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Carb Ice

J

jlisler

Well Known Member
I never gave much credence to carb icing on my Lycoming O-320 knowing that the carb is mounted on the bottom of the oil pan. I always figured there would be enough heat from the oil to keep everything nice and warm. I have to admit I very seldom pull the carb heat control (maybe a dozen times in 560 hours) so today was no different. I also did not put much stock in the little heat muff from Vans thinking it was marginal at best.

On my Continental C-85 in the Cessna 140A, I have actually seen the outside of the carb completely encased in blue ice on a humid 70 deg day. There was not a hint of icing inside the carb though since the engine ran fine. However I always use carb heat on that engine.

So the weather today was 1200' with 10 miles visibility and the OAT was 43 deg. These conditions gave me my first real life, certified run in with carb ice! I had been easing forward on the throttle to maintain cruise RPM until I figured out RPMs were dropping without a reduction in throttle position. Another dead giveaway was the engine was starting to run rough. I pulled on the carb heat and instantly the RPMs started to rise by almost 200 revs and the roughness disappeared. The little heat muff actually works. I am in the "it can happen" camp now.
 
Lycomings are much less prone to it.
Particularly in an RV with its tight cowling, but hopefully no one thinks they are immune to it.
I regularly see signs of it during the winter months here in the Pacific Noth West, but only at low power sitting on the ground.
 
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I was on my long student solo cross country about half way between the second pair of airports when I had a rough running engine. Fortunately I was not far from an airport so I bailed to the field. As I was headed that direction I did all the things you are supposed to do including carb heat and in pretty short order is was running better but by that point I was on base leg so I landed. Found a shop that would take a look in case it was something else, phoned my instructor and was on my way to complete the trip as planned. Fast forward several years and I had one of my students on his long solo cross country using the same airports and he has the same problem, in roughly the same place and bailed to the same airport.
 
I usually remove carb heat muff during summer time. This year on trip to AK I was strongly advised by a local to have operational carb heat system. I was glad to have it. Several times I had signs of carb ice usually at lower power setting as Scott noted. Was worried about air filter icing as well.




Sorry inspector, I had carb ice and I can prove it :D

 
Yep

Jerry, a local acquaintance of mine landed his 172 in a pasture last month, after the engine quit.

The mechanic couldn't find anything wrong and the engine ran just fine. I asked the pilot if he thought about carb heat when the RPM's started going down and he said, "Carb heat was the furthest thing from my mind."

Go figure.

Remember guys, a loss of RPM's with a carburetor is usually a sure sign of ice.

Best,
 
I've got a carb ice detector in my Cessna 180, which also rarely gets carb ice. If the light comes on, though, I've got ice.

I bought another one for my RV-3B, since it'll be carbureted too. It comes in versions so that you can set it up as needed.

It's from Aircraft Spruce, works well, and it's here.

The only connection I've got to this device is that I'm a happy user of it.

Dave
 
I have had precisely one instance of carb ice in 500 hours of flying. The vast majority of my time has been behind Lycomings, with the exception being about 20 hours in a C150 a decade or so back. My one eye-opener occurred in my Cherokee 180; I was returning from a short cross-country in early October; temps were right around freezing, and I ended up flying through a heavy rain shower as I neared my home base. When rpm started to drop, it took a few seconds before the lightbulb went off; I had never had a hint of carb ice in years of flying Pipers, which, like RV's, rarely experience it. Application of heat immediately restored normal rpm and smoothness. It was a great reminder that it can in fact occur in any airplane given the right circumstances.
 
carb ice

A few tips regarding carb ice...

be aware of the conditions that allow it to occur... in any carbureted engine

don't let it get too bad before you catch it or it might be too late to clear it

when you put on the carb heat, do it before you close the butterfly or ice in the carb might cause the engine to quit.

I pull the heat on before every landing to make sure the carb is clear. On the lyc in my rv , if its clear I turn it off again.



CM
 
Was flying with a student in his 1965 C150. The little Continental usually runs smooth as silk. We were returning from the practice area and I noticed the engine starting to run a little rough. RPM's were still around 2400. I told him to pull carb heat and we got a quick rpm drop that was quickly followed by an increase in rpms and a smooth running engine again. It really got my students attention. It was the first time that I have had problems with carb ice at a high power setting. The weather near freezing with fairly high humidity.
 
My Dad ended up with silence after a full power climb to 2000 ft in a C172 on floats. He always thought you couldn't get ice at full throttle. When he powered back to cruise he put on carb heat and the engine stopped dead. He was over a turf farm and put it down with no damage. Nothing wrong with the engine. He installed a carb temp guage after that. He noticed that the carb temp was the lowest at full power, which makes sense if you think about it. Engine was a lyc O320.
 
Carb heat every time I descend?

I just started taking flying lessons so I can be ready when I finish my plane this summer. I am flying in a Warrior and the instructor has me put on carb heat every time I descend. I don't remember using it that much when I flew years ago. It is making me consider adding FI so I don't have that to think about.

I have a carb temp gauge with my G3X system and have the carb ice detector Dave mentioned I may install too. Considering I live in the mountains where I may have more times favorable to carb ice, maybe the FI is the answer.
 
rockwoodrv9 said:
I just started taking flying lessons so I can be ready when I finish my plane this summer. I am flying in a Warrior and the instructor has me put on carb heat every time I descend. I don't remember using it that much when I flew years ago. It is making me consider adding FI so I don't have that to think about.

I have a carb temp gauge with my G3X system and have the carb ice detector Dave mentioned I may install too. Considering I live in the mountains where I may have more times favorable to carb ice, maybe the FI is the answer.
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That's how they taught it at UND when I was there a decade ago, running carb'd P28As. Got carbon ice once on a night solo xc, very low altitude on an "entry route" for home base. Almost put it down on the interstate but carb heat solved it.
 
