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pilot should also request a RAIM prediction for the departure
airport. Some GPS receivers have the capability to predict
RAIM availability. The pilot should also ensure that the
required underlying ground-based navigation facilities and
related aircraft equipment appropriate to the route of flight,
terminal operations, instrument approaches for the destination,
and alternate airports/heliports will be operational for the ETA.
If the required ground-based facilities and equipment will
not be available, the flight should be rerouted, rescheduled,
canceled, or conducted under VFR.
Except for programming and retrieving information from
the GPS receiver, planning the flight is accomplished in a
similar manner to conventional NAVAIDs. Departure WP,
DP, route, STAR, desired approach, IAF, and destination
7-31
Figure 7-29. A GPS Stand-Alone Approach.
airport are entered into the GPS receiver according to the
manufacturer’s instructions. During preflight, additional
information may be entered for functions such as ETA, fuel
planning, winds aloft, etc.
When the GPS receiver is turned on, it begins an internal
process of test and initialization. When the receiver is
initialized, the user develops the route by selecting a WP
or series of WPs, verifies the data, and selects the active
flight plan. This procedure varies widely among receivers
made by different manufacturers. GPS is a complex system,
offering little standardization between receiver models. It is
the pilot’s responsibility to be familiar with the operation of
the equipment in the aircraft.
The GPS receiver provides navigational values such as track,
bearing, groundspeed, and distance. These are computed from
the aircraft’s present latitude and longitude to the location of
the next WP. Course guidance is provided between WPs. The
pilot has the advantage of knowing the aircraft’s actual track
over the ground. As long as track and bearing to the WP are
matched up (by selecting the correct aircraft heading), the
aircraft is going directly to the WP.
GPS Instrument Approaches
There is a mixture of GPS overlay approaches (approaches
with “or GPS” in the title) and GPS stand-alone approaches
in the United States.
NOTE: GPS instrument approach operations outside the
United States must be authorized by the appropriate country
authority.
While conducting these IAPs, ground-based NAVAIDs are
not required to be operational and associated aircraft avionics
need not be installed, operational, turned on, or monitored;
however, monitoring backup navigation systems is always
recommended when available.
Pilots should have a basic understanding of GPS approach
procedures and practice GPS IAPs under visual meteorological
conditions (VMC) until thoroughly proficient with all
aspects of their equipment (receiver and installation) prior
to attempting flight in instrument meteorological conditions
(IMC). [Figure 7-29]
All IAPs must be retrievable from the current GPS database
supplied by the manufacturer or other FAA-approved
source. Flying point to point on the approach does not
assure compliance with the published approach procedure.
The proper RAIM sensitivity will not be available and the
CDI sensitivity will not automatically change to 0.3 NM.
Manually setting CDI sensitivity does not automatically
change the RAIM sensitivity on some receivers. Some existing
nonprecision approach procedures cannot be coded for use
with GPS and will not be available as overlays.
7-32
GPS approaches are requested and approved by ATC using
the GPS title, such as “GPS RWY 24” or “RNAV RWY 35.”
Using the manufacturer’s recommended procedures, the
desired approach and the appropriate IAF are selected from
the GPS receiver database. Pilots should fly the full approach
from an initial approach waypoint (IAWP) or feeder fix unless
specifically cleared otherwise. Randomly joining an approach
at an intermediate fix does not ensure terrain clearance.
When an approach has been loaded in the flight plan, GPS
receivers will give an “arm” annunciation 30 NM straight
line distance from the airport/heliport reference point. The
approach mode should be “armed” when within 30 NM
distance so the receiver will change from en route CDI
(±5 NM) and RAIM (±2 NM) sensitivity to ±1 NM terminal
sensitivity. Where the IAWP is within 30 NM, a CDI
sensitivity change will occur once the approach mode is
armed and the aircraft is within 30 NM. Where the IAWP
is beyond the 30 NM point, CDI sensitivity will not change
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