Which are the three types of structural icing?

The three types of structural icing are categorized as rime, clear, and mixed, making this answer the most accurate.

Rime ice forms when supercooled water droplets freeze rapidly upon contact with an aircraft's surface, resulting in a white, opaque ice texture. This type of icing is generally less hazardous and forms at lower temperatures.

Clear ice, on the other hand, occurs when large supercooled droplets freeze more slowly, leading to a transparent and heavier ice accumulation. This type poses more significant hazards to flight, as it is denser and more difficult to remove.

Mixed icing is a combination of both rime and clear ice, occurring when both large and small supercooled droplets are present in the same environment. This type of icing can create unpredictable and dangerous conditions for aircraft, as it exhibits the characteristics of both rime and clear icing.

Understanding these types of icing is critical for pilots and air traffic controllers, as it informs them about potential hazards and helps guide operational decisions during flight. The other options do not accurately represent the recognized categories of structural icing as defined in aviation literature.