FAA Commercial Pilot Airplane (CAX)WeatherHard
A pilot is flying through an area forecast to have a high probability of supercooled large droplets (SLD). What type of icing is primarily associated with SLD, and what are its characteristics?
- AFrost, characterized by a white, crystalline deposit that forms on cold surfaces.
- BClear ice, characterized by a hard, smooth, and transparent layer that can be very difficult to detect and remove.
- CMixed ice, characterized by an irregular and very rough surface, combining properties of rime and clear ice.
- DRime ice, characterized by a milky, opaque, and brittle layer.
Show answer & explanationAnswer & explanation
Correct answer: B. Clear ice, characterized by a hard, smooth, and transparent layer that can be very difficult to detect and remove.
Supercooled large droplets (SLD), including freezing rain and freezing drizzle, are the primary cause of clear ice. These large droplets spread out significantly upon impact before freezing, creating a very cohesive, hard, smooth, and transparent layer of ice. This type of ice is particularly dangerous because it can accumulate rapidly, distort airfoil shape severely, and is often difficult to detect visually due to its transparency.
Why the other options are wrong
- A. Frost is formed by sublimation, not by supercooled liquid droplets impacting the aircraft.
- C. Mixed ice is a combination, but SLD are specifically linked to the clear ice component.
- D. Rime ice forms from small supercooled droplets and is opaque/milky.
Supercooled Large Droplets (SLD)
Water droplets larger than typical cloud droplets that remain in liquid form at temperatures below 0°C.
- Includes freezing rain and freezing drizzle.
- Causes severe clear icing due to their ability to spread before freezing.
- Extremely hazardous to aircraft, as de-icing systems may be overwhelmed.
Memory trick: SLD's a clear threat, spreading wide, hard to get.