AIM 

3/21/24 

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

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C145(), 

Airborne Navigation Sensors Using the (GPS) Augmented by the Wide Area Augmentation System (WAAS); 

or TSO

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C146(), Stand

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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

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138, 

Airworthiness Approval of Positioning and Navigation Systems. 

2. 

GPS/WAAS operation must be conducted in accordance with the FAA

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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 Air Missions 

(NOTAMs) 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 originated when WAAS assets are out of service and impact the 

service area. Area

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wide WAAS NOT AVAILABLE (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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Navigation Aids