frost on the wing

[Jose]

The other day I went flying, pretty close to the shortest day of the year, to preserve night currency. I took advantage of a day that wasn't brutally cold - in fact it was above freezing, so I didn't need preheat or thermal underwear. It was good to get in the air after several months of not flying hardly at all (we had the longest, most beautiful fall but I was stuck indoors doing two shows at the same time). I had to taxi over a bit of an ice berm in front of the wheels, but it wasn't a problem, and the pavement was wet from the melting ice (we had several inches of ice storm a week or so ago which is still around).

By the time I got in the air, I was happy and all was well with the world. After doing some night full stop landings, I followed I-84 up to Beacon and back just to "go somewhere" and then came home. By now temperatures were just below freezing, but it was clear and so I didn't give it much consideration.

Landed without incident, braking was good (and was also reported good by aircraft before me), and I taxiied to the ramp, a relatively unfamiliar part of the airport since we moved the airplanes. The airplane seemed to be sliding a bit, as if there was ice on the pavement. Well, of course there was; the wet pavement had frozen in the interim. I was afraid of that, and this meant that putting the plane away would not be as easy as taking it out. After a struggle I did manage to get it pushed back over the ice berms (pulling up on the wing while pushing back helped, as did pulling with the tiedown ropes when I got close enough). But when I was pretty much done, I noticed there was frost on the wings, which hadn't been there before.

Which got me thinking - maybe the FAA isn't so crazy after all. If frost can form while the plane is just sitting there, why could it not form while the plane is flying? (yeah, there's some frictional heating, but we could lower the temp a bit more, no?) And if frost isn't such a good thing to have on takeoff, it's probably not so good in flight either.

Any thoughts? Have you seen this before?

Jose
--
You can choose whom to befriend, but you cannot choose whom to love.
for Email, make the obvious change in the address.

[Bob Noel]

In article >,
Jose > wrote:

> Which got me thinking - maybe the FAA isn't so crazy after all. If frost can
> form while the plane is just sitting there, why could it not form while the
> plane is flying? (yeah, there's some frictional heating, but we could lower
> the temp a bit more, no?) And if frost isn't such a good thing to have on
> takeoff, it's probably not so good in flight either.
>
> Any thoughts? Have you seen this before?

This in-flight frost is called ice. I've never experienced icing conditions
but alway thought it was the leading edges that collect ice.

--
Bob Noel
(goodness, please trim replies!!!)

[Jose]

> This in-flight frost is called ice. I've never experienced icing conditions
> but alway thought it was the leading edges that collect ice.

Well, duh... but I'm referring to "ice" accumulation when not flying through "visible" moisture. No rain, no cloud, just clear 10 mile visibility air. And the frost was not on the leading edges (since it was not due to impact with droplets) but rather, on the flat parts of the wing which have cooled radiatively. This is different enough from regular inflight airframe ice that I thought it warranted a new word, at least for now.

Jose
--
You can choose whom to befriend, but you cannot choose whom to love.
for Email, make the obvious change in the address.

[Bertie the Bunyip[_19_]]

Bob Noel > wrote in
:

> In article >,
> Jose > wrote:
>
>> Which got me thinking - maybe the FAA isn't so crazy after all. If
>> frost can form while the plane is just sitting there, why could it
>> not form while the plane is flying? (yeah, there's some frictional
>> heating, but we could lower the temp a bit more, no?) And if frost
>> isn't such a good thing to have on takeoff, it's probably not so good
>> in flight either.
>>
>> Any thoughts? Have you seen this before?
>
> This in-flight frost is called ice. I've never experienced icing
> conditions but alway thought it was the leading edges that collect
> ice.
>

Can form on other parts of the wing depending on the airfoil and your speed
/angle of attack as well as the temp and the droplet/crystal size. The
inertial seperation of the moisture from the air can deposit it in strange
places. Not an issue in most lightplanes where it's going to form mostly on
the leading edge. But if you get the airplane slow you might get some on
the bottom of the wing and some airplanes, like the ATR 42, get it on the
top at higher AoAs, which is a bad thing.
Jets don't usually get ice on the wing in flight at all. They can , but
usually only on approach when they're dirty. It does happen, though.
Nothing to do with friction heating, by the way, but again, the behaviour
of the droplets as the surrounding air meets the leading edge is the factor
that dictates this.


