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AUTOMATIC FLIGHT CONTROL SYSTEM
INTERCEPTING AND FLYING A DME ARC
The AFCS will intercept and track a DME arc that is part of the active flight plan provided that GPS
Navigation Mode is engaged, GPS is the active navigation source on the CDI, and the DME arc segment is
the active flight plan leg. It is important to note that automatic navigation of DME arcs is based on GPS.
Thus, even if the APR key is pressed and LOC or VOR Approach Mode is armed prior to reaching the Initial
Approach Fix (IAF), Approach Mode will not activate until the arc segment is completed.
If the pilot decides to intercept the arc at a location other than the published IAF (i.e. ATC provides vectors
to intercept the arc) and subsequently selects Heading Mode or Roll Mode, the AFCS will not automatically
intercept or track the arc unless the pilot activates the arc leg of the flight plan and arms GPS Navigation
Mode. The AFCS will not intercept and fly a DME arc before reaching an IAF that defines the beginning of the
arc segment. Likewise, if at any point while established on the DME arc the pilot deselects GPS Navigation
Mode, the AFCS will no longer track the arc.
AUTOPILOT AND YAW DAMPER OPERATION
Refer to the POH for specific instructions regarding emergency procedures.
NOTE:
The autopilot and optional yaw damper (not available in the SR20) operate the 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. Autopilot operation is independent of the yaw damper.
The yaw damper reduces Dutch roll tendencies, coordinates turns, and provides a steady force to maintain
directional trim. It can operate independently of the autopilot and may be used during normal hand-flight
maneuvers. Yaw rate commands are limited to 6 deg/sec by the yaw damper.
FLIGHT CONTROL
Pitch and roll commands are provided to the servos based on the active flight director modes. Yaw commands
are provided by the yaw servo. 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.
P
a
itch
XiS and
The autopilot pitch axis uses pitch rate to stabilize the aircraft pitch attitude during 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 adapter may be used to provide manual electric trim
(MET). This allows the aircraft to be trimmed using a control stick switch. Manual trim commands are
generated only when the MET Switch are pressed. Trim speeds are coupled with airspeed to provide a
more consistent response.
When the autopilot is engaged, the MET Switch does not respond.
NOTE:
Pilot's Guide for the Cirrus SR2x with Cirrus Perspective by Garmin
524
t
riM
190-00820-11 Rev. A
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