Which combination correctly describes the two main drag components affecting total drag on a wing?

• A. Skin friction drag and wave drag.
• B. Induced drag and wave drag.
• C. Profile drag and interference drag.
• D. Induced drag and parasite drag.

Answer: (D)

The key idea is that total wing drag comes from two broad sources: induced drag and parasite drag. Induced drag is created by the wing’s lift because the spinning air and trailing vortices near the wingtips create a pressure imbalance that drags the wing downward as it generates lift. This component is most noticeable at lower speeds and decreases as speed increases and the wing operates at a higher lift-to-drag ratio.

Parasite drag covers all drag not directly tied to lift. It includes skin friction (the viscous shear of air along the wing surface), form or profile drag (pressure drag from the wing’s shape), and interference drag (how the wing’s flow is affected by nearby surfaces and joints). This component grows with speed and becomes more significant at higher speeds.

Wave drag is a part of parasite drag that specifically arises near transonic speeds, so it isn’t treated as a separate main category here.

That’s why the correct pairing is induced drag and parasite drag: it captures the lift-dependent drag and the non-lift-related drag that together make up the total drag on a wing.