What is the contamination called that can develop on an aircraft surface beneath snow?

The contamination that develops on an aircraft surface beneath snow is referred to as clear ice. This phenomenon occurs when the snow layers on the aircraft melt slightly due to the heat from the aircraft surface or environmental factors, causing the water from the melting snow to flow underneath. If the temperatures are low enough, this water can freeze again, leading to the formation of a solid, transparent layer of ice.

Clear ice is particularly concerning because it can be harder to detect compared to other types of ice, and it can significantly affect the aircraft's aerodynamics by altering its shape and weight distribution. This makes it imperative for ground crews to thoroughly remove all snow and verify the underlying surface is clean and free of any clear ice formation. Understanding this contamination helps ensure safety and compliance with de-icing procedures before flight.