In straight-and-level flight, with wing spoilers extended and speed and load factor constant, what happens to drag and lift?

• A. CD decreases; CL increases.
• B. CD increases; CL remains unchanged.
• C. CD remains unchanged; CL decreases.
• D. CD increases; CL increases.

Answer: (B)

In straight-and-level flight the lift produced must balance the weight, so the lift needed doesn’t change if speed and load factor stay the same. With the same speed and weight, the lift coefficient required to maintain equilibrium remains the same. Wing spoilers introduce extra drag by disturbing the flow and adding surface area, so the drag coefficient increases. The same flight condition means the lift coefficient stays basically unchanged, even though drag rises.