Carburetor Icing - Yes, In the Summer!

[Hedley]

Yes, in the summer. Don't let it happen to you. I have seen dewpoints of +20C recently. There's lots of moisture in the air, and if the dewpoint spread is small ...

This is especially important to you, if you have a TCM (Continental) engine such as the O-200 in the C150 or O-470 in the C182 which hang the carburetor out in the open. Franklin engines are known for this, too.

With the Lycomings, carb ice is much less of a problem - as long as the oil is up to temperature, because the carb is bolted to the crankcase. However, during the first flight of the day your oil is cold.

Idling out, with the throttle almost closed, is a great way to build carb ice. I just saw a C150 lose engine power on takeoff, I suspect due to carb icing. Fortunately he had enough runway to land and stop without any damage.

If you suspect that your aircraft and conditions are prone to the development of carb ice, please burn the ice out of your carburetor before takeoff.

You do this by running the engine up to 1700 RPM, applying full carb heat, leaning the mixture for max RPM, and waiting for 30 seconds. Then push the carb heat and mixture and throttle all the way into the dashboard, release the brakes and immediately commence your takeoff roll.

Some aircraft even recommend taking off with carb heat!

As always, do what the POH says ... and I hope I didn't bruise anyone's delicate ego by stopping them from crashing.

[mag check]

The worst aircraft I have flown for carb ice is the 182. I remember some flights in the summer, or down in florida in the winter with the 182 where it was constantly occuring. I fnally made a joke about it, as it would shudder along clearing the ice; get the margarita blender ready, here comes another batch of ice.

The small continentals can be very bad though, and if you are unaware, you won't be able to clear it. This can occur when the power is pulled back for a long time, in a descent, and the ice builds, but the exhaust muff is also cooling down. If you wait too long, there won't be enough heat to melt the ice, and you can't put the power on to make more heat. Not a good situation.

[Hedley]

the power is pulled back for a long time, in a descent

Right - any time the throttle is closed with a carburetor, you are at a risk of building ice.

So any time the power is reduced from cruise power, you want full carb heat on.

And remember, any time the carb heat is on, re-lean the mixture for max RPM - yes, in a descent. This will make more heat in the exhaust.

Lest you think that carburetor icing won't bite you ... here's a pop quiz.

How did Cairns airfield at Ft Rucker get it's name?

Also: ever heard of Grant McConachie, CEO of Canadian Pacific Airlines?

[Big Pistons Forever]

How the engine is installed has a big impact on susceptability to icing. There is a myth that Lycoming engiens are not prone to icing. I too, used to think this untill I flew the Islander (Lycoming O 540), one of the worst airplanes for carb ice I have ever flown. The Piper Apache (Lycoming O320) is another bad one.

[C-GPFG]

Isn't winter air generally too dry for carb ice? In 2200hrs of carb engine flying I can only remember getting carb ice in late summer/early fall.

[YOWza]

O-470 in the C182

The worst aircraft I have flown for carb ice is the 182

+1 for each of you. That thing's more effective at producing ice than a Frigidaire with Automatic Icemaker.

[niss]

First time I experienced CI was last week flying back to Springwater from YKF. I was at about 5000' and vis wasn't fantastic due to haze. I was humming along and then noticed a slight change in the noise from the engine, checked my tach and saw the RPM come down ever so slowly. First thought was hit the Carb Heat then she ran like shit, smoothed out a bit. Carb heat cold and the rest of the flight was uneventful.

It was kind of nerve wracking being the first time I had actually experienced it but my first thought was go for carb heat so I guess that was pretty good.

I also remembered my instructors driving it into me: If you have carb ice, and you turn on the carb heat, you want it to run like shit, do not shut it off until it smooths out!

Thanks for the reminder Hedley!

[LousyFisherman]

It was kind of nerve wracking being the first time I had actually experienced it but my first thought was go for carb heat so I guess that was pretty good.

My worry was if it isn't carb icing what do I do? I was extremely happy when she started running rough after pulling the carb heat. But very, very scary the first time!

LF

[niss]

It was kind of nerve wracking being the first time I had actually experienced it but my first thought was go for carb heat so I guess that was pretty good.

My worry was if it isn't carb icing what do I do? I was extremely happy when she started running rough after pulling the carb heat. But very, very scary the first time!

LF

Well that's why when I was reaching for the CH I was keeping my eyes out for possible landing sites. Not easy if you are up in the bush but I was (semi)comfortable over farm country.

[PostmasterGeneral]

Another vote for the 182 here. I remember a few summers back I was Vfr ott down in Seattle even at 12,500 I was getting carb ice that needed to be cleared about every 4 minutes. I ended up just leaving th carb heat knob pulled part way out for the whole flight.

