Which type of moisture is associated with the creation of structural icing?

The type of moisture associated with the creation of structural icing is visible moisture. Visible moisture refers to any form of water that can be seen, including clouds, rain, snow, and mist. When aircraft encounter this type of moisture while flying in conditions where temperatures are at or below freezing, the water can freeze upon contact with the cold surfaces of the aircraft, leading to structural icing.

Visible moisture plays a crucial role in the formation of ice because it indicates the presence of supercooled water droplets. These droplets can remain liquid even at temperatures below freezing and can freeze instantly when they come into contact with a surface that is colder than the freezing point of water. This phenomenon is particularly hazardous during winter weather and in specific atmospheric conditions, emphasizing the need for pilots to be aware of visible moisture conditions during flight.

Frost, while related to moisture, is a specific type of ice formation due to the cooling of water vapor on surfaces and doesn't occur under the same conditions that lead to structural icing from visible moisture. Condensed moisture is a broader category and doesn't specifically indicate the conditions that lead to icing, and absence of moisture would not result in any moisture-related concerns at all. Thus, visible moisture is the key element in the icing process.