FAA Private Pilot Airplane (PAR)Weather Theory and ServicesHard
A pilot flying through cumuliform clouds with large supercooled water droplets encounters ice accumulating in a smooth, transparent layer on the wing's leading edge that is difficult to remove. What type of structural icing is this most likely to be?
- AClear ice
- BMixed ice with a rough, milky appearance
- CFrost
- DRime ice
Show answer & explanationAnswer & explanation
Correct answer: A. Clear ice
Clear ice forms when large supercooled water droplets, typically found in cumuliform clouds or freezing rain, strike the airframe and freeze slowly, spreading out before fully freezing to form a smooth, transparent, and dense layer that adheres strongly and is hard to remove.
Why the other options are wrong
- B. Mixed ice is a combination showing a rough, mixed appearance, not the smooth clear description given.
- C. Frost forms on a parked aircraft from sublimation of water vapor, not in flight from droplet impact.
- D. Rime ice forms from small supercooled droplets in stratiform clouds, producing a rough, milky, opaque, brittle deposit—the opposite of what's described.
Clear Ice (Structural Icing)
Clear ice is a smooth, transparent, and dense form of structural icing that forms when large supercooled water droplets strike the aircraft and freeze slowly, commonly found in cumuliform clouds or freezing rain.
- Formed by large supercooled droplets found in cumuliform clouds
- Freezes slowly, spreading before solidifying, creating a smooth glassy layer
- Difficult to remove and can significantly alter airfoil shape
- Contrast with rime ice, which is rough, opaque, and forms from small droplets in stratiform clouds
Memory trick: Clear ice = clear & slick, Rime ice = rough & white