Which of the following geometric and aerodynamic parameters enhance the lateral-directional Dutch roll damping ratio $\zeta_{dr}$ of an aircraft?

(A) Increasing vertical tail size (larger vertical tail volume fraction $V_v$)

(B) Installing a yaw damper integrated into the rudder flight control system

(C) Increasing wing dihedral angle excessively while keeping vertical tail small

(D) Sweeping the wings sharply forward without a vertical fin

Answer Key:

A,B

### Solution: Dutch roll is damped primarily by weathercock stability derivative $C_{n,\beta}$ and yaw damping derivative $C_{n,r}$, both provided by a large vertical tail (A) and active yaw dampers (B). Excessive dihedral increases roll-due-to-sideslip $C_{l,\beta}$, which degrades Dutch roll damping (C and D are false). Correct: A, B.

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