BTDT, in a Lear descending into Baton Rouge after a flight in the high 30
flight levels. Mucho ice on the bottoms of the wings.

Bob

"Stan Prevost" wrote in message
...

"Bob Gardner" wrote in message
. ..
Jim Carter's experience is telling. When a cold-soaked airframe descends
into the clouds it is going to collect a lot of ice in a hurry. Where
does the "quickly warmed" idea come from?


It doesn't even have to get into the clouds. A cold soaked airplane
descending into humid air can accumulate a layer of frost, thickness of
which depends on time of exposure, humidity, and how cold the airplane
was. This is an exception to the common theory that visible moisture is
required for accumulation of airframe icing. It has happened to me in a
Saratoga, I landed with still 1/4 inch or so of ice under the wings, where
the inboard fuel tanks are located, and a little elsewhere. Never passed
through a cloud or any kind of visible moisture, had been flying a couple
of hours at 16,500 or so, saw ice accumulating during descent through
warmer air. The thin skin without any thermal mass beneath it apparently
warmed rapidly enough to accumulate little and shed it, whereas the fuel
tanks had enough thermal mass to keep the ice frozen.

The recent FAA regional counsel letter about icing conditions included
areas of high humidity with near freezing temperature as known icing
conditions. It has widely been hooted down, but is not entirely wrong.