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2.0 nm during the en route phase of flight.
Aircraft is within 31 nm of the destination airport (i.e., terminal area).
The scale linearly ramps down to 1.0 nm over a distance of 1 nm.
Aircraft is leaving the departure airport. The scale is set to 1.0 nm once the
aircraft is over 30 nm from the departure airport. It begins to gradually ramp up to
2 nm when the flight phase changes from terminal (TERM) to en route (ENR).
During GPS approach operations, the scale gradually transitions down to an angular
scale.
Aircraft is 2.0 nm before the final approach fix. Scaling tightens from 1.0 nm to
Selecting a lower value (0.3 nm or 1.0 nm) prevents the selection of higher scale
settings during ANY phase of flight. Example: If you select 1.0 nm, the unit uses
this setting for en route and terminal phases, and ramps down further during
approach.
Horizontal alarm limits (HAL) are used to compare against GPS position integrity.
These protection limits follow the CDI scale, unless the corresponding flight phase
requires a lower HAL. For example, the selected scale setting is 1.0 nm, but full-scale
deflection during approach still follows the approach scale setting (0.30 nm).
Approach
Terminal
En Route
Oceanic
At the default setting, the scale sets to
0.30 nm or Auto
1.00 nm or Auto
2.00 nm or Auto
Auto
0.30 nm
1.00 nm
2.00 nm
2.00 nm
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