Ahrs Operation - Garmin G3X Touch Pilot's Manual

System Overview

AHRS OPERATION

The Attitude and Heading Reference System (AHRS) performs attitude, heading,
and vertical acceleration calculations for the G3X Touch System, utilizing GPS,
magnetometer, and air data, in addition to information from its internal sensors.
Attitude and heading information are updated on the PFD while the AHRS receives
appropriate combinations of information from the external sensor inputs.
The AHRS (GSU 25D) corrects for shifts and variations in the Earth's magnetic field by
applying the Magnetic Field Variation Database. The Magnetic Field Variation Database
is derived from the International Geomagnetic Reference Field (IGRF). The IGRF is a
mathematical model that describes the Earth's main magnetic field and its annual rate
of change. The database is updated approximately every 5 years via a GDU software
update. Failure to update this database could lead to erroneous heading information
being displayed to the pilot.
Magnetometer Data
AHRS Normal
Operation
Loss of GPS, magnetometer, or air data inputs is communicated to the pilot by
message advisory alerts. Any failure of the internal AHRS inertial sensors results in loss
of attitude and heading information (indicated by red 'X' flags over the corresponding
flight instruments). If the G3X Touch senses the magnetic heading measurement is
valid, but possibly outside of the internal accuracy limits, the numeric heading value on
the PFD is displayed in yellow.
24
Garmin G3X Touch
GPS Data
Air Data
AHRS no- AHRS no-Mag/
Mag Mode no-Air Mode
Heading Invalid
™ Pilot's Guide for Certified Aircraft
Magnetometer Data
Air Data
AHRS
no-GPS
Mode Attitude/Heading Invalid
190-02472-00 Rev. D