Lycoming Carb Heat

Bob Gardner wrote:
: I once read a report about carb heat use published by the NTSB (which, of
: course, I can't lay hands on now). In it, they pointed out the hazard of
: having disparate methods of carb heat use depending on engine and airframe,
: and suggested that full carb heat be applied any time the power was reduced
: below cruise power...no matter who made the engine or airframe. They felt
: that this standardization would have a positive effect on accident rates.

Perhaps, but I don't like to apply the carb heat unless I know it's needed.
In particular, there are situations where ice crystals would harmlessly flow through
the induction system. If carb heat (especially *partial* carb heat) is added, they
can melt enough to stick. Then you'd be stuck with an iced engine, below freezing,
and not enough heat to melt it.

Maybe I'm overly paranoid about it. I have had carb ice twice in Cherokees...
one with an O-320 in a long descent, and one in cruise (relatively low power in misty
weather at low altitude). Application was a non-issue once I saw the MP 2" below what
I set it. I'll agree that on an IMC missed or legitamate go-around the pucker factor
(and timing constraints) would be more of an issue.

I think that the Cessna left it in the POH from the O-300 Continental days as
a CYA when the switched to Lycoming. Never a good reason to change it, so left it was
it was required before.

-Cory


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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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