Pilot's Guide

1-4
Garmin G500H Pilot’s Guide
190-01150-02 Rev. F
Foreword
Sec 1
System
Sec 2
PFD
Sec 3
MFD
Sec 4
Hazard
Avoidance
Sec 5
Additional
Features
Sec 6
Annun.
& Alerts
Sec 7
Symbols
Sec 8
GlossaryAppendix A
Appendix B
Index
1.1.4 GRS 77H
The GRS 77H is an Attitude and Heading Reference System (AHRS) unit that
provides aircraft attitude information to the G500H display. The unit contains
advanced accelerometers and rate sensors. In addition, the GRS 77H interfaces
with both the GDC 74H Air Data Computer and the GMU 44 magnetometer.
The GRS 77H also utilizes GPS data forwarded from the GDU 620. Actual
attitude and heading information is sent to the GDU 620 using an ARINC 429
digital interface.
Figure 1-4 GRS 77H AHRS
The IGRF (International Geomagnetic Reference Field) model is contained
in the GRS 77H and is only updated once every five years. The IGRF model
is part of the Navigation Database. At system power-up, the IGRF models in
the GRS 77H and in the Navigation Database are compared, and if the IGRF
model in the GRS 77H is out of date, the user is prompted to update the IGRF
model in the GRS 77H. The prompt will appear after the G500H splash screen
is acknowledged on the MFD.
1.1.5 GMU 44
The GMU 44 magnetometer senses the earth’s magnetic field. Data is sent
to the GRS 77H AHRS for processing to determine aircraft magnetic heading.
This unit receives power directly from the GRS 77H and communicates with the
GRS 77H using a RS-485 digital interface.
Figure 1-5 GMU 44 Magnetometer