What does impact icing refer to?

Impact icing specifically refers to ice that forms as a result of the aircraft flying through supercooled liquid water droplets. This type of icing occurs when these liquid droplets strike the exterior surfaces of the aircraft and freeze almost immediately upon contact. The induction system can also encounter supercooled water droplets, which can lead to icing within the engine's air intake. Such icing in the induction system can obstruct airflow, affecting engine performance.

The other answers describe different aspects or effects of icing on aircraft but do not capture the specific phenomenon of impact icing. Ice on the leading edge of the wing and on the tail section (as mentioned in other choices) typically involves ice accumulation that develops gradually when the aircraft is exposed to conditions conducive to freezing. Ice accumulation on various aircraft surfaces during flight can also occur but does not uniquely define impact icing. Hence, the focus on the induction system highlights the critical nature of impact icing and its operational significance.