Bertie

[Bertie the Bunyip[_19_]]

Jose > wrote in news:R6Rbj.59158$eY.11166
@newssvr13.news.prodigy.net:

>
>

You can get frost on the wing if the wing is colder than the air around and
the air is nice and moist, but it's pretty unlikely unless you're getting
into some very low temps and then some fairly damp air. IOW you've been at
altitude.



Bertie

[F. Baum]

On Dec 24, 9:28*am, Jose > wrote:
> Which got me thinking - maybe the FAA isn't so crazy after all. *If frost can form while the plane is *just sitting there, why could it not form while the plane is flying? *(yeah, there's some frictional heating, but we could lower the temp a bit more, no?) *And if frost isn't such a good thing to have on takeoff, it's probably not so good in flight either.
>
> Any thoughts? *Have you seen this before?
>
> Jose
>

What happens is that the wing and fuel get super cooled in flight at
extremely low temps. If the wings and fuel are cold soaked enough any
moisture contacting the wing may form frozen contamination. This
forms on the upper surfaces after landing especially if you have alot
of fuel remaining. Certain times of the year you will see this alot on
the bottom surfaces of the wing where the fuel tanks are.
F Baum

[Jose]

> If the wings and fuel are cold soaked enough any
> moisture contacting the wing may form frozen contamination. This
> forms on the upper surfaces after landing especially if you have alot
> of fuel remaining.

What would prevent this from happening in flight? (n.b. in my case the ambient flight temps were just below freezing - radiative cooling may have lowered the wing temp =some= more, but a =lot= more?)

Jose
--
You can choose whom to befriend, but you cannot choose whom to love.
for Email, make the obvious change in the address.

[quietguy]

On Dec 24, 11:32*am, Jose > wrote:
> What would prevent this from happening in flight?

Sublimation. The airflow around the wing evaporates deposited ice
crystals fast enough to keep visible frost from forming unless the
relative humidity is near 100% (i.e., when there's visible moisture).
Then, depending mainly on the droplet size, you'll get either rime
(frost by another name) or clear icing. Takes a hell of a wind to
cause rapid-enough sublimation, though: I've seen parked airplanes get
frosty even when gusts were in the forties.

[Bertie the Bunyip[_19_]]

Jose > wrote in
:

>> If the wings and fuel are cold soaked enough any
>> moisture contacting the wing may form frozen contamination. This
>> forms on the upper surfaces after landing especially if you have alot
>> of fuel remaining.
>
> What would prevent this from happening in flight? (n.b. in my case
> the ambient flight temps were just below freezing - radiative cooling
> may have lowered the wing temp =some= more, but a =lot= more?)
>

Well, nothng if it's wet enough outside, but it's unlikely you're going to
get a low altitude airplane and it's fuel cold enough to do it in flight.
It happens often on airliners if they've been at altitude for extended
periods and they get th efuel down to low temps and then descend into
moisture.


Bertie

[Neil Gould]

Recently, Jose > posted:

> [...] But when I was pretty much done, I
> noticed there was frost on the wings, which hadn't been there before.
>
> Which got me thinking - maybe the FAA isn't so crazy after all. If
> frost can form while the plane is just sitting there, why could it
> not form while the plane is flying? (yeah, there's some frictional
> heating, but we could lower the temp a bit more, no?) And if frost
> isn't such a good thing to have on takeoff, it's probably not so good
> in flight either.
>
> Any thoughts? Have you seen this before?
>
During my student pilot days, I took off solo in a Tomahawk that had a
good coating of frost on the wings. Its performance was sluggish, but not
long after I wrestled it into the air the frost dissipated. I learned a
lot that day!

Neil

[M[_1_]]

On Dec 24, 8:28 am, Jose > wrote:

>
> Which got me thinking - maybe the FAA isn't so crazy after all. If frost can form while the plane is just sitting there, why could it not form while the plane is flying? (yeah, there's some frictional heating, but we could lower the temp a bit more, no?) And if frost isn't such a good thing to have on takeoff, it's probably not so good in flight either.

