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G1000 System Maintenance Manual Page 2-1
190-00903-00 Rev. A
SECTION 2
SYSTEM OVERVIEW
This section describes the major subsystems of the G1000. Because G1000 configurations vary
depending on specific aircraft, this section is only a guideline. Refer to the OEM maintenance
documentation for aircraft specific system information.
2.1 G1000 FLIGHT INSTRUMENTATION
The GRS 77 AHRS, GDC 74B Air Data Computer, and GMU 44 Magnetometer supply the
G1000 with flight instrumentation data. The data consists of aircraft attitude, heading, altitude,
airspeed, vertical speed, and outside air temperature information, all displayed on the PFD (the
same data is displayed on the MFD in reversionary mode). Data outputs from the GRS 77 and
GDC 74B are sent directly to the PFD via ARINC 429. Additional communications paths
connect the GRS and GDC 74B to GIA 63W units providing quadruple redundant capability.
The GRS 77 receives GPS data from both GIAs, airspeed data from the GDC 74B, and magnetic
heading from the GMU. Using these three external sources, combined with internal sensor data,
the GRS accurately calculates aircraft attitude and heading (Figure 2-1).
In addition to using internal sensors, the GRS 77 uses GPS information, magnetic field data and
air data to assist in attitude/heading calculations. In normal mode, the GRS 77 relies upon GPS
and magnetic field measurements. If either of these external measurements is unavailable or
invalid, the GRS 77 uses air data information for attitude determination. Four GRS 77 modes of
operation are available 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.
Figure 2-1. GRS 77 Block Diagram
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