When does airframe icing typically occur?

Airframe icing typically occurs when temperatures are at or below freezing and there is visible moisture present in the atmosphere. This situation allows for supercooled liquid water droplets to exist, which can freeze upon contact with the aircraft's surface, leading to the formation of ice.

When the temperature is at or below zero degrees Celsius, and combined with moisture from clouds, precipitation, or fog, the conditions are ripe for icing. The ice accumulation can significantly affect aircraft performance by increasing drag, reducing lift, and potentially leading to more serious aerodynamic issues.

The other options describe scenarios where airframe icing is less likely or impossible. For instance, high-altitude clouds containing moisture generally exist at lower temperatures, but their altitudes might mean temperatures are well below freezing. Dry, cold air lacks moisture, which is essential for icing to occur, and warm weather with humidity would not lead to icing conditions, as the temperature remains above freezing. Understanding these factors is crucial for pilots to avoid and manage icing conditions effectively.