Hi there,
Option 1: You do not select AP1 after APP is armed. You have AP2 and A/Thr operating, you are CATIII single.
Option 2. You want for whatever reasons 2 APs. So you engage AP1 after APP is armed (I understand in your case A/thr Ch1 was the problem and not AP1). FMGC1 becomes master, A/thr fails again (if not transient failure). So you have 2APs but no Autothrust. You are CATII.
Regards.
Edit: Respect Rudderrudderrat
