Which statement best describes drag?

• A. Drag is the force that produces lift.
• B. Drag has no impact on aircraft speed.
• C. Drag is the forward thrust generated by engines.
• D. Drag is the resistance to forward motion directly opposed to thrust.

Answer: (D)

Drag is the aerodynamic resistance that opposes an aircraft’s motion through the air, acting opposite to the direction of travel and opposite to thrust. It’s the force engines must overcome to keep moving forward. In steady, level flight, thrust balances drag so the aircraft maintains a constant speed. Lift comes from the wing’s air pressure difference and is not produced by drag. Saying drag has no impact on speed is incorrect because more drag means the engines must produce more thrust (or the aircraft must fly slower) to maintain the same speed. And drag is not forward thrust; thrust is the forward force from the engines, while drag resists that forward motion.