Decent into Cleveland

Have been inactive for many years.

About 20 years ago, when flying up from the south, I got suckered in.
The tops slowly rose untill I was flying at over 15,000 (Mooney 201)
near Cleveland, It was clear on top and the temp was in the mid 40s
on the ground, and the freezing level was high enough so I wasn't
worried.

When cleared for decent, ice formed at an incredible rate - must have
picked up over an inch of rime in seconds near the tops. Once below
the sun heated top layer, the accumulation virtually quit. Breaking
out below at about 4,000, the temp was already well above freezing,
but no ice was dissapearing.

While being vectored into the approach, I ran some test to make sure
the plane was behaving normally and was capable of climbing. On hind
site, I should have refused the approach clearance and waited for the
ice to fall off.

Anyhow, after having read accounts about people stalling on final and
etc., I brought her in about 20 knots fast over the numbers and
chopped everything. I damn near overran a 5,000 ft. runway - the
sucker didn't want to land.

Rime ice, I have since found, can lower the stall speed (raises the
dragg). It increases the leading edge of the wing. This was verified
by test I did for a senior project in a wind tunnel using an airfoil,
rubber cement, and sugar. The Reynolds number was way off for that
test, so it could be suspect. However, I had occassion to take to one
of the crew of the icing planes over at NASA who confirmed all this
and it sure would account for my landing problem above.

Anyhow, after parking the plane, ice was still falling off in big
chunks for 10 or 15 min.

I question the "sun-heated" part of your post. The sun heats the earth,
which in turn heats the atmosphere from the bottom up. Most ice is found in
the top one-third of any cloud. It does take a while for ice to sublimate
off...I have picked up ice climbing through a layer out of Seattle that
didn't disappear for about 30 minutes, and this was in a Baron.

Glad that it worked out, though.

Bob Gardner


"john cop" wrote in message
om...
Have been inactive for many years.

About 20 years ago, when flying up from the south, I got suckered in.
The tops slowly rose untill I was flying at over 15,000 (Mooney 201)
near Cleveland, It was clear on top and the temp was in the mid 40s
on the ground, and the freezing level was high enough so I wasn't
worried.

When cleared for decent, ice formed at an incredible rate - must have
picked up over an inch of rime in seconds near the tops. Once below
the sun heated top layer, the accumulation virtually quit. Breaking
out below at about 4,000, the temp was already well above freezing,
but no ice was dissapearing.

While being vectored into the approach, I ran some test to make sure
the plane was behaving normally and was capable of climbing. On hind
site, I should have refused the approach clearance and waited for the
ice to fall off.

Anyhow, after having read accounts about people stalling on final and
etc., I brought her in about 20 knots fast over the numbers and
chopped everything. I damn near overran a 5,000 ft. runway - the
sucker didn't want to land.

Rime ice, I have since found, can lower the stall speed (raises the
dragg). It increases the leading edge of the wing. This was verified
by test I did for a senior project in a wind tunnel using an airfoil,
rubber cement, and sugar. The Reynolds number was way off for that
test, so it could be suspect. However, I had occassion to take to one
of the crew of the icing planes over at NASA who confirmed all this
and it sure would account for my landing problem above.

Anyhow, after parking the plane, ice was still falling off in big
chunks for 10 or 15 min.

*****didn't disappear for about 30 minutes, and this was in a Baron.****


I thought we were in a Bonanza!

Best,
Karl

"Bob Gardner" wrote in message .net...
I question the "sun-heated" part of your post. The sun heats the earth,
which in turn heats the atmosphere from the bottom up. Most ice is found in
the top one-third of any cloud.

I don't think this works with a heavy cloud deck and clear on top
where you get little sun penetration. I would think there would have
to be a warmer boundry layer at the tops. This would certainly
account for the much heavier concentration of super cooled moisture.
There was no question the really heavy icing was right at the tops -
you could hear the stuff applying itstelf.


It does take a while for ice to sublimate
off...I have picked up ice climbing through a layer out of Seattle that
didn't disappear for about 30 minutes, and this was in a Baron.

Sumblimate, yes, but I expected the stuff to fall off pretty quickly
once the temp was well above freezing. It didn't - probably took a
long time to warm the plane up.


Glad that it worked out, though.


Me too.

I would suspect your OAT to be incorrect.

Ice invariably will melt off fast, and in big chunks, below the freezing
level.

Karl

Different trip.

