I thought I'd read pretty much all of the C152 manual, but didn't remember reading that bit. So I just pulled out a manual, and sure enough, there it is - not sure how I missed it. Here's a more complete quote:
Carburetor ice, as evidenced by an unexplained drop in RPM, can be removed by application of full carburetor heat. Upon regaining the original RPM (with heat off), use the minimum amount of heat (by trial and error) to prevent ice from forming. Since heated air causes a richer mixture, readjust the mixture setting when carburetor heat is to be used continuously in cruise flight.
I have to admit I have a problem with this. The scenario is that I've detected, and successfully removed, carb ice. I then, by trial and error, set the carb heat partially on. My trial and error proved be in error, and I soon notice more carb ice forming, so I use full carb heat to remove it... and now what? Am I expected to remember the position the carb heat was in previously, and select a position which is slightly hotter? But how do I know where it was set to initially? How do I know that I haven't inadvertantly selected a colder position than the previous one? There is no indication or markings to show the carb heat position, so this seems a little random to me.
What I've always done, and what I will continue to do unless someone can tell me
how to follow the POH to the letter, is apply regular carb heat to check for and remove ice, and, if I notice ice building up regularly in the cruise, use full carb heat.
Planemad_bk - this is a story which I have heard many times, but which contradicts the POH, and which I have yet to see any good evidence for.
FFF
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