Originally Posted by
CONF iture
The Captain called : The wings to flat horizon the standby horizon
I would not take
that as an indication that the PFD(s?) was/were wrong. Indeed, if the CPT was seated in the 3rd seat, the standby horizon was the most "accessible" for him.
Switching to "#3" source fits in the logic to try to get rid of the initial ADR fault (
speed indication).