FAA Sport Pilot Airplane (SPA)WeatherHard
While climbing through a cumuliform cloud layer with large supercooled water droplets, a pilot notices ice forming on the wing's leading edge that is clear, hard, and very difficult to remove. What type of structural icing is this?
- AFrost
- BMixed ice
- CClear ice
- DRime ice
Show answer & explanationAnswer & explanation
Correct answer: C. Clear ice
Clear (glaze) ice forms when large supercooled water droplets, typical in cumuliform clouds, spread out and freeze slowly, producing a smooth, hard, transparent ice layer that adheres strongly and is difficult to remove.
Why the other options are wrong
- A. Frost forms on the ground from sublimation of water vapor, not from flight through clouds.
- B. Mixed ice is a combination of rime and clear ice with an irregular appearance, not purely clear and hard.
- D. Rime ice is rough, milky white, and forms from small droplets freezing quickly, typically in stratiform clouds.
Structural Icing Types
Aircraft structural icing forms when supercooled water droplets freeze on contact with the airframe; the type depends on droplet size and cloud type.
- Clear ice: large droplets, cumuliform clouds, smooth and hard
- Rime ice: small droplets, stratiform clouds, rough and milky
- Mixed ice: combination of clear and rime characteristics
Memory trick: 'Clear ice: glassy and stubborn, like a frozen lake on the wing'