Garmin GNC 420 Instructions Manual

Page 1

190-00643-00  REV. A

400/500 SERIES FDE PREDICTION INSTRUCTIONS

NOTE: These instructions assume the user has experience operating the applicable 400/500 Series Unit and is familiar with the 

operation of RAIM.  The fi gures in this addendum are derived from the 400/500 Series units. The information in this document 

applies to all 400/500 units unless otherwise stated.

FAULT DETECTION AND EXCLUSION (FDE)

The GARMIN 400/500 Series Main and GPS Software version 3.00 and higher (Figure 1) incorporate Fault Detection and 

Exclusion (FDE) display interface and control, satisfying the requirements for “GPS as a Primary Means of Navigation for Oceanic/

Remote Operations” per FAA Notice N8110.60. 

FDE consists of two distinct parts, fault detection and fault exclusion. The fault detection part detects the presence of an 

unacceptably large pseudorange error (and presumably, position error) for a given mode of fl ight. Upon the detection, fault 

exclusion follows and excludes the source of the unacceptably large pseudorange error, thereby allowing navigation to return to 

normal performance without an interruption in service. To enhance safety, FDE functionality is provided for other phases of fl ight 

(non-precision approach, terminal, en route).  The FDE functionality for non-oceanic fl ight phases adheres to the same missed alert 

probability, false alert probability, and failed exclusion probability specifi ed by N8110.60.

The following 400/500 Series Units are affected:

• GPS 400

• GNC 420/420A

• GNS 430/430A

• GPS 500 (TAWS)

• GNS 530/530A (TAWS)

Figure 1. Software Version Screen

PRE-DEPARTURE VERIFICATION OF FDE

An FDE prediction must be performed prior to departure for a fl ight plan involving:

• Oceanic/Remote operation where GPS is to be the sole source of navigation per FAA Notice 8110.60

• U.S. Area Navigation (RNAV) routes, Standard Instrument Departures (SIDs), or Standard Terminal Arrival Routes (STARs) if a 

NOTAM indicates a GPS satellite (or satellites) is scheduled to be out-of-service, per FAA AC 90-100 “U.S. Terminal and En Route 

Area Navigation (RNAV) Operations”

Prior to departure, the operator must use the FDE Prediction Program supplied with the 400/500 Trainer Software to 

demonstrate that there are no outages in the capability to navigate on the specifi ed route of fl ight (the FDE Prediction Program 

determines whether the GPS constellation is robust enough to provide a navigation solution for the specifi ed route of fl ight).