Icing occurs when:

Icing occurs when:

• A. When air is warm and dry
• B. At high altitude with dry air
• C. When temperature below freezing and supercooled droplets are present
• D. In dry, clear conditions

Answer: (C)

Icing forms when liquid water droplets in the air are supercooled and strike a surface, freezing on contact. The key idea is that there must be liquid moisture in subfreezing air that can freeze when it touches the aircraft. Below-freezing temperatures alone don’t cause ice; there has to be droplets that are still liquid because they’re supercooled. When those droplets encounter a surface like a wing or propeller, they freeze rapidly and ice builds up. That’s why the best description is: there’s a temperature below freezing and supercooled droplets are present in the air. In such conditions, visible moisture—clouds, fog, rain, or drizzle—provides the liquid droplets that can freeze on impact. The other scenarios lack the necessary liquid moisture: warm, dry air has little to no moisture to freeze; high altitude with dry air suggests a lack of enough droplets to form ice; and dry, clear conditions have no moisture to begin with.

Icing forms when liquid water droplets in the air are supercooled and strike a surface, freezing on contact. The key idea is that there must be liquid moisture in subfreezing air that can freeze when it touches the aircraft. Below-freezing temperatures alone don’t cause ice; there has to be droplets that are still liquid because they’re supercooled. When those droplets encounter a surface like a wing or propeller, they freeze rapidly and ice builds up.

That’s why the best description is: there’s a temperature below freezing and supercooled droplets are present in the air. In such conditions, visible moisture—clouds, fog, rain, or drizzle—provides the liquid droplets that can freeze on impact.

The other scenarios lack the necessary liquid moisture: warm, dry air has little to no moisture to freeze; high altitude with dry air suggests a lack of enough droplets to form ice; and dry, clear conditions have no moisture to begin with.