Cockpit Reference Guide

Garmin G1000 Cockpit Reference Guide for the Cessna Nav III
190-00384-08 Rev. A
SECTION 11 – ABNORMAL
OPERATION
11-3
11.6 DEAD RECKONING
WARNING: DR Mode is inherently less accurate
than the standard GPS/WAAS Mode due to the
lack of satellite measurements needed to deter-
mine a position. Changes in wind speed and/or
wind direction 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.
While in Enroute or Oceanic phase of flight, if the
G1000 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 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.
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 G1000 stops navigating in GPS
Mode.
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’ is 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. 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 PFD.
Normal navigation using GPS/WAAS source data
resumes 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 be used for navigation.
Figure 11-4 Dead Reckoning Indications
Symbolic Aircraft
(Map pages and Inset Map)
CDI ‘DR’ Indication on PFD
As a result of operating in DR Mode, all GPS-derived
data is computed based upon an estimated position and is
displayed as yellow text on the display to denote degraded
navigation source information. This data 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 and MFD
• Track Bug
• All Bearing Pointer Distances
• Active Flight Plan distances, bearings, and ETE
values