Spar (aviation)

A spar or wing spar is the supporting component of an airplane wing ( airfoil ). The bar- shaped bar has the task, to take out of the air and inertial forces resulting shear forces and bending moments. It consists of two components that perform different tasks. The straps take on the normal forces of the bending moments. The shear web absorbs the transverse forces and directs the thrust between the straps.

Application in the wing

The spar has to fulfill as a supporting component of an airfoil ( airplane wing ) the task of the air and inertial forces (including buoyancy and landing forces) take the resulting shear forces and bending moments, and has both strength criteria and stiffness criteria. He usually has a bar shape and consists of two components, which take on different tasks. The straps ( shown in cross section gray on the right ) take on the normal forces of the bending moments. The shear web (shown in black ) absorbs the transverse forces and directs the thrust between the straps.

The spar must be so stiff that it can accommodate the results from the air and inertial forces transverse forces and bending moments and the wing not to place undue deformed. At the same time the strength of the belt must be sufficient to bear the loads. Since aircraft wings can deform greatly, bars are based on the theory of higher order. In this play especially with high curvature, the pressure forces on the shear web an important role.

With the exception of the box beam pass all the bars of open cross-sections. Open cross-sections have a low torsional and Wölbsteifigkeit. Beams with open cross-section are thus not adapted to receive the torsion moment of the blade. Therefore, aircraft wings are equipped with an additional, closed profile, the Torsionsnase.

Aircraft wings may have more than one bar depending on the aircraft type and design. Such wings are called multi Holmer. In some cases, there may be both a main and a secondary spar.

Designs

Spars are built in aircraft riveted metal construction made of sheet metal or machined from solid aluminum ( from a block of material worked out ).

In aircraft, the plastic construction beams from fiber - plastic composites are constructed. The straps are made in this design of a unidirectional layer. The shear web is made of a fabric of less than 45 °, the so-called AWV45. In wings of plastic construction the closed wing shell takes on the task of Torsionsnase.

For an aircraft in the timber construction of the spar is made of layered wood. The shear web is made ​​of plywood locked.

Other areas of application

Spars ( the vertical tail, for example ) used in rotor blades, such as wind turbines and helicopters, as well as stabilizers.