frost on the wing

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
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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!!!)

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
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You can choose whom to befriend, but you cannot choose whom to love.
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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

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

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

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

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.

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

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