Garmin GPS 155XL Pilot's Manual & Reference page 138

TROUBLE-
APPENDIX
G
SHOOTING
Q & A
0.3 nm
1 nm
1 nm
5 nm
CDI Scale Transition
128
MAP
FAF
2 nm
30 nm
1 minute
When does turn anticipation begin, and what bank angle is expected?
The GPS 155XL will smooth adjacent leg transitions based upon a nominal 15º
bank angle (with the ability to roll up to 25º) and provide three pilot cues for turn
anticipation: 1) The waypoint annunciator will flash 15 seconds before the turn point
and glow steadily 2 seconds prior to the turn anticipation point. Begin the turn when
the annunciator goes steady. 2) A flashing 'next dtk' prompt will appear on the GPS
155XL' s CDI field. Set the HSI to the next dtk value when the waypoint annunciator
starts flashing. 3) The To/From indicator on the GPS CDI will flip momentarily to
indicate that you have crossed the midpoint of the turn. For more information on
turn anticipation, see page 73.
When does the CDI scale change, and what does it change to?
Whenever an approach is selected and armed, the GPS 155XL will begin a smooth
CDI scale transition from the 5.0 nm to the 0.3 nm scale 30 nm from the destination
airport (see left). The CDI scale will remain at the 0.3 nm scale from the FAF to the
MAP during the active approach. If you are in a missed approach situation, and
would like to return the CDI to the 1 nm scale, you
may deactivate the approach by releasing the GPS
APR switch from the ARM position.
Why does my CDI not respond like a VOR
when the GPS SEQ switch is set to HOLD?
Unlike a VOR, the CDI scale used on GPS equip-
ment is based on the cross-track distance to the
desired course, not an angular relationship to the
destination. Therefore, the CDI deflection on the
GPS will be consistent regardless of the distance to
the destination, and will not become less sensitive
when you are further away from the destination. For
more information on the CDI scale, see page 99.
2 2
nm nm
5 nm 5 nm 5 nm 5 nm
GPS VOR