If you want some good first hand carb ice time all you need to do is get some IFR flying in the Continental powered C-182s. They are the worst I have come across.
 
Cajun98 said:
Was flying with a student in his 1965 C150. The little Continental usually runs smooth as silk. We were returning from the practice area and I noticed the engine starting to run a little rough. RPM's were still around 2400. I told him to pull carb heat and we got a quick rpm drop that was quickly followed by an increase in rpms and a smooth running engine again. It really got my students attention. It was the first time that I have had problems with carb ice at a high power setting. The weather near freezing with fairly high humidity.
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THE OAT DOES NOT NEED TO BE ANYWHERE NEAR FREEZING TO GET CARB ICE!
 
Carb ice once in RV6 in 700 hrs

Flying from WI to Pine Bluff AR last Halloween for the formation flying clinic was the first time I experienced carb icing in my RV. I noticed a slight roughness in the engine (O 360) and after a minute monitoring it, to make sure it was not my imagination, I pulled on carb heat and it immediately cleared up. I don't us carb heat during decent or landing since it has not been an issue and have not changed my procedures since.
 
Operating my -4 mainly off of a grass strip, I've put myself in the habit of applying carb heat for taxiing, minimizing the chance of carb ice and with the ram air gate closed, blocking grass and other debris from entering the intake and filter. I also make it a habit to use it upon throttle reduction for downwind pattern entry. It's there, what not?
 
rockwoodrv9 said:
I just started taking flying lessons so I can be ready when I finish my plane this summer. I am flying in a Warrior and the instructor has me put on carb heat every time I descend. I don't remember using it that much when I flew years ago. It is making me consider adding FI so I don't have that to think about.

I have a carb temp gauge with my G3X system and have the carb ice detector Dave mentioned I may install too. Considering I live in the mountains where I may have more times favorable to carb ice, maybe the FI is the answer.
Click to expand...

I currently own and fly a Warrior II, which uses an O-320-D3G. The POH specifies to use carb heat only when there is actual indication of carb ice. I have had 2 or 3 instances of suspected carb ice so far (slightly rough running engine or drop in rpm), all at low cruise power on moderately cold and humid days. So far, application of carb heat has quickly remedied the condition in less than a minute or so. The Lycoming O-320 manual calls for carb heat only on indication of carb ice, with special vigilance required on "damp, cloudy, foggy, or hazy days, regardless of the outside air temperature."
 
I use a manifold pressure gauge in my fixed-pitch C-170 as a carb ice detector. If I notice as little as 1/4 inch MP drop without changing throttle setting or altitude, it's probably time for carb heat. I see it most often while cruising relatively close to an overcast.
 
+2 on that. I've read carb ice can form up to 60deg F. I've had it in clear air in a 172N. My instructor drilled it into me to use it on every approach. On unpaved surfaces have it off to avoid sucking grass or other debris into the engine.
 
1001001 said:
I currently own and fly a Warrior II, which uses an O-320-D3G. The POH specifies to use carb heat only when there is actual indication of carb ice. I have had 2 or 3 instances of suspected carb ice so far (slightly rough running engine or drop in rpm), all at low cruise power on moderately cold and humid days. So far, application of carb heat has quickly remedied the condition in less than a minute or so. The Lycoming O-320 manual calls for carb heat only on indication of carb ice, with special vigilance required on "damp, cloudy, foggy, or hazy days, regardless of the outside air temperature."
Click to expand...

Thanks for this info. I think the instructor is trying to make sure I understand the risk of carb ice. It was below freezing each of the days of my lessons and overcast. We never noticed a rough engine, but every time I cut power or dropped down, he made sure I had the heat on.

I am glad to hear it isn't as big of an issue with the RV's. That doesn't mean be careless in using heat so it is probably a good habit to get into anyway.
 
The reason to use carb heat all the time on landing training aircraft is that many of them routinely descend with the power at idle. And with power at idle the signs of carb icing will be few or none - until you need to add power and find that the engine has quit and is just windmilling!
 
Here in Qld Australia we can get carbie ice at any time of year, but it is more prevalant in Summer when we get temps at ground level in the 30 to 35deg C range but very high humidity.
I have never had it in the RV4, but C150s were very prone to it. It is usually not common in winter with 15 deg C or thereabouts.
 
The collective "we" of aviation has known about the problem of carb ice for a very long time. We have expended lots of effort trying to teach student pilots how to avoid it. We still watch airplanes go down every year because of it.

Why not just build the engine such that it can't get carb ice in the first place?

(Pulls pin, lobs grenade, ducks)
 
Category: Never Again

Charles in SC said:
If you want some good first hand carb ice time all you need to do is get some IFR flying in the Continental powered C-182s. They are the worst I have come across.
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Very much agree! (C182) There I was 3000' IMC, got dark, losing altitude, trim, retrim, hmmm, retrim again hmmmm, throttle, hmmmm , up (incrementally) to full throttle, hmmmm CARB ICE:eek:. Wow, what a wonderful feeling when the power comes back! And retrimming too. Ahhhh, back to normal. Oops, lost DME, VOR, radio. Used way too many of my pilot skills and back-up options that flight, and not enough judgement. I found there is no fear like flying in the abyss, no electronic navigation and no radio contact and the minutes are adding up flying by compass to (hopefully) a friendly airport 20 min away. Oh, when radio came back, the hand mike went TU too (had a backup). Yes, for real. . . . another chapter in the story . . for later.

Lesson learned.
 
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