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Thread: Carb Heat Temperature gauge/detector

  1. #1

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    Default Carb Heat Temperature gauge/detector

    Good morning,
    I am considering adding a carb ice detector to my Tri Pacer. Do any of you folks have one on your airplanes? If so - what do you think about itís usefulness and which one do you use?
    Thank you, Marsha

  2. #2
    Smokeypilot's Avatar
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    Default Re: Carb Heat Temperature gauge/detector

    Some digital engine analyzers have it as an option. I have carb temp on my jpi analyzer. It was very easy to incorporate. I don’t use it much, but it is interesting to see the temps in there in various conditions.

  3. #3
    Steve Pierce's Avatar
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    Default Re: Carb Heat Temperature gauge/detector

    I have not had many issues with carb ice on Lycoming engines with the carb bolted to the oil sump but do know of two cases personally where a Tri-Pacer and a Super Cub's engines quit suddenly when operating at reduced power, both around a lake and there was high relative humidity. No other abnormality was found. Easy to add a temp probe in the carburetor. There is a lead plug already in the carburetor throat that is drilled out a tapped to facilitate installing the temperature probe. Several options for temperature indication both in stand alone gauges and add-ons to engine monitors.

    A friend who lives in the Pacific Northwest was having carb ice issues in his Cessna 180. These engines have an induction Y under the engine that is in open air and I have seen ice on them when doing engine runs on the ground. That led down a rabbit hole with lots of good information including a paper on Light Aircraft Piston Engine Carburetor Ice Detector/Warning Device Sensitivity/Effectiveness that I have uploaded here. The below link detector, the "Iceman" carbice detector by ARP, uses an optical probe with a light, when ice forms and reduces the light intensity a warning device sounds.
    https://www.aircraftspruce.com/catal...icedetect2.php
    Attached Files Attached Files

  4. #4
    akflyer's Avatar
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    Default Re: Carb Heat Temperature gauge/detector

    I have had carb ice more times than I can count on my pacer during AK summers (only once in the winter). No matter the day or conditions I have gotten in the habit of pulling carb heat every so often during flight and especially during descents.

    The air is heated by the sump AFTER it goes through the carb, not before.

  5. #5
    Steve Pierce's Avatar
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    Default Re: Carb Heat Temperature gauge/detector

    Quote Originally Posted by akflyer View Post
    The air is heated by the sump AFTER it goes through the carb, not before.
    I agree but I also think some of that heat transfers through the sump to the carburetor bowl. I am also spoiled by operating in a pretty dry environment. Was out all morning at 85 degrees and never pulled carb heat, clear skies and bright sun but if it was that temp and moisture I would be pulling it. I see Marsha is in Florida and I know how humid it can be there.

  6. #6
    Gilbert Pierce's Avatar
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    Default Re: Carb Heat Temperature gauge/detector

    Lifted off a grass strip in my Vagabond and the engine quit about 10í off the runway. Set it down, got out and put my hand on the carb. It was ice cold.

    Took off again with carb heat on no issue. It was 60F and dew point was probably about 60. Got home and checked the icing chart. Surprise, I was in the high risk part of the chart. Also I was using auto fuel.
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  7. #7
    tnowak's Avatar
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    Default Re: Carb Heat Temperature gauge/detector

    On my A65 powered Vag the carb heat is set to hot all the time, except when I start the take-off run.
    Same for when I throttle back for landing. Set to hot before slowly pulling the throttle..
    TonyN

  8. #8

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    Default Re: Carb Heat Temperature gauge/detector

    In all my years of flying I have never had carb ice with an O-320, O-360 or O-235. The TriPacer Owners manual even says not to use carb heat unless carb ice conditions prevail. I've seen a number of O-320 powered airplanes (Pacer and TriPacer on floats) that fouled the plugs using carb heat when it wasn't needed. About the only Lycoming powered airplane that I have had carb ice problems with has been the Maule 235 (carbureted version). I have no idea why, but both the M5-235 and the MX7-235 that I used to fly were the worst ice makers I ever flew! Could be that Maule specifies a different carburetor for the O-540 for their installation or could be the induction system.

    Continental engines are totally different with no heat transfer to the carburetor from the oil pan. I've had many times where a Continental will ice up when you wouldn't expect it to, I've also seen the carburetor on Continentals totally frosted over on the outside right after shutdown. On my Howard, except for take off, you would run carb heat all the time on the R985 to maintain 32 degrees C on the carb temp gage. It had an automatic mixture control carburetor and the mixture was set based on pressures and carb temp.

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