Which of the following statement(s) is/are true about the ribs of an airplane wing with semi–monocoque construction?
Show Hint
- For a rectangular planform wing, the dimensions of the ribs DO NOT depend on their spanwise position in the wing.
- Ribs increase the column buckling stress of longitudinal stiffeners connected to them.
- Ribs increase plate buckling stress of the skin panels.
- Ribs help in maintaining aerodynamic shape of the wing.
The Correct Option is B, C, D
Solution and Explanation
Step 1: Structural role of ribs.
In semi–monocoque construction, the load–carrying structure consists of skin, stringers, spars, and ribs.
- Spars carry primary bending.
- Stringers carry axial stresses and resist column buckling.
- Ribs are transverse frames: they shape the airfoil, support the skin, and tie the stringers/spars.
Step 2: Assess each statement.
(A) Incorrect: Even in a rectangular planform, ribs at root and tip may differ (thickness, cutouts, taper for systems). So rib dimensions do depend on spanwise position.
(B) True: By tying longitudinal stiffeners (stringers), ribs shorten their effective column length, raising their critical buckling stress.
(C) True: Ribs subdivide skin panels into smaller effective spans, thereby raising skin plate buckling stress.
(D) True: Ribs enforce the wing's aerodynamic contour (airfoil shape), preventing distortion under load.
Final Answer:
\[
\boxed{(B),\ (C),\ (D)}
\]
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\includegraphics[width=0.5\linewidth]{29.png}
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