Navigation Database; Terrain Phase Of Flight; Nearest Airport Criteria & Terrain Phase Of Flight - Garmin GNS 530W Pilot's Manual & Reference

Navigation Database

As explained in the "Premature Descent Alerting
(PDA)" section, the Garmin Terrain premature descent
alerting (PDA) algorithms utilize data contained in the
Navigation Database. It is therefore important to also
have the latest Navigation Database installed to ensure
correct Terrain alerting.

Terrain Phase of Flight

The Terrain Phase of Flight definitions are listed
below:
En Route Phase - Defined as when the conditions
for Terminal, Approach, and Departure Phases are not
met.
Terminal Phase - Defined as when all three of the
following conditions are met:
• The aircraft is 15 NM or less from the destination
runway.
• The distance to the destination runway threshold
is decreasing.
• The aircraft is at or below (lower than) a straight
line drawn between the two points specified in the
table below (relative to the destination runway).
Distance to Runway
15 NM
5 NM
Approach Phase - Defined as when all three of
the following conditions are met:
• The distance to the destination runway threshold
is equal to or less than 5 NM.
• The height above the destination runway thresh-
old elevation is equal to or less than 1000 feet.
• The distance to the destination runway threshold
is decreasing.
Height above Runway
3500 feet
1900 feet
Departure Phase - Defined as when all five of the
following conditions are met:
• It has been determined that the aircraft was previ-
ously "on-ground."
• The aircraft has a vertical velocity greater than
zero.
• The aircraft has a ground speed greater than 35
knots.
• The aircraft has an altitude greater than 150 feet
AGL and less than 1500 feet AGL.
• The aircraft is within 15 NM of the departure
airport.
NOTE: There are additional factors beyond what is
outlined above that may alter the determined TERRAIN
flight phase.
Nearest Airport Criteria & Terrain Phase of Flight
Changes to the Nearest Airport Criteria Page affect
how the Terrain system performs. The nearest airport
list is used to derive the terrain destination airport
when there is no loaded active flight plan or when
deviating from the active flight plan (whenever the
terrain algorithms go into estimation mode). In turn,
the nearest airport list is used to determine the terrain
phase of flight. The terrain phase of flight dictates
the Required Terrain Clearance (RTC) levels at which
Forward Looking Terrain Avoidance (FLTA) alerting
occurs, as described later in the Forward Looking
Terrain Avoidance section. Premature Descent Alerting
(PDA) is also affected as described later in the PDA
section.
2 - NAV PAGES
Terrain Operation
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