polyhedral

A polyhedral wing is one where the dihedral angle, the angle at which the wing rises from the fuselage, is not constant from root to tip. Instead, the wing is divided into sections, each set at a different angle to the horizontal. This creates a series of distinct planes rather than a single continuous slope, hence the geometric term.

The classic configuration places a shallow or negative dihedral inboard, near the fuselage, and a steeper positive dihedral outboard toward the wingtip. A wing might rise at 2 degrees for the first 30 percent of its span, then shift to 5 degrees for the remainder. The transition typically occurs at a strong structural point, such as a wing break or at a landing gear attachment point, where the geometry can change without weakening the structure.

Polyhedral geometry solves real aerodynamic and structural problems. A shallow inboard angle reduces bending moment at the root, where the wing must carry the greatest load. The steeper outboard section restores lateral stability at the tip, where a flat wing would allow the aircraft to roll too easily in turbulence. The result is better handling characteristics and lower structural weight than a single dihedral angle would allow. Many general aviation aircraft, particularly high-wing designs, use polyhedral to improve stability without requiring a stiff, heavy wing.

In the maintenance environment, polyhedral design affects how you measure wing geometry and how you assess damage. A bent or buckled section on a polyhedral wing is immediately obvious because it disrupts the planned angle transition. Wing survey measurements must account for the known geometry; a wing at the correct polyhedral angles will show different heights at different span stations, and a technician unfamiliar with the aircraft type might wrongly interpret this as damage.

Polyhedral differs from a simple dihedral wing, which rises at a constant angle along its entire span, and from anhedral, where the wing slopes downward from root to tip. High-speed jets often use anhedral or minimal dihedral because they rely on other control mechanisms for stability. The term itself comes directly from geometry: poly-, many, and hedron, a surface or plane.