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Dihedral

When comparing a low wing airplane to a high wing airplane, a number of differences are seen. One of the most obvious, and most important to the flight characteristics, is the angle at which the wings are attached to the plane. If a line is drawn across the front of the plane through the center of lift, as represented by the blue dot, an angle is formed between the line and the wingtip. This angle is called dihedral. On the high wing plane, the line runs through the wing forming very little dihedral. On the low wing, there is a very noticeable dihedral angle. Dihedral helps in the lateral or roll stability of the airplane. Not only is there a center of lift on the airplane, there is also a center of weight as represented by the yellow dot.

In a coordinated, undisturbed turn, the center of lift and the center of weight remain in line thru the vertical axis of the airplane. This is due to the action of centrifugal force. But if the turn is disrupted as by a gust of wind, the center of weight and center of lift are no longer in line. The center of weightwill try to shift in the same direction as the roll of the turn. The high wing airplane has a natural action to correct for the disruption. Since the center of weight is located below the center of lift, the weight of the airplane will try to come to rest directly under the center of lift, just like a pendulum. However, in a low wing plane, since the center of weight is above the center of lift, the weight will continue in the same direction of the roll, just like a tall mast on a ship.

When the low wing plane is in a bank, the lower wing to the inside of the turn has less of a bank angle than the higher wing on the outside of the turn. This allows the lower wing to develop more vertical lift than the higher wing. It is the developed vertical lift that will raise the lowered wing, counteracting the force of the weight to continue into the roll. The pilot is able to make simple control adjustments without over correcting.

If a gust of wind disrupts the coordinated turn. . .