An airplane wing is much more than a curved surface that makes lift. Inside the wing is a strong frame that carries forces from air pressure, fuel, engines, and landing loads. The main parts are spars, ribs, stringers, and skin, which work together like beams, formers, and a shell.
Understanding wing structure helps explain how aircraft can be both lightweight and strong.
Key Facts
- Lift acts upward on the wing, while weight, fuel, and engine loads often act downward, creating bending.
- A spar is a main spanwise beam that carries much of the wing bending load.
- Ribs run chordwise from leading edge to trailing edge and give the wing its airfoil shape.
- Stringers run along the span and help stiffen the skin against bending and buckling.
- Stress = force / area, so sigma = F / A.
- The wing box, formed by spars, ribs, and skin panels, can be sealed and used as a fuel tank.
Vocabulary
- Spar
- A spar is a strong beam running from the wing root toward the wing tip that carries major bending and shear loads.
- Rib
- A rib is a shaped structural piece that runs from the leading edge to the trailing edge and holds the airfoil shape.
- Stringer
- A stringer is a long, narrow stiffener attached to the skin to help resist bending and prevent buckling.
- Wing box
- The wing box is the strong central section of a wing formed by spars, ribs, and skin panels.
- Skin
- The skin is the outer covering of the wing that helps form the aerodynamic surface and carries part of the load.
Common Mistakes to Avoid
- Thinking the skin is only a cover is wrong because modern wing skin often carries significant tension, compression, and shear loads.
- Confusing ribs with spars is wrong because ribs run chordwise to shape the airfoil, while spars run spanwise to carry major bending loads.
- Assuming the wing is hollow and empty is wrong because the wing contains structure, control systems, wiring, and often sealed fuel tank spaces.
- Ignoring buckling is wrong because thin metal or composite panels can fail by wrinkling or collapsing even when the material has not snapped.
Practice Questions
- 1 A wing panel has 12 ribs equally spaced along a 5.5 m span section. If the first and last ribs are at the ends, what is the spacing between adjacent ribs?
- 2 A spar cap carries a force of 18000 N over a cross sectional area of 0.003 m^2. Calculate the stress using sigma = F / A.
- 3 A designer adds more stringers under the wing skin but keeps the same skin thickness. Explain how this can help the wing resist buckling and keep its shape during flight.