[DG] [DG11] dual autopilots and hunting

[shparrot]

I recently installed two ACU 400's and two type 3 rams. Obviously only one can be powered at any given time. I daisy chained the two ACU's off of one rudder sensor. One of your moderators indicated that could create problems so I disconnected the second ACU. Both units work perfectly without the rudder sensor, however if I connect the ACU to the rudder sensor it sometimes goes into violent oscillation, perhaps once an hour, more often if the weather is rough. I can stop this by grabbing and briefly holding the wheel. I've run setup as indicated in the manual and ensured that the system is thoroughly bled. Any suggestions.

[Derek - Raymarine - Moderator]

Hi shparrot

Thank you for your enquiry.

The advice you received was correct, only one system can be conncted to a rudder reference unit at a time, also make sure the system that is reconnected to the rudder reference unit is power cycled after the connection too. Unless the ACU is power cycled it will not recognise the rudder reference is connected.

The next issue is the positional instability, more guidance can be found here where the issue is most likely associated with rudder damping, which should be increased to 8 or 9 to stop the oscillation.

regards
Derek