There are 2 FACs, normally FAC 1 is in use and FAC 2 is in standby. If a failure is detected on any channel of FAC 1, FAC 2 takes over the corresponding channel.
When a FAC is disengaged (push button set to off) but still valid, the flight envelope function of the FAC remains active.
Flight Envelope Function:
1. PFD speed scale management
Min/max speed computation
Manoeuvring speed computation
2. Alpha-floor protection.
FAC 1 must be serviceable for dispatch, FAC 2 may be inoperative with certain conditions.
The FCOM provides for FAC resetting by switching off and back on, there is no procedure involving pulling circuit breakers.
FAC 1 CBs are on the overhead panel and reachable from the seats, FAC 2 CBs are on the rear panel and couldn't be reached from the Captains seat.
Even if both FACs failed the immediate problems would be limited to flying in alternate law with protections lost, max speed 320kts and rudder with care above 160kts. There are further considerations for landing but these would not have been immediate.