FZFG? Freezing Fog-a Beautiful Reason to Leave the Plane in the Hangar
Dear SkyMom:
We live in Poplar Grove and recently experienced several days of “freezing fog” which coated the trees in the area and continued to accumulate over the days, because the temps were in the 20’s and it wouldn’t melt. My beautiful wife noted how pretty it was. I said if it was similar to the icing in the clouds that an airplane experiences she wouldn’t be so impressed, but rather scared. Just 20 miles north, into Wisconsin, there was no evidence of this in the trees, just like unpredictable icing.
Can you enlighten us on this phenomenon?
Thanks,
Your Fascinated, Freezing Friends
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Well hello, my favorite fabulous freezing friends!
Right you are, freezing fog is a condition caused by supercooled water droplets. What does that mean? The surface tension of water prevents it from freezing unless it is in contact with a surface or has formed around condensation nuclei from a temperature of 0 degrees Celsius (32F) down to around -40C, where it will freeze, regardless. Should these supercooled water droplets find themselves in contact with a surface at a temp below zero, they’ll form a lovely coat of ice. This explains how you get such gorgeous frosted formations on the trees, the hangars, and any other convenient collecting surface unlucky enough to be skulking around below freezing, which surely does include the surface of your airplane. In flight, freezing fog stops being pretty awfully fast. Freezing fog can cause a rapid buildup of ice on the surface of an aircraft moving through it as supercooled droplet after supercooled droplet meets the chilled skin of the plane. Bad deal. If an aircraft isn’t certified for flight into known icing, don’t even think about it. Even if you ARE certified for it, think again. The rate of accumulation is impressive, occasionally akin to that of freezing rain. This is just not a place you want to be. It makes a much better day for photography than for flying.
Freeze frame: Your wife is right; it’s very beautiful. And you are right; from inside the cockpit, it’s really, really not. Isn’t it fun to find one more thing you two can agree on? Glad to hear that you’re enjoying the weather from the ground when conditions won’t allow you to take to the air,
Mom
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