Definition
The vertical or central portion of a structural beam that connects the upper and lower flanges (caps), carrying primarily the shear loads transmitted through the beam.
Plain English
On an I-shaped or similar beam, the web is the flat middle piece that joins the top and bottom edges. It mostly handles the sideways or twisting forces trying to slide one part of the beam past another.
Context Anchor
Seen in aircraft structure discussions, maintenance manuals, and inspection descriptions of wings, fuselage frames, and other load-carrying parts.
Derivation
From Old English 'webb,' meaning a woven fabric stretched between two edges. The middle sheet of a beam was called a web because, like fabric stretched between two rails, it spans flat between the upper and lower caps.
Why Pilots Care
Wing spars are beams. Damage, corrosion, or buckling in the web of a spar reduces the wing's ability to carry shear loads and is a serious airworthiness concern during inspections.
Analogy
On a steel I-beam, the web is the vertical middle plate between the top and bottom parts. It is not the outside edge; it is the connecting wall between the edges.
Intuition Check
Web does not mean a spider web here. It means the flat connecting part of a structural beam.
Example Sentence 1
The mechanic inspected the web of the main wing spar for cracks and signs of corrosion.
Example Sentence 2
Designers increased the thickness of the spar web to handle higher shear loads in the new wing.