Which of the following aerodynamic design features enhance the lateral-directional stability (Dutch roll damping and dihedral effect) of an airplane?

(A) Wing geometric dihedral angle ($\Gamma > 0$)

(B) Adequately sized vertical tail fin (high directional stability $C_{n\beta}$)

(C) Wing sweepback angle

(D) Severe wing anhedral angle

Answer Key:

A,B,C

### Solution: Wing dihedral provides stabilizing roll moment due to sideslip ($C_{l\beta} < 0$), vertical tail provides directional weathercock stability ($C_{n\beta} > 0$), and wing sweepback also increases effective dihedral effect. Severe anhedral reduces dihedral effect. Correct: A, B, C.

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