Garmin GPS 400 Pilot's Manual And Reference page 162

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APPENDIX D
SHOOTING
What is RAIM, and how does it affect approach operations?
RAIM is an acronym for Receiver Autonomous Integrity 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 protec-
tion limit (2 nautical miles for oceanic and en route, 1 nm for terminal and 0.3 nm for non-precision approaches).
During oceanic, en route and terminal phases of flight, RAIM will be available nearly 100% of the time. Because of the tighter protection
limit on approaches, there may be times when RAIM is not available. The GPS 400 automatically monitors RAIM and will warn you with an
alert message (see Section 10) when it is not available, and the INTEG annunciator (
screen. If RAIM is not available when crossing the FAF, the pilot must fly the missed approach procedure. The GPS 400's RAIM prediction
function (see page 120) will also allow you to see whether RAIM will be available for a specified date and time.
If RAIM is not predicted to be available for the final approach course, the approach will not become active—as indicated by an
"Approach is not active" message, a "RAIM not available from FAF to MAP" message and the INTEG annunciator.
Appendix D: Troubleshooting Q & A
This section is designed to answer some of the common questions regarding the GPS 400's
capabilities 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 iv. GARMIN is dedicated to supporting its products and customers.
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