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airspace they were trying to avoid by using an
outdated database. If you don't have a current
database in the receiver, disregard the moving map
display for critical navigation decisions.
(3) In addition, waypoints are added,
removed, relocated, or re-named as required to meet
operational needs. When using GPS to navigate
relative to a named fix, a current database must be
used to properly locate a named waypoint. Without
the update, it is the pilot's responsibility to verify the
waypoint location referencing to an official current
source, such as the Airport/Facility Directory,
Sectional Chart, or En Route Chart.
(c) Antenna Location
(1) 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.
(2) 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.
(3) 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
14CFR Part 43. Consult with your mechanic to
ensure compliance with the regulation, and a safe
installation.
4. As a result of these and other concerns, here
are some tips for using GPS for VFR operations:
(a) Always 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.
(b) Check 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.
2/14/08 AIM
Navigation Aids 1-1-27
(c) While 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.
(d) Plan 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.
(e) Another 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.
5. In 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
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