A longeron is a main longitudinal structural member of an aircraft. It is a spar-like unit that runs lengthwise of the fuselage or spanwise of a wing. These continuous members connect to many formers, ribs, and the skin, forming a load-bearing framework in conjunction with stringers. Because they transfer stresses from the skin to the frames, longerons carry the primary load of the entire structure. They are located farther apart laterally than stringers and are aided by bulkheads, creating a sturdy framework for the aircraft.
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Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is a longeron in aircraft?
A longeron is a load-bearing unit of a framework, specifically a fore-and-aft framing member of an airplane fuselage. Longerons run lengthwise along the airplane's fuselage and are spar-like structures. They are used in conjunction with stringers to form structural frameworks and connect to many formers along the length of the airplane.
Longerons are longitudinal members in a fuselage that are few in number and run all along the fuselage length. Longerons are spaced further apart laterally than stringers, which are numerous in number and installed between formers over very short distances. Stringers act as stiffeners, while formers, frames, bulkheads, and ribs are vertical structural members of an airframe structure.
What is the function of longerons in aircraft?
The primary function of longerons is to help transfer skin loads to internal structure. They transfer loads and stresses from the skin to formers. Longerons distribute loads across the airframe and support primary bending loads. They handle axial loads resulting from bending stresses. Longerons support compressive loads. Longerons and stringers carry the majority of normal bending stresses. They attach to multiple formers and bulkheads and contribute to torsional stiffness of the body.
What is the structure of a longeron in aircraft?
Longerons are continuous spar-like structures that run the full length of the fuselage, connecting many formers and giving the airframe its primary longitudinal strength. They are typically aluminum alloy extrusions formed into ‘U’ or ‘T’ sections, chosen so that each longeron behaves as a two-force member carrying only axial load. Because longerons are of larger cross-section than stringers, they form the main corners of the fuselage. When viewed from the end, vertical and horizontal longerons give the structure a square or rectangular shape. These lengths of tubing are welded in place or mechanically fastened to create a well-braced framework, and the longeron is backed by stringers that are installed only between adjacent formers.
