fuselage
The main body of an aerospace vehicle; the long central structure of an aircraft to which the wings (or rotors), tail, and engines are attached, and which accommodates crew and cargo.
fuselage: the aircraft's pressure tube and load-bearing frame
The fuselage is the central structural tube of an aircraft, running from nose to tail. It forms a sealed pressure vessel in pressurized aircraft, carrying crew, passengers, cargo, and fuel, while serving as the primary attachment point for wings, horizontal and vertical stabilizers, landing gear, and engines. In unpressurized aircraft or those operating below 10,000 feet, the fuselage still provides structural integrity but without maintaining a pressure differential.
Fuselage construction varies by aircraft type and design philosophy. Large commercial transports typically use a semi-monocoque structure: a thin aluminum or composite skin (0.040 to 0.090 inches thick) reinforced by internal stringers, frames, and longerons that run spanwise. Smaller aircraft may use monocoque construction with no internal reinforcement, relying entirely on skin bending stiffness. Military jets often employ titanium or advanced composites in high-temperature zones near engines. Pressurized fuselages must withstand repeated cycles of cabin pressurization, typically 8 to 9 pounds per square inch differential, which stresses the skin and fasteners continuously.
Fuselage structural failures are rare but catastrophic. The primary failure mode is fatigue cracking in the skin or around rivet holes, initiated by pressurization cycles combined with bending loads during flight. Corrosion of aluminum under fasteners or in areas with trapped moisture accelerates crack growth. Maintenance inspections focus on detecting skin cracks, fastener looseness, and corrosion using visual examination, eddy current testing, and sometimes ultrasonic thickness measurement. Repair patches must follow strict guidelines: a patch must extend at least one rivet spacing beyond visible damage and use materials matching the original alloy temper.
The term fuselage derives from the French word fuseau, meaning spindle or tapering body, reflecting the elongated streamlined shape optimized for aerodynamic efficiency and pressurization strength. Early fabric-covered aircraft had fuselages of welded steel tubing or wood frames; the shift to metal semi-monocoque construction began in the 1930s and became standard by the 1940s.
Fuselage design is constrained by pressurization requirements, aerodynamic drag, structural bending and torsion during maneuvering, and crash safety standards. Commercial aircraft fuselages typically have a circular or near-circular cross-section ranging from 6 feet 1 inch (Boeing 737 and Airbus A320) to 7 feet 10 inches (Boeing 747 upper deck), providing optimal resistance to hoop stress while maximizing usable volume. Military transports and cargo aircraft often trade this for a larger rectangular cross-section to accommodate outsized loads.