Dave, I've had the same concerns.? I fly off of a private grass strip with lots of grass, dirt and dust around.? I do push the carb heat off as soon as I touch down on landing, and I don't taxi around with it turned on.? I do, however, do a good carb heat check on run-up.? I've only had two known encounters with carb ice, and they both happened in high humidity conditions when I was taxiing out for take-off.? In one case the engine almost quit while taxiing.? Carb heat cleared it up.? In the other case, all seemed normal, but when I ran the engine up to 1700 RPM and then pulled on carb heat, the engine coughed and spit a few times, and then smoothed out, and when I pushed the carb heat back in, the RPM went up to 1850 RPM instead of the 1700 that I started with.? Evidently the carb had loaded up with ice during taxi, and when I did the run up, it melted the ice out resulting in higher RPM when the ice was gone and the heat was turned back off. ? My standard procedure now is to watch how high?the RPM's come back up to when I turn the carb heat back off.? If the RPMs come above 1700 RPM, that's an indication to me that I may have had some carb ice, and I'll do a second carb heat application just to make sure it's all gone.? I also make sure I?leave the carb heat on long enough during a run-up to melt the ice, not just long enough to see the RPM drop.
One factor in all this is that on our engines, the carbs are basically hanging in mid air on that intake spider.? They don't really get any transfer of heat from the crankcase or the oil sump like the Lycos do.? So the only heat the carb sees is?what it gets from the application of carb heat. Best Regards,? Wayne DelRossi Alon N5618F -----Original Message----- From: [email protected] To: [email protected] Sent: Wed, 25 Feb 2009 5:11 pm Subject: [ercoupe-tech] Carb Heat when on the ground Maybe it is unfounded but I have a problem pulling on the carb heat when I'm on the ground. I use it in the pattern but as soon as I touch down the first thing I do is turn off the carb heat. The engine is pulling unfiltered air into the carb when the carb heat is on. Here in the midwest flying off of grass strips in the dry hot summer there is a lot of dust moving around. Compound that with spring plowing and fall harvest and there is a fair amount of dust that can be pulled into the carb. Dave Crispin N2356H
