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AIM 

6/17/21 

NOTE

 

WAAS receivers certified prior to TSO

C145b and 

TSO

C146b, even if they have LPV capability, do not 

contain LP capability unless the receiver has been 
upgraded. Receivers capable of flying LP procedures must 
contain a statement in the Aircraft Flight Manual (AFM), 
AFM Supplement, or Approved Supplemental Flight 
Manual stating that the receiver has LP capability, as well 
as the capability for the other WAAS and GPS approach 
procedure types. 

4. 

WAAS provides a level of service that 

supports all phases of flight, including RNAV (GPS) 
approaches to LNAV, LP, LNAV/VNAV, and LPV 
lines of minima, within system coverage. Some 
locations close to the edge of the coverage may have 
a lower availability of vertical guidance. 

c.  General Requirements 

1. 

WAAS avionics must be certified in 

accordance with Technical Standard Order (TSO) 
TSO

C145(), Airborne Navigation Sensors Using 

the (GPS) Augmented by the Wide Area Augmenta-
tion System (WAAS); or TSO

C146(), Stand

Alone 

Airborne Navigation Equipment Using the Global 
Positioning System (GPS) Augmented by the Wide 
Area Augmentation System (WAAS), and installed in 
accordance with AC 20

138, Airworthiness Ap-

proval of Positioning and Navigation Systems. 

2. 

GPS/WAAS operation must be conducted in 

accordance with the FAA

approved aircraft flight 

manual (AFM) and flight manual supplements. Flight 
manual supplements will state the level of approach 
procedure that the receiver supports. IFR approved 
WAAS receivers support all GPS only operations as 
long as lateral capability at the appropriate level is 
functional. WAAS monitors both GPS and WAAS 
satellites and provides integrity. 

3. 

GPS/WAAS equipment is inherently capable 

of supporting oceanic and remote operations if the 
operator obtains a fault detection and exclusion 
(FDE) prediction program. 

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

 

!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

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

 

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

 1311191200EST.  

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

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