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I live in the Florida Keys. I've been in the military and worked inside the Beltway. I've had 22 technical books and two novels published. I fly, boat, dive, shoot, and swim pretty damn well.

Thursday, July 24, 2008

Carb Ice: Even in Florida, Even in Summer


I learned to fly in Miami, I keep my plane in the Florida Keys, and I've only flown outside the state a few times. The flight school in Miami never said a word about carb icing or carb heat. (They didn't say much about leaning the engine either!)

Then, I went for tailwheel training and spin training. I was fortunate to link up with an instructor who first reamed me a good one and then really taught me about carb icing... even (or ESPECIALLY) in Florida. I fly over water 90% of the time. (Why don't I have an amphib?... I ask myself that a lot.. and then I remember .. 4X the maintenance.! ) The humidity is always high.

THIS ARTICLE discusses a tragic accident in Florida in the summer due to carb ice. It's written by a good author and is recommended reading

Carb icing can and will get you in the summer in Florida with any normally aspirated engine. The chart in the article is a little small.. I am displaying a bigger chart here that, along with a more technical discussion, is at THIS FAA Website. Note the slope of that Relative Humidity line. It's the humidity that drives the equation. If my tach drops below 2200 RPM, I pull the carb heat. That's the rule in my cockpit.

ADDED: I just checked and the report from the AWOS at 9:30 AM on the ground at 10' MSL says the temp is 28c and dew point 23c. So, according the chart I'm in the clear... just BARELY.. now, how about at 1000' MSL? ooops.

ADDED: See also this chart that includes more relative humidity lines.

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