heated communal hangar are gone.  >$100 for 20 minutes seems a little rich...  Need to find a safe, effective alternative.

 

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13 hours ago, xcrmckenna said:

 

This morning I had an extended experience with frost on my plane. My plane is hangared in a mostly enclosed T hangar. I got up to the airport at 6:30 this morning. The thermostat next to the plane said it was 27. There was no frost on the plane. I thought great we will be able to go fly. I pulled it out from under the covering and almost instantly I could see frost creeping along the wings. By the time I finished the preflight the plane was pretty well frosted over. I have only had to deal with frost on my plane once but it was warm enough by the time I got to the plane I was able to wipe the frost right off. But I knew I wasn’t flying this morning till this frost was gone. I didn’t have any deicer and first I sprayed just a little of the wash all stuff to see if it would take it off. Lol, it froze so fast...

 

My guess--the fact you could see the frost develop that quickly suggests some kind of supercooled situation.  I'm in OR too, and it was well below freezing overnight, and it was very clear last night.  I could see significant radiation fog in the valley.  That means the ground was cold enough to create an inversion layer, and that will trap humidity in the thin layer near the ground to near saturation.  You probably had a thin layer of condensation on the plane that suddenly froze once you disturbed it by moving the plane.

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My guess--the fact you could see the frost develop that quickly suggests some kind of supercooled situation.  I'm in OR too, and it was well below freezing overnight, and it was very clear last night.  I could see significant radiation fog in the valley.  That means the ground was cold enough to create an inversion layer, and that will trap humidity in the thin layer near the ground to near saturation.  You probably had a thin layer of condensation on the plane that suddenly froze once you disturbed it by moving the plane.

What would you suggest I could do to the plane before I pull it out of the hangar? Have the wings covered through the night or just rub tks on it?


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Not sure how you could cover the wings, but that might help reduce condensation settling on the wing surfaces overnight.  Otherwise, an enclosed hangar will reduce the exposure to the humidity, but there's not much else you can do.  At least if it's sunny it won't take too long to melt if you let it sit out.

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14 hours ago, kpaul said:

Never say never, forecast has a "wintery mix" headed to the south east

Tuesday, we were in the mid-70s; yesterday, temps fell all day and night; today is hovering below 40°F all day. Forecasting rain / snow mix tomorrow morning, with no accumulation.

Fortunately I just bought milk and bread Tuesday evening, and the wife buys gigantic packages of TP. We're set to stay home and watch the mess!

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the overnight temps were probably not much lower than the morning temp of 27°F, in the shade... this drives RH towards 100%...

'equilibrium' and overnight temperature swings, don't want to coexist. The plane will always lag, as its heat capacity is higher than air...

Important idea... Getting the wing temps up to (or warmer than) the air temp, keeps the moisture from falling out of solution and depositing...

Choices we have...

1) keep moisture off the wings... that’s a tough one.  I see plastic film used on car windshields to do this...

2) warm the wings so the moisture doesn't deposit on them.  Sunshine and space heaters... (enclosed hangar works this way)

3) warm the wings so the moisture doesn't freeze on them.  Lots of sunshine and OAT above freezing....

4) Put something on the wings that keeps moisture from freezing.  (TKS or alcohol as mentioned above)

5) Check the label carefully for anything being sprayed on the paint.  The RV anti-freeze is typically alcohol, water and pigment. All of an edible variety... the pigment is helpful for seeing where it has landed.  Could cause staining...

6) Getting to equilibrium.... taxi the plane around, do the run-up and watch the OATs...

7) Look into the latest theory of polishing the frost to minimize its effect.  (I'm not a fan, but it is better than the alternative of ignoring it)

8) I have been stuck outside for an hour waiting for the angle of the sun to increase to warm things up....

A summary of things I have read around here...

Best regards,

-a-

 

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It was more likely that moving the plane out from cover allowed it to be exposed to radiant cooling from black body radiation to the sky at that time of the morning. At 6:30 am the sun was likely not up yet, but just getting light to the east. The planes skin then cooled just enough to allow the condensation and frost formation.    In any case, you were close enough to the freezing point that a mix of isopropyl alcohol (freezing point  -128.2°F)  would work well.  As soon as the sun comes up it will melt a thin layer of frost off very quickly.

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