Garmin GPS 155TSO, Owner'S Manual

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When the aircraft is within 2 nm of the FAF along the inbound course to the final
approach (see left), the ACTV annunciator will illuminate on the GPS APPR switch,
and the GPS 155 will enter the active approach phase. The CDI will now scale down
to the 0.3 nm sensitivity. If you wish to deactivate the approach during the active
phase, simply release the GPS APPR switch from the ‘ARM’ position. This will return
the CDI scale to 1 nm setting and provide less sensitive CDI deflection in missed
approach conditions.
The GPS SEQ switch is used to select manual or automatic waypoint sequencing
of waypoints. Setting the GPS SEQ switch to the HOLD position holds your current
‘active to’ waypoint as your navigation reference and prevents the GPS from sequenc-
ing to the next waypoint.
When the GPS SEQ switch is set to the AUTO position, automatic waypoint
sequencing is selected. Whenever the GPS SEQ switch is engaged, the HOLD annun-
ciator will illuminate and the GPS will continue navigating to the waypoint regardless
of your position relative to other waypoints.
The GPS SEQ switch must be set to the HOLD position any time you are deviat-
ing from the flight sequence of an approach (e.g., when you are flying radar vectors)
or when you must cross the same waypoint twice in succession (e.g., IAF and FAF at
the same waypoint). Whenever the GPS SEQ switch is set to the HOLD position, the
GPS 155 allows you to select the desired course to/from a waypoint using the HSI,
much like a VOR
64
APPROACH NAVIGATION
GPS SEQ Switch
CDI Scale ramping during approach.
0.3 nm
30 nm
2 nm
FAF
MAP
1 nm
1 nm
5 nm
1 minute
GPS SEQ
AUTO ACTV
GPS SEQ
AUTO HOLD
155man (GOOD) 7/24/98 1:57 PM Page 64