Which type of drag is inherent whenever an airfoil is producing lift, and is inseparable from lift?

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

Answer: (B)

Induced drag is the drag that comes directly from lifting the wing. When a wing generates lift, the air must be deflected downward to create those lift-producing vortices at the tips. That deflection creates a downwash and a backwards component of force on the air, which shows up as a drag component along the flight path. In other words, as long as the wing is producing lift, some drag must accompany it, and that is induced drag.

This drag increases with the amount of lift the wing produces (higher lift requires stronger downwash, hence more induced drag) and decreases with better wing design (higher aspect ratio and efficient wingtip devices reduce it). The relationship is commonly summarized by Cd_i ≈ Cl^2/(π AR e), highlighting why high-aspect-ratio wings reduce induced drag for a given lift.

Parasite drag, form drag, and skin friction are not tied to lift. They come from the airframe’s shape and surface and tend to dominate at higher speeds, whereas induced drag is the portion inherently tied to producing lift at any speed.