Garmin Flight Deck 100 User Manual

190-00728-04  Rev. A

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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.

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 valid.

A failure of the air data input has no effect on AHRS output while AHRS is operating in normal 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).

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”).

For a detailed description of all annunciations and alerts, refer to Appendix A.  Refer to the Airplane 

Flight Manual (AFM) for additional information regarding pilot responses to these annunciations.

When an LRU or an LRU function fails, a large red “X” is typically displayed on windows associated with the 

failed data (Figure 1-24 displays all possible flags and responsible LRUs).  Upon system power-up, certain windows 
remain invalid as equipment begins to initialize.  All windows should be operational within one minute of power-
up.  If any window remains flagged, the system should be serviced by a Garmin-authorized repair facility.