Which of the following is NOT a listed use for plywood in aircraft construction?

• A. Wing ribs
• B. Gusset plates
• C. Aircraft skin
• D. Interior panels

Answer: (A)

Plywood in aircraft construction is favored for flat, curved surfaces that can be formed from sheets and carried across loads through a continuous skin or panel. Its strength comes from laminating thin veneers, which makes it excellent for exterior skins that need a smooth, aerodynamic surface and for interior panels where finish, weight, and ease of fabrication matter. In some wooden-structure designs, plywood can also serve as gusset plates to tie together wake points or joints, taking advantage of its rigid, flat form.

Wing ribs, however, are part of the wing’s primary load path and must resist bending and twisting under aerodynamic loads. They are typically built from solid wood or laminated wood strands, or from metal, chosen for their specific bending stiffness and grain orientation. A flat plywood sheet doesn’t provide the right combination of bend characteristics and grain direction for ribs, so it isn’t a listed use for plywood.