Simrad AP25 Manual page 129

The two most important parameters that determine the
performance of the automatic steering are Rudder and Counter
Rudder.
Rudder sets the rudder gain which is the ratio between the
commanded angle and the heading error.
• Too little Rudder and the autopilot fails to keep a steady
• Too much Rudder gives unstable steering and reduces speed.
• Low speed requires more Rudder than high speed.
See also "Minimum Rudder" on page 115.
Note !
Counter Rudder is the parameter that counteracts the effect of
the boats turn rate and inertia. For a short time period it is
superimposed on the proportional rudder response as provided
by the heading error. It may sometimes appear as if it tends to
make the rudder move to the wrong side (counter rudder).
The best way of checking the value of the Counter Rudder
setting is when making turns. The figures illustrate the effects off
various Counter Rudder settings.
20221495F
Too little Rudder
Too much Rudder
course.
Counter rudder setting too
low, overshoot response
Counter rudder setting too high,
sluggish and creeping response
Configuration and setup
Course to steer
Course to steer
New course
New course
127