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6/17/21 

AIM 

second type indicates that the RAIM integrity 
monitor has detected a potential error and that there 
is an inconsistency in the navigation solution for the 
given phase of flight. Without RAIM capability, the 
pilot has no assurance of the accuracy of the GPS 
position. 

4. 

Selective Availability.  Selective Availability 

(SA) is a method by which the accuracy of GPS is 
intentionally degraded. This feature was designed to 
deny hostile use of precise GPS positioning data. SA 
was discontinued on May 1, 2000, but many GPS 
receivers are designed to assume that SA is still 
active. New receivers may take advantage of the 
discontinuance of SA based on the performance 
values in ICAO Annex 10. 

b.  Operational Use of GPS. 

U.S. civil operators 

may use approved GPS equipment in oceanic 
airspace, certain remote areas, the National Airspace 
System and other States as authorized (please consult 
the applicable Aeronautical Information Publica-
tion). Equipage other than GPS may be required for 
the desired operation. GPS navigation is used for both 
Visual Flight Rules (VFR) and Instrument Flight 
Rules (IFR) operations. 

1.  VFR Operations 

(a) 

GPS navigation has become an asset to 

VFR pilots by providing increased navigational 
capabilities and enhanced situational awareness. 
Although GPS has provided many benefits to the 
VFR pilot, care must be exercised to ensure that 
system capabilities are not exceeded. VFR pilots 
should integrate GPS navigation with electronic 
navigation (when possible), as well as pilotage and 
dead reckoning. 

(b) 

GPS receivers used for VFR navigation 

vary from fully integrated IFR/VFR installation used 
to support VFR operations to hand

held devices. 

Pilots must understand the limitations of the receivers 
prior to using in flight to avoid misusing navigation 
information. (See TBL 1

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6.) Most receivers are 

not intuitive. The pilot must learn the various 
keystrokes, knob functions, and displays that are 
used in the operation of the receiver. Some 
manufacturers provide computer

based tutorials or 

simulations of their receivers that pilots can use to 
become familiar with operating the equipment. 

(c) 

When using GPS for VFR operations, 

RAIM capability, database currency, and antenna 
location are critical areas of concern. 

(1) 

RAIM Capability. VFR GPS panel 

mount receivers and hand

held units have no RAIM 

alerting capability. This prevents the pilot from being 
alerted to the loss of the required number of satellites 
in view, or the detection of a position error. Pilots 
should use a systematic cross

check with other 

navigation techniques to verify position. Be 
suspicious of the GPS position if a disagreement 
exists between the two positions. 

(2) 

Database Currency. Check the curren-

cy of the database.  Databases must be updated for 
IFR operations and should be updated for all other 
operations. However, there is no requirement for 
databases to be updated for VFR navigation. It is not 
recommended to use a moving map with an outdated 
database in and around critical airspace. Pilots using 
an outdated database should verify waypoints using 
current aeronautical products; for example, Chart 
Supplement U.S., Sectional Chart, or En Route 
Chart. 

(3) 

Antenna Location. The antenna loca-

tion for GPS receivers used for IFR and VFR 
operations may differ. VFR antennae are typically 
placed for convenience more than performance, 
while IFR installations ensure a clear view is 
provided with the satellites. Antennae not providing 
a clear view have a greater opportunity to lose the 
satellite navigational signal. This is especially true 
in the case of hand

held GPS receivers. Typically, 

suction cups are used to place the GPS antennas on 
the inside of cockpit windows. While this method has 
great utility, the antenna location is limited to the 
cockpit or cabin which rarely provides a clear view 
of all available satellites.  Consequently, signal losses 
may occur due to aircraft structure blocking satellite 
signals, causing a loss of navigation capability. These 
losses, coupled with a lack of RAIM capability, could 
present erroneous position and navigation informa-
tion with no warning to the pilot. While the use of a 
hand

held GPS for VFR operations is not limited by 

regulation, modification of the aircraft, such as 
installing a panel

 or yoke

mounted holder, is 

governed by 14 CFR Part 43. Consult with your 
mechanic to ensure compliance with the regulation 
and safe installation. 

(d) 

Do not solely rely on GPS for VFR 

navigation. No design standard of accuracy or 

Navigation Aids 

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