@SAMPUBLIUS, with reference to post #2959
http://www.pprune.org/rumours-news/553569-air-asia-indonesia-lost-contact-surabaya-singapore-148.html#post8850384, "
BUT still unclear if pushing buttons either RESETS the FAC or totally kills it as in Circuit breaker . ."
Recycling either FAC pb on the overhead panel
disengages the FAC but retains flight envelope protections.
Pulling the CBs to reset the FACs, (
the term "reset" is used in the FCOMs to describe the pulling-and-resetting of Circuit Breakers on the A320), kills the FAC and as has been stated by several posters, is prohibited when the aircraft is in flight.
With reference to the "GerryAirways" article,
if true, one does have to loosen the seatbelt to reach the aft-overhead panel, but not to reach the FAC switches which are on the main overhead panel.
From the FCOM, ATA 22, Auto Flight:
The aircraft has two flight augmentation computers (FACs) that perform four main functions:
• Yaw function
– Yaw damping and turn coordination
– Rudder trim
– Rudder travel limitation
• Flight envelope function
– PFD speed scale management
. Minimum/maximum speed computation
. Maneuvering speed computation
– Alpha-floor protection
• Low-Energy Warning function
• Windshear detection function
In performing these functions the FAC uses independent channels :
- Yaw damper
- Rudder trim
- Rudder travel limit
- Flight envelope
Each FAC interfaces with the elevator aileron computers (ELACs) when the APs are disengaged, or with the FMGS when at least one AP is engaged.
Both FACs engage automatically at power-up.
The pilot can disengage or reset each FAC (in case of failure) by means of a pushbutton on the flight control overhead panel.
When a FAC is disengaged (FAC pushbutton set off) but still valid, the flight envelope function of the FAC remains active.
If both FACs are valid, FAC1 controls the yaw damper, turn coordination, rudder trim, and rudder travel limit, and FAC2 is in standby.
FAC1 keeps the aircraft within the flight envelope through FD1 ; FAC2 performs this function through FD2.
If a failure is detected on any channel of FAC1, FAC2 takes over the corresponding channel.