Which type of aircraft structure uses both a skin and supporting framework to achieve its strength?

The correct answer is semi-monocoque, as this aircraft structure combines a lightweight skin with a supporting framework known as stringers and formers, which together enhance strength and rigidity while reducing weight. This design is inherently more efficient than a monocoque structure that relies primarily on its outer skin for support, making it less capable of handling concentrated loads or damage. The semi-monocoque architecture allows for a more distributed load across the structure and is commonly used in modern aircraft due to its favorable combination of strength and lightweight characteristics.

In contrast, a truss structure utilizes a framework of beams and rods to support the load, which can be more severe in terms of weight for larger aircraft. Composite structures are made from materials like carbon fiber or fiberglass, which can provide excellent strength-to-weight ratios, but they may still rely on a supporting framework, not necessarily the skin. Understanding these distinctions is crucial for grasping the structural philosophies employed in various aircraft designs.