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6/17/21 

AIM 

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

of

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

C145/

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) equip-
ment; 

(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

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

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, iono-
sphere effects, solar activity, multi

path error, 

satellite communications, GPS repeaters, and even 
some systems onboard the aircraft. In general, these 
types of unintentional interference are localized and 
intermittent. Of greater and growing concern is the 
intentional and unauthorized interference of GPS 
signals by persons using “jammers” or  “spoofers” to 
disrupt air navigation by interfering with the 
reception of valid satellite signals. 

Performance

Based Navigation (PBN) and Area Navigation (RNAV) 

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