Icing Airmets

"C J Campbell" wrote in message
...

"Dave" wrote in message
ink.net...
| I'd like to know how you get in icing when the temperature is +5. I have
| never seen ice until the the gauge reads 0 or below.

Icing occurs when liquid water freezes on an airplane surface that is
below
freezing. The aircraft may have been cooled earlier when it flew through a
layer.

Almost. Icing occurs when a below freezing aircraft encounters supercooled
water. Supercooled water does not exist above 0C.

Mike
MU-2

Mike Rapoport wrote:
"C J Campbell" wrote in message
...

"Dave" wrote in message
hlink.net...
| I'd like to know how you get in icing when the temperature is +5. I have
| never seen ice until the the gauge reads 0 or below.

Icing occurs when liquid water freezes on an airplane surface that is

below

freezing. The aircraft may have been cooled earlier when it flew through a
layer.


Almost. Icing occurs when a below freezing aircraft encounters supercooled
water. Supercooled water does not exist above 0C.


True, but only partially correct.

Above-freezing water will still freeze and cling to your below-freezing
airframe. In fact, the preferred migration of liquid and of
not-condensed water vapour is "from warm to cold". So moisture will
migrate to the below-freezing airframe.... you can even get a thin sheet
of ice forming in absolutely clear air, simply from the condensation of
the water vapour. (similar to your glasses fogging when you come inside
from the cold)


Until such time as the airframe finally warms up to ambient and sheds
the ice.

This is not about frustration, but about trying to understanding how
FAA comes up with airmets. An airmet is supposed to be issued when
moderate icing is expected. If they are issuing an airmet every time
there are clouds and freezing temperatures (or even above freezing),
then what about light icing?




ArtP wrote in message . ..
On 26 Jan 2004 10:08:44 -0800, (Andrew
Sarangan) wrote:

For example, right now the freezing level is at 5000 ft,
MEA is at 2500 ft, yet we have an airmet Z that goes all way from SFC
to 18k.

Since the published icing conditions occur from +5 to -20 C, a
freezing level at 5000 would mean icing potentially below 3000 feet.
The MEA may be 2500 but the normal minimum IFR altitudes would be
either 3000 or 4000 feet depending on direction and that is known
icing conditions. I am sorry this frustrates you but depending on
where you live a big chunk of winter is off limits to small GA
aircraft trying to fly IFR.

On 27 Jan 2004 17:05:49 -0800, (Andrew
Sarangan) wrote:

This is not about frustration, but about trying to understanding how
FAA comes up with airmets. An airmet is supposed to be issued when
moderate icing is expected. If they are issuing an airmet every time
there are clouds and freezing temperatures (or even above freezing),
then what about light icing?

Unless your plane is certified for known icing then airmet or not any
icing potential means you can't legally fly. Arguing over moderate
versus light is academic since either is prohibitive..

This is not about frustration, but about trying to understanding how
FAA comes up with airmets. An airmet is supposed to be issued when
moderate icing is expected. If they are issuing an airmet every time
there are clouds and freezing temperatures (or even above freezing),
then what about light icing?
Unless your plane is certified for known icing then airmet or not any
icing potential means you can't legally fly. Arguing over moderate
versus light is academic since either is prohibitive..

The other crazy thing is people are arguing over 2 degrees F. I don't
care how accurate your thermometer is, but if you are that close
to potential icing, get out of there. +5 certainly gives you the
margin and sure the FAA will err on the larger side but still,
are you watching the OAT in your instrument scan....."one more
degree drop and I turn around....." Crazy.

Gerald

Gerald Sylvester ) wrote:

are you watching the OAT in your instrument scan....."one more
degree drop and I turn around....." Crazy.

LOL!

--
Peter












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ArtP wrote in message . ..
On 27 Jan 2004 17:05:49 -0800, (Andrew
Sarangan) wrote:

This is not about frustration, but about trying to understanding how
FAA comes up with airmets. An airmet is supposed to be issued when
moderate icing is expected. If they are issuing an airmet every time
there are clouds and freezing temperatures (or even above freezing),
then what about light icing?

Unless your plane is certified for known icing then airmet or not any
icing potential means you can't legally fly. Arguing over moderate
versus light is academic since either is prohibitive..

But what if the airplane were certified for known ice? Would it not matter then?

On 28 Jan 2004 06:46:28 -0800, (Andrew
Sarangan) wrote:


Unless your plane is certified for known icing then airmet or not any
icing potential means you can't legally fly. Arguing over moderate
versus light is academic since either is prohibitive..

But what if the airplane were certified for known ice? Would it not matter then?

Many people claim that the only function of certified deice equipment
in a small GA aircraft is to give you time to get out of that
condition. If you look at the definition of light and moderate icing,
a certified system should be able to handle them. It is also my
understanding that the level of icing encountered is more complicated
than a linear relationship to temperature so that temperatures near
freezing don't necessarily imply less accumulation than lower
temperatures.