It was nice, the aircraft had a carb temp gauge, so it was easy to keep it above freezing using that. And yes, even with a 15 degree OAT, the carb temp was right around -2. Nice to be able to see that in real time.

[iflyforpie]

O-300s are ice magnets as well...

[mag check]

I ended up just leaving th carb heat knob pulled part way out for the whole flight.

That is a very dangerous practice. With partial carb heat, ice can form so fast that the engine can quit. Much safer to periodicly apply full heat, or add full heat, and lean properly and fly like that if the icing is really bad.

[Hedley]

mag check: normally, that's correct but note that PMG said:

the aircraft had a carb temp gauge

which allows the pilot to safely use partial carb heat to set the temperature in the carburetor above freezing to avoid the formation of ice.

Remember: every time the carb heat goes on, re-lean the (now rich) mixture!

[Youngback]

I used to get severe carb ice in my '86 Ford Escort Wagon. Bad enough that the fuel consumption would sky rocket (50L per 100km) and I would have the pedal on the floor and only doing 50km/h. Only solution was to pull over and wait 10 minutes for the engine heat to melt everything. I seriously considered putting a carb heat valve on my car.

Lesson: Don't buy an '86 Ford Escort Wagon. It is seriously unpopular with women when you pull over to let the carb warm up. Then there's the looks. Oh, and the only microchip on the car, located on the rotor, breaks below -50*C.

[HavaJava]

Just a note for pilots flying low horsepower engines...

You can still get carb ice even with full carb heat selected. I was flying a Fleet Canuck (85 h/p continental) with a OAT of 2 degrees and dewpoint of 0 degrees. I had carb heat on for a good part of the flight and selected it to full on about 2 minutes before starting descent for landing. I selected idle turning base (to practice a simulated engine failure) and cleared the engine at 500 AGL (I noticed the engine was a bit rough, but not too bad at this point). As I flared the prop stopped. The engine just couldn't produce enough heat at idle to melt the building carb ice.

From this point on when the weather was conducive to carb ice, I always made sure to do a power-on approach. This was a bit difficult in the Fleet because it doesn't have any flaps so it involved a full slip all the way down the approach.

[Hedley]

severe carb ice in my '86 Ford Escort Wagon

The original 2-barrel carburetor induction system in my 1970 350 V-8 Camaro had a carb heat system with a vacuum-controlled valve and a hose running up from a muff around one exhaust manifold.

All that stuff went in the trash when I put the 1 5/8 inch headers on it and a cast-iron 4-bbl intake manifold with a Rochester Quadrajet with those tiny primaries and huge secondaries, later replaced with an Edelbrock Performer aluminum intake manifold and a 600 cfm "square" Holley - what an awesome induction system, compared to the original.

I experimented with various exhaust systems after the headers, but what I preferred best was actually a very quiet exhaust, so that you could clearly hear the air being sucked into the carburetor. Marvellous sound!

[Youngback]

The original 2-barrel carburetor induction system in my 1970 350 V-8 Camaro had a carb heat system with a vacuum-controlled valve and a hose running up from a muff around one exhaust manifold.

All that stuff went in the trash when I put the 1 5/8 inch headers on it and a cast-iron 4-bbl intake manifold with a Rochester Quadrajet with those tiny primaries and huge secondaries, later replaced with an Edelbrock Performer aluminum intake manifold and a 600 cfm "square" Holley - what an awesome induction system, compared to the original.

Well, my vacuum controlled valve was rusted shut and the thin dryer hose connecting it to the carburetor was full of holes (among many other parts of the car). You had a Camaro. I wasn't dropping another dime on my car. I felt guilty and ripped off putting anything other than 87 octane in the tank. Then the custom molded plastic grille that Ford spent a few thousand Zimbabwe dollars on came off in a windstorm in 2007. Yes, I was sad to part with the Blue Dragon.

Sorry to 'jack the thread. Please continue.

[bushhopper]

normally below -5C there is no carb icing problems.

Carb icing is most prone to happen between -5C to 30C. So I am not sure why you are surprised that you got carb icing. Thats why GS is very important.

[fish4life]

0-200 on an old style 150 was my worst carb icing experience, wasn't making proper power on take off seemed to take a lot of runway but got off then it just wouldn't climb but I was too new to realize what had happened at the time until i did a circuit at 300' (because i could barely climb anymore) and then when I pulled the carb heat in the downwind it ran really rought and i figured it out and from there it was clear sailing

[zed]

Anyone have experience with engines that are running off of automotive fuel. I know the numbers provided say that it should be more likely for carburetor icing to occur, but am just looking to see what people have experienced with real engines in real life.