The dihedral construction of an aircraft wing provides lateral stability about which axis?

• A. Vertical axis
• B. Longitudinal axis
• C. Lateral axis
• D. Normal axis

Answer: (B)

Dihedral creates a restoring roll moment, giving the aircraft stability about the roll axis. When a sideslip occurs, the lower wing sits in a different part of the relative wind and its angle of attack increases more than the upper wing, producing more lift on that wing. That extra lift raises the low wing and lowers the high wing, rotating the aircraft back toward wings-level. This is roll stability about the longitudinal axis, not stability about the vertical (yaw) or lateral (pitch) axes.