Posted for "Douglas W. Johnson, MD" <Lancair1@bellsouth.net>:
At altitude, I sometimes need to help the servos out with manual inputs for
large/rapid course changes due to the stiffness of the control boots around
the aileron axis.  At low altitudes, the wandering off heading I noticed
occurred with the NAV function only when the box was slaved to my GPS.  STEC
told me that anytime flying slaved to a GPS, one should have both NAV/APR
buttons active, as the GPS tone was too pure for the NAV button to track
alone.  Seems to work well--not wandering off since.
Doug Johnson
654DM