You still have it partly backwards on droplet size. In general, large
droplets are worse, primarily because they take more time to freeze and end
up freezing behind the protected surfaces leaving a "ridge" of ice on the
top and bottom of the wing. The ridge then functions as a spoiler. I do
recall reading that when the drops get really large (huge), like in
freezing rain they do not form the high drag shapes of drizzle size drops.
So basically the *effects* of icing get worse as droplet size increases to
some maximium size and then diminishes.

Droplet size is related in some way (I forget exactly what way) to
temperature with large drops being unlikely at really cold temperatures, so
the 0C to -10C caution range is useful since you will only find moderate or
greater icing at temps below -10C where there is a lot of vertical movement
like in cumulus, cumulonimbus and (occasionally) wave clouds.

Small radius surfaces indeed collect more ice than large ones because the
"preasure wave" they form as they advance through the air does not extend as
far forward.

Mike
MU-2


"Tarver Engineering" wrote in message
...

"Roy Smith" wrote in message
...
"O. Sami Saydjari" wrote:

This question is a question on physcial phenomena, NOT on regulation
(so
I am starting a new thread).

As I understand it, icing happens between +2C and -10C.

There was just a posting from Mike Rapoport in which he said he's seen
icing as cold as -20C.

Icing is statistical in nature and contrary to pilot observations to the
contrary, is more a function of the size of the droplets, than some
exacting
temperature range. FAA studied icing under a program tittled to reflect
"large droplet" icing, but the results of the study were the opposite of
the
observed information. (large vs small droplets) You are in more danger of
an icing event where the size of the droplets is small and the airplane is
small.