Carb Heat

shdw said:
But this doesn't make sense either, "Once on the ground, he removed carb heat, full power, flaps up, just like the checklist said. At about 300ft AGL he experienced a partial engine failure." Carb ice doesn't develop easily at full power and it is even less likely that it developed in a matter of 10 seconds at full power.
Carb ice doesn't just snap appear, it is a steadily increasing process.
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For repetition and reinforcement, I will repeat: Carb ice can form around the carb intake as quickly as the fog that appears on a mirror when you breath over it.
Quite often I have seen a small trainer engine develop carb ice after the run-up. There was some slight build up during the taxi-out, but was undetected by the student. The normal run-up with the carb heat check is enough carb heat to burn out the slight coating of ice, and the student pilot never notices it. During the minute or two (sometimes five with students) between run-up and full power for take-off, a slight ice coating had occured, but the full throttle blew it out.

That's what usually happens, but when the right conditions come together, the ice build-up is more than the full throttle application can eliminate.

So, put the carb heat back on after your run-up, and take it off after you have full throttle.

On a touch 'n go - leave the heat on until full throttle.

And pull the heat on at least 30 seconds before reducing power in the pattern.
 
nosehair said:
Doh! :crazy: I thought we were talkin' carb icing - y'know? On a clear cold day?
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oh, so no chance of airframe icing. roger that!
I still would think twice if I was getting severe carb icing but then again I have not experienced carb ice much (ok, at all) in my career.
 
nosehair said:
Yes, it is. Mainly warm air. :insane:
But you are right about being careful of dusty polluted air since the warmed air is bypassing the air filter. Normally, on the cold below freezing mornings when this is advisable, the air is very cold and clear.
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I'm not worried about the air, I'm worried about whats on the ground, and getting blown around by the prop. Yeah, warm air. I get it.:)
 
It may differ from aircraft to aircraft on the location of the intakes but if you were using carb heat on the ground and say it were to take in some rocks or FOD...well wouldnt it have to miss the turning prop and go between the prop and cowling to go into the intake? thats some rock i'd say!
 
mattc206 said:
It may differ from aircraft to aircraft on the location of the intakes but if you were using carb heat on the ground and say it were to take in some rocks or FOD...well wouldnt it have to miss the turning prop and go between the prop and cowling to go into the intake? thats some rock i'd say!
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no sh$t, if you are worried about rocks getting into your carb then you must have been the pilot in the movie 2012.
 
subpilot said:
no sh$t, if you are worried about rocks getting into your carb then you must have been the pilot in the movie 2012.
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Finer particles of dust and debris. Just like why don't you use alternate engine air on the ground, its unfiltered air that's getting into the engine, and the bits of dust which aren't present at altitude could prematurely wear your motor. Check carb heat in the runup, but I would take off with it, and I wouldn't taxi around with it unless you have to to keep the airplane running.
 
mattc206 said:
It may differ from aircraft to aircraft on the location of the intakes but if you were using carb heat on the ground and say it were to take in some rocks or FOD...well wouldnt it have to miss the turning prop and go between the prop and cowling to go into the intake? thats some rock i'd say!
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Wierder things have happened. What about a gum wraper that gets picked up, blown into the cowling, sucked into the carb hear duct, gets piched inbetween the valve and the seat, and gets stuck there. Yes, with the precision fit of a valve and seat, it could cause leakage, and high leakdown. Or lets say that it's some gum with the thin aluminum on the wraper, and it makes it way down to the rings, and sticks a ring. It get's hot and the ring causes the cyl. to quit makeing compression. Now that 100hp in the best of days in your 150 now is only worth 75hp, and your over the mountains.


I know some of these things seem far fetched, but I have seen stranger things when I was turnning wrenches on cars.


Edit: One of your roles as a pilot is to mitigate risks. This is one you have complete control over, so control it well.
 
subpilot said:
no sh$t, if you are worried about rocks getting into your carb then you must have been the pilot in the movie 2012.
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You know I liked the movie but I couldn't help but think, "you know, you won't have to be dodging buildings and what not if you climb..."
 
futurepilot1 said:
I was getting ready for my lesson yesterday, when my CFI and another student got into a discussion about Carb Heat. The student had had a partial engine failure due to carb ice. He was doing a touch and go. He had applied full carb heat during the descent. Once on the ground, he removed carb heat, full power, flaps up, just like the checklist said. At about 300ft AGL he experienced a partial engine failure. It didn't die completely, just had a huge power loss and sputtered. He was able to get enough power to turn around and use the perpendicular RWy for a landing. Now the curious part. My CFI said it sounded like he did everything correct, but the student said his CFI told him that, due to the cold conditions he should have kept carb heat on the whole time. My CFI said that was incorrect. Comments?? Thoughts?? I was under the impression that, when the engine is running, outside air temperature has little to do with Carb icing.:dunno:
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Taking off with the carb heat on is about the same as taking off with less than take off power with the carb heat off.
 
