11.6 Dead Reckoning - Garmin G1000 Reference Manual

11.6 DEAD RECKONING

If at any time the G1000 detects an invalid GPS solution
or is unable to calculate a GPS position, the system will
automatically revert to Dead Reckoning (DR) mode. In DR
mode, the G1000 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.
DR mode is indicated on the G1000 by the appearance
of the letters 'DR' superimposed in yellow over the 'own
aircraft' symbol as shown in Figure 11-4. In addition, 'DR'
will be prominently displayed, also in yellow, on the HSI
slightly above and to the right of the aircraft symbol on the
CDI as shown in Figure 11-4. Lastly, but at the same time,
a 'GPS NAV LOST' alert message will appear on the PFD.
Normal navigation using GPS/WAAS source data
will resume automatically once a valid GPS solution is
restored.
It is important to note that estimated navigation
data supplied by the G1000 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 your 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 G1000 through DR while there is no heading and/or
airspeed data available should not for
DR mode is inherently less accurate than the
standard GPS/WAAS mode due to the lack of satellite
measurements needed to determine a position. Changes
in wind speed and/or wind direction will compound the
relative inaccuracy of DR mode. Because of this degraded
accuracy, the crew must maintain position awareness using
other navigation equipment until GPS-derived position
data is restored.
navigation.
Garmin G1000 Cockpit Reference Guide for the Cessna Nav III
SECTION 11 – ABNORMAL
CDI 'DR' Indication on PFD
Figure 11-4 Dead Reckoning Indications
As a result of operating in DR mode, all GPS-derived
data will be computed based upon an estimated position
and will be displayed as yellow text on the map to denote
degraded navigation source information.
includes the following:
• Navigation Status Box fields except Active Leg, TAS,
and DTK
• GPS Bearing Pointer
• Wind data and pointers in the Wind Data Box on
the PFD
• Track Bug
• All Bearing Pointer Distances
• Active Flight Plan distances, bearings, and ETE
values
Also, while the G1000 is in DR mode, the autopilot will
not couple to GPS, and both TAWS and Terrain Proximity
will be disabled. Additionally, the accuracy of all nearest
information (airports, airspaces, and waypoints) will be
questionable. Finally, airspace alerts will continue to
function, but with degraded accuracy.
OPERATION
Symbolic Aircraft
(Map pages and Inset Map)
This data
11-3