Which type of icing requires immediate avoidance?

Severe icing is characterized by rapid accumulation of ice on the aircraft's critical surfaces, which can significantly impair the performance and control of the aircraft. This type of icing can pose a serious safety hazard, leading to reduced lift, increased drag, and potential for engine malfunction if ice forms in the engine air intake. Pilots are trained to recognize severe icing conditions and prioritize avoidance because the risks involved can escalate quickly.

In contrast, light, moderate, and trace icing conditions, while still requiring caution and management, do not typically present the immediate and critical threats that severe icing does. Light icing may be manageable with de-icing equipment or techniques, moderate icing can usually be handled with some adjustments and awareness, but severe icing necessitates immediate action to ensure safety.