What are the two primary types of icing that affect aircraft?

The two primary types of icing that affect aircraft are induction icing and structural icing. Induction icing occurs when ice forms in the aircraft's engine air intake or induction system, obstructing airflow to the engine and potentially causing a reduction in engine performance or even failure. This type of icing is particularly concerning in colder weather when supercooled water droplets are present, as they can freeze upon contact with engine components.

Structural icing, on the other hand, refers to the accumulation of ice on the external surfaces of the aircraft. This can include wings, tail, and other control surfaces, which can adversely affect the aircraft's aerodynamics by increasing weight and altering airflow. This type of icing can lead to significant reductions in lift and control effectiveness, making it critical for pilots to be aware of the conditions that may contribute to structural icing formation.

Other options refer to different concepts that do not accurately describe the primary forms of icing affecting aircraft. Additionally, the terminology used in the question pertains specifically to the categories of icing crucial for understanding aviation safety and operation.