The purpose of aircraft wing dihedral is to

• A. Increase vertical stability
• B. Increase lateral stability
• C. Increase thrust
• D. Increase camber

Answer: (B)

Wing dihedral provides stability around the roll axis. When the airplane rolls to one side, the lower wing moves into a position where its wing is effectively more pointed into the oncoming air, so it generates more lift than the upper wing. That extra lift on the low wing raises it and reduces lift on the high wing, creating a restoring roll that brings the aircraft back toward wings-level. This is why dihedral mainly increases lateral stability. It doesn’t directly affect thrust, nor does it change camber or pitch stability.