AIM

8/15/19

1

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32

Navigation Aids

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

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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

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Area

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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

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only opera-

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

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1

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17 for these

requirements).

9.

Unlike TSO

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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

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1

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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

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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
removing the 

 

NA

 (Alternate Minimums Not

Authorized) symbol from select RNAV (GPS) and
GPS approach procedures so they may be used by
approach approved WAAS receivers at alternate
airports. Some approach procedures will still require
the 

 

NA

 for other reasons, such as no weather

reporting, so it cannot be removed from all
procedures. Since every procedure must be individu-
ally evaluated, removal of the 

NA

 from RNAV

(GPS) and GPS procedures will take some time.

NOTE

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Properly trained and approved, as required, TSO-C145()
and TSO-C146() equipped users (WAAS users) with and
using approved baro-VNAV equipment  may plan for
LNAV/VNAV DA at an alternate airport. Specifically
authorized WAAS users with and using approved
baro-VNAV equipment may also plan for RNP 0.3 DA at the
alternate airport as long as the pilot has verified RNP
availability through an approved prediction program.

d. Flying Procedures with WAAS

1.

WAAS receivers support all basic GPS

approach functions and provide additional capabilit-
ies. One of the major improvements is the ability to
generate glide path guidance, independent of ground
equipment or barometric aiding. This eliminates
several problems such as hot and cold temperature
effects, incorrect altimeter setting, or lack of a local
altimeter source. It also allows approach procedures
to be built without the cost of installing ground
stations at each airport or runway. Some approach
certified receivers may only generate a glide path
with performance similar to Baro

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VNAV and are

only approved to fly the LNAV/VNAV line of minima
on the RNAV (GPS) approach charts. Receivers with
additional capability (including faster update rates
and smaller integrity limits) are approved to fly the
LPV line of minima. The lateral integrity changes
dramatically from the 0.3 NM (556 meter) limit for
GPS, LNAV, and LNAV/VNAV approach mode, to