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The GNC 300 works in conjunction with a set of external switches and your
OBS/HSI to fly GPS approaches. The external switches are used to control GPS func-
tions, and contain illuminated annunciators to indicate when functions are active.
Your installation must also have annunciators for waypoint arrival and GPS messages.
The NAV/GPS switch determines which data (GPS or NAV1) will be displayed on
the HSI and used by the autopilot/flight director. The current selection will be
indicated by an annunciator light. If power to the GNC 300 is lost, the system will
automatically revert to NAV1.
The GPS APR switch is used to arm or deactivate an approach, and indicates the
current approach phase status (‘ARM’ or ‘ACTV’). The GNC 300 will automatically
arm a selected approach 30 nm from the airport. If the pilot wishes to terminate
the approach or fly the missed approach, the GPS APR switch may be pressed to
disarm/deactivate the approach at any time and return the CDI scale sensitivity to
the 1.0 nm setting. The GPS APR switch may also be used to rearm the approach
at any time before reaching the FAF. If the selected approach is disarmed before
the FAF, the unit will prompt you to re-arm the approach 3 nm before the final
approach fix.
73
APPROACH NAVI-
GATION
GPS Approach
Arm Approach Mode
The external GPS APR switch will automatically
be set to the ARM position 30 nm from the desti-
nation airport. Once the approach is armed, the
unit will provide a smooth transition from the 5.0
to 1.0 nautical mile scale, and down to 0.3 nm
within 2 nm inbound to the FAF. If the approach
is manually disarmed, it may be re-armed at any
time (before reaching the FAF) by pressing the
GPS APR switch.
SECTION
6
APPROACH NAV
GPS APR Switch/
Auto Arming
GPS APR
ARM ACTV
GPS APR
ARM ACTV
NAV GPS
NAV ACTV
NAV GPS
ARM GPS
GPS APR
CTV
300 7/14/98 8:50 AM Page 73