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APPENDIX C
Troubleshooting Q & A
213
190-00357-00 Rev E
What is RAIM, and how does it affect approach opera-
tions?
RAIM is an acronym for Receiver Autonomous Integ-
rity Monitoring, a GPS receiver function that performs a
consistency check on all tracked satellites. RAIM ensures
that the available satellite geometry will allow the receiver
to calculate a position within a specified protection limit
(4.0 NM for oceanic/remote and 2.0 NM for en route,
1.0 NM for terminal and 0.3 NM for non-precision ap-
proaches).
Duringoceanic,enrouteandterminalphasesofight,
RAIM isavailable nearly 100%of the time.Because of
the tighter protection limit on approaches, there may be
times when RAIM is not available. The 500W-series unit
automatically monitors RAIM and warns you with an alert
message (see Section 12) when it is not available, and the
INTEG annunciator ( ) appears at the bottom
left corner of the screen. If RAIM is not available when
crossing the FAF, the pilot must fly the missed approach
procedure. The 500W-series unit RAIM prediction func-
tion (see Section 9 Aux Pages - Utility Page - RAIM Predic-
tion) also allows you to see whether RAIM will be available
for a specified date and time.
NOTE: RAIM prediction is not directly related to
WAAS integrity.
RAIM integrity prediction is performed by the
internal GPS receiver and is performed at all times.
WAAS integrity is reported by the WAAS satellite
system and only works within the WAAS service
volume. WAAS approaches require WAAS integrity.
Outside of the WAAS service volume, such as an Oce-
anic flight, RAIM prediction will be used.
Appendix C
Troubleshooting Q & A
This Appendix is designed to answer some of the
common questions regarding the 500W-series capa-
bilities and operation. If you have a problem operating
the unit, read through this appendix and refer to the
reference section noted. If you don’t find answers to
your particular question here, use the index to find the
appropriate section elsewhere in this manual. If, after
reading through the appropriate reference section, you
still haven’t found the answer to your question, please
see your authorized dealer or contact Garmin directly
at the address or phone numbers listed on page ii.
Garmin is dedicated to supporting its products and
customers.