FAA Airline Transport Pilot (ATM)Meteorology and Weather ServicesMedium
An aircraft flying through a layer of stratiform clouds at -12°C composed of small supercooled water droplets accumulates a rough, milky-white, opaque ice deposit on the leading edges of the wings. This description is characteristic of which type of icing?
- ARime ice
- BFrost
- CClear ice
- DMixed ice
Show answer & explanationAnswer & explanation
Correct answer: A. Rime ice
Rime ice forms when small supercooled droplets freeze rapidly on impact, trapping air and producing a rough, opaque, milky-white appearance, typically in stratiform clouds with lower liquid water content. Clear ice forms from larger droplets that spread before freezing, producing a smooth, transparent, glassy layer.
Why the other options are wrong
- B. Frost forms on a cold surface exposed to clear air with visible moisture, not inside a cloud.
- C. Clear ice is smooth and transparent, forming from large supercooled droplets, not small ones.
- D. Mixed ice is a rough, irregular combination of both rime and clear ice characteristics.
Rime Ice
A rough, milky-white, opaque form of structural icing that forms when small supercooled water droplets freeze instantly on contact with an aircraft surface.
- Common in stratiform clouds with low liquid water content
- Freezes quickly, trapping air bubbles giving milky appearance
- Less aerodynamically disruptive than clear ice but still hazardous
Memory trick: Rime = 'rough & rime-y', freezes fast like flash-frozen ice