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Section 4
Approaches, SIDs and STARs
The GPS 155’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 155 are executed using the GPS route features covered in Section 3, so it’s
important to understand routes before attempting approach navigation.
A GPS approach is a sequence of waypoints linked together into a subroute
which replaces your destination airport waypoint when selected. They may be based
on an existing RNAV, VOR or NDB approach procedure, or be an entirely new
approach created specifically for GPS. Regardless of what type of approach a GPS
procedure is based on, the procedure is flown as a sequence of route legs in the active
route. Once a GPS approach is selected, the GPS 155 will provide guidance to each
waypoint in the approach in sequence, starting with the initial approach fix (IAF).
Flying a GPS approach with the GPS 155 can be broken down into three phases:
approach selection, approach arming and the active approach: 1) Approach
selection is simply the step of choosing the desired approach for the destination air-
port. 2) Arming the approach makes sure the unit is ready to begin the automatic
sequencing and CDI adjustment required for approach navigation. 3) The active
approach tightens the accuracy requirements and CDI sensitivity one step further to
meet TSO standards for the non-precision approach.
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APPROACH NAVIGATION
Overview
Once an approach is selected, the GPS 155 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’
designator to the immediate left of the waypoint.
In many instances, there may be approach way-
points in the GPS approach that are not shown on
the approach plate. These waypoints are usually
intermediate fixes designed to help the GPS pro-
vide smooth navigation along the approach path.
155man (GOOD) 7/24/98 1:57 PM Page 62