At what temperature is ice likely to form in the engine inlet?

Ice formation in the engine inlet is primarily influenced by the temperature and moisture content of the air. When considering the conditions under which ice can form, visibly moist air is a significant factor. This refers to the air containing enough moisture that it can contribute to ice crystal formation, especially when cooled.

The correct choice emphasizes the combination of visibly moist air and a temperature of 45 degrees Fahrenheit. At this temperature, while it is above freezing, the presence of moisture in the air can lead to conditions where ice can start to form in the engine inlet. As moist air cools, it can reach the dew point where water vapor begins to condense or freeze, especially in high-speed airflow, such as that found in an engine inlet.

Conditions such as high humidity combined with cooler temperatures, like 30 degrees Fahrenheit, can also lead to ice formation, but the selection made emphasizes the specific scenario of visibly moist air at a higher temperature where ice can still begin to form. This indicates that the potential for ice formation is not restricted to below freezing temperatures but can occur under certain humidity conditions even above those temperatures.