What does dihedral describe in aircraft design?

• A. The positive acute angle between the lateral axis and a line through the center of a wing or horizontal stabilizer
• B. The engine thrust vector direction
• C. The vertical tail height
• D. The airspeed indicator reading

Answer: (A)

Dihedral is the upward tilt of the wings from root to tip. This tilt is a positive acute angle, effectively described as the angle between the aircraft’s lateral axis and a line drawn through the center of a wing or horizontal stabilizer. In practice, it means the wings are higher at the tips than at the roots. This geometric arrangement contributes to lateral stability: when the airplane experiences a sideslip or a roll, the lower wing experiences a greater angle of attack and generates more lift, producing a restoring moment that tends to level the wings. The other choices refer to engine thrust direction, vertical tail height, or an instrument reading, none of which describe the wing’s dihedral.