How does induced drag change with increasing speed?

How does induced drag change with increasing speed?

• A. Increases
• B. Decreases
• C. Remains constant
• D. Becomes negative

Answer: (B)

Induced drag comes from the wingtip vortices created to generate lift, and it grows with how much lift the wing must produce. In level flight at a constant weight, you can maintain the same lift with a smaller angle of attack as you speed up, so the required lift coefficient drops. Since the induced-drag tendency is tied to the square of the lift coefficient, and lift coefficient falls roughly as 1 over speed squared, induced drag ends up decreasing roughly as 1 over speed squared. In short, faster in level flight means less induced drag.

Induced drag comes from the wingtip vortices created to generate lift, and it grows with how much lift the wing must produce. In level flight at a constant weight, you can maintain the same lift with a smaller angle of attack as you speed up, so the required lift coefficient drops. Since the induced-drag tendency is tied to the square of the lift coefficient, and lift coefficient falls roughly as 1 over speed squared, induced drag ends up decreasing roughly as 1 over speed squared. In short, faster in level flight means less induced drag.