Use partial heat ONLY when you have instrumentation that tells you what is
going on in the venturi...there are several devices on the market, some of
them optical, others temperature-related. Without such instrumentation, it
is full heat or none. Go to the Textron-Lycoming web page for more info.

Bob Gardner

"John Kirksey" wrote in message
news:g20rd.14599$%C6.279@trnddc02...
I'm starting to get geared up for my written test, and was finally reading
[thoroughly] the chapter on systems last night. I was reading about carb
heat and how it works and was surprised to learn that the temperature in
the
venturi section could be as much as 50 degrees below the outside air
temperature, and that ideal conditions for carb heat were between 50 and
70
degrees with high relative humidity (stuff you guys all know).

Anyhoo, we went flying on Saturday and it was about 58 degrees out with
1800' broken and 2700' overcast in light mist (looked overcast all the way
to me, but it did lighten up after a while). That sounds like a good
scenario for carb icing to me. We were going to try a mini-cross country
to
a local airport, but decided to do some pattern work since we wouldn't be
legal VFR without skimming the treetops, dodging towers, etc....

My question is, in these or similar conditions, would you consider using
at
least partial carb heat to help prevent icing, or periodically turn the
carb
heat on to clear out any ice that may have formed? Is there ever a time
when
you would use carb heat as a preventive measure?


John K.
Student Pilot
Somewhere between solo, X-country, the ground, and space