Autopilot Operation; Flight Control; Engaging The Autopilot - Garmin G1000 Pilot's Manual

7.4 AUTOPILOT OPERATION

Refer to the POH for specific instructions regarding emergency procedures.
NOTE:
Cessna Nav III' s autopilot operates 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.

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 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 (MET).
This allows the aircraft to be trimmed using a control wheel switch rather than the trim wheel. Manual trim
commands are generated only when both halves of the MET 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.

ENGAGING THE AUTOPILOT

Autopilot engagement/disengagement is not equivalent to servo engagement/disengagement. Use
NOTE:
the 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. Engagement
is indicated by a green 'AP' annunciation in the center of the AFCS Status Box. The flight director engages in
Pitch and Roll Hold modes when initially activated.
190-00498-01 Rev. A
Autopilot Engaged
Figure 7-26 Autopilot Engaged
Garmin G1000 Pilot's Guide for Cessna Nav III
AUTOMATIC FLIGHT CONTROL SYSTEM
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