Garmin Flight Deck 100 Marine Instruments User Manual


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190-00728-04 Rev. A
Embraer Prodigy
®
Flight Deck 100 Pilot’s Guide
321
FLIGHT MANAGEMENT
5.12 ABNORMAL OPERATION
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 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bytheappearanceoftheletters‘DR’superimposedinyellowoverthe‘ownaircraft’symbol
asshowninFigure5-147.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 5-147. 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/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 yellow text on the display to denote degraded navigation source information as shown in Figure
5-147.
Also, while the system is in DR Mode, the autopilot does not couple to GPS, and TAWS is disabled. Additionally,
theaccuracyofallnearestinformation(airports,airspaces,andwaypoints)isquestionable.Finally,airspacealerts
continue to function, but with degraded accuracy.
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