Aeronautical Information Manual (AIM), page 77

Index   76 -- Page 77 -- 78

IAWP, FAWP, MAHWP on a procedure turn). Care
must be exercised to ensure that the receiver is
sequenced to the appropriate waypoint for the
segment of the procedure being flown, especially if
one or more fly-overs are skipped (for example,
FAWP rather than IAWP if the procedure turn is not
flown). The pilot may have to sequence past one or
more fly-overs of the same waypoint in order to start
GPS automatic sequencing at the proper place in the
sequence of waypoints.

(10) Incorrect inputs into the GPS receiver

are especially critical during approaches. In some

cases, an incorrect entry can cause the receiver to

leave the approach mode.

(11) A fix on an overlay approach identi-
fied by a DME fix will not be in the waypoint
sequence on the GPS receiver unless there is a
published name assigned to it. When a name is
assigned, the along track distance (ATD) to the
waypoint may be zero rather than the DME stated on
the approach chart. The pilot should be alert for this
on any overlay procedure where the original
approach used DME.

(12) If a visual descent point (VDP) is

published, it will not be included in the sequence of

waypoints. Pilots are expected to use normal piloting
techniques for beginning the visual descent, such as


(13) Unnamed stepdown fixes in the final
approach segment may or may not be coded in the
waypoint sequence of the aircraft's navigation
database and must be identified using ATD.
Stepdown fixes in the final approach segment of
RNAV (GPS) approaches are being named, in
addition to being identified by ATD. However, GPS
avionics may or may not accommodate waypoints
between the FAF and MAP. Pilots must know the
capabilities of their GPS equipment and continue to
identify stepdown fixes using ATD when necessary.

(f) Missed Approach

(1) A GPS missed approach requires pilot
action to sequence the receiver past the MAWP to the
missed approach portion of the procedure. The pilot
must be thoroughly familiar with the activation
procedure for the particular GPS receiver installed in
the aircraft and must initiate appropriate action after
the MAWP. Activating the missed approach prior to
the MAWP will cause CDI sensitivity to immediately

change to terminal (±1NM) sensitivity and the
receiver will continue to navigate to the MAWP. The
receiver will not sequence past the MAWP. Turns
should not begin prior to the MAWP. If the missed
approach is not activated, the GPS receiver will
display an extension of the inbound final approach
course and the ATD will increase from the MAWP
until it is manually sequenced after crossing the

(2) Missed approach routings in which the

first track is via a course rather than direct to the next

waypoint require additional action by the pilot to set

the course. Being familiar with all of the inputs

required is especially critical during this phase of

(g) GPS NOTAMs/Aeronautical Informa-

(1) GPS satellite outages are issued as
GPS NOTAMs both domestically and internation-
ally. However, the effect of an outage on the intended
operation cannot be determined unless the pilot has a
RAIM availability prediction program which allows

excluding a satellite which is predicted to be out of

service based on the NOTAM information.

(2) The terms UNRELIABLE and MAY

NOT BE AVAILABLE are used in conjunction with
BE AVAILABLE are advisories to pilots indicating
the expected level of service may not be available.
UNRELIABLE does not mean there is a problem
with GPS signal integrity. If GPS service is available,
pilots may continue operations. If the LNAV or
LNAV/VNAV service is available, pilots may use the
displayed level of service to fly the approach. GPS
operation may be NOTAMed UNRELIABLE or
MAY NOT BE AVAILABLE due to testing or
anomalies. (Pilots are encouraged to report GPS
anomalies, including degraded operation and/or loss

of service, as soon as possible, reference paragraph
1-1-13.) When GPS testing NOTAMS are published
and testing is actually occurring, Air Traffic Control
will advise pilots requesting or cleared for a GPS or
RNAV (GPS) approach that GPS may not be
available and request intentions. If pilots have
reported GPS anomalies, Air Traffic Control will
request the pilot's intentions and/or clear the pilot for
an alternate approach, if available and operational.

Navigation Aids 1-1-23

Page 77 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   76 -- Page 77 -- 78