Induced Drag Coefficient

This formula estimates the drag penalty created whenever a wing generates lift: the wing must create lower pressure below and higher pressure above, which forces the airflow to turn downward and leaves a trailing vortical wake. That downwash tilts the lift vector slightly rearward, producing induced drag; the effect grows with lift demand, so it scales with the square of the lift coefficient. A wing with larger aspect ratio and better span efficiency spreads lift more evenly along the span, weakens the tip vortices, and therefore reduces induced drag.

Use this when analyzing lift-related drag on wings, especially in low-speed flight, takeoff, landing, climb, or for comparing wing planforms in aerodynamic design. It is also useful in performance calculations where lift coefficient, aspect ratio, and span efficiency are known or estimated.

• Using the formula with drag coefficient data from cruise conditions without checking whether lift is actually the dominant drag contribution
• Forgetting that induced drag depends on C_L squared, so doubling lift coefficient quadruples induced drag
• Confusing aspect ratio with wing area instead of using AR = b^2 / S