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C 180 Carb ice

Redbaron180

Redbaron180

Registered User
Lopez Island WA
My C180 has an O-470 L and I've flown it about 1400 hours. It gets carb ice at what I expect is average amounts for a continental. A friend of mine just bought a 1960 180 with an O-470 U. It makes ice in unbelievable amounts. When ice starts to build the manifold pressure increases until you pull the heat, then it drops very low as the ice melts then back to normal. I have thousands of hours in carborated planes and I've never noticed an increase in MP with ice. The only thing I can figure is ice is building downflow of the MP pick up point on the intake, which sounds pretty dangerous. We were flying formation through the mountains a couple weeks ago and the U was making ice like mad and the L didn't make any. What gives? maybe there is a leak in the MP gage line and the pick up point freezes up? But mine looses MP with ice. Strange.
 
Kinda interesting how your friend's U model responds to ice. Too bad we can't get as little as 10% ethanol legalized in the fuel as carb ice wouldn't be a factor anymore.
Marty
 
I live in Houston, Tx so my summer icing conditions are few and far between. :D In the winter though, it can stay 40 degrees and humid for months. Never once had my O-470U or O-470J ice up. It's something I'm always wary of though, and I have a carb temp gauge.
 
Marty,

Actually, I seriously doubt that ethanol fuels would have any influence on carburetor icing.

Isopropyl alcohol is approved as an anti icing additive, and it sure doesn't stop carb icing.

Much of the more "normal" carb icing occurs UPSTREAM of the fuel in any case, I believe.

MTV
 
MTV
Wow, that sure is different than my understanding of carb ice. How can ice build upstream of the fuel mixture? Doesn't the evaporation of the fuel into the air, cool it and freeze the moisture to the walls of the carb throat and possibly the intake manifold?
 
Sorry, thinking throttle plate icing. There are two distinctly different flavors of carb ice, and my mind was drifting :oops: . Been doing that a lot lately....

You're right. Whether ethanol fuels would influence carb icing or not is a good question.

MTV
 
mvivion wrote
Whether ethanol fuels would influence carb icing or not is a good question
Click to expand...
Talk to Texas Skyways about that subject-----they've got some actual experience. :D
Marty
 
While not an expert myself, I have heard from a couple of different sources that if a carb is new/freshly rebuilt to the tightest of standards, that it is more prone to icing than one with some wear on it. Might be that your buddy's -U fits that description. I'm sure someone here can add to that one way or another.

Unrelated to your post, I once was leaving Whitehorse, YT. C180 picked up carb ice with climb power. Not in the clouds, but on a cloudy day. Was even more inexperienced than I am now, but was always taught that carb ice was only a problem during reduced power settings. Not the case, lesson learned.

gb
 
Is isopropyl alcohol added to prevent ice crystal formation in fuel? I don't see how it could prevent carb ice formation if the ice formed is from condensation of water from the air going through the carb.
 
The different inductions styles on 180's, and the way the cowl directs cooling may have as much to do with carb ice as anything. My old 57 would ice up taxiing down the float pond every day. Some of the newer ones did not ice so bad, but hey, that is why you have heat.
 
Jim Michael wrote
Is isopropyl alcohol added to prevent ice crystal formation in fuel? I don't see how it could prevent carb ice formation if the ice formed is from condensation of water from the air going through the carb.
Click to expand...

Years ago people would add alcohol to the water in the radiator to keep it from freezing. The place I get my aircraft oil from also mixes windshield washer fluid by combining methanol and water. Doesn't it seem pretty likely that as air, laden with moisture, and fuel mixed with a fair amount of ethanol combine in the carb, that ice buildup wouldn't happen? The little bit of isopropyl that MTV is talking about probably wouldn't make a difference in my opinion.
Marty
 
My understanding of carb icing is that the venturi effect of the carb on moisture laden air causes the moisture in the air to condense out onto the walls and the butterfly of the carb. Cold air cannot hold as much water vapour as warm air, hence the reason for rain and carb ice. The added action of fuel evaporation and wind chill causes the temperature of the carb and its butterfly to fall below zero. The water vapour goes from a gas straight to a solid in a process known as deposition which is the opposite of sublimation. So it's the relative humidity of the surrounding air thats the important factor and carb ice can form at temperatures as high as 28 degrees Celsius with high humidity conditions. I have experienced this in Florida.
 
For what it's worth, I've had my 180 for 12 years, with three different engines including the current 0-520 and have not experienced a single carb ice event. I do have a carb temp gauge and it registers in the yellow "caution" zone 100% of the time during a normal flight.

Stewart
 
I thought surely there would be some wisdom on this site as to why two apparently identical induction systems could build ice so differently. Oh well I guess that is why there is a carb heat knob..........
 
We all LEARNED what carb icing is from the 470 in the C-180.

