Surfaces & computers click a surface or computer
Simplified top-down view — not for operational use. Click a control surface or a flight control computer.
Click a surface or computer above to see what it does →
The computer network
ELAC · 2 units
Elevator Aileron Computers. Primary authority over ailerons and elevators, and the main computers running Normal Law. ELAC 1 is master by default.
SEC · 3 units
Spoiler Elevator Computers. Drive the spoilers and can take over elevator/THS control if both ELACs fail. Also feed speedbrake and ground spoiler logic.
FAC · 2 units
Flight Augmentation Computers. Handle the rudder (yaw damping, rudder trim, rudder travel limiter) and feed data to the flight envelope/speed displays.
Control laws
NORMAL LAW
- Default law, active with enough computers & hydraulics healthy
- Full envelope protection: load factor, pitch attitude, high AoA, high speed, bank angle
- Sidestick commands a flight path rate, not raw surface deflection
ALTERNATE LAW
- Triggered by certain multiple failures (e.g., loss of an ELAC + a SEC)
- Load factor protection generally retained
- High AoA and high bank angle protections lost — replaced by simple stall/overspeed warnings
DIRECT LAW
- Sidestick deflection maps directly to surface deflection
- No protections at all
- Automatically set for landing gear extension in Alternate Law
MECHANICAL BACKUP
- Last resort if all relevant computers are lost
- Rudder via cables, pitch trim via the mechanical trim wheel
- No ailerons, elevators or spoilers electrically commanded