FAA Aircraft Dispatcher Complete Practice Exam

Structural ice is likely to develop when the aircraft is flying through visible water at temperatures of 0°C or colder. This is because the presence of visible moisture, such as rain, snow, or cloud droplets, combined with sub-freezing temperatures creates the ideal conditions for ice accumulation on the aircraft's surfaces.

When the aircraft flies through this visible moisture during cold conditions, any water droplets that come into contact with the aircraft will not freeze instantly on contact but will instead form ice as they accumulate on the wings, tail, and other surfaces. This phenomenon can significantly impact aircraft performance, including lift, drag, and control, necessitating careful awareness and management by pilots and dispatchers.

In contrast, the other scenarios presented involve conditions that either do not promote ice formation or are outside the thresholds where ice can be expected to accumulate. For instance, flying through visible moisture at any temperature doesn't guarantee ice will form unless temperatures are at or below freezing. Similarly, temperatures above 0°C generally prevent ice from accumulating. Therefore, the scenario describing visible water at temperatures of 0°C or colder outlines the specific conditions under which structural ice is most likely to develop.