According to Boeing, when do icing conditions exist?

According to Boeing, when do icing conditions exist?

• A. When the temperature is between 10°C and -10°C with visible moisture
• B. When temperature is above 0°C with fog
• C. Temperature below -40°C with no moisture
• D. Any temperature with rain

Answer: (A)

Icing conditions happen when the air contains visible moisture and the temperature is within a range where liquid water droplets can exist and freeze on contact with the aircraft. In Boeing’s materials, that range is given as between 10°C and -10°C with visible moisture. Within this band, droplets can be supercooled, so when they strike a surface they rapidly freeze, building up ice on wings, the nose, and other surfaces. Understanding why this matters helps connect the idea: moisture in the air (fog, clouds, rain, or drizzle) provides the droplets that can freeze, and the temperature must be around the freezing point where those droplets stay liquid long enough to contact the aircraft but are cold enough to freeze quickly. Why the other options aren’t the right fit here: icing isn’t typically described as occurring at temperatures well above freezing with fog, because the droplets would not reliably freeze on contact. Very cold air with no moisture can’t produce icing since there’s nothing to freeze. And rain can cause icing only when temperatures and moisture conditions align in the appropriate range, not “any temperature.” The stated choice captures the scenario Boeing uses: visible moisture present and a temperature window around freezing where icing is likely.

Icing conditions happen when the air contains visible moisture and the temperature is within a range where liquid water droplets can exist and freeze on contact with the aircraft. In Boeing’s materials, that range is given as between 10°C and -10°C with visible moisture. Within this band, droplets can be supercooled, so when they strike a surface they rapidly freeze, building up ice on wings, the nose, and other surfaces.

Understanding why this matters helps connect the idea: moisture in the air (fog, clouds, rain, or drizzle) provides the droplets that can freeze, and the temperature must be around the freezing point where those droplets stay liquid long enough to contact the aircraft but are cold enough to freeze quickly.

Why the other options aren’t the right fit here: icing isn’t typically described as occurring at temperatures well above freezing with fog, because the droplets would not reliably freeze on contact. Very cold air with no moisture can’t produce icing since there’s nothing to freeze. And rain can cause icing only when temperatures and moisture conditions align in the appropriate range, not “any temperature.” The stated choice captures the scenario Boeing uses: visible moisture present and a temperature window around freezing where icing is likely.