190-01115-01 G3X™/G3X Touch™ Avionics Installation Manual
Rev. AV Page 16-2
hold modes even if all GDU displays in the aircraft are unavailable.
GSA 28 autopilot servos can be used to control the trim system in an aircraft. When the autopilot is
disengaged, the servos can adjust the trim speed based on the current aircraft airspeed. This allows the trim
to run slower at high airspeeds and faster at low airspeeds. When the autopilot is engaged in the air, the
servos can adjust the trim control to minimize the force on the primary controls. This helps make sure the
aircraft will be properly trimmed when the autopilot is later disengaged. This feature works the same
whether using a 3rd party trim motor or a GSA 28 as the trim actuator. When using a GSA 28 as the trim
actuator, the following must be considered:
• The GSA 28 cannot hold a fixed position when disengaged, as the shaft will turn freely. It can only
be used in installations where the trim actuator does not need to hold a fixed position when
powered off. An acceptable application is the GSA 28 driving a manual pitch trim system using
capstan and bridle cables.
• When used as the trim servo, the GSA 28 communicates using the CAN bus (same as the other
servos communicate), no RS-232 or other data connection is required. The GSA 28 needs to be ID
strapped appropriately for the pitch trim location (see Section 23.13.5
and Figure 24-1.9).
• The GSA 28 should be connected to the CWS/DISCONNECT input. For manual electric trim, trim
inputs from the stick or relay should be wired directly to the GSA 28 being used as the trim
actuator, as well as the main autopilot servo for that axis.
During the flight test phase, the trim system is configured and set up after the primary autopilot
performance has been properly configured. This is done so the pilot can focus on properly adjusting the
performance of the primary autopilot system without having the auto-trim functionality interfere.
NOTE
Make sure basic autopilot functionality is properly adjusted before enabling trim control
for any servo.
16.1.1 Status LED
The GSA 28 has an LED on its outer case that indicates its current status. See Section 31.1.1
for details.
16.2 Equipment Available
Table 16-1 GSA 28 Part Numbers
Model Assembly Part Number Unit Only Part Number
GSA 28 Servo Actuator, Unit
Only
010-01068-00 011-02927-00
010-01068-20 011-02927-20*
*Requires minimum software level of v8.71 or higher
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