Garmin GPS 155XL TSO - Manual (Page 136)

126
APPENDIX
G
TROUBLE-
SHOOTING
Q & A
What does the GPS APR switch do? What is ‘arming’ an approach?
The GPS APR switch must be set to the ARM position for an approach to enter the
active phase. It may be left in the ARM position to simplify approach operation. Its
main function is to provide the pilot with a quick method of deactivating the approach
and returning the CDI scale to the 1 nm scale in the event of a missed approach. For
more on the GPS APR switch and arming approaches, see pages 74-75.
What does the GPS SEQ switch do and when do I use it?
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, and the GPS will automatically select the
next waypoint in the route once the aircraft has crossed the present active-to waypoint.
AUTO HOLD
Automatic sequencing of waypoints Manual sequencing- ‘HOLDs’ on selected waypoint
Change in HSI does not affect CDI deflection Manually select course to next waypoint from HSI
Always navigates ‘TO’ the active waypoint Will indicate ‘TO’ or ‘FROM’ waypoint
Must be set to AUTO for approach to go active Approach will not go active
The GPS SEQ switch must be set to the HOLD position any time you are deviating
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., a procedure turn or
holding pattern). Whenever the GPS SEQ switch is set to the HOLD position, the GPS
155XL allows you to select the desired course to/from a waypoint using the HSI, much
like a VOR, and display a to/from flag for the active-to waypoint. In the AUTO posi-
tion, the CDI will always display a ‘TO’ indication for the next waypoint once you’ve
crossed the active waypoint. Refer to page 88 for an approach example using a HOLD.
155xlb manual 1/12/99 4:06 PM Page 126