190-01115-01
G3X/G3X Touch Installation Manual - Installation Preparation
Rev. AC
Page 2-8
2.1.1.13 Transponder
The G3X system can interface to any Garmin transponder with a digital interface (all models except the
GTX 320). The transponder code, operating mode, and flight ID can all be displayed and controlled via the
GDU displays.
A panel-mount transponder such as the GTX 327, 328, 330, 335 and 345 can be controlled either from the
GDU displays or via the transponder’s front-panel interface. Remote-mount transponders such as the GTX
23ES, 32, 33, 35R/45R and GTX 335R/345R lack front-panel controls, and are controlled only via the
GDU displays.
The transponder connects via RS-232 to the #1 ADAHRS unit, which relays transponder data to the rest of
the G3X system via the CAN bus. The ADAHRS provides pressure altitude data to the transponder, so a
separate altitude encoder is not required.
In a G3X system with a transponder and a GTN, the transponder is typically controlled by the G3X system,
not the GTN. Note that the GTX 23ES and GTX 35R/45R can only be controlled by the G3X system, not
by the GTN.
The GTX 23ES, 33ES, 35R, 45R, 330ES, 335/335R and GTX 345/345R are Mode S transponders with
extended squitter capability. When provided with a GPS position source that meets the TSO performance
requirements specified in 14 CFR 91.227, these transponders are an acceptable method of complying with
the requirements for ADS-B Out. Compliant GPS position sources include the GPS 20A, GTN, GNS
WAAS units, or the internal WAAS GPS contained in certain models of the GTX 335/345. The GDU GPS
receiver does not meet the TSO GPS requirements, thus it is not sufficient to provide position data to a
transponder for ADS-B Out compliance.
Certain transponders support ADS-B or TIS-A traffic data, and/or FIS-B weather data. See below for
information on traffic (
) and weather (
For information on connecting and configuring a transponder with the G3X system, refer to
and
. Refer to
for information on performing periodic tests of the
transponder.
2.1.1.14 Autopilot
The G3X system features an advanced digital flight director and autopilot, based around the GSA 28 smart
autopilot servo. Servo installation kits are available for numerous popular aircraft, and universal
installation brackets are available for other aircraft. Up to three GSA 28 servos are supported (pitch, roll,
and yaw damper). GSA 28 servos can optionally control aircraft electric trim motors; this keeps the aircraft
in trim when the autopilot is engaged, and also provides trim motor speed control and stuck-switch
protection when hand-flying. The GSA 28 servos also support enhanced stability and protection features
(ESP) which increase safety when hand-flying. For GSA 28 installation information, refer to
and
. For G3X autopilot and ESP setup and adjustment information, refer to
or
. Refer to the G3X Pilot’s Guide or G3X Touch Pilot’s Guide for information on G3X autopilot
and flight director operation.
The GMC 305/307 mode control panel is an optional accessory that provides a convenient set of dedicated
controls for the G3X autopilot and flight director. The GMC 307 supports all the features of the GMC 305,
and adds dedicated control knobs for heading and altitude. The GMC also adds important redundancy by
allowing control of basic autopilot modes even when power is removed from all GDU displays; this is
provided by an RS-232 connection from the GMC to the GSA 28 roll servo. For GMC 305/307 installation
information, refer to
, and
In a G3X Touch system with GDU 4XX displays, all autopilot and flight director functions can be
controlled either from the GDU display or the GMC control panel. In a legacy G3X system with GDU 37X
