Icing is insidious.
Even a trace amount will disrupt the flow of air over your wing.
You should be afraid of it if you don’t have de-icing capability. Even with de-icing capability, the airlines will take precautions by increasing the landing speed to account for poor airflow.
So what are the four types of ice you will run into as a pilot?
Clear ice: forms when large drops hit the aircraft and freeze slowly. It looks just like it sounds: clear.
Rime ice: forms when small drops hit the aircraft and freeze rapidly. It usually looks like super thick frost. Milky white.
Here is a picture of the two:
Mixed ice: a mixture of clear and rime ice.
Frost: ice crystal deposits formed by sublimation when the departure and dew point are below freezing.
You will encounter frost on chilly mornings if your airplane isn’t hangared. You MUST remove ALL frost before you takeoff.
You essentially become a test pilot when you take off with frost on the wing. The airspeeds in the aircraft owner’s manual go out the door. You have no idea what the stall and landing speeds are now.
With frost you either need to wait for it to melt it off, manually remove it, or pay for de-icing.
Why do you need to know the four types?
Well, it may be a question on a check ride, but more importantly you need to be able to give ATC an accurate PIREP.
I admit I didn’t know the difference between the two until recently. Shame on me! I can’t believe I am admitting this.
ATC has asked me many times for icing reports. I always say: “mixed,” but that’s a lie. Sometimes I see only in Rime ice.
For further exploration of the topic check out these resources from NASA. In case you didn’t know, NASA is the leader in aircraft ice research and testing.
Books on Severe Weather and Icing:
Aircraft Icing: A Pilot’s Guide by Terry Lankford
Severe Weather Flying by Dennis Newton
Weather Flying by Robert Buck
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