FMS Degradation
Once inhibited, sensors will not be monitored or used by the system, and the system will not re-enable those sensors in the event of a failure. The system will revert to Dead Reckoning or no position until an available sensor with a valid position is available.
This portion of the guide discusses enroute and terminal Flight Management System (FMS) degradation and Dead Reckoning (DR). For information on final approach degradation behavior, see the Approaches portion in Procedures given earlier in this section.
The FMS will operate in either the GPS or the DR position fixing mode, depending on the available sensors. If enabled and available for use, GPS 1/GPS 2 will have priority, and SBAS will be used if available. If one GPS sensor fails, the system will automatically transition to the other GPS sensor.
If GPS is lost and the system is unable to recover a signal, or if both GPS sensors fail, the "GPS LOI" (Loss of Integrity) annunciation is displayed in amber on the PFW. Also, a system message concerning the loss of GPS will be generated.