How to Calculate Dihedral Angles

Most airplane wings are not horizontal from the root to the tip. Many wings are angled slightly up. This angle is called the "dihedral," and it is a design specification that increases the roll stability of the airplane. When the airplane rolls slightly in one direction, one wing becomes more horizontal and the other becomes more vertical. The causes the lift to increase on the horizontal wing and decrease on the vertical wing, which, in turn, causes a correction to the roll perturbation.

Things You'll Need

• Tape measure
• Scientific calculator

Instructions

1. Park the aircraft so the wing extends over a level surface.

2. Measure the distance from the wing root to the ground and from the wingtip to the ground. The wing root is the point where the wing connects to the fuselage. These measurements must be made perpendicular to the ground.

3. Subtract the wing root measurement from the wingtip measurement. If the wings have dihedral, this will be a positive number. If they have anhedral, it will be negative.

4. Measure the horizontal extension of the wing. This is the horizontal distance between the wing root and an imaginary vertical line that connects the wingtip to the ground. If the value for wingspan is available, you can divide that value by 2 for a good approximation.

5. Divide the height difference (Step 3) by the horizontal distance and use the calculator to determine the inverse tangent of the result. This is the dihedral angle for the wing.

References

• Aircraft Design: A Conceptual Approach; Daniel P. Raymer; 1989