FAA Private Pilot Airplane (PAR)Weather Theory and ServicesMedium
While flying through a layer of stratiform clouds at an outside air temperature of -8°C, a pilot notices ice forming on the wing leading edge that appears rough, opaque, and milky white rather than smooth and transparent. This type of icing is known as:
- AClear ice
- BMixed ice
- CRime ice
- DFrost
Show answer & explanationAnswer & explanation
Correct answer: C. Rime ice
Rime ice forms when small supercooled water droplets, typical of stratiform clouds, freeze rapidly on contact, trapping air and creating a rough, milky, opaque appearance. Clear ice forms from larger droplets in cumuliform clouds and is smooth and transparent, while frost forms on a parked aircraft, not in flight.
Why the other options are wrong
- A. Clear ice is smooth and transparent, typically from large supercooled droplets in cumuliform clouds.
- B. Mixed ice combines features of both rime and clear ice, not the pure rough, opaque description given.
- D. Frost forms on a stationary aircraft through sublimation, not during flight through clouds.
Rime Ice
Rime ice is a rough, opaque, milky-white ice that forms when small supercooled water droplets freeze rapidly on contact, most commonly in stratiform clouds.
- Forms from small droplets that freeze quickly, trapping air
- Rough, brittle, and opaque in appearance
- Common in stratiform clouds with light-to-moderate icing
Memory trick: Rime is rough and rice-like white; Clear is smooth and see-through