Carb Temperature Gauge

DKirkpatrick

DKirkpatrick

Pre-takeoff checklist
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DKirkpatrick
reworking the panel on my C172D. Want to fly IFR and distance flights.
Does anyone recommend installing a Carb Temp Gauge? Or have experience with these good or bad?
Seems to me that this would be a good gauge to watch for icing because of the probe mounted right at the Carburetor, and would be helpful flying thru cloud layers.
Would appreciate some "been there done that" advice.
thanks
dan
 
I don't know if the O-300 is an icemaker like the O-200, but I like having a carb temp gauge in mine.
 
yeah, the ice maker in my fridge broke and of course can't find a guy to repair... seems like an alternate universe these days.
engine is a oncoming O0360, forgot to mention that.
My mechanic wants me to put in an engine analyzer, but that seems like alot of expense... money that will probably be needed for buying gas thanks to the wisdom of our new "constraints" on oil and pipelines in the US. GA can thank those guys at the polls in a few mos.
 
Lycoming O-360... spellcheck is helping me out alot
 
I agree, with an O-300/C-145, I'd definitely get a carb temp gauge. I flew a 170 that would ice up in a heartbeat and I was glad when the owner added that gauge.
 
DKirkpatrick said:
anyone recommend installing a Carb Temp Gauge
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I certainly would. The engine is the single most important piece of equipment on the plane, and in a carb'd plane that little venturi plays a critical role in bringing us to the sky and back safe. A few of our club planes have carb temp gauges, some analog, and at least a few are integrated into the JPI. I love it, brings piece of mind flying in the clouds when it's near or just above freezing out and seeing the carb temp in the green. Some people may not recognize carb ice until it's too late, remember, carb heat pulls heat off the exhaust manifold, and that little metal tube will cool down quick once the engine stops chooching

PS.. I hate the idea of "cracking the carb heat" to get it just warm enough.. even past the gauge there is still a temp drop as the air goes into the venturi, you don't want to heat the air just enough to make ice further down the tube where it's harder to get. So, in my opinion, carb heat is either off or full on. No in between

DKirkpatrick said:
GA can thank those guys at the polls in a few mos
Click to expand...
If only there were enough of us to make a difference!!
 
I have had one for years. It will just show when temperature is conducive to carburetor icing but humidity is a big factor so temperature alone is not super useful.
I have always wondered why instrument makers did not make a gauge that factored temperature and humidity and then displayed percentage probability of icing.
 
I’m not sure this applies to fixed wing as much as us on the RW side.

Robinson had a few carb ice issues on decent, carb heat indicated OK, what they found was by closing the throttle, you make a low pressure system on the engine side of the throttle butterfly, which is upstream of the sensor, this can result in icing and the engine gupping out when you go to reapply throttle.

Now for the airplane guys you don’t have a sprag clutch, so that bing spinning prop on the front will probably save you from this

But something to keep in mind.
 
yes, it's been converted to the Lyc O-360 engine...
and I appreciate the "all or nuthin" comment RE applying carb heat. My only worry is, what if you pull it on all at once and it causes some big ol' chunk in the system to move, as opposed to bringing up the temp slowly and letting the ice dissipate slowly. Probably my un-mechanical mind's bad thinking
 
I just don't like IFR on top, and coming thru a thick bank of grey on a cold day... without an eye on some gauge probed into my carburetor. I believe in carb heat.... hate that windmilling prop sound
 
FWIW, Lycoming Service Instruction No. 1148C (https://www.lycoming.com/content/service-instruction-no-1148c) advises the "all or nothing" approach unless you have a temp gauge.

If you run partial heat, you risk melting any frost-like ice at the front of the carb, which can then run back through and re-freeze. By the time you realize you need heat, it is less effective against the solid ice than it would have been against the frost-like ice at the start. Slowly bringing the temp up and melting ice off incrementally is NOT what you want to be doing. Run full heat. Of course if you have a temp gauge, than I’d say it’s fine to occasionally ‘stoke’ the carb to keep it warm as a preventative measure.
 
kshaw said:
I have always wondered why instrument makers did not make a gauge that factored temperature and humidity and then displayed percentage probability of icing.
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There are too many variables, one of which is the throttle position. The carb temp sensor is in the venturi, but ice forms around the edge of a mostly-closed throttle plate too. There's a bigger pressure and temp drop there than in the venturi and you can get ice there even if the gauge shows a temp above zero. The gauge is a poor substitute for training and knowledge.
 
good coaching. buying an indicator.
thanks for the responses
dan
 
I would definitely recommend Electronics International.
 
I have a JPI 830, carb heat is one of the things it has. It is very enlightening to see what the temp does when you close the throttle. Open carb heat all the way, close the throttle all the way, results in carb temp in the 100 to 130 degree range! Part throttle will cause icing temperatures, fully closed in my 520 not so much. BUT, I have had carb ice shortly after takeoff its a bit spooky when you reach to turn the prop back and instead of a slight reduction in RPM you lose several hundred in a few seconds. I now keep an eye on carb temp on take off in humid conditions.
A couple months back I was being forced lower and lower due to bad weather, eventually I was 250' skimming the bottoms of the clouds with what appeared to be clouds to the surface about 2 miles out. I kept pulling back the throttle to slow down so I had more time to figure out what to do and where to go. I kept a very close eye on the carb temp and was using carb heat actively as it was moderate rain, 100% humidity with an air temp in the mid 30's. After a couple minutes, I found a gas well service road and set it down, for the night. Without carb temp, I would have been totally guessing on whether I was going to have the engine shut off or not.
 
Tantalum said:
...
PS.. I hate the idea of "cracking the carb heat" to get it just warm enough.. even past the gauge there is still a temp drop as the air goes into the venturi, you don't want to heat the air just enough to make ice further down the tube where it's harder to get. So, in my opinion, carb heat is either off or full on. No in between
...
Click to expand...

100% agree. On or off.
 
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