The frost on your wings was most certainly formed after your landed.
It happened to me a few times on some very clear cold days. I fly a
low wing Grumman and I could see the frost started to form as I slowly
taxi back to the ramp.

If you depart in such condition, it would be a good idea to spray
propylene glycol (RV antifreeze, not the automobile antifreeze) on
your wings and horizontal stablizers before taxi out, after you clear
out all the frost.

[Bush]

I've iced up to the ailerons in a Warrier, cold fuel can play a part
here too.

Bush

On Mon, 24 Dec 2007 16:28:33 GMT, Jose >
wrote:

>The other day I went flying, pretty close to the shortest day of the year, to preserve night currency. I took advantage of a day that wasn't brutally cold - in fact it was above freezing, so I didn't need preheat or thermal underwear. It was good to get in the air after several months of not flying hardly at all (we had the longest, most beautiful fall but I was stuck indoors doing two shows at the same time). I had to taxi over a bit of an ice berm in front of the wheels, but it wasn't a problem, and the pavement was wet from the melting ice (we had several inches of ice storm a week or so ago which is still around).
>
>By the time I got in the air, I was happy and all was well with the world. After doing some night full stop landings, I followed I-84 up to Beacon and back just to "go somewhere" and then came home. By now temperatures were just below freezing, but it was clear and so I didn't give it much consideration.
>
>Landed without incident, braking was good (and was also reported good by aircraft before me), and I taxiied to the ramp, a relatively unfamiliar part of the airport since we moved the airplanes. The airplane seemed to be sliding a bit, as if there was ice on the pavement. Well, of course there was; the wet pavement had frozen in the interim. I was afraid of that, and this meant that putting the plane away would not be as easy as taking it out. After a struggle I did manage to get it pushed back over the ice berms (pulling up on the wing while pushing back helped, as did pulling with the tiedown ropes when I got close enough). But when I was pretty much done, I noticed there was frost on the wings, which hadn't been there before.
>
>Which got me thinking - maybe the FAA isn't so crazy after all. If frost can form while the plane is just sitting there, why could it not form while the plane is flying? (yeah, there's some frictional heating, but we could lower the temp a bit more, no?) And if frost isn't such a good thing to have on takeoff, it's probably not so good in flight either.
>
>Any thoughts? Have you seen this before?
>
>Jose

[Peter R.]

On 12/24/2007 11:28:36 AM, Jose wrote:

> But when I was pretty much done, I noticed there was frost on the wings,
> which hadn't been there before.

I have experienced this a few times. Two memorable times were once after
landing at Niagara Falls airport and once after landing in Plattsburgh, NY.
In these two cases it was after dark, the sky was clear, and the temperatures
were very cold (perhaps around 0 to -10 degrees F). In each situation the
aircraft's wings and horizontal stabilizer frosted over within minutes of
landing.

--
Peter

[[email protected]]

On Dec 24, 11:07 am, quietguy > wrote:
> On Dec 24, 11:32 am, Jose > wrote:
>
> > What would prevent this from happening in flight?
>
> Sublimation. The airflow around the wing evaporates deposited ice
> crystals fast enough to keep visible frost from forming unless the
> relative humidity is near 100% (i.e., when there's visible moisture).
> Then, depending mainly on the droplet size, you'll get either rime
> (frost by another name) or clear icing.

Frost forms when the metal radiates its heat into the clear
sky faster than the surrounding air, so that it gets cooler than the
air and the moisture condenses on it in the form of frost. In flight,
the air moving around the wing keeps it at the same temperature as the
wing and frost won't form. Other forms of ice will, in the right
conditions, but they're not frost. They're impact ice, supercooled
water droplets that freeze when they hit the wing and anything else in
the way. Frost forms directly from vapour to solid without going
through the liquid phase.

>Takes a hell of a wind to
> cause rapid-enough sublimation, though: I've seen parked airplanes get
> frosty even when gusts were in the forties.

That's hoarfrost, related to impact icing. Not sublimation. It's
the same supercooled water droplets found in ice fog.

Dan