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There is important information to know when using the GPS for IFR navigation and instrument
approaches. As a part of the system integrity, the GPS receiver monitors and predicts satellite
orbital position and geometry. The process of monitoring and predicting satellite position is
known as Receiver Autonomous Integrity Monitoring (RAIM). RAIM verifies the predicted
orbital position of the satellite or satellites used for a particular approach matches the actual
orbital position(s). If the positions do not match, the accuracy of the GPS position data may not
meet non-precision approach requirements. In this case, the GPS receiver will generate a message
notifying the pilot that GPS data should not be used for the approach. RAIM outages may occur
due to an insufficient number of satellites, unsuitable satellite position, terrain masking, aircraft
dynamics (changes in pitch or bank angle) or improper barometric altitude data input.
Prior to any IFR GPS operation, the pilot must check for planned GPS outages at the departure
and destination airports by either calling an FSS preflight briefer or checking online NOTAM
information using "KGPS" as the airfield identifier. The military provides airfield specific GPS
RAIM (M-series) NOTAM's for non-precision approach procedures at military airfields. During
longer flights, predictive RAIM at the destination should be checked manually by using the Status
5 (STA5) page of the KLN 900. This may provide early indications that an unscheduled satellite
outage has occurred since takeoff. Predictive RAIM cannot account for terrain masking problems
associated with flights in the vicinity of mountainous terrain, for unplanned satellite outages or for
internal equipment malfunctions. Since the relative positions of the satellites are constantly
changing, prior experience with the airport does not guarantee reception at all times, and RAIM
availability should always be checked.
For the purposed of alternate field selection a compatible and
operational non-GPS approach SHALL exist at the alternate airport.
The Super NAV 5 page has been specifically designed to provide most of the functions needed
for non-precision approaches. This page provides an interface that presents pertinent navigation
information, a way to access the flight plan, and a graphic presentation of the present position
relative to the flight plan waypoints. You will find this page to be very useful in conducting non-
precision approaches. It can be accessed by selected the NAV 5 page on both the left and right
side of the GPS console.
When conducting GPS approaches it is important to understand the differences between the OBS
and LEG modes of operation of the KLN900. The OBS mode provides no automatic sequencing
between waypoints. OBS mode only provides navigation to the active waypoint by way of the
course dialed into the OBS knob below the CDI. When the GPS is in OBS mode, rotating the
OBS knob will rotate the course select line, but will not change course select line when in LEG
mode. LEG mode provides Automatic Waypoint Sequencing, navigation to the active waypoint
via a direct routing from your present position and Turn Anticipation. When using Turn
Anticipation, the waypoint (WPT) light will begin to flash 20 seconds prior to turn. When the
light goes steady, begin the turn to the new course. This will be used when flying approaches or
any time the WPT is a Fly-Over WPT. OBS mode is used when holding, conducting a procedure
turn outbound or when intercepting a final approach course via radar vectors. LEG mode is used

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