Induced drag varies with airspeed in which way?

• A. Induced drag increases with airspeed
• B. Induced drag remains constant with airspeed
• C. Induced drag decreases as airspeed increases
• D. Induced drag is independent of airspeed

Answer: (C)

Induced drag comes from the wing’s lift-producing vortices and downwash. For a given weight and configuration, flying faster means you can generate the same lift with less angle of attack, which reduces the strength of the wingtip vortices and the downwash. The mathematical relationship shows that induced drag is inversely proportional to the square of airspeed, so as speed increases, induced drag falls off.

That’s why, when you accelerate, the induced component of drag decreases, while at slower speeds—where you must lift more and use a higher angle of attack—the induced drag rises.