Garmin GNS 430A, GNC 420A, GPS 500, GNC 420, GNS 530 Pilot’s Guide Addendum

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 solu­tion 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.

190-00181-15 REV. A

FDE INTERFACE AND CONTROL

• RAIM Prediction—TheRAIM prediction user-interface remains the same for all units in the 400/500 Series.

RAIM is an acronym for Receiver Autonomous Integrity Monitoring, a GPS receiver function that performs a
consistency check on all tracked satellites. RAIM ensures that the available satellite geometry will allow the receiver
to calculate a position within a specifi ed protection limit (2 nautical miles for oceanic and en route, 1 nm for
terminal, and 0.3 nm for non-precision approaches).

During oceanic, en route and terminal phases of fl ight will be available nearly 100% of the time. Because of the
tighter protection limits on approaches, there may be times when RAIM is not available. The 400/500 Series Unit
automatically monitors RAIM and will warn you with an alert message (see the applicable Pilot’s Guide) when it
is not available, and the INTEG annunciator will appear at the bottom left corner of the screen. If RAIM is not
available when crossing the FAF, the pilot must fl y the missed approach procedure. The unit’s RAIM prediction
function will also allow you to see whether RAIM will be available for a specifi ed date and time. NOTE: If RAIM is

not predicted to be available for the fi nal approach course, the approach will not become active-as indicated
by an “Approach is not active” message, a “RAIM not available from FAF to MAP” message and the INTEG
annunciator.

• CDI/Alarms—allows you to defi ne the scale for the GNS 430’s on-screen course deviation indicator. The scale
values represent full scale defl ection for the CDI to either side. The default setting is “Auto”. At this setting, the
CDI scale is set to 5 nm during the en route and oceanic/remote phases of fl ight. Within 30 nm of your destination
airport the CDI scale gradually ramps down to 1.0 nm (terminal area). Likewise when leaving your departure
airport the CDI scale is set to 1.0 nm and gradually ramps up to 5 nm beyond 30 nm (from the departure airport).
Oceanic fl ight phase (OCN) begins when the aircraft is more than 200 nm from the nearest airport.

During approach operations the CDI scale gradually ramps down even further, to 0.3 nm. This transition normally
occurs within 2.0 nm of the fi nal approach fi x (FAF). If a lower CDI scale setting is selected (i.e., 1.0 nm or 0.3
nm) the higher scale settings will not be selected during ANY phase of fl ight. For example, if 1.0 nm is selected,
the GNS 430 will use this for the en route and terminal phase and ramp down to 0.3 nm during an approach.
Note that the Receiver Autonomous Integrity Monitoring (RAIM) protection limits listed below follow the selected
CDI scale and corresponding modes:

CDI Scale RAIM Protection (no display)

Auto (oceanic) 4.0 nm

±5.0 nm or Auto (en route) 2.0 nm

±1.0 nm or Auto (terminal) 1.0 nm

±0.3 nm or Auto (approach) 0.3 nm

An “Auto” ILS CDI selection allows the GNS 430 to automatically switch the external CDI from the GPS receiver
to the VLOC receiver, when established on the fi nal approach course. Or, select “manual” to manually switch the
external CDI connection, as needed. An arrival alarm, provided on the CDI / alarms page, may be set to notify
you with a message when you have reached a user-defi ned distance to the fi nal destination (the direct-to waypoint
or the last waypoint in a fl ight plan). Once you have reached the set distance (up to 99.9 units), an “Arrival at
[waypoint]” message will be displayed.

190-00181-15 Rev. A

Figure 2. CDI Enroute/Oceanic (OCN) Scale