Under which conditions is airframe icing in flight most likely to form?

Under which conditions is airframe icing in flight most likely to form?

• A. Temperature above 20°C and clear skies
• B. Temperature below 5°C with visible moisture in the air
• C. Hot, humid air with dust
• D. Any temperature with precipitation

Answer: (B)

Icing in flight occurs when visible moisture is present in the air and the airframe is cold enough for the moisture to freeze on impact. When you fly through clouds, fog, drizzle, or rain in subfreezing conditions, supercooled water droplets strike the aircraft and rapidly freeze on contact, building ice. Choosing a condition with visible moisture and temperatures below about freezing captures the essential factors: there must be liquid droplets in the air and the surface temperature must be low enough for those droplets to freeze. The stated condition—temperature below 5°C with visible moisture—fits this: it encompasses subfreezing temperatures where icing is possible and includes the presence of visible moisture. The other options miss key requirements. Warm temperatures with clear skies provide no moisture to form ice. Hot, humid air with dust isn’t the typical moisture-droplet environment that causes icing on the airframe. And precipitation alone doesn’t guarantee icing; if the air is above freezing, many precipitations won’t freeze on contact, and icing is less likely.

Icing in flight occurs when visible moisture is present in the air and the airframe is cold enough for the moisture to freeze on impact. When you fly through clouds, fog, drizzle, or rain in subfreezing conditions, supercooled water droplets strike the aircraft and rapidly freeze on contact, building ice.

Choosing a condition with visible moisture and temperatures below about freezing captures the essential factors: there must be liquid droplets in the air and the surface temperature must be low enough for those droplets to freeze. The stated condition—temperature below 5°C with visible moisture—fits this: it encompasses subfreezing temperatures where icing is possible and includes the presence of visible moisture.

The other options miss key requirements. Warm temperatures with clear skies provide no moisture to form ice. Hot, humid air with dust isn’t the typical moisture-droplet environment that causes icing on the airframe. And precipitation alone doesn’t guarantee icing; if the air is above freezing, many precipitations won’t freeze on contact, and icing is less likely.