FAA Private Pilot Helicopter (PRH)WeatherMedium
During a preflight weather briefing, a pilot notes a forecast for 'moderate rime icing' at the planned cruising altitude. Which characteristic best describes moderate rime icing?
- ARough, milky ice that forms slowly and is easy to remove.
- BLarge, clear ice formation that is difficult to remove.
- CBrittle, opaque, milky white ice that forms rapidly.
- DThin, smooth layer of ice that causes minimal performance degradation.
Show answer & explanationAnswer & explanation
Correct answer: C. Brittle, opaque, milky white ice that forms rapidly.
Rime ice forms when small supercooled water droplets freeze on impact with the aircraft. It's characterized by its opaque, milky white appearance, its brittle nature, and its tendency to form rapidly, often in conditions of low water content and temperatures between -10°C and -20°C.
Why the other options are wrong
- A. This description is partially incorrect; rime ice forms rapidly and is not necessarily easy to remove, despite being milky.
- B. This describes clear ice, which forms from larger supercooled water droplets.
- D. This describes a very light or trace amount of icing, not moderate rime icing, and rime ice is typically rough, not smooth.
Rime Ice
Rime ice is an opaque, white, and granular ice formation that occurs when small supercooled water droplets freeze instantly upon impact with an aircraft. It typically forms in stratiform clouds and at colder temperatures.
- Opaque, milky white appearance.
- Brittle and rough texture.
- Forms rapidly, often at colder temperatures (-10°C to -20°C).
Memory trick: Clear Rime Mixed: Icy Types You'll Find.