What are the two types of parasite drag?

Parasite drag is a type of drag that acts on an aircraft due to its movement through the air and is independent of the aircraft's lift generation. It can be broken down into two main components: form drag and skin friction drag.

Form drag is created by the shape of the aircraft as it moves through the air. This drag arises from the pressure differences around the aircraft created by airflow turbulence and separation of the air from the aircraft's surface. Anything that disrupts the airflow, such as the bulky structure of an aircraft, contributes to this form of drag.

Skin friction drag, on the other hand, is caused by the friction of the air molecules sliding over the surface of the aircraft. It is influenced by the surface texture of the aircraft — for example, a smooth surface experiences less skin friction drag compared to a rough surface.

Together, these two types of parasite drag determine how much drag an aircraft experiences as it moves through the air, affecting its overall efficiency and performance. Understanding these concepts is essential for aerodynamics and aircraft design, highlighting the importance of minimizing both form and skin friction drag to improve flight performance.