DEAD RECKONING MODE
Dead Reckoning Mode only functions in En-route (ENR)
phase of flight. In all other phases, an invalid GPS
solution produces a “NO GPS POSITION”
annunciation on the map and the GTN 650 Nxi stops
using GPS.
It is important to note that estimated navigation data supplied by the GTN 650Nxi in
DR Mode may become increasingly unreliable and must not be used as a sole
means of navigation. If while in DR Mode airspeed and/or heading data is also lost or
not available, the DR function may not be capable of accurately tracking estimated
position and, consequently, the system may display a path that is different than the
actual movement of the aircraft. Estimated position information displayed by the GTN
650 Xi through DR while there is no heading and/or airspeed data available shall not be
used for navigation.
DR Mode is inherently less accurate than the standard GPS/SBAS Mode due to the lack
of satellite measurements needed to determine a position.
Changes in wind speed and/or wind direction
compound the relative inaccuracy of DR Mode.
Because of this degraded accuracy, other navigation
equipment must be relied upon for position awareness
until GPS-derived position data is restored.
DR Mode is indicated on the GTN 650Xi by the appearance of the letters ‘DR’
superimposed in yellow over the ‘own aircraft’ symbol.
In addition, ‘DR’ is prominently displayed in yellow on the aircraft symbol. Also, the
CDI deviation bar is removed from the display. Lastly, but at the same time, a ‘GPS
NAV LOST’ alert message appears on the display.
Normal navigation using GPS/SBAS source data resumes automatically once a valid
GPS solution is restored. As a result of operating in DR Mode, all GPS- derived data is
computed based upon an estimated position and all external outputs dependent on
GPS position are flagged.
While the GTN 650Xi is in DR Mode, some terrain functions are not available.
Additionally, the accuracy of all nearest information (airports, airspaces, and waypoints)
is questionable. Finally, airspace alerts continue to function, but with degraded
accuracy.
RAIM AVAILABILITY
Because of tighter protection limit on approaches, there may be times when RAIM is
not available. The GTN 650Xi automatically monitors RAIM and warns with an alert
message when it is not available.
During GNSS approaches, if RAIM is not available when crossing the FAF, the missed
approach procedure must be flown
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