ELECTRICAL CONTROL
- In normal operations, ELAC2 controls the elevators and the horizontal stabilizer, and the green and yellow hydraulic jacks drive the left and right elevator surfaces respectively.
The THS is driven by N° 1 of three electric motors.
- If a failure occurs in ELAC2, or in the associated hydraulic systems, or with the hydraulic jacks, the system shifts pitch control to ELAC1. ELAC1 then controls the elevators via the blue hydraulic jacks and controls the THS via the N° 2 electric motor.
- If neither ELAC1 nor ELAC2 is available, the system shifts pitch control either to SEC1 or to SEC2, (depending on the status of the associated circuits), and to THS motor N° 2 or N° 3.
MECHANICAL CONTROL
Mechanical control of the THS is available from the pitch trim wheel at any time, if either the green or yellow hydraulic system is functioning.
Mechanical control from the pitch trim wheel has priority over electrical control.
ACTUATION
Elevators
- Two electrically-controlled hydraulic servojacks drive each elevator.
Each servojack has three control modes :
- Active : The jack position is electrically-controlled.
- Damping : The jack follows surface movement.
- Centering : The jack is hydraulically retained in the neutral position.
- In normal operation :
- One jack is in active mode.
- The other jack is in damping mode.
- Some maneuvers cause the second jack to become active.
- If the active servojack fails, the damped one becomes active, and the failed jack is automatically switched to the damping mode.
- If neither jack is being controlled electrically, both are automatically switched to centering mode.