C152: Use of Carb Heat

I’ve noticed that the default C152 Checklist and the JPL checklist do not include the use of carb heat on approach. When I took PPL, two instructors from different airports said to apply carb heat on approach. I’m trying to figure out why this difference. They also included a brief check of carb heat by pulling it on and pushing it off. Is it because I live in a cooler, more moist area than others? What have you learned about the use of carb heat?

I’m not home to check, but don’t some of the default Cessnas have fuel injection and no carb heat?

I’ve never flown a fuel injected recip, so I have always pulled the Carb Heat once I reduce power below the green arc.

Don’t know why else it would be omitted.

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I learned to fly and flew in generally warmer climes. Carb heat was checked as part of before takeoff checks but was generally only used if carb icing was considered likely on descent and in the circuit. Which, where we were, was pretty uncommon. Descending from high altitude sure. In the circuit, not so much. And quite frankly I cannot recall having a single incidence of carb icing. Admittedly in the later years I flew fuel injected aircraft exclusively.

Edit: Recognise that the dangers of carb icing are so severe that one should ALWAYS err on the safe side. The associated loss of a small amount of power when using carb heat is no hardship if it prevents icing. Always using it in the circuit is not a bad idea I suspect

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Even at temps as low as 10C you can get carb icing. The general rule I learned for in-flight use was:

  • Any time you’re on approach
  • Any time the engine is being operated in flight with the tachometer below the green arc (including the bottom end)
  • Regularly (every 10-15 minutes?) in flight at night or on a cold weather day to check for carb icing (hold it for a few seconds. If the engine sputters and splats and the RPM increases noticeably, you had icing)

To add to that:

  • Any time you’re on the ground idling the engine if it’s cold outside (think, subzero temps just after engine start and you gotta warm the engine up quickly to reduce wear)
  • During the run up to make sure the carb heat works

That’s my experience flying a 152 in southern Ontario in all 4 seasons

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Also watch the warm humid days — cold dry winter days pose less threat of carb icing.

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This looks like what I remember and I’m in Michigan, so a similar climate to yours. I remember doing the run-up check as well as part of the routine. The cool and cold weather checks were also stressed. I asked the question because I wanted to be sure my training was not unique to me or my location.

Everyone who’s responded so far uses carb heat for some reason, yet at least some checklists I’ve seen never mention carb heat ever being pulled out (ON). [Note the default C152 in MSFS only takes the checklist through takeoff, however]. One C152 training supplement lacks a description of the use of carb heat on a routine basis. It’s too bad because it will not teach what it seems we collectively agree to be proper use.

Thank you all for sharing your knowledge regarding this topic. I will include it in my personal MSFS C152 checklist. I’ve marked @Eefoe’s post as the solution only because you have to select one post and it was the most complete.

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These are great rules of thumb! But are these conditions simulated in MSFS anyway? Will it make any difference using carb heat in the sim (not reality)? Either with the default C152 or with the JPL version.

Found this yesterday: No carb icing
Also found this checklist, which includes proper use of carb heat: C152 Checklist

In addition, I checked the default C152 by setting the throttle to 1700 rpm, then added carb heat. I think there is a very slight difference in rpm / engine sound, on the order of 100 rpm, which would be correct according to information I’ve found (difference should not be greater than 125 rpm). It takes awhile for any change to settle in.

Me reading all those rules: I’ll just use it always. o.o

One of the best explanations I’ve ever seen:

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