What are the longitudinal structural members of a semi-monocoque fuselage called?

Longerons and stringers are essential components of a semi-monocoque fuselage design, providing necessary structural support and stiffness to the overall structure. Longerons run parallel to the length of the fuselage and are typically attached to the outer skin, helping to resist axial loads and distributing stresses along the length of the aircraft. Stringers, on the other hand, run transversely and are placed perpendicular to the longerons, playing a critical role in maintaining the shape of the fuselage and providing resistance to buckling and local deformations.

In contrast, stiffeners and cross members may be found in various structural applications but are not the specific terminology used for the longitudinal members in a semi-monocoque structure. Beams and trusses refer to different types of structures not specifically associated with fuselage design, while ribs and spars are components related more to wing and other structural elements rather than the fuselage itself. Understanding this nomenclature is essential for accurately discussing the components and function of an aircraft's fuselage.