AIM

4/3/14

1−1−20

Navigation Aids

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 informa-

tion 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

14 CFR 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.

(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

14 CFR 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

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.

c. VFR Waypoints

1.

VFR 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

used as a tool to supplement current navigation

procedures. The uses of VFR waypoints include

providing navigational aids for pilots unfamiliar with

an area, waypoint definition of existing reporting

points, enhanced navigation in and around Class B