190-01115-01 G3X/G3X Touch Installation Manual - GDU 37X Config and Post Install Checkout
Rev. AC
Page 33-38
33.4.5.2 General Autopilot Description (for configuration)
The GSA 28 based autopilot system is a fully integrated, high performance autopilot that can control up to
three axes of an aircraft. Each GSA 28 servo is also capable of managing the trim control for its axis. The
following four subsections (roll, pitch, yaw, and trim) are provided to aid the pilot/installer in
understanding/configuring the Garmin GSA 28 autopilot system.
Roll Servo
All GSA 28 autopilot systems require a servo to control the roll axis of an aircraft. A single axis GSA 28
installation that controls only the roll axis is sometimes referred to as a “wing-leveler”.
The roll servo follows roll steering commands from the G3X display so the airplane will hold a desired roll
angle, follow a desired heading, or follow the lateral component of a flight plan.
During the flight test phase of the autopilot checkout, the roll servo aggressiveness will be adjusted to get
the desired in-fight performance. The “Roll Servo Gain” setting is used to set the aggressiveness of the roll
servo. A larger number will cause the roll servo to more aggressively control the aircraft, and a smaller
number will cause the roll servo to less aggressively control the aircraft.
Pitch Servo
Most GSA 28 autopilot systems consist of both a roll and pitch servo allowing for full 2-axis control of the
aircraft.
The pitch servo follows vertical guidance commands from the G3X display so the airplane will hold a
desired pitch angle, vertical speed, airspeed, or altitude, and also follow the vertical component of a flight
plan.
Vertical control of the aircraft is all based on controlling the pitch angle with two additional sub-modes for
vertical speed and airspeed. What this means is that the basic pitch mode performance must be properly
adjusted before changing settings that adjust the vertical speed and airspeed based modes.
NOTE
Ensure pitch mode functionality is properly adjusted before attempting to adjust vertical
speed or airspeed mode performance
During the flight test phase of the autopilot checkout, the pitch servo aggressiveness will be adjusted to get
the desired in-fight performance. The “Pitch Servo Gain” setting is used to set the aggressiveness of the
pitch servo. A larger number will cause the pitch servo to more aggressively control the aircraft, and a
smaller number will cause the pitch servo to less aggressively control the aircraft.
