What constitutes the threshold for a runway to be considered contaminated?

A runway is considered contaminated when it has a significant amount of substances that could adversely affect aircraft performance during operations, particularly during takeoff and landing. The standard threshold for contamination is more than 25% coverage by substances such as snow, ice, or water.

This threshold is important because when more than 25% of the runway is covered, it typically leads to reduced friction, increased stopping distances, and a higher risk of hydroplaning or loss of control. Consequently, it is crucial for pilots and air traffic controllers to assess runway conditions accurately to ensure the safety of all aircraft operations.

Understanding this threshold helps in making informed decisions regarding takeoff and landing, as well as in assessing the need for action such as de-icing or runway closures to maintain operational safety.