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Section 5
Approaches, SIDs and STARs
The GPS 155XL’s approach navigation mode allows you to fly non-precision
approaches to airports with GPS and overlay procedures using information contained
on your Jeppesen NavData
®
card. GPS approaches are similar to existing IFR
approach procedures, but provide additional course and distance information for a
higher level of accuracy, efficiency and safety. The non-precision approaches available
in the GPS 155XL are executed using the GPS route features covered in Section 4, so
it’s important to understand routes before attempting approach navigation. A GPS
approach is a sequence of waypoints linked together as an approach route which
replaces your destination airport waypoint when selected. It may be based on an
existing RNAV, VOR or NDB approach procedure, or be an entirely new approach
created specifically for GPS. Regardless of the type of approach on which a GPS pro-
cedure is based, the procedure is flown as a sequence of route legs in the active route.
The GPS 155XL’s auto-arming feature provides automatic control of the two
phases of approach operations: arm approach and active approach. The arm
approach phase consists of selecting an approach from the database and ensuring that
the receiver is ready to begin the tighter integrity monitoring and CDI adjustment
required for approach navigation. The active approach phase tightens the accuracy
requirements and sensitivity one step further to meet TSO standards for the non-pre-
cision approach. Auto-arming of the approach will occur once you are within 30 nm
of the destination airport, and will be indicated by an ‘ARM’ message on the external
GPS APR switch. The approach will then transition to the active phase when the air-
craft is within 2 nm of the FAF along the inbound course to the final approach fix.
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Once an approach is selected, the GPS 155XL will
replace the destination airport with the appropri-
ate approach waypoints. The initial approach fix,
final approach fix and missed approach point
waypoints are indicated by an ‘if’, ‘ff’ and ‘mp’
designation to the immediate left of the waypoints.
In many instances, there may be approach way-
points in the GPS approach that are not shown on
the approach plate. These approach waypoints are
usually intermediate fixes designed to help the
GPS provide smooth navigation along the
approach path.
SECTION
5
APPROACH NAV
Overview
155xlb manual 1/12/99 4:06 PM Page 74