Garmin G900X Pilot’s Guide 190-00726-00 Rev. J16SYSTEM OVERVIEWSYSTEMOVERVIEWFLIGHTINSTRUMENTSEISAUDIO PANEL& CNSFLIGHTMANAGEMENTHAZARDAVOIDANCEAFCSADDITIONALFEATURESAPPENDICESINDEXAHRS OPERATIONNOTE: Aggressive maneuvering while AHRS is not operating normally may degrade AHRS accuracy.The Attitude and Heading Reference System (AHRS) performs attitude, heading, and vertical accelerationcalculations for the G900X System, utilizing GPS, magnetometer, and air data in addition to information fromits internal sensors. Attitude and heading information are updated on the PFD(s) while the AHRS receivesappropriate combinations of information from the external sensor inputs.The AHRS (GRS 77) corrects for shifts and variations in the Earth’s magnetic field by applying the MagneticField Variation Database. The Magnetic Field Variation Database is derived from the International GeomagneticReference Field (IGRF). The IGRF is a mathematical model that describes the Earth’s main magnetic field and itsannual rate of change. The database is updated approximately every 5 years. See the Appendices for informationon updating the Magnetic Field Variation Database. The system will prompt you on startup when an update isavailable. Failure to update this database could lead to erroneous heading information being displayed to thepilot.Attitude/Heading InvalidAHRSno-GPSModeAHRS NormalOperationAHRS no-Mag ModeAHRS no-Mag/no-Air ModeHeading InvalidavailableavailableunavailableunavailableavailableunavailableunavailableavailableAir DataMagnetometer Dataunavailableavailable GPS DataMagnetometer DataAir DataFigure 1-12 AHRS Operation
