Structural Members

Structural Members 

Tie

Ties are members subject purely to tension (pulling). Because tension will not cause the tie to buckle, it does not need to be rigid, although it often is. Ties can be made from rigid items, such as tubes, or simply from wire, like the bracing wires on a biplane.

Struts

Struts carry compression loads. Because compressive loads can cause the member to buckle, the design of a strut is less simple than a tie. If overloaded, struts will fail in one of two ways: a long, thin strut will buckle; a short, thick strut will collapse by cracking or crushing, as the material from which it is made is overstressed. A medium strut may do either, or even both, depending on its dimensions and on other factors. Tubes make excellent struts, because the material is evenly loaded, so that the strength-to-weight ratio is high in compression.

Beams

Beams carry loads at an angle (often at right angles) to their length, and so are loaded primarily in bending. Many of the major parts of an airframe are beams, such as the main spars. The fuselage and wings themselves are structural members, and are beams, because they support the bending loads imposed by weight, inertia and aerodynamic loads

Types ob beams

1-Spar

In a fixed-wing aircraft, the spar is often the main structural member of the wing, running spanwise at right angles (or thereabouts depending on wing sweep) to the fuselage. The spar carries flight loads and the weight of the wings while on the ground. Other structural and forming members such as ribs may be attached to the spar or spars, with stressed skin construction also sharing the loads where it is used.

2-Longeron & stringer

In aircraft fuselage, stringers are attached to formers (also called frames)^{[citation needed]} and run in the longitudinal direction of the aircraft. They are primarily responsible for transferring the aerodynamic loads acting on the skin onto the frames and formers. In the wings or horizontal stabilizer, longerons run spanwise^{[clarification needed]} and attach between the ribs. The primary function here also is to transfer the bending loads acting on the wings onto the ribs and spar.

Web

Webs are thin sheets carrying shear loads in the plane of the material. Ribs and the skin itself are shear webs. Thin sheets are ideal for carrying shear, especially if they are supported so that they resist buckling.

Former

A former is a structural member of an aircraft fuselage, of which a typical fuselage has a series from the nose to the empennage, typically perpendicular to the longitudinal axis of the aircraft. The primary purpose of formers is to establish the shape of the fuselage and reduce the column length of stringers to prevent instability. Formers are typically attached to longerons, which support the skin of the aircraft.

The Former-and-Longeron technique was adopted from boat construction (also called stations and stringers), and was typical of light aircraft built until the advent of structural skins, such as fiberglass and other composite materials. Many of today's light aircraft, and homebuilt aircraft in particular, are still designed in this way.