FAA Commercial Pilot Airplane (CAX)WeatherMedium
A pilot is planning a flight through an area with reported moderate rime icing. What are the characteristics of moderate rime icing?
- AA mix of both rime and clear ice, forming an irregular and very rough surface.
- BSmall ice particles that freeze on impact, typically forming a milky, opaque, and brittle layer.
- CLarge, clear ice particles that spread out and freeze on impact, forming a hard, smooth, and transparent layer.
- DIce that forms on aircraft surfaces at temperatures well below freezing, typically below -15°C, and is easy to remove.
Show answer & explanationAnswer & explanation
Correct answer: B. Small ice particles that freeze on impact, typically forming a milky, opaque, and brittle layer.
Rime ice forms when small supercooled water droplets strike an aircraft and freeze rapidly on impact. This rapid freezing traps air, giving it a milky, opaque, and brittle appearance. Moderate rime icing implies that the rate of accumulation is such that even short encounters become hazardous, and de-icing/anti-icing equipment may be required.
Why the other options are wrong
- A. This describes mixed ice, which has characteristics of both rime and clear ice.
- C. This describes clear ice, which forms from larger supercooled droplets that spread before freezing.
- D. Ice can form at various temperatures; the description of easy removal is not characteristic of moderate icing, which is a significant hazard.
Rime Ice
An opaque, milky, and brittle ice formation that results from the rapid freezing of small supercooled water droplets on impact with an aircraft surface.
- Forms at colder temperatures than clear ice, typically -10°C to -20°C.
- Less dense than clear ice, but can significantly alter airfoil shape.
- Often associated with stratiform clouds.
Memory trick: Rime is milky and brittle, clear is glass, mixed is both, a dangerous mass.