GRT Avionics, Inc.
May 2019
Sport EX/Horizon EX Install. Manual
8
Rev. A
2-2-2: AHRS
The Sport EX/Horizon EX can receive two sets of AHRS data. Typically, one set of AHRS
d
ata comes from the DU’s internal AHRS while the second comes from a serial port
connection to an external AHRS. This only applies to the Sport EX, with the Horizon EX
requiring both sets of data to come from external AHRS sources. The external AHRS
connection may come from a standalone AHRS unit or from the internal AHRS of a
separate Sport EX display unit. Providing the EFIS with multiple attitude sources allows
for automatic cross-
checking of the attitude data. An “AHRS Miscompare” warning will
occur if the roll and pitch attitude differ more that the test threshold. Either set of AHRS
data can be chosen by the pilot to drive the EFIS. The EFIS will default to “BOTH,” a
composite of the two AHRS data sets.
2-2-3: Autopilots
An autopilot provides the greatest benefit for the cost of almost any addition to the
airplane. It is an essential tool for single pilot IFR and highly beneficial for any VFR pilot
that undertakes cross-country flights. The autopilot frees up the pilot to perform other vital
tasks, such as looking for traffic, radio tuning, evaluating imminent weather, etc
… We
highly recommend it for all airplanes, with the exception of those that are not flown cross-
country. If you have chosen not to install an autopilot, but may do so in the future, we
recommend installing the servo wiring at the very least, and possibly installing the servo
mounting kits as well. This will make the addition of the servo easier in the future. This
also increases the value of the airplane for any future owner if it is sold without an autopilot
installed.
2-2-4: Autopilot Using GRT Avionics Servos
An autopilot using GRT Servos provides excellent performance and is the easiest
configuration to implement. The installation will require wiring for the servos, mounting
kits to attach the servos to your airplane, a power-switch for the servos and an
engage/disengage button. A single serial port is used to control both the roll and pitch
servos.
When using multiple GRT EFIS display units, any display unit can function as the Autopilot
Mode Controller. Adding an autopilot switch to a second display unit ensures functionality
in the event that the primary autopilot-controlling display unit fails.
2-2-5: Trio Avionics and TruTrack Flight Systems External Autopilots
Most of our customers use GRT Servos for their autopilot needs. However, airplanes with
existing autopilots can still interface with any GRT EFIS. This is accomplished via a serial
output from the EFIS for lateral-only steering. Autopilots that provide vertical steering
require an ARINC 429 adapter to receive GPSS and GPSV commands, which requires
the use of both a serial input and an output from the EFIS.
