Garmin G1000 NXi, Руководство пилота

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190-02177-02 Rev. A
Garmin G1000 NXi Pilot’s Guide for the Cessna NAV III
SY
STEM
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INSTRUMENTS
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GEMENT
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AFCS
ADDITIONAL
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TURES
APPENDICES
INDEX
247
FLIGHT MANAGEMENT
5.10 ABNORMAL OPERATION
DEAD RECKONING MODE
This section discusses the Dead Reckoning mode of operation and the subsequent indications.
NOTE: Dead Reckoning Mode only functions in Enroute (ENR) or Oceanic (OCN) phase of flight. In all other
phases, an invalid GPS solution produces a “NO GPS POSITION” annunciation on the map and the system
stops using GPS.
While in Enroute or Oceanic phase of flight, if the system detects an invalid GPS solution or is unable to
calculate a GPS position, the system automatically reverts to Dead Reckoning (DR) Mode. In DR Mode, the
system uses its last-known position combined with continuously updated airspeed and heading data (when
available) to calculate and display the aircraft’s current estimated position.
It is important to note that estimated navigation data supplied by the system 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 system through DR while there is no heading and/or
airspeed data available should 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 system by the appearance of the letters ‘DR’ superimposed in amber over the
‘own aircraft’ symbol on the MFD. In addition, ‘DR’ is prominently displayed in amber on the HSI slightly
below and to the left of the aircraft symbol on the CDI. The CDI deviation bar remains, but is removed from the
display after 20 minutes in DR Mode. The autopilot will remain coupled in DR mode as long as the deviation
info is available (20 min.) Lastly, but at the same time, a ‘GPS NAV LOST’ alert message appears on the PFD.
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
is displayed as amber text on the display to denote degraded navigation source information as shown in the
following figure. If the VSD Inset is selected on the MFD, ‘VSD Not Available’ will be displayed.
While the system 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.