Bob

"karl gruber" wrote in message
...
*****didn't disappear for about 30 minutes, and this was in a Baron.****


I thought we were in a Bonanza!

Best,
Karl

Look at any text on the atmosphere and you will learn that temperature
decreases with altitude, cloud cover not withstanding (absent an inversion).
The sun does not heat clouds.

Bob Gardner

"john cop" wrote in message
om...
"Bob Gardner" wrote in message
.net...
I question the "sun-heated" part of your post. The sun heats the earth,
which in turn heats the atmosphere from the bottom up. Most ice is found
in
the top one-third of any cloud.

I don't think this works with a heavy cloud deck and clear on top
where you get little sun penetration. I would think there would have
to be a warmer boundry layer at the tops. This would certainly
account for the much heavier concentration of super cooled moisture.
There was no question the really heavy icing was right at the tops -
you could hear the stuff applying itstelf.


It does take a while for ice to sublimate
off...I have picked up ice climbing through a layer out of Seattle that
didn't disappear for about 30 minutes, and this was in a Baron.

Sumblimate, yes, but I expected the stuff to fall off pretty quickly
once the temp was well above freezing. It didn't - probably took a
long time to warm the plane up.


Glad that it worked out, though.


Me too.

"Bob Gardner" wrote in message news:GwAhb.535167$cF.206989@rwcrnsc53...
Look at any text on the atmosphere and you will learn that temperature
decreases with altitude, cloud cover not withstanding (absent an inversion).
The sun does not heat clouds.

Look, I am no atmospheric expert, but the above is just a plain silly
statement (less charitable types might say stupid). What do you think
happens to all that energy? It ALL get reflected back into space?

Clouds, which you should know even from just from watching the weather
on TV, are insulators of sorts. This means that the sun's energy (the
part that doesn't get reflected) get absorbed by the cloud as it is
transmitted through it. If were an ideal insulating situation, the
temp gradation would be linear, but, obviously, its not (gas laws and
all that), but the principle is the same. My bet is the energy
transfer to the clouds is greatest at the tops and reduces with
altitude according to some unknowable (too many variables) function.
If your statement were correct, the temp at the tops would be the same
during the day as during the night which is, I think, silly. This
does not mean the temp is going to rise as you climb (gas laws again).
What is does mean is that the cloud's capacity to absorb moisture (or
supper cooled stuff) very near the tops could be substantially greater
than near the bottoms.

Read this, and google on cloud temperatures.

http://www.cpc.ncep.noaa.gov/product...uv_clouds.html

When you look at a satellite shot, the whitest clouds are the coldest....at
their tops.

I have attended a whole bunch of international icing conferences hosted by
the FAA, with meteorologists and aerodynamicists from all over the world in
attendance, and I have read the papers they presented at those conferences.
I have written and lectured on airframe icing. Simply stated, you are wrong.

Bob Gardner

"john cop" wrote in message
om...
"Bob Gardner" wrote in message
news:GwAhb.535167$cF.206989@rwcrnsc53...
Look at any text on the atmosphere and you will learn that temperature
decreases with altitude, cloud cover not withstanding (absent an
inversion).
The sun does not heat clouds.

Look, I am no atmospheric expert, but the above is just a plain silly
statement (less charitable types might say stupid). What do you think
happens to all that energy? It ALL get reflected back into space?

Clouds, which you should know even from just from watching the weather
on TV, are insulators of sorts. This means that the sun's energy (the
part that doesn't get reflected) get absorbed by the cloud as it is
transmitted through it. If were an ideal insulating situation, the
temp gradation would be linear, but, obviously, its not (gas laws and
all that), but the principle is the same. My bet is the energy
transfer to the clouds is greatest at the tops and reduces with
altitude according to some unknowable (too many variables) function.
If your statement were correct, the temp at the tops would be the same
during the day as during the night which is, I think, silly. This
does not mean the temp is going to rise as you climb (gas laws again).
What is does mean is that the cloud's capacity to absorb moisture (or
supper cooled stuff) very near the tops could be substantially greater
than near the bottoms.

john cop wrote:

Look, I am no atmospheric expert, but the above is just a plain silly
statement (less charitable types might say stupid). What do you think
happens to all that energy? It ALL get reflected back into space?

If you think about the characteristics of glass in the visible spectrum, and
consider that clouds behave similarly in the infrared, you might be a little
more charitable.