Pilot's Guide

190-00663-03 Rev. A
Garmin G1000 Pilot’s Guide for the Beechcraft C90A/GT/GTi
19
SYSTEM OVERVIEW
AHRS FAiluRe
Failure of the internal AHRS inertial sensors may result in loss of attitude and heading information
(indicated by red ‘X’ flags over the corresponding flight instruments).
GPS inPut FAiluRe
The system provides two sources of GPS information. If a single GPS receiver fails, or if the information
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 reliable. Unavailable or unreliable air data or magnetometer data in addition to
GPS failure results in loss of all attitude and heading information.
NOTE: In-flight initialization of AHRS, when operating without any valid source of GPS data and at true
air speed values greater than approximately 200 knots, is not guaranteed. Under these rare conditions, it
is possible for in-flight AHRS initialization to take an indefinite amount of time which would result in an
extended period of time where valid AHRS outputs are unavailable.
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, if the aircraft is airborne, the heading output
on the PFD does become invalid (as indicated by a red “X”).
AiR DAtA inPut FAiluRe
Failure of the air data input has no effect on the AHRS output while AHRS is receiving valid GPS
information. 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).
GRS 7800 OPERATION (OPTIONAL)
In primary mode, the GRS 7800 AHRS relies upon GPS and magnetic field measurements (air data is not
used). If either GPS or magnetometer data is unavailable or unreliable, the AHRS uses the remaining inputs
for attitude/heading determination. In DG Free Mode, the magnetometer data is replaced by a heading value
set by the flight crew. Four AHRS modes of operation are available (Figure 1-14) and depend upon the
combination of available sensor inputs. Loss of GPS or magnetometer sensor inputs is communicated to the
pilot by message advisory alerts. Refer to the Flight Instruments section for further discussion of DG Free
Mode.