Section 12: Fault Detection And Exclusion; Detection And Exclusion - Garmin GNS 430 Pilot's Manual And Reference

SECTION 12: FAULT DETECTION
AND EXCLUSION
FDE is an acronym that stands for Fault Detection and
Exclusion. FDE was incorporated in the Garmin GNS
430 Main and GPS Software version 3.00 and higher.
FDE algorithms, provide a basis for approval per the
requirements for 'GPS as a Primary Means of Navigation for
Oceanic/Remote Operations' per FAA Notice N8110.60.
The oceanic flight phase is used by the GNS 430 when the
aircraft is more than 200 nm from the nearest airport. FDE
requires no pilot interaction during flight, but predicting
the capability of the GPS constellation to provide service
during a flight is done by the pilot prior to departure.

12.1 DETECTION AND EXCLUSION

FDE consists of two distinct parts, fault detection
and fault exclusion. The detection function refers to
the capability to detect a satellite failure which can affect
navigation.
excludes one or more failed satellites and prevent them
from being used during navigation. This allows the GPS to
return to normal performance without interruption. The
process is entirely automated and does not require pilot
interaction during flight. On the Satellite Status Page,
the pilot can view information related to FDE operation.
To enhance safety, FDE functionality is provided for
other phases of flight (non-precision approach, terminal,
enroute). The FDE functionality for non-oceanic flight
phases adheres to the same missed alert probability, false
alert probability, and failed exclusion probability specified
by N8110.60.
Figure 12-1 shows satellite number 9 exclusion during
oceanic phase of flight. No message notifying the user
of exclusion appears. In addition to the EPE and DOP
fields, there is the Horizontal Uncertainty Level (HUL)
field which displays a 99% confidence level that the
aircraft position is within a circle with a radius of the value
displayed in the HUL field.
GNS 430 Pilot's Guide and Reference
SECTION 12 – FAULT DETECTION
AND EXCLUSION
Upon detection, the exclusion function
Oceanic
Excluded Satellite
Mode
(Checkered Pattern)
Figure 12-1 Satellite Status Page
Horizontal
Uncertainty
Level
12-1