Which of the following is NOT a type of parasite drag?

• A. Form drag
• B. Skin friction drag
• C. Interference drag
• D. Induced drag

Answer: (D)

The key idea is the difference between parasite drag and drag that’s produced by lift. Parasite drag is the drag that isn’t created by generating lift; it comes from the aircraft’s shape, surface roughness, and how different parts interfere with each other. Form drag comes from the overall shape and cross-section of the aircraft, skin friction drag comes from air sticking to and sliding over surfaces, and interference drag comes from the way airflow interacts between components like the wing and fuselage.

Induced drag, on the other hand, is the drag that arises specifically because the wing is producing lift. It’s tied to the lift machinery of the wing and the vortices at the tips; as speed changes, induced drag behaves differently than parasite drag—it generally decreases as speed increases. Because it is generated by lift rather than by the aircraft’s shape or surface, it’s not classified as parasite drag.

So the option that is not a parasite drag type is induced drag.