Garmin GNS 430 Pilot's Manual And Reference page 193

• Approach Phase – Defined as when all three of the
following conditions are met:
1) The distance to destination runway
threshold is equal to or less than 5 nm.
2) The height above the destination runway
threshold elevation is equal to or less than
1900 feet.
3) The distance to the destination runway
threshold is decreasing.
• Departure Phase – Defined as when all five of the
following conditions are met:
1) It has been determined that the aircraft was
previously 'on-ground'.
2) The aircraft has a vertical velocity greater
than zero.
3) The aircraft has a groundspeed greater than
35 knots.
4) The aircraft has an altitude greater than 150
feet AGL and less than 1500 feet AGL.
5) The aircraft is within 15 nm of the departure
airport.
NOTE: There are additional factors beyond those
outlined in the preceding paragraphs that may
alter the determined TERRAIN flight phase.
Nearest Airport Criteria and Terrain Phase of
Flight
Changes to the Nearest Airport Criteria Page (Figure
11-4) 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 (when 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 in
Section 11.3. PDA alerting is also affected as described in
Section 11.3.
As an example, if the pilot configures the unit to
include only airports with runways 5000 feet or longer,
only these are added to the Nearest Airport List. The
terrain phase of flight is affected in that all airport runways
under 5000 feet are not included in terrain calculations.
During a cross-country flight with this configuration, only
airports runways 5000 feet or greater cause the unit to go
into Terminal or Approach Mode from Enroute mode. If
the pilot makes an emergency landing at an airport that
did not show up in the Nearest Airport List, FLTA alerts
would be issued throughout the descent.
GNS 430 Pilot's Guide and Reference
Figure 11-4 Nearest Airport Criteria Page
SECTION 11
TERRAIN
11-5