B737-700/800/900 Flight Controls
Yaw Control
The rudder provides yaw control about the
airplane’s vertical axis. The A and B FLT
CONTROL switches control hydraulic shutoff
valves for the rudder and the standby rudder.
The rudder provides yaw control about the
airplane’s vertical axis. The A and B FLT
CONTROL switches control hydraulic shutoff
valves for the rudder and the standby rudder.
- Each set of rudder pedals is
mechanically connected by cables
to the input levers of the main and
standby rudder PCUs.
At speeds above approximately 135 kts, both hydraulic system A and B
pressure are each reduced within the main PCU by approximately 25%
each. This function limits full rudder authority in flight after takeoff and
before landing.
pressure are each reduced within the main PCU by approximately 25%
each. This function limits full rudder authority in flight after takeoff and
before landing.
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 the SMYD computers provide continuous system monitoring. 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 he rudder. This gives rudder assist to help turn the airplane when
control of the ailerons is through manual reversion.
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 the SMYD computers provide continuous system monitoring. 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 he rudder. This gives rudder assist to help turn the airplane when
control of the ailerons is through manual reversion.
Flight Controls SGR
