No asymmetry or skew protection is provided through the alternate (electrical) flap drive
system.
When using alternate flap extension the LE flaps and slats are driven to the full extended
position using power from the standby hydraulic system. In this case the ALTERNATE
FLAPS master switch energizes the standby pump and the ALTERNATE FLAPS position
switch, held in the down position momentarily, fully extends the LE devices.
Note: The LE devices cannot be retracted by the standby hydraulic system.
Positioning the ALTERNATE FLAPS master switch to ARM:
- Activates the standby electric motor–driven pump.
- Closes the trailing edge flap bypass valve.
- Arms the ALTERNATE FLAPS position switch
- Allows the standby system to power the leading edge flaps and slats and thrust
reversers.
Yaw Damper
The yaw damper system consists of a main and standby yaw damper. Both yaw dampers
are controlled through Stall Management/Yaw Damper (SMYD) computers. The SMYD
computers receive inputs from both ADIRUs, both control wheels and the YAW DAMPER
switch. SMYDs provide yaw damper inputs to the main rudder power control unit (PCU) or
standby rudder PCU, as appropriate. Either yaw damper is capable of providing dutch roll
prevention, gust damping and turn coordination. Yaw damper operation does not result in
rudder pedal movement. Only main yaw damper inputs are shown on the yaw damper
indicator. The pilot can override either main or standby yaw damper inputs using either the
rudder pedals or trim inputs. During normal operation the main yaw damper uses hydraulic
system B and theSMYD computers provide continuous system monitoring.
