Monocoque (French: “single shell”) is a structural design philosophy where the outer skin of a structure carries all or most of the loads — bending, torsion, and shear — without a separate internal skeleton. A pure monocoque has no internal frame; a semi-monocoque adds internal stiffeners (spars, ribs, stringers, bulkheads) to prevent the skin from buckling under compression, while the skin still carries a significant share of the load.
Most UAV airframes above the hobby scale are semi-monocoque: the fuselage is a skin tube stiffened by bulkheads and longerons, and the wing is a skin-covered torque box formed around one or two spars with periodic ribs.
3D-printed UAV components can approach true monocoque construction. A printed fuselage tube with 3–4 perimeter walls and moderate infill is effectively a monocoque — the “skin” (perimeter walls) and “structure” (infill) are printed as a single continuous part. This eliminates the assembly step of attaching skin to frame and is one of the key advantages of additive manufacturing for airframe production.
Foam-core composite construction is another near-monocoque approach: the foam core defines the shape and resists compression, while the fiberglass or carbon skin carries tension and shear. This is the primary construction method for the Shahed-136 and similar expendable UAV families.