Garmin GTN 635 User Manual - Page 14
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Also for Garmin GTN 635: Activation Instructions (46 pages), Manual Supplement (31 pages), Errata (4 pages), User Manual (22 pages), Flight Manual (49 pages), Pilot's Manual (28 pages)
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WFDE PREDICTION PROgRAM INSTRuCTIONS
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INTERPRETINg ThE FDE PREDICTION RESulTS
The GPS/FDE Availability Results screen provides either a "GO" or "STOP" status for the GPS, RAIM, FDE, LNAV RAIM,
and LNAV/VNAV & LPV minima availability. A yellow flag is a possible result for an FDE prediction for a non-Oceanic
prediction (see Figure 12).
A "GO" status indicates that there are enough satellites available during the flight to meet the requirements of that category.
It is possible to have multiple FDE Availability outages during the flight and the status may still be a "GO," as long as none of
the outages exceeds the selected maximum allowable outage.
A "STOP" status is the result of a predicted loss of satellite availability. An FDE Availability or RAIM availability failure
occurs when sufficient satellites are not available for a period longer than the maximum allowable outage (as selected in the
Flight Setup page and viewed in the Setup Information box on the GPS/FDE Availability Results screen) and will produce a
"STOP" status.
A yellow flag indicates an FDE outage in a non-Oceanic (En Route/Terminal) type prediction. Because FDE availability is
not required for En Route/Terminal operations the yellow flag is only a caution to the pilot indicating that there may be an
FDE outage when flying the flight plan. The selected flight plan may be flown despite the caution flag. A "STOP" status can
appear in the FDE outage section only when an Oceanic prediction results in an FDE outage.
More satellites are needed to provide FDE availability than are needed for RAIM. More satellites are needed to provide
RAIM availability than are needed for basic GPS availability. A GPS Availability failure occurs when there is the loss of the
ability to compute a position. This is expected to be accompanied by a an FDE availability failure and a RAIM availability
failure.
• For Oceanic/Remote navigation predictions the displayed result should be "FDE is available for this route." In the
event of a predicted outage, the flight should be delayed, canceled, or re-routed where FDE requirements can be
met.
• For U.S. RNAV routes, SIDs, or STARs navigation predictions, the displayed result should be "RAIM is available for
this route." In the event of a predicted outage, the flight should be delayed, canceled, or re-routed where RAIM
requirements can be met.
• For an LNAV approach at the arrival waypoint predictions, the displayed result should be "LNAV RAIM is available."
In the event that LNAV RAIM is not available, flight planning should include an approach that is not based on GPS
navigation equipment.
• For an LNAV/VNAV, LP, or LPV approach at the arrival waypoint predictions, the displayed result should be "LNAV/
VNAV, LP, & LPV minima may be used for flight planning at the arrival waypoint for the estimated arrival time."
In the event of an "LNAV/VNAV, LP, & LPV minima should not be used for flight planning at the arrival waypoint
for the estimated arrival time" result, flight planning should include an approach that has at least LNAV minima (if
based on GPS navigation equipment) or an approach that is not based on GPS navigation equipment. The prediction
of LNAV/VNAV, LP, and LPV approach availability performed by the WFDE Prediction Program only check for the
visibility of WAAS satellites at the arrival waypoint. It does not consider the WAAS service volume or the current
state of the WAAS system. Pilots should check NOTAMS for WAAS system outages at their planned arrival."
NOTE: Since (due to unforeseen circumstances) actual departure times often differ from planned departure times,
it is good practice to perform predictions for several possible departure times.
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Figure 13 Prediction Results Icons
GARMIN WAAS FDE PREDICTION PROGRAM INSTRUCTIONS
190-00643-01 Rev. E
2/28/2011 1:24:36 PM