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source, such as the Airport/Facility Directory,
Sectional Chart, or En Route Chart.
18.2.3.3Antenna Location
a)In many VFR installations of GPS receivers,
antenna location is more a matter of convenience than
performance. In IFR installations, care is exercised to
ensure that an adequate clear view is provided for the
antenna to see satellites. If an alternate location is
used, some portion of the aircraft may block the view
of the antenna, causing a greater opportunity to lose
navigation signal.
b)This is especially true in the case of hand−helds.
The use of hand−held receivers for VFR operations is
a growing trend, especially among rental pilots.
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 only and is rarely
optimized to provide a clear view of available
satellites. Consequently, signal losses may occur in
certain situations of aircraft−satellite geometry,
causing a loss of navigation signal. These losses,
coupled with a lack of RAIM capability, could
present erroneous position and navigation information
with no warning to the pilot.
c)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
Part43. Consult with your mechanic to ensure
compliance with the regulation, and a safe
installation.
18.2.4As a result of these and other concerns, here
are some tips for using GPS for VFR operations:
18.2.4.1Always check to see if your unit has RAIM
capability. If no RAIM capability exists, be
suspicious of your GPS position when any
disagreement exists with the position derived from
other radio navigation systems, pilotage, or dead
reckoning.
18.2.4.2Check the currency of the database, if any.
If expired, update the database using the current
revision. If an update of an expired database is not
possible, disregard any moving map display of
airspace for critical navigation decisions. Be aware
that named waypoints may no longer exist or may
have been relocated since the database expired. At a
minimum, the waypoints planned to be used should
be checked against a current official source, such as
the Airport/Facility Directory, or a Sectional
Aeronautical Chart.
18.2.4.3While hand−helds can provide excellent
navigation capability to VFR pilots, be prepared for
intermittent loss of navigation signal, possibly with
no RAIM warning to the pilot. If mounting the
receiver in the aircraft, be sure to comply with
14CFR Part 43.
18.2.4.4Plan flights carefully before taking off. If
you wish to navigate to user−defined waypoints,
enter them before flight, not on−the−fly. Verify your
planned flight against a current source, such as a
current sectional chart. There have been cases in
which one pilot used waypoints created by another
pilot that were not where the pilot flying was
expecting. This generally resulted in a navigation
error. Minimize head−down time in the aircraft and
keep a sharp lookout for traffic, terrain, and obstacles.
Just a few minutes of preparation and planning on the
ground will make a great difference in the air.
18.2.4.5Another way to minimize head−down time
is to become very familiar with your receiver’s
operation. Most receivers are not intuitive. The pilot
must take the time to 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. Take the time to learn about your
particular unit before you try to use it in flight.
18.2.5In summary, be careful not to rely on GPS to
solve all your VFR navigational problems. Unless an
IFR receiver is installed in accordance with IFR
requirements, no standard of accuracy or integrity has
been assured. While the practicality of GPS is
compelling, the fact remains that only the pilot can
navigate the aircraft, and GPS is just one of the pilot’s
tools to do the job.
AIP ENR 4.1−25
United States of America 15 MAR 07
Federal Aviation Administration Nineteenth Edition
18.3VFR Waypoints
18.3.1VFR waypoints provide VFR pilots with a
supplementary tool to assist with position awareness
while navigating visually in aircraft equipped with
area navigation receivers. VFR waypoints should be
　
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