# What is the reason why dihedrals are used when building a plane? [duplicate]

How does dihedral affect flight characteristics of a plane? I know it increases stability, however is it the only reason why it is implemented? If so, aren’t there more effective methods to stabilize the plane?

• Welcome to aviation.SE! We have a number of questions about dihedral already that might answer some or all of yours, e.g. here, here, here. Do any of those help? Aug 24 '20 at 15:57
• Does this answer your question? What kind of dihedral would be most stable? Aug 24 '20 at 18:22
• As explained in the help center, you should indicate the current state of your research. Aug 24 '20 at 19:11

Because when an airplane rolls to a bank angle, the airplane begins to slip toward the lowered wing. If the wings are mounted with a dihedral, this causes two things: the inside wing will experience an increased angle of attack, and the outside wing experiences a decrease in angle of attack. This combination causes an imbalance in the lift forces on the wings resulting in a rolling moment about the center of mass and returning the airplane to a wings level condition.

Dihedral angle is much more common on low wing airplanes, since the location of the CG above the CL creates a static unstable roll condition when the airplane is banked. Dihedral angle can be used on high wing aircraft as well to enhance roll stability along with the pendulum effect of the CG below the CL e.g. a Cessna 172 still employs a slight dihedral angle to its wings.

In the age of digital flight control systems dihedral angles to wings are not absolutely necessary, though for light airplanes and gliders it’s far more elegant to design the airplane with a slight natural static and dynamic stability in all three axes. Aircraft designers also work to ensure that airplanes have more authoritative directional stability than lateral stability from a dihedral angle to prevent unwanted Dutch rolling tendencies.

• "Having CG above CL creates a static unstable roll condition", I'll save our PK a few years of journalism, it's having CG "above" center of lateral drag (as plane slips sideways) creates a static unstable roll condition. Putting the wing high actually raises the CG, allowing for more side area underneath it. The designer then rebalances with an upward vertical stabilizer, the "classic" high winger. The designer can add a touch of dihedral as needed, as it improves roll stability, as well as "self righting tendency" recovering to straight and level from a bank. Shame they closed this. Aug 25 '20 at 11:53

First let's define dihedral.

It's when there is an angle between the wing root and the wing tip. Usually a positive angle.

Dihedrals wing are desinged to increase the lateral stability of the airplane. For example, if there is a wind gust (updraft on the right wing) that makes the airplane roll to the left, the result will be a lowered left wing and a raised right wing.

With the dihedral, the lowered wing (left one) has a greater AOA than the raised wing, therefore producing more lift and bringing the dropped wing back to it's original position.