FAA Instrument Flight Instructor (FII)WeatherEasy
A pilot flying in IMC encounters clouds containing large supercooled water droplets at an OAT of -8°C. Which type of structural icing is most likely to form on the airframe?
- ARime ice
- BFrost
- CClear ice
- DHoarfrost
Show answer & explanationAnswer & explanation
Correct answer: C. Clear ice
Large supercooled droplets spread out over the surface before freezing completely, producing a smooth, dense, transparent layer known as clear ice. Rime ice forms from small droplets that freeze instantly, trapping air and creating a rough, milky appearance, which is more typical of stratiform clouds with smaller droplet sizes.
Why the other options are wrong
- A. Rime ice forms from small droplets that freeze quickly, not large ones.
- B. Frost forms on the ground or parked aircraft, not from in-flight droplet impingement.
- D. Hoarfrost is a ground-based deposition process, not an in-flight icing type.
Clear Ice Formation
Clear ice forms when large supercooled water droplets strike an airframe and spread before freezing, creating a smooth, dense, and hard-to-remove ice layer.
- Associated with large droplet size, typical of cumuliform clouds
- Occurs commonly between 0°C and -10°C
- Most hazardous type due to weight and difficulty shedding
Memory trick: Clear ice is 'Clean and Smooth' from big drops that spread before freezing.