Garmin GNC 420 Pilot's Manual Addendum

190-00181-15  REV. A

400/500 SERIES 

PILOT’S GUIDE ADDENDUM

Fault Detection and Exclusion (FDE) Interface

NOTE: This addendum assumes 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 apply to the GNS 430. The same information applies to the 

other 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

• GNS 530/530A 

Figure 1. 

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. 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 solu-

tion for the specifi ed route of fl ight). Refer to the instructions that came with your 400/500 Trainer Software for complete 

details on using the FDE Prediction Program.