What effect does high relative humidity have on the potential for engine icing?

High relative humidity significantly increases the likelihood of engine icing. This is because high humidity means there is more moisture present in the air. When temperatures drop, especially in the presence of supercooled water droplets, this moisture can freeze upon contact with engine components, such as the induction system.

In addition, the process of supercooled droplets can occur when humid air flows through the engine and encounters colder surfaces. The droplets can freeze and form ice, which obstructs air intake and can lead to reduction in engine performance or even engine failure. Therefore, the more humid the air is, the greater the potential for icing conditions to develop.

The other options — reducing the probability of icing, having no effect, or stabilizing airflow — do not accurately reflect the dynamics of how humidity interacts with engine operation under cold conditions. Understanding this relationship is crucial for pilots and operators to anticipate and mitigate risks associated with engine icing, particularly in humid environments at low temperatures.