AIM 

4/20/23

 

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10

Performance

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Based Navigation (PBN) and Area Navigation (RNAV)

on a procedure affected by an expired or unsatisfactory flight inspection, or a procedure that is based upon a recently
decommissioned NAVAID.

4.

Pilots may not substitute for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach

segment. This restriction does not refer to instrument approach procedures with “or GPS” in the title when using GPS or
WAAS. These allowances do not apply to procedures that are identified as not authorized (NA) without exception by a
NOTAM, as other conditions may still exist and result in a procedure not being available. For example, these allowances
do not apply to a procedure associated with an expired or unsatisfactory flight inspection, or is based upon a recently
decommissioned NAVAID.

5.

Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure

based on a VOR, TACAN or NDB signal, is allowable. The underlying NAVAID must be operational and the NAVAID
monitored for final segment course alignment. 

6.

For the purpose of paragraph c, “VOR” includes VOR, VOR/DME, and VORTAC facilities and “compass locator”

includes locator outer marker and locator middle marker.

d. Alternate Airport Considerations.

 For the purposes of flight planning, any required alternate airport must

have an available instrument approach procedure that does not require the use of GPS. This restriction includes
conducting a conventional approach at the alternate airport using a substitute means of navigation that is based
upon the use of GPS. For example, these restrictions would apply when planning to use GPS equipment as a
substitute means of navigation for an out

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of

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service VOR that supports an ILS missed approach procedure at

an alternate airport. In this case, some other approach not reliant upon the use of GPS must be available. This
restriction does not apply to RNAV systems using TSO

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C145/

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C146 WAAS equipment. For further WAAS

guidance, see paragraph 1

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18.

1.

For flight planning purposes, TSO-C129() and TSO-C196() equipped users (GPS users) whose

navigation systems have fault detection and exclusion (FDE) capability, who perform a preflight RAIM
prediction at the airport where the RNAV (GPS) approach will be flown, and have proper knowledge and any
required training and/or approval to conduct a GPS-based IAP, may file based on a GPS-based IAP at either the
destination or the alternate airport, but not at both locations.  At the alternate airport, pilots may plan for
applicable alternate airport weather minimums using:

(a)

Lateral navigation (LNAV) or circling minimum descent altitude (MDA);

(b)

LNAV/vertical navigation (LNAV/VNAV) DA, if equipped with and using approved barometric

vertical navigation (baro-VNAV) equipment;

(c)

RNP 0.3 DA on an RNAV (RNP) IAP, if they are specifically authorized users using approved

baro-VNAV equipment and the pilot has verified required navigation performance (RNP) availability through
an approved prediction program.

2.

If the above conditions cannot be met, any required alternate airport must have an approved instrument

approach procedure other than GPS that is anticipated to be operational and available at the estimated time of
arrival, and which the aircraft is equipped to fly.

3.

This restriction does not apply to TSO-C145() and TSO-C146() equipped users (WAAS users). For

further WAAS guidance, see paragraph 1

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18.

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4. Recognizing, Mitigating and Adapting to GPS Interference (Jamming or Spoofing)

a.

The low

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strength data transmission signals from GPS satellites are vulnerable to various anomalies that

can significantly reduce the reliability of the navigation signal. Because of the many uses of GPS in aviation (e.g.,
navigation, ADS

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B, terrain awareness/warning systems), operators of aircraft using GPS need to be aware of

these vulnerabilities, and be able to recognize and adjust to degraded signals. Aircraft should have additional
navigation equipment for their intended route.

b.

GPS signals are vulnerable to intentional and unintentional interference from a wide variety of sources,

including radars, microwave links, ionosphere effects, solar activity, multi

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path error, satellite communications,