AIM

8/15/19

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31

Navigation Aids

4.

Air carrier and commercial operators must

meet the appropriate provisions of their approved
operations specifications.

5.

Prior to GPS/WAAS IFR operation, the pilot

must review appropriate Notices to Airmen (NOT-
AMs) and aeronautical information. This
information is available on request from a Flight
Service Station. The FAA will provide NOTAMs to
advise pilots of the status of the WAAS and level of
service available.

(a)

The term MAY NOT BE AVBL is used in

conjunction with WAAS NOTAMs and indicates that
due to ionospheric conditions, lateral guidance may
still be available when vertical guidance is
unavailable. Under certain conditions, both lateral
and vertical guidance may be unavailable. This
NOTAM language is an advisory to pilots indicating
the expected level of WAAS service (LNAV/VNAV,
LPV, LP) may not be available.

EXAMPLE

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!FDC FDC NAV WAAS VNAV/LPV/LP MINIMA MAY
NOT BE AVBL 1306111330-1306141930EST 

or 

!FDC FDC NAV WAAS VNAV/LPV MINIMA NOT AVBL,
WAAS LP MINIMA MAY NOT BE AVBL
1306021200-1306031200EST

WAAS MAY NOT BE AVBL NOTAMs are
predictive in nature and published for flight planning
purposes. Upon commencing an approach at
locations NOTAMed WAAS MAY NOT BE AVBL,
if the WAAS avionics indicate LNAV/VNAV or LPV
service is available, then vertical guidance may be
used to complete the approach using the displayed
level of service. Should an outage occur during the
approach, reversion to LNAV minima or an alternate
instrument approach procedure may be required.
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.

(b)

WAAS area-wide NOTAMs are origin-

ated when WAAS assets are out of service and impact
the service area. Area

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wide WAAS NOT AVAIL-

ABLE (AVBL) NOTAMs indicate loss or
malfunction of the WAAS system. In flight, Air

Traffic Control will advise pilots requesting a GPS or
RNAV (GPS) approach of WAAS NOT AVBL
NOTAMs if not contained in the ATIS broadcast.

EXAMPLE

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For unscheduled loss of signal or service, an example
NOTAM is: !FDC FDC NAV WAAS NOT AVBL
1311160600

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 1311191200EST.  

For scheduled loss of signal or service, an example
NOTAM is: !FDC FDC NAV WAAS NOT AVBL
1312041015- 1312082000EST.

(c)

Site

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specific WAAS MAY NOT BE

AVBL NOTAMs indicate an expected level of
service; for example, LNAV/VNAV, LP, or LPV may
not be available. Pilots must request site

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specific

WAAS NOTAMs during flight planning. In flight,
Air Traffic Control will not advise pilots of WAAS
MAY NOT BE AVBL NOTAMs.

NOTE

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Though currently unavailable, the FAA is updating its
prediction tool software to provide this site-service in the
future.

(d)

Most of North America has redundant

coverage by two or more geostationary satellites. One
exception is the northern slope of Alaska. If there is
a problem with the satellite providing coverage to this
area, a NOTAM similar to the following example will
be issued:

EXAMPLE

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!FDC 

4/3406

 (PAZA A0173/14) ZAN NAV WAAS SIGNAL

MAY NOT BE AVBL NORTH OF LINE FROM
7000N150000W TO 6400N16400W. RMK WAAS USERS
SHOULD CONFIRM RAIM AVAILABILITY FOR IFR
OPERATIONS IN THIS AREA. T-ROUTES IN THIS
SECTOR NOT AVBL. ANY REQUIRED ALTERNATE
AIRPORT IN THIS AREA MUST HAVE AN APPROVED
INSTRUMENT APPROACH PROCEDURE OTHER
THAN GPS THAT IS ANTICIPATED TO BE OPERA-
TIONAL AND AVAILABLE AT THE ESTIMATED TIME
OF ARRIVAL AND WHICH THE AIRCRAFT IS
EQUIPPED TO FLY. 1406030812-1406050812EST .

6.

When GPS

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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.

EXAMPLE

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Here is an example of a GPS testing NOTAM: 
!GPS 

06/001

 ZAB NAV GPS (INCLUDING WAAS, GBAS,