Trim Motor Interface - Garmin G3X Installation Manual

The 011-02951-00 stop bracket kit is supplied with four #4-40 screws used to attach the bracket to the
front face of the servo. The screws provided are 0.25" long. This length of screw is appropriate if there is
no bracket or spacers in-between the stop bracket and servo. If a mounting bracket or spacers of thickness
.040" or greater will be place in-between the stop bracket and servo, longer screws should be used to
mount the stop bracket. It is recommended the thread engagement into the GSA 28, as measured from the
front face of the servo shall be 0.112" – 0.25". If screws other than what is provided will be used, be sure
to use thread locking compound or a proper thread locking patch combined with the lock washers
provided. Also be sure to follow the recommended tightening torque specified in
CAUTION
If screws are being used to mount the stop bracket to the front face of the GSA 28
are different than the screws provided with the stop bracket kit, care must be
taken to ensure these screws are not long enough to contact moving parts inside
the GSA 28. Maximum screw insertion, as measured from the front of the
GSA 28, must be less than 0.25" to avoid contact with parts inside the GSA 28.
CAUTION
To avoid the possibility of contaminating the internal rotating mechanisms of the
GSA 28, do not apply thread locking compound directly to the stop bracket
attachment holes in the front face of the servo. Instead, apply a small amount of
thread locking compound to the threads of the stop bracket screws before the
screws are inserted. Thread locking compound is not required upon initial
installation of the included stop bracket screws, which are supplied with thread
locking compound already applied.

9.5.2.3 Trim Motor Interface

The GSA 28 provides an optional interface between the pilot's electric trim switch and a 14 Vdc trim
motor. When the GSA 28 servo is engaged (i.e. autopilot on), it automatically drives the connected trim
motor as required to relieve control forces for the associated pitch, roll, or yaw axis. When the GSA 28
servo is not engaged (i.e. autopilot off), it provides manual electric trim (MET) functionality by running
the trim motor in response to pilot input. The GSA 28 can be configured to automatically reduce the speed
of the trim motor at higher airspeeds, in order to provide finer control of trim tab position. In the event that
power to the GSA 28 is removed, a fail-safe system connects the trim input switch directly to the trim
motor. In this condition, the trim switch powers the trim motor directly and the motor runs at its full speed
when the switch is pressed. The same condition also occurs if a trim switch and motor are connected to the
GSA 28, but the trim control function is disabled.
NOTE
The GSA 28 supports a single trim switch input only. For use with multiple trim switches
(e.g. pilot and co-pilot), a third-party trim interface unit or relay board is required. See
Figure C-1.6 for additional details.
G3X Installation Manual - GSA 28 Installation
Page 9-6
Figure 9-6.2.
190-01115-01
Rev. L