Autopilot And Yaw Damper Operation; Flight Control - Garmin G900X Pilot's Manual

AUTOMATIC FLIGHT CONTROL SYSTEM

7.5 AUTOPILOT AND YAW DAMPER OPERATION

Refer to the AFM for specific instructions regarding emergency procedures.
NOTE:
The autopilot and yaw damper operate flight control surface servos to provide automatic flight control. The
autopilot controls the aircraft pitch and roll attitudes following commands received from the flight director. Pitch
autotrim provides trim commands to the pitch trim servo to relieve any sustained effort required by the pitch
servo. The yaw damper reduces Dutch roll tendencies and coordinates turns.

FLIGHT CONTROL

Pitch and roll commands are provided to the servos, based on the active flight director modes. Servo motor
control limits the maximum servo speed and torque. The servo mounts are equipped with slip-clutches set to
certain values. This allows the servos to be overridden in case of an emergency.
PITCH AXIS AND PITCH TRIM
The autopilot pitch axis uses pitch rate to stabilize the aircraft pitch attitude during upsets and flight
director maneuvers. Flight director pitch commands are rate- and attitude-limited, combined with pitch
damper control, and sent to the pitch servo motor. The pitch servo measures the output effort (torque) and
provides this signal to the pitch trim servo. The pitch trim servo commands the motor to reduce the average
pitch servo effort.
When the autopilot is not engaged, the pitch trim servo may be used to provide manual electric trim.
This allows the aircraft to be trimmed using a control stick switch rather than the trim wheel. Manual trim
commands are generated only when both halves of the MEPT Switch are operated simultaneously. Trim
speeds are scheduled with airspeed to provide more consistent response.
ROLL AXIS
The autopilot roll axis uses roll rate to stabilize aircraft roll attitude during upsets and flight director
maneuvers. The flight director roll commands are rate- and attitude-limited, combined with roll damper
control, and sent to the roll servo motor.
YAW AXIS
The yaw damper uses yaw rate and roll attitude to dampen the aircraft' s natural Dutch roll response. It also
uses lateral acceleration to coordinate turns. Yaw damper operation is independent of autopilot engagement.
518 Garmin G900X Pilot's Guide 190-00726-00 Rev. J