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Carburetor Heat

in General Tech Discussion 13 years ago
Noticed that when using carburetor heat that there is no noticeable drop in RPM with the 912ULS Rotax. Other aircraft I have flown all have a noticeable RPM drop when applying carburetor heat. Is this unique to the 912ULS Rotax or is something missing to prevent the RPM drop? Noticed that the airbox seems to be large for this engine. It does not require applying carburetor heat unless necessary (whatever that means), so most times when reducing RPM for landing carburetor heat is not used. Does the large airbox make it vulnerable for carburetor icing?

  • Re: Carburetor Heat

    by » 13 years ago

    Hi Roland,

    Not really seeing any rpm drop when you apply carb heat can be pretty normal on a Rotax 912. They didn't always have carb heat and many experimental's today with a Rotax don't have carb heat. The carb heat is by far more normal today in the Rotax than it was 10 years ago. It is harder to get carb icing with a variable throat carb, but yes it does happen. Most of the guys I know with it don't ever seem to use it. You can get an after market system that keeps icing away. There is an electric system, but it pulls power all the time. Then there is a hot water system that feeds off your coolant lines and that works very well. I think many of the really tight cowled engines that don't get rid of heat well probably don't have as much to worry about as those carbs are fairly hot during flight, but I have no research or data to back that up.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Carburetor Heat

    by » 13 years ago

    The reason you don't see a large drop in RPM is because the CV style carbs used on the 912 series engines are auto leaning(to a point) so they automatically compensate for the heated(thinner) air when carb heat is applied. The up-draft style carbs used on Lycoming and Conti's do not have this feature, therfore the heated less dense air causes those engines to run rich resulting in an RPM drop. This is one of the advanatages of a ROTAX over the older technology engines which you have to manually lean, expecially as you go up in altitude, one less thing for the pilot to worry about! :)
      
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  • Re: Carburetor Heat

    by » 11 years ago

    Hi Roger,

    I'm looking at putting carb heat on a 912 ULS in a Just Highlander. The cowling is fairly tight but I live in the mountains. I am considering one of the water-powered systems. You mention that they have a good record. Is this the sort of thing you are thinking of:

    http://www.lockwood.aero/p-2603-carb-heater-for-912912uls-new-style-casted.aspx

    or is there something else I should be looking at?

    Many Thanks

    Julius
      
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  • Re: Carburetor Heat

    by » 11 years ago

    That one will work.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Carburetor Heat

    by » 11 years ago

    Great. Many thanks Roger.
    Thank you said by: anthony foran
      
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