Which type of ice is considered the most dangerous for aircraft?

Clear ice is considered the most dangerous type of ice for aircraft due to its unique formation characteristics and the significant challenges it poses to flight operations. Unlike rime ice, which has a more porous and brittle structure, clear ice forms when supercooled water droplets freeze on contact with the aircraft's surface, creating a smooth, heavy layer of ice. This type of ice is particularly hazardous because it adds substantial weight to the aircraft and disrupts the airflow over wings and control surfaces, leading to severe aerodynamic loss of lift and control issues. The smooth finish of clear ice makes it more difficult for de-icing systems to effectively remove it, increasing the risk of ice accumulation.

In contrast, rime ice tends to form at lower temperatures and creates an uneven surface that can be more easily managed than clear ice. Mixed ice combines characteristics of both clear and rime ice, but the presence of clear ice makes it especially concerning in terms of aircraft performance and safety. Light ice typically refers to a minimal accumulation of ice, which is less of a concern compared to the significant impacts of clear ice. Thus, the dangers presented by clear ice warrant its classification as the most dangerous type of ice for aircraft operation.