What type of icing forms on aircraft surfaces when supercooled droplets freeze on impact and is transparent and hard to spot?

• A. Rime ice
• B. Freezing rain
• C. Clear ice
• D. Mixed ice

Answer: (C)

Clear ice forms when larger supercooled droplets strike the aircraft surface and freeze slowly, flowing together into a smooth, glassy coating. Because this ice is transparent, it blends with the underlying surface and is hard to spot, especially from the cockpit or in low-contrast lighting. This smooth, glossy layer alters the airfoil shape and increases weight without obvious visual cues, making it particularly hazardous. Rime ice, by contrast, comes from smaller droplets that freeze quickly, trapping air and leaving a rough, opaque layer that’s easier to see. Mixed ice contains both textures, and freezing rain describes a glaze of clear ice that can form when liquid rain freezes on contact. The key idea is that transparent, hard-to-detect ice is clear ice.