I'm sure it's doing exactly as its meant to do within the limitations of FSX. The reason it would give better deflection on the ground is so you can taxi using rudder peddles.

Cristiano, the idea of the Yaw damper is to reduce the amount of Yaw (left to right movement of the nose/tail) on the aircraft. It stops the plane from behaving like a dog wagging its tail and therefore making everyone inside pretty sick. In FSX, the yaw damper works by limiting the amount of rudder movement rather than applying an opposite rudder input to yaw on the real aircraft.

In short, yes the 737 is doing exactly what it should. Very small yaw movements with the YD on and the full range of rudder movements with the YD off.

Markoz, I wonder if the difference in movement could be caused by different rudder calibrations between your and Cristiano's sims?

Cheers, Nathan