G1000 Reference Guide - SkyHoppers

SECTION 6 – AUTOMATICFLIGHT CONTROL6.4 AUTOPILOT OPERATIONNOTE: Refer to the AFM for specific instructionsregarding emergency procedures.Cessna Nav III’s autopilot operates flight controlsurface servos to provide automatic flight control. Theautopilot controls the aircraft pitch and roll attitudesfollowing commands received from the flight director.Pitch autotrim provides trim commands to the pitch trimadapter to relieve any sustained effort required by thepitch 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 incase of an emergency.Pitch Axis and Pitch TrimThe autopilot pitch axis uses pitch rate to stabilize theaircraft pitch attitude during upsets and flight directormaneuvers. Flight director pitch commands are rate- andattitude-limited, combined with pitch damper control, andsent to the pitch servo motor. The pitch servo measuresthe output effort (torque) and provides this signal to thepitch trim adapter. The pitch trim servo commands themotor to reduce the average pitch servo effort.When the autopilot is not engaged, the pitch trim servomay be used to provide manual electric trim. This allowsthe aircraft to be trimmed using a control stick switchrather than the trim wheel. Manual trim commands aregenerated with the MET Switch. Trim speeds are scheduledwith airspeed to provide more consistent response.Roll AxisThe autopilot roll axis uses roll rate to stabilize aircraftroll attitude during upsets and flight director maneuvers.The flight director roll commands are rate- and attitudelimited,combined with roll damper control, and sent tothe roll servo motor.Engaging the AutopilotNOTE: Autopilot engagement/disengagement isnot equivalent to servo engagement/disengagement.Use the CWS Button to disengage thepitch and roll servos while the autopilot remainsactive.When the AP Key is pressed, the autopilot and flightdirector (if not already engaged) are activated. Engagementis indicated by a green ‘AP’ annunciation in the center ofthe AFCS Status Box. The flight director engages in Pitchand Roll Hold modes when initially activated.Autopilot EngagedFigure 6-26 Autopilot Engaged6-22Garmin G1000 Cockpit Reference Guide for the Cessna Nav III190-00384-07 Rev. A