Abnormal Operation - Garmin G950 Pilot's Manual

5.12 AbNORMAL OPERATION

This section discusses the Dead Reckoning mode of operation and the subsequent indications.
Dead Reckoning Mode only functions in Enroute (ENR) or Oceanic (OCN) phase of flight. In all other
NOTE:
phases, an invalid GPS solution produces a "NO GPS POSITION" annunciation on the map and the G950
stops using GPS.
While in Enroute or Oceanic phase of flight, if the G950 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 G950 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 G950 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 G950 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/WAAS 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 G950 by the appearance of the letters 'DR' superimposed in yellow over the 'own
aircraft' symbol as shown in Figure 5-143. In addition, 'DR' is prominently displayed in yellow on the HSI slightly
above and to the right of the aircraft symbol on the CDI as shown in Figure 5-143. 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.
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 as shown in Figure
5-143.
Also, while the G950 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.
190-01146-00 Rev. A Garmin G950 Pilot's Guide for the Tecnam P2006T
FLIGHT MANAGEMENT
267