How is induction icing categorized?

Induction icing is categorized based on the processes that contribute to its formation, specifically involving fuel evaporation, impact, and throttle position. When air enters the engine, it can cool rapidly, especially when there's a throttle increase, which causes a drop in pressure and temperature. This can lead to moisture in the air freezing and forming ice, which can block the airflow and affect engine performance.

The reference to fuel evaporation adds another layer, as the evaporation of fuel in the intake manifold can further cool the air and moisture present, enhancing the conditions for icing. Impact icing refers to the ice that forms due to the impact of supercooled droplets on surfaces that are below freezing. Hence, this categorization addresses the mechanisms at play during the induction system operation, especially under specific environmental conditions.

The other options do not appropriately tackle the specific operational factors that lead to induction icing. For instance, categorizing by air pressure does not fully capture the nuances of the processes involved, while altitude may not be as directly relevant to the mechanisms that produce icing in the induction system. Similarly, while the source of ice may be relevant in other contexts, it does not specifically explain how induction icing forms through these operational influences.