No one should expect to replicate the experience Stewart B has had.
Many of these engine need to be run with partial carb heat from beginning to end of a flight, in certain conditions. I am amazed that SB has had "not a single event".

I am convinced that certain models/inductions/cowl-scoop-styles (model years) are worse than others, But not a single event???

A recent early-180 rebuild that I did has an O-470"R" with a "K" induction 'y' , a second generation cowl scoop, and a LEES equal length Cessna 206 exhaust system modified for the 180(all field-approved, and I mentioned the exhaust in case some of you 'engineer' types were wondering what kind of exhaust-scavenging this baby has). It doesn't carb ice much at lower throttle settings, but seems to make ice every takeoff out of it's home base at Lake Hood.

DAVE

:-?
 
StewartB said:
For what it's worth, I've had my 180 for 12 years, with three different engines including the current 0-520 and have not experienced a single carb ice event. I do have a carb temp gauge and it registers in the yellow "caution" zone 100% of the time during a normal flight.

Stewart
Click to expand...

Stewart-

How the heck do you go through 3 engines in 12 years? Are you renting it out or what?

Tim
 
behindpropellers said:
StewartB said:
For what it's worth, I've had my 180 for 12 years, with three different engines including the current 0-520 and have not experienced a single carb ice event. I do have a carb temp gauge and it registers in the yellow "caution" zone 100% of the time during a normal flight.

Stewart
Click to expand...

Stewart-

How the heck do you go through 3 engines in 12 years? Are you renting it out or what?

Tim
Click to expand...
Airplane purchased with 1100 hr 0-470 (1500 hr TBO). Engine replaced at 1300+ with factory reman 0-470 and flown for a little over 100 hours before the crank was condemned in the TCM crank fiasco. My plane sat through two successive summers for that issue. Finally converted the reman to accept a 520 crank and converted the engine and installation to 0-520 via Pponk's STC.


Dave,

I can't explain why my plane hasn't made ice. I know the reputation of the 0-470 series for icing. I figured the reputation for ice was exaggerated. In my time with this plane it has been a complete non-issue as reported, and that's the truth.

Stewart
 
It's not always icing, but just cooling of the induction system that makes problems. The fuel is vaporized in the carb venturi, but gets cooled in the induction tubes and turns back to liquid, and liquid fuel does not ignite very well. Take the cowl off a old 180 on a sub zero day and try to run it. Without the cowl keeping the intake tubes out of the breeze it will barely run. A restrictor plate over the airfilter actually helps it run better. Running partial carb heat on these engines when it is extermely cold is SOP, you do what ever you need to do to keep the fire lit.

Real carb icing can happen in ANY carbed engine under the right conditions. It can sneak up on you and bite you right in the ass, always be thinking about it when conditions are right for it.
 
The answer to winter issues for me is cylinder preheat. My engine doesn't like to run without it. It'll run smooth as silk from start-up in -30* with it.

I'm curious now about the carb ice thing. Why do some planes ice and not others? Why some dramatically more than others? I'm going to ask all my 180-driving friends what they experience. What about all the 180 drivers that read this? Please chime in.

Stewart
 
[/b]Daryl Baker wrote
Good info on carb ice at this web site. Ethanol gasoline will make carb ice form at higher ambient temperatures due to the higher heat of vaporization of alcohol vs. gasoline.
Click to expand...
Interesting article how adding Prist(EGME) to avgas can cut down on carb icing. I agree with the cooling effect that methyl and ethyl alcohol has as it evaporates----that's why you can get more power from an engine because the cooler the air the more can be packed into the combustion chamber. What I can't figure out, according to the article,is EGME cuts down chances of carb ice but not alcohol( a known antifreeze). Evidently the alcohol/gasoline mix cools the air in the carb, causing ice, but doesn't mix with it so where does mixing occur?
Marty
 
I thought Prist was a fuel system deicer similar to isopropyl alcohol. That is, I thought it eliminated ice in the tanks and lines. My quick drains are frozen most of the time in the winter. I have occasionally added isopropyl and get rid of it, but the alcohol isn't good for the fuel bladders. I never considered a fuel system deicer as a measure to prevent carb ice. In general, since alcohol absorbs the water and sends it through the carb, I'd think it would increase carb ice. I'd rather be patient until the temps warm enough to drain the sumps and pour the water on the ground.

Stewart
 
The way I understand alcohol and water is that when combined the water can't solidify into ice. If you don't have enough alcohol to encapsulate all the water then that is when ice can occur. I posted this icing question on an E85 forum I go to where some people are loving ethanol because of the performance and price compared to special race gas they need in their high performance engines. Hopefully someone over there that builds race engines will have some input.
Marty
 
Stewart,

Isopropyl alcohol should not damage fuel system components, including bladders. That is a concern with Ethanol and Methanol, but supposedly not with Isopropyl.

The manufacturers suggest up to a 1 % solution for anti-icing/de-icing in aircraft with reciprocating engines.

MTV
 
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