Have you heard of dihedral angles? Most commercial airplanes don’t have completely flat and straight wings. When looking at the tarmac on your next flight, you may notice that they have curved wings. This curvature is represented by a dihedral angle. What are dihedral angles exactly, and why do airplanes have them?
Overview of Dihedral Angles
A dihedral angle is the angle between an airplane’s left and right wings. It’s essentially an angle from the horizontal point of an airplane’s wings. Most airplanes have a dihedral angle of just a few degrees, resulting in a slight angle — typically an upward angle — of the airplane’s wings.
Dihedral angles can be positive or negative. A positive dihedral angle means the airplane’s wingtips are higher than the horizontal point of its wings. A negative dihedral angle, on the other hand, means the airplane’s wingtips are lower than the horizontal point of its wings. Negative dihedral angles are also known as “Anhedral angles.”
Why Airplanes Have a Dihedral Angle
You might be wondering why airplanes have a dihedral angle. While some airplanes do, in fact, have flat and straight wings, most of them have curved wings. Curved wings such as this result in a dihedral angle. This isn’t done for aesthetics. Rather, dihedral angles improve the lateral stability of wings.
Lateral stability reflects an airplane’s ability to resist rolling while maintaining an appropriate flight level. Airplanes with a dihedral angle can easily return to their original position after experiencing turbulence.
When an airplane with a dihedral angle rolls, the lower wing will generate more lift than the higher wing. This difference in lift produces a resistive force that essentially pushes the airplane back to flight level. If an airplane doesn’t have a dihedral angle, it won’t experience this effect. The airplane may still be able to roll, but it will experience more turbulence due to the lack of a dihedral angle.
What Is the Dihedral Effect?
Dihedral angles receive their namesake from the dihedral effect. The dihedral effect is the level of roll moment an airplane produces relative to the level of sideslip.
If an airplane with a dihedral angle has a non-zero angle of sideslip, it will produce the dihedral effect. One of the airplane’s wings will be tilted up from the horizontal point. The dihedral effect is beneficial because it helps to stabilize the airplane’s roll axis.
