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6/17/21 

AIM 

(c) 

Site

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

specific 

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

NOTE

 

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

 

!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

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

 

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

06/001

 ZAB NAV GPS (INCLUDING WAAS, GBAS, 

AND ADS-B) MAY NOT BE AVAILABLE WITHIN A 
468NM RADIUS CENTERED AT 330702N1062540W 
(TCS 093044) FL400-UNL DECREASING IN AREA 
WITH A DECREASE IN ALTITUDE DEFINED AS: 
425NM RADIUS AT FL250, 360NM RADIUS AT 
10000FT, 354NM RADIUS AT 4000FT AGL, 327NM 
RADIUS AT 50FT AGL. 1406070300-1406071200. 

7. 

When the approach chart is annotated with 

the 

 symbol, site

specific WAAS MAY NOT BE 

AVBL NOTAMs or Air Traffic advisories are not 

provided for outages in WAAS LNAV/VNAV and 
LPV vertical service. Vertical outages may occur 
daily at these locations due to being close to the edge 
of WAAS system coverage. Use LNAV or circling 
minima for flight planning at these locations, whether 
as a destination or alternate. For flight operations at 
these locations, when the WAAS avionics indicate 
that LNAV/VNAV or LPV service is available, then 
the vertical guidance may be used to complete the 
approach using the displayed level of service. Should 
an outage occur during the procedure, reversion to 
LNAV minima may be required. 

NOTE

 

Area

wide WAAS NOT AVBL NOTAMs apply to all 

airports in the WAAS NOT AVBL area designated in the 
NOTAM, including approaches at airports where an 
approach chart is annotated with the 

 symbol. 

8. 

GPS/WAAS was developed to be used within 

GEO coverage over North America without the need 
for other radio navigation equipment appropriate to 
the route of flight to be flown. Outside the WAAS 
coverage or in the event of a WAAS failure, 
GPS/WAAS equipment reverts to GPS

only opera-

tion and satisfies the requirements for basic GPS 
equipment. (See paragraph 1

1

17 for these 

requirements). 

9. 

Unlike TSO

C129 avionics, which were 

certified as a supplement to other means of 
navigation, WAAS avionics are evaluated without 
reliance on other navigation systems. As such, 
installation of WAAS avionics does not require the 
aircraft to have other equipment appropriate to the 
route to be flown. (See paragraph 1

1

17 d for more 

information on equipment requirements.) 

(a) 

Pilots with WAAS receivers may flight 

plan to use any instrument approach procedure 
authorized for use with their WAAS avionics as 
the planned approach at a required alternate, with 
the following restrictions. When using WAAS at 
an alternate airport, flight planning must be based 
on flying the RNAV (GPS) LNAV or circling minima 
line, or minima on a GPS approach procedure, or 
conventional approach procedure with “or GPS” in 
the title. Code of Federal Regulation (CFR) Part 91 
non

precision weather requirements must be used for 

planning. Upon arrival at an alternate, when the 
WAAS navigation system indicates that LNAV/ 
VNAV or LPV service is available, then vertical 
guidance may be used to complete the approach using 
the displayed level of service. The FAA has begun 

Navigation Aids 

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