The principal chordwise structural members in wings, stabilizers, and
other airfoils are the ribs.
They are the formers for airfoils,
giving them shape and rigidity and transmitting stresses from the
skin to the spars. Ribs are designed to resist compression and shear
loads and come in three general types: reinforced, truss, and former.
Reinforced and truss ribs are relatively heavy compared to former
ribs, and they are used only at points of great stress. Former ribs
are located at frequent intervals throughout the airfoil. Rib repair
by patching and insertion is shown in Figures 2-15 and 2-16,
Former ribs are made of formed sheet metal and are
The bent-over portion of a former rib, shown in
Figures 2-15 and 2-16, is the rib's flange.
The vertical portion,
generally made with lightening holes, is the web.
lessen the rib's weight without loss of strength.