Is carb heat either off or on in a Cessna 150?

Question

I thought it was either off or on, with nothing inbetween, but my POH seems to say something about using partial carb heat somewhere (p 4-17)

Answer 1

It should be either off (fully) or on (fully). Some carburated aircraft have a guage which indicates the temperature in the carburator but not the Cessna 150. At least none Ive flown. You dont want to use it unless you need it ie. engine running rough and losing power, then use full hot until you melt the ice which wont take long, then go back to cold. On really cold days -20 and below when carb ice isnt a problem you will find it advantages to turn it on before landing or touch and go for better engine response.

Answer 2

Carb heat is there to prevent ice from forming in the carb.  Ice can form on days as warm as 80.  Ice happens when conditions are favorable, i.e., the temp and dew point are less than or equal to one degree apart.  On those days there is sufficient moisture in the air for instantaneous formation of ice, usually in low rpm conditions.

Follow your instructor's directives here.  Mine said to pull it (full on) when I pull the power on downwind approach to landing.  He said to do away with it as soon as you touched down, in case you needed to perform a go-around.  What i normally did was to keep my little finger out when advancing the throttle, and if the carb heat was on, my little finger would hit it, reminding me to shut it off.

As for the temp it's possible, I speak from experience. I had it happen to me on a clear day, with ambient temperature at 79 degrees faranheit (sp?)

Hope that helps.  Good luck in your training..

Answer 3

Carb heat is controlled by a butterfly valve in the air intake hose, operated by a push/pull cable.  You can move the cable in or out part way to get something less than full heat, but most instructors don't recommend it.

Answer 4

either fully on or off, and dont leave it on for extended periods because you negate the de-icing effects. 10 seconds cycle is a good way to do it.