ppragman said:
Finer particles of dust and debris. Just like why don't you use alternate engine air on the ground, its unfiltered air that's getting into the engine, and the bits of dust which aren't present at altitude could prematurely wear your motor. Check carb heat in the runup, but I would take off with it, and I wouldn't taxi around with it unless you have to to keep the airplane running.
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Right, that's what I mean - when the temp/humidity/dew point all come together so that you start getting carb ice immediately on start-up. If you live in a dry (relatively dry) climate, and don't get out into swampy land, maybe you have never experienced it, but it happens routinely in humid climates. The rough sputtering hard to keep it idling at 1000 rpm on cold (freezing) mornings is due in part to the carb ice building. Selective applications of carb heat will keep the ice cleared and make you aware of the severity of the build-up.

I'm not talking about a rote application of carb heat, which is all we get in flight school. I didn't mean to apply carb heat when there is obvious stuff in the air, and to be aware of what is in the air, or what else you may be doing when checking for carb ice. The point is to make it a knowledgeable check of current conditions in current environment - take it away from the rote "pull it out - check rpm drop - push it in" mechanical check that most people do - if at all.
 
nosehair said:
I didn't mean to apply carb heat when there is obvious stuff in the air, and to be aware of what is in the air, or what else you may be doing when checking for carb ice.
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You still don't get it, it isn't the air that those arguing this are discussing. Like I asked earlier, "Who sweeps your taxi and ramp area?" The prop kicks up dust, dirt, gravel, and whatever else is on the ground into the air. That crap gets sucked into and can cause serious damage, reducing the life of the engine. It doesn't matter if you have the cleanest air in the world, unless you have your taxiways and ramps swept hourly you are going to get crap in the engine.

Let me ask you this, if the engine dies on the ground because of carb heat is it really going to endanger you? No. Point is, keep it running, if it sputters apply a little power and maybe some carb heat for a few seconds then take the carb heat off. If it happens to die because you didn't do it fast enough then who cares, you are on the ground. But taxiing, even with it partially or fully out is going to reduce your engine life, period.

Haven't you ever wondered why cars have HUGE air filters and an airplane has a 1/2 inch dinky air filter? It is because traveling on the ground = crap gets kicked up that requires heavy filtering.
 
wjmiller3 said:
The Seminole is less likely to get carb ice anyway cause the intake is behind and below the engine, so its air is heated a little to begin with. And the one time I ever did get carb ice in a seminole was at cruise power. And as for running over square...... Your dangerous!!:D
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The carburetor is on the side of the seminole engine, called a side-draft carburetor. It's location minimizes the profile of the engine and thus reduces drag. Typical single-engine piper's have the up-draft carburetors, where the carburetor is underneath and heated by the oil pan.
 
General Comment-
Nosehair is not over in the deep end of the pool.

One side is saying it is potential hazardous to bring unfiltered air into the engine...true. You are right.

The other side is saying that on some times the carb heat needs to be applied on the ground...fact, or you can call for a tow, it is that simple.

We had a student and instructor buy the farm, in the local area many years ago due to Carb Ice on take-off.
I'll take the unfiltered air.
 
Douglas said:
We had a student and instructor buy the farm, in the local area many years ago due to Carb Ice on take-off.
I'll take the unfiltered air.
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We are talking about for general taxi, at least I am. If you need it on takeoff to keep the engine from shutting off, by all means that is smart. But if the engine dies from you taxiing, who cares? If it ends up crapping out during taxi, restart it, use some carb heat to clean it then taxi without carb heat again, using it periodically to clear it.

Taxiing around with unfiltered air is absolutely horrible for the engine. You might as well sit and throw gravel in your engine.
 
tgrayson said:
The NTSB reports have many cases of carb icing and suspected carb icing at cruise and even takeoff power. A good chunk of the above chart shows the non-zero probability of icing at cruise power, which I would interpret to be green arc on the Cessnas.

The Cessnas also have procedures for maintaining partial carb heat at cruise if conditions warrant.
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:yeahthat:

I've gotten carb ice well above the bottom of the green arc in a Cessna 150.
 
shdw said:
If you need it on takeoff to keep the engine from shutting off, by all means that is smart. But if the engine dies from you taxiing, who cares? If it ends up crapping out during taxi, restart it, use some carb heat to clean it then taxi without carb heat again, using it periodically to clear it.
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Now you're gettin' it - that's what I'm trying to say. 'Cept for the 'who cares' part. I'm sayin' what it's takin' ta keep it runnin' and how to be aware of the stuff (carb ice) in general.

You're hittin' it hard on the dirty intake stuff. Good. awareness and caution on both sides. Use all available information.
 
nosehair said:
You're hittin' it hard on the dirty intake stuff. Good. awareness and caution on both sides. Use all available information.
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I have no idea how we landed in agreement, but I will take it. lol

I do know that I agree it can't be rote. All flight tasks require some form of intellectual processing.
 
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