What is the definition of a dihedral wing?

A dihedral wing is defined as a wing that is raised towards the wingtips. This design creates an upward angle of the wings relative to the horizontal plane of the aircraft when viewed from the front or rear. The increasing angle from the fuselage to the wingtips enhances lateral stability. When an aircraft with dihedral wings rolls to one side, the lower wing generates a greater angle of attack and, consequently, more lift, which helps return the aircraft to level flight. This characteristic is particularly beneficial in maintaining stability during turbulent flight conditions.

In contrast, a flat wing across does not offer the same stability benefits of a dihedral design. A wing that slopes downward towards the wingtips (often termed an anhedral wing) would have opposite aerodynamic effects and generally leads to increased roll instability. A wing with a variable angle during flight typically refers to wings with variable geometry or sweep, which is unrelated to the dihedral concept. Thus, the key feature of a dihedral wing is its upward angle at the tips, which contributes significantly to the aircraft's stability.