airframe

An airframe is the primary structural system of an aircraft, comprising the fuselage, wings, empennage (tail assembly), control surfaces, and landing gear. It provides the load-bearing framework that supports payload, fuel, and equipment, while shaping the aircraft’s aerodynamic performance. The propulsion system, avionics, and most systems are not considered part of the airframe, though they interface with it.

Airframes are designed to withstand aerodynamic and flight loads, while minimizing weight and ensuring safety, reliability, and maintainability. Engineers consider static strength, fatigue life, stiffness, flutter, and crashworthiness. Degree of integration between components varies with design philosophy, from thin-walled metallic structures to all-composite airframes.

Common materials include aluminum alloys for traditional designs and carbon-fiber-reinforced polymers and other composites for newer aircraft, sometimes reinforced with titanium in high-stress areas. Manufacturing techniques range from riveting and bolting in metal structures to adhesive bonding and autoclave curing for composites. The wing and fuselage are designed as load-bearing surfaces with internal stringers, ribs, and frames, while the empennage provides stability and control.

Airframes undergo testing and certification per aviation authorities (for example, the FAA and EASA) to demonstrate structural integrity and safety. Tests cover static strength, fatigue, and flutter, and production airplanes are subject to periodic maintenance of the airframe, including inspections and, as they age, life-extension or replacements of components.

In aviation practice, the term airframe may refer to the entire airframe assembly. Airframe hours denote accumulated flight time of the airframe excluding propulsion or system replacements, reflecting wear and fatigue exposure. The airframe's design influences performance, reliability, and maintenance costs across the aircraft’s life cycle.