Same material and thickness Upper flange Spar web Lower flange Patch Patch Damage Case A Case B Rib Reinforcement plate Original damaged web area Clean holes smooth Pick up rivets along flange— add reinforcing rivets spaced  3 /4" as shown, maintaining  2 1 /2 times rivet diameter for  proper edge Reinforcement  material—same as  original and of  same gauge or one  gauge heavier. If web stiffener is within  1 /2"  of hole and is not damaged. Drill out stiffener rivets.  After repair is made, rivet  stiffener at original location.  Add new stiffener if stiffener  is damaged. Figure 4-190.  Wing spar repair.  Figure 4-191.  Wing rib repair. 4-109