fuselage

Fuselage is the primary structural body of an aircraft, to which wings, tail surfaces, and landing gear are attached. It forms the central shell that houses the crew, passengers, and cargo, and contains essential systems such as avionics, hydraulics, electrical systems, and fuel. The fuselage also serves as the pressure vessel in most fixed-wing aircraft, protecting occupants at cruising altitudes.

Fuselage design balances aerodynamics, structural efficiency, and interior layout. Most modern airframes use a stressed-skin construction, in which the skin carries a significant portion of the loads, reinforced by frames and stringers. Some designs rely on a truss or semi-monocoque structure. Materials include aluminum alloys for traditional airframes and composites, such as carbon fiber reinforced polymers, for weight reduction and stiffness.

Cross sections are typically circular or oval to resist pressurization loads and minimize drag. The forward section generally contains the cockpit, the midsection houses passengers or cargo, and the aft section connects to the tail assembly. The fuselage length, cross-section, and door layout are optimized for payload, range, and accessibility. Fuselages can be pressurized or unpressurized; passenger airliners and military transports are usually pressurized.

In helicopters, the term still refers to the main body of the aircraft, while in spacecraft the term may describe the primary body of the vehicle. The concept emphasizes the structural and functional core of the aircraft.