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Wing Spars

Wing Spars

  • Is defined that are the principal structural members of the wing. They correspond to the longerons of the fuselage. They run parallel to the lateral axis of the aircraft, from the fuselage toward the tip of the wing, and are usually attached to the fuselage by wing fittings, plain beams, or a truss.
  • Spars may be made of metal, wood, or composite materials depending on the design criteria of a specific aircraft. Wooden spars are usually made from spruce.
  • They can be generally classified into four different types by their cross-sectional configuration , they may be (A) solid, (B) box-shaped, (C) partly hollow, or (D) in the form of an I-beam.
  •  Lamination of solid wood spars is often used to increase strength. Laminated wood can also be found in box-shaped spars. The spar has had material removed to reduce weight but retains the strength of a rectangular spar.
  • As can be seen, most wing spars are basically rectangular in shape with the long dimension of the cross-section oriented up and down in the wing.
  • Currently, most manufactured aircraft have wing spars made of solid extruded aluminum or aluminum extrusions riveted together to form the spar.
  • The increased use of composites and the combining of materials should make airmen vigilant for wings spars made from a variety of materials.
  • In an I–beam spar, the top and bottom of the I–beam are called the caps and the vertical section is called the web. The entire spar can be extruded from one piece of metal but often it is built up from multiple extrusions or formed angles.
  • The web forms the principal depth portion of the spar and the cap strips (extrusions, formed angles, or milled sections) are attached to it. Together, these members carry the loads caused by wing bending, with the caps providing a foundation for attaching the skin.
  • Although the spar shapes are typical, actual wing spar configurations assume many forms. For example, the web of a spar may be a plate or a truss . It could be built up from lightweight materials with vertical stiffeners employed for strength.
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