Pilot's Guide

190-00663-02 Rev. B

Garmin G1000 Pilot’s Guide for the Hawker Beechcraft C90A/GT/GTi

SYSTEM OVERVIEW

AHRS OPERATION

NOTE: Refer to the Appendices for speciﬁc AHRS alert information.

NOTE: Aggressive maneuvering while AHRS is not operating normally may degrade AHRS accuracy.

In addition to using internal sensors, the GRS 77 AHRS uses GPS information, magnetic ﬁeld data and air

data to assist in attitude/heading calculations. In normal mode, the AHRS relies upon GPS and magnetic

ﬁeld measurements. If either of these external measurements is unavailable or invalid, the AHRS uses air

data information for attitude determination. Four AHRS modes of operation are available (see Figure 1-13)

and depend upon the combination of available sensor inputs. Loss of air data, GPS, or magnetometer sensor

inputs is communicated to the pilot by message advisory alerts.

The AHRS (GRS 77) 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. See the Appendices for

information on updating the Magnetic Field Variation Database. The system will prompt you on startup when

an update is available. Failure to update this database could lead to erroneous heading information being

displayed to the pilot.

Attitude/Heading Invalid

AHRS

no-GPS

Mode

AHRS Normal

Operation

AHRS no-

Mag Mode

AHRS no-Mag/

no-Air Mode

Heading Invalid

available

unavailable

available

unavailable

available

Air Data

Magnetometer Data

unavailable

available

GPS Data

Magnetometer Data

Air Data

Figure 1-13 AHRS Operation