The YAW DAMPER Switch automatically moves to OFF, the amber YAW DAMPER light
illuminates and the YAW DAMPER switch cannot be reset to ON when any of the following
conditions occur:
- SMYD senses a yaw damper system fault,
- SMYD senses that the yaw damper does not respond to a command,
- B FLT CONTROL switch is positioned to OFF or STBY RUD.
During manual reversion flight (loss of hydraulic system A and B pressure), both
FLT CONTROL switches are positioned to STBY RUD. In this case, the YAW DAMPER
switch can be reset to ON and the standby hydraulic system powers the standby yaw
damper. During Standby Yaw Damper operation, movement of the control wheel sends a
signal to the standby rudder PCU to move the rudder. This gives rudder assist to help turn
the airplane when control of the ailerons is through manual reversion.
Elevator Feel System
The elevator feel computer provides simulated aerodynamic forces using airspeed (from
the elevator pitot system) and stabilizer position. Feel is transmitted to the control columns
by the elevator feel and centering unit. To operate the feel system the elevator feel
computer uses either hydraulic system A or B pressure, whichever is higher. When either
hydraulic system or elevator feel pitot system fails, excessive differential hydraulic pressure
is sensed in the elevator feel computer and the FEEL DIFF PRESS light illuminates.
