User Guide

190-00571-00 Rev. A Garmin G1000 System Overview for the Beechcraft A36/G36
2-13
SYSTEM OVERVIEW
AHRS Operation
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
(primary) mode, the AHRS relies upon GPS and magnetic
field measurements. If either of these external measure-
ments is unavailable or invalid, the AHRS uses air data in-
formation for attitude determination. Four AHRS modes
of operation are available (see table below) and depend
upon the combination of available sensor inputs. Loss of
air data, GPS, or magnetometer sensor inputs is commu-
nicated to the pilot by message advisory alerts.
GPS Input Failure
The G1000 system provides two sources of GPS infor-
mation. If a single GPS receiver fails, or if the informa-
tion provided from one of the GPS receivers is unreliable,
the AHRS seamlessly transitions to using the other GPS
receiver. An alert message informs the pilot of the use of
the backup GPS path. If both GPS inputs fail, the AHRS
continues to operate in reversionary ‘No GPS’ mode so
long as the air data and magnetometer inputs are available
and valid.
AHRS Mode
Available AHRS Functions Available Sensor Inputs
Pitch Roll Heading
GPS Input
(At least one)
GMU 44
Magnetometer
GDC 74A
Air Data Computer
Normal/Primary X X X X X X
Reversionary:
No GPS
X X X - X X
Reversionary:
No Magnetometer
X X - X - X
Reversionary:
No Magnetometer
No Air Data
X X - X - -
Air Data Input Failure
A failure of the air data input has no effect on AHRS
output while AHRS is operating in normal/primary mode.
A failure of the air data input while the AHRS is operating
in reversionary ‘No GPS’ mode results in invalid attitude
and heading information on the PFD (as indicated by red
‘X’ flags).
Magnetometer Failure
If the magnetometer input fails, the AHRS transitions
to one of the reversionary ‘No Magnetometer’ modes and
continues to output valid attitude information. However,
the heading output on the PFD does become invalid (as
indicated by a red ‘X’).
NOTE: Please refer to the Annunciations and
Alerts Pilot’s Guide for specific AHRS alert infor-
mation.
NOTE: Pilots should be aware that aggressive
maneuvering in any of the three reversionary
modes listed below can degrade AHRS accu-
racy.