Garmin G1000 Pilot's Manual

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Contents

Garmin G1000 Pilot's Manual Manual pdf 345 page image

190-00498-01 Rev. A Garmin G1000 Pilot’s Guide for Cessna Nav III 7-27AUTOMATIC FLIGHT CONTROL SYSTEM7.4 AUTOPILOT OPERATIONNOTE: Refer to the POH for specific instructions regarding emergency procedures.Cessna Nav III’s autopilot operates flight control surface servos to provide automatic flight control. The autopilotcontrols the aircraft pitch and roll attitudes following commands received from the flight director. Pitch autotrimprovides trim commands to the pitch trim servo to relieve any sustained effort required by the pitch servo.FLIGHT CONTROLPitch and roll commands are provided to the servos, based on the active flight director modes. Servo motorcontrol limits the maximum servo speed and torque. The servo mounts are equipped with slip-clutches set tocertain values. This allows the servos to be overridden in case of an emergency.PITCH AXIS AND TRIMThe autopilot pitch axis uses pitch rate to stabilize the aircraft pitch attitude during upsets and flightdirector maneuvers. Flight director pitch commands are rate- and attitude-limited, combined with pitchdamper control, and sent to the pitch servo motor. The pitch servo measures the output effort (torque) andprovides this signal to the pitch trim servo. The pitch trim servo commands the motor to reduce the averagepitch servo effort.When the autopilot is not engaged, the pitch trim servo may be used to provide manual electric trim (MET).This allows the aircraft to be trimmed using a control wheel switch rather than the trim wheel. Manual trimcommands are generated only when both halves of the MET Switch are operated simultaneously. Trim speedsare scheduled with airspeed to provide more consistent response.ROLL AXISThe autopilot roll axis uses roll rate to stabilize aircraft roll attitude during upsets and flight directormaneuvers. The flight director roll commands are rate- and attitude-limited, combined with roll dampercontrol, and sent to the roll servo motor.ENGAGING THE AUTOPILOTNOTE: Autopilot engagement/disengagement is not equivalent to servo engagement/disengagement. Usethe CWS Button to disengage the pitch and roll servos while the autopilot remains active.When the AP Key is pressed, the autopilot and flight director (if not already engaged) are activated. Engagementis indicated by a green ‘AP’ annunciation in the center of the AFCS Status Box. The flight director engages inPitch and Roll Hold modes when initially activated.Figure 7-26 Autopilot EngagedAutopilot Engaged