Carb Ice - It Can Happen Quickly

Getting a lot of carb ice lately here in Central Illinois, conditions have been very good for formation. It happened about as quick as I have ever had it a few days ago - climb out at about 1000 feet AGL - just minutes after take off. I happened to have a GoPro pointed at the exhaust. I wanted to share this video with everyone to keep carb ice in mind. I would appreciate any comments or tips from others with "Ice Machines" like mine, a 1954 PA18 L21B, Supercub with a Lycoming 0-320 A2B.

http://youtu.be/v0JbPvVNCWI

I have an O-290D powered J5A which I used to fly in Seattle, Washington, where there is plenty of moisture and carb ice. On runup after mag drop and carb heat check, while finishing the rest of the items on my predeparture checklist and taxiiing into position for takeoff, I left my carb heat on full. Then just before takeoff roll started, I would shut off carb heat. It seemed to help - I never had carb ice on takeoff. I had it once at cruise at 2600 RPM. I also would get it at idle just after start while taxiing to the runup pad. Lycomings should be less susceptible to carb ice due to carb mount directly to oil sump. But the oil and sump need to be hot in order for that to work. Is your engine running too cold? My oil temp used to barely get above 160 degrees on cold winter days.
-Joel Marketello

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Originally Posted by jam0552@msn.com

I have an O-290D powered J5A which I used to fly in Seattle, Washington, where there is plenty of moisture and carb ice. On runup after mag drop and carb heat check, while finishing the rest of the items on my predeparture checklist and taxiiing into position for takeoff, I left my carb heat on full. Then just before takeoff roll started, I would shut off carb heat. It seemed to help - I never had carb ice on takeoff. I had it once at cruise at 2600 RPM. I also would get it at idle just after start while taxiing to the runup pad. Lycomings should be less susceptible to carb ice due to carb mount directly to oil sump. But the oil and sump need to be hot in order for that to work. Is your engine running too cold? My oil temp used to barely get above 160 degrees on cold winter days.
-Joel Marketello

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Yes, it is a cold engine - on that flight with a 60 degree temp, my engine temp barely got to 180/190. Below 40 I have an Oil cooler cover that snaps in place

I had an interesting experience in my Luscombe 8A / A-65 that after thinking about it, I attribute to carb ice. Flight was from Ft worth area to Auburn, AL around Sept or Oct some years ago. WX was bkn & vis unrestricted with a strong SE flow from the Gulf of Mexico carrying lots of moisture. I was using 3,500 to get out of the turbulence from the winds. Surface temps were about 70F plus. I had about an hour plus left in my right tank, needed gas and tried three times to get into a field in either LA or MS, but ran out of rudder on roll out each time due to X-wind. A crowd was gathering. If a crowd gathers while your'e doing something aviation related, you should do something else. I diverted to a nearby unattended field and tied down. Needing gas, I started walking and someone gave me a lift to a gas station. I bought 10 gal of unleaded regular (no ethanol) and the guy drove me back to the plane. The engine data plate did say "min 73 octane." I had no STC, but I hated to be stranded. I put 10 gal of reg autogas in the left tank, departed on the right tank and set sail for AL.

I switched to the left tank at 3,500 and it ran fine. but it slowly lost RPM after 15 minutes. I switched to the right tank for a minute or two and it returned to normal. So back to the left. Same thing. I flew this way, switching tanks, for over an hour until I found another gas stop.

After pondering this for some weeks, I reasoned that the auto gas was vaporizing much more than the the 100LL and cooling the carb enough to ice it up in the warm, damp air. The 100LL with less vaporizing, allowed it to self de-ice. Until then I thought that knew Continentals and ice. I got all my PPL training in J-3s, owned a Champ and flew a lot of injected TCM's. My last plane was an injected Beech. But I had zero experience with auto gas in airplanes. There is a reason that an STC is required. Ethenol would make it far worse.

Bob

Nice Camera set up!!!! That's slick!!! I want one!!!

Quote:

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Originally Posted by jam0552@msn.com

I have an O-290D powered J5A which I used to fly in Seattle, Washington, where there is plenty of moisture and carb ice. On runup after mag drop and carb heat check, while finishing the rest of the items on my predeparture checklist and taxiiing into position for takeoff, I left my carb heat on full. Then just before takeoff roll started, I would shut off carb heat. It seemed to help - I never had carb ice on takeoff.

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That's the way I learned to do it, too, way back in the dawn o' time. I've been flying various Fly Babies in the Seattle area for 25 years, and have only two instances of carb ice. The first one was in the foothills of the Cascades with visible moisture. Engine started running rough, I applied carb heat, and turned downhill.

The second one *probably* was carb ice. Last winter, I was in the pattern for landing. I turn the carb heat on just before turning base, then follow with a partial power reduction, with power off full on final. This time, the throttle stuck when I tried to do the full power reduction. I was a bit nonplused, but the throttle freed itself a few seconds later. I'm thinking that ice may have briefly jammed the carburetor butterfly.

Ron Wanttaja