Which of the following is a wing component that helps define the wing's cross-section?

• A. Wing Flap
• B. Ribs
• C. Spar
• D. Skin

Answer: (B)

The cross-section of a wing—the airfoil shape at each station—is defined by the ribs. Each rib establishes the curved contour, thickness, and camber at its station, forming the basic profile when the skin is laid over them to create a smooth surface. The spar runs spanwise and provides structural support against bending, but it doesn’t set the cross-sectional shape. A flap can change the local camber and trailing-edge shape when deployed, but the fundamental cross-section comes from the rib framework. The skin simply finishes the surface over those ribs. So the ribs are the component that defines the wing’s cross-section.