On Dec 1, 1:50 pm, "Maxwell" wrote:


You seem to think that within 10 seconds of loosing power from an carb ice
condition, that the engine and heat exchanger on the exhaust have cooled to
the point that it's impossible for them to deice the carb. And the simply is
not true, and I have proven that many times while actually flying in winter
conditions.

You had claimed that you had had a *complete* engine failure. It is
obvious that you did not, and that the thing was still firing enough
to generate some heat. Here's the quote:

If a Lyc or Continental dies due to carb ice, it isn't going to
restart either. It needs air and fuel to generate heat to get the ice
out, and a pilot who lets things deteriorate until the thing is dead
is faced with a forced landing whether it's a direct-drive engine or a
geared engine.

Not true, been there and done it.

Ten seconds is a long time. I am an aircraft mechanic as well as
a CPL and CFI, and I work on those exhaust systems from which the carb
heat is taken. A 172's heat muff is a small open-faced shroud around
one exhaust riser, and collects very little heat. The Lycoming doesn't
need so much, with its carb heated by the hot oil sump. Other
aircraft, especially Continental-powered airplanes, have a shroud
around the muffler; a 150 has two small, stainless-steel mufflers, one
of which supplies carb heat. That muffler is about 14" long and four
inches in diameter and weighs about two pounds. The metal is no more
than .025" thick. Air is passed around it under the shroud all the
time to keep it cool, and when carb heat is applied, that air is
directed to the carb intake insted of being dumped overboard.
If the engine stops firing altogether due to carb ice, that
muffler will cool off so fast it's not funny. It will aready have
cooled greatly if tghe engine was idling for any length of time, and
if carb ice was forming the power loss would just cool it off further.
These aren't automobile exhaust systems with heavy cast manifolds,
where the pipe is minimum .063" and the mufflers are several layers of
sheet steel.
The accident database I pointed out earlier is full of
needless forced landings just because carb ice wasn't understood. So
many folks think it's a threat only in the winter and can't figure out
why it's happening in the summer. It's been experienced at temps as
high as +40°C (100F), with suffficiently high dewpoints. It can happen
down to -20°C, below which all supercooled atmospheric water has
frozen, but some folks have gotten themselves some carb ice by using
the carb heat and melting that moisture, and having it refreeze in the
carb or intake runners. We operate in temps as low as -25°C here but
give up after that. Some commercial operators keep flying down to -40
or lower. The worst icing is found between 0 and +15°C
http://ibis.experimentals.de/images/...omcaassl14.gif

Dan

Dan