Iced up Cirrus crashes

"Stefan" wrote:
Before guessing and posting, you should read...

That's some great advice you're handing out there, Stefan.

Is a laminar flow wing more susceptible to loss of lift due to icing then a
standard wing? And, along the same lines, is there any difference between
how composites react to icing versus aluminum?

Michael

Michael 182 wrote:
"... is there any difference between how composites react to icing
versus aluminum?

Michael

Michael, I am training in a Diamond DA-20 C1, incidentally, the only
composite airplane on my flight schools ramp. I am flying in upstate
SC. This morning, at 8:15 the top surfaces of the wings on the C1 were
iced significantly, as was the nose and fuselage (tail boom). Outside
air temp was 41*F/Overnight low was 40*F. Plane is tied-down, morning
sun was directly on wing surfaces, no intervening shadows. My lesson
was delayed, of course.

Curious, I checked the other planes on the ramp-all of which are
aluminum. NONE had icing on any surface. Through a very unscientific
"hand touch" test I determined the composite surfaces "felt" much
colder than the aluminum surfaces.

I would be very interested in learning more about the heat/cold
transfer dynamics of aluminum versus composites. Pure speculatin'
though, I would bet from my limited experience that the composite will
ice faster or retain ice longer than similarly exposed aluminum. But,
there's always someone who knows more about it than me-so maybe they
will chime in.

Pete

greenwavepilot wrote:

Pure speculatin'
though, I would bet from my limited experience that the composite will
ice faster or retain ice longer than similarly exposed aluminum.

I would bet that the composite will ice more slowly and retain the ice longer.
It will lose or gain heat more slowly than aluminum.

George Patterson
He who would distinguish what is true from what is false must have an
adequate understanding of truth and falsehood.

George, I did some research and found the following thermal
conductivity values (Note these figures are for a standard temperature
of 25*C):

Aluminum,
Pure=237 watts/meter*Kelvin

Fiberglass,
Paper Faced=.046 watts/meter*Kelvin

So, what I should have inferred from my non-aviation experience with
these materials is confirmed by the above thermal conductivity values.
That is, aluminum is a good heat conductor-it can either gain or lose
heat very quickly. Fiberglass on the other hand is a good insulator.
It does not lose or gain heat very rapidly. Thus once "set" at a
temperature, it will tend to remain there longer than aluminum.

Therefore I would agree that versus fiberglass the aluminum surfaces
will cool to icing temperatures faster, and conversely will heat to
non-icing temperatures faster. The composite will cool more slowly,
but once cooled, will retain that temperature much longer, meaning like
I discovered this morning, my composite plane will/may be iced when the
Cessnas, Pipers and Mooneys won't.

During the preflight "Hand Checking Of All Surfaces" has added meaning
for a composite driver.

Pete

greenwavepilot wrote:

The composite will cool more slowly,
but once cooled, will retain that temperature much longer,

If you fly high and descend fast on a reasonably humid day, you'll see
condensation on the wings after the flight.

Stefan

("greenwavepilot" wrote)

snip
Michael, I am training in a Diamond DA-20 C1, incidentally, the only
composite airplane on my flight schools ramp. I am flying in upstate
SC. This morning, at 8:15 the top surfaces of the wings on the C1 were
iced significantly, as was the nose and fuselage (tail boom). Outside
air temp was 41*F/Overnight low was 40*F. Plane is tied-down, morning
sun was directly on wing surfaces, no intervening shadows. My lesson
was delayed, of course.


There can be a thermal "dip" right before sunrise, right about at wingtip
height. Duck hunters and deer hunters will confirm (and curse) this
temperature phenomenon - forget what it's called.

41F overnight? 40F at 8:15? And still ice?

So it either go down to 32F at or near your wing, or it was below 32F a
number of feet, maybe many, many feet above your wing? Or your wing was 32F
at some point in the early morning? Wonder what it was?

Also wonder what the height of the temp reading instrument is?

Our local airport can report 40F with an overnight low of 36F yet there will
sometimes be "white-ice-dew" on the grass those mornings - usually in the
fall. We keep track of this because of our flower garden and outside plants.
Minnesota flowers in late October are a night-by-night proposition. Ooh,
there go the Impatiens.

Our airport's automated weather reporting station is less than two miles
away. Plus geologically, we are all at an identical elevation sharing the
same glacially flat sandy river bottom. This area was all sod farms just a
few years back - no other farming is sustainable in this area. Anyway, we
usually always agree with the airport temps - here at home, in the car,
neighbors thermometer, etc.

37F-40F and frost on the grass in the morning is common here.


Montblack

Montblack wrote:
("greenwavepilot" wrote)

snip

Michael, I am training in a Diamond DA-20 C1, incidentally, the only
composite airplane on my flight schools ramp. I am flying in upstate
SC. This morning, at 8:15 the top surfaces of the wings on the C1 were
iced significantly, as was the nose and fuselage (tail boom). Outside
air temp was 41*F/Overnight low was 40*F. Plane is tied-down, morning
sun was directly on wing surfaces, no intervening shadows. My lesson
was delayed, of course.

There can be a thermal "dip" right before sunrise, right about at wingtip
height. Duck hunters and deer hunters will confirm (and curse) this
temperature phenomenon - forget what it's called.

41F overnight? 40F at 8:15? And still ice?

So it either go down to 32F at or near your wing, or it was below 32F a
number of feet, maybe many, many feet above your wing? Or your wing was 32F
at some point in the early morning? Wonder what it was?

The temperature of a surface that's radiating heat to a clear night sky
can drop considerably below the ambient air temperature. So it's
possible for frost to form even when the air temperature never gets
down to freezing.

Peter wrote:

The temperature of a surface that's radiating heat to a clear night sky
can drop considerably below the ambient air temperature.

Err... no.

Stefan

the 'hand test' isn't an accurate measure of temperature. When you get
up in the morning your carpet will be the same temp as the tile, but
the tile will 'feel' much colder. The tile takes more energy (than
carpet) to raise its temp which is energy sucked out of you. Since tile
sucks more out of you for any given temp change it will 'feel' colder.

-lance smith