My carb iced up!

pigpenracing

pigpenracing

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Well,
I have been flying for 12 years and last weekend was the first time I got carb ice. I was flying back home right when the cold front hit and the ceiling got to about 1500 feet. We went under the clouds and turned up the heater because it got cold. We were over town at pattern altitude about 6 miles from the airport. The engine instantly started running rough to the point it almost quit. I pushed the mixture rich and pulled carb heat. It cleared up right away. This happened when it was running at 2500 rpm in my 172. I just read last week about this happening to someone else. Most folks think a carb will only ice up with the power pulled way back.
 
2500 RPM, 1000 feet, leaned, cold day, in a 172. Are you sure you weren't detonating? That's contrary to the POH, which says full rich below 3000 (DA).

What did the oil temperature look like?

Carb ice shouldn't be quite that sudden, though detonation sure can be.
 
It was just barely leaned. Not enough to cause any problems. There was a big conversation last week on the biplane forum about this. After reading that I thought to pull carb heat right away.
 
In a 172 ,doesn't the checklist for landing call for,full rich carb heat on.
 
frfly172 said:
In a 172 ,doesn't the checklist for landing call for,full rich carb heat on.
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Yes it does. I was not landing. I was cruising over town at 2500 rpm. I thought that was in my post.
I am full rich with heat on every landing.
 
I sometimes get ice in my 172N/180 on cool, moist winter days, even at low cruise power settings (2300-2400 rpm). And yes, it's carb ice; brief application of carb heat restores lost rpm.
 
pigpenracing said:
Yes it does. I was not landing. I was cruising over town at 2500 rpm. I thought that was in my post.
I am full rich with heat on every landing.
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Eeep, careful with the full rich. Especially down here in CTW with 110 in the summer and 4000' DA even on the ground.

We need to do a fly-out to Brenham for lunch!
 
Carb or fuel ice can occur at any throttle setting, being a function of temperature and humidity (fuel vaporization effect). Throttle icing occurs when the throttle is in the almost closed position for landing (venturi effect).
 
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I keep the chart in with my check list.
 

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Got it once in cruise to the point where the engine took a dump. Came back pretty quickly after carb heat. I was already on the glide path to an airport by then, though.
 
asicer said:
This is false. The POH that I have for the 172M, N, and SP does not say this.
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C-172N Page 4-15 Enroute Climb "The mixture should be full rich below 3000 feet"

I fully concede it does not say you should be full rich all the time you are below 3000 feet.

Brian
 
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brcase said:
C-172N Page 4-15 Enroute Climb "The mixture should be full rich below 3000 feet"

I fully concede it does not say you should be full rich all the time you are below 3000 feet.

Brian
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Yup, this was my point. The "full rich below 3000 feet" only applies to climbs and it was pretty clear that the OP was not climbing from the scud running description.
 
brcase said:
C-172N Page 4-15 Enroute Climb "The mixture should be full rich below 3000 feet"

I fully concede it does not say you should be full rich all the time you are below 3000 feet.

Brian
Click to expand...

It's fine to be leaned at low power.

2500 RPM is not low power. It's climb power at 1000 MSL.
 
MAKG1 said:
It's fine to be leaned at low power.

2500 RPM is not low power. It's climb power at 1000 MSL.
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It was only leaned a couple of clicks... It was not leaned aggressively.
Carb ice was the issue.
I put this post up to give other people information that carb ice can form at anytime, not for you to be a know it all again MAKG!
 
MAKG1 said:
It's fine to be leaned at low power.

2500 RPM is not low power. It's climb power at 1000 MSL.
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Not sure what the OP was flying exactly but in a C-172N 2500RPM in standard conditions, level flight is 75% power, Descending 2500 can be significantly less than 75% power.

Brian
 
pigpenracing said:
I put this post up to give other people information that carb ice can form at anytime...
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Has this inspired you to invest in a carb temp gauge? :wink2:

BTW, thanks for sharing.
 
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I get carb ice at least a couple of times a year in my 182. It actually happened this morning. Odd, too, since the air was so dry.
 
asicer said:
Has this inspired you to invest in a carb temp gauge? :wink2:

BTW, thanks for sharing.
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I need to get one of those, too. Especially considering how humid it gets around here. I've been fortunate and haven't yet experienced carb ice.
 
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