6.8 INSTALLATION OF ANTENNAS
6.8.1 GENERAL INFORMATION
Installations must be made by qualified personnel, and in accordance with Federal
Regulations. Refer to FAA Advisory Circular 43.13-2b for General installation
guidelines. A copy of the FAA Advisory Circular can be obtained at www.faa.gov. Look
for Advisory Circulars under the Regulatory/Advisory heading on the FAA home page.
6.8.2 GENERAL LOCATION
The location of any antenna system on the aircraft is very important. Antenna
locations on aircraft that provide unobstructed line-of-sight views of the transmitted or
received signals are preferred. When possible, keep antennas at least 36” from any
other antenna. On any aircraft, antennas should not be mounted in the proximity of
engine exhaust.
6.8.3 MOUNTING LOCATION
The specific mounting location is very important due to curvatures and uneven
surfaces encountered on various aircraft skins. A flat surface is the desired antenna
mounting location. Minor aircraft skin curvature can be accommodated with the use of
a gasket where supplied. DO NOT over torque the mounting screws in an attempt to
reduce gaps between the antenna base plate and aircraft mounting surface. If gaps
over .020” appear between the base plate and mounting surface, use of a mounting
saddle is recommended.
6.8.4 AIRCRAFT SKIN SURFACE AND MOUNTING PREPARATION
The electrical bonding of the antenna to the aircraft ground is highly important. If this
is not done properly, antenna performance characteristics may become distorted and
nulls may appear in the antenna radiation pattern. This, in turn, may cause erratic
navigational readings or signal drop out. The electrical bonding of the antennas to the
aircraft skin is best accomplished by direct metal-to-metal contact of the antenna base
to the aircraft skin. To accomplish this, the aircraft paint in the mounting area will
need to be removed and the surface alodined to protect aluminum against corrosion.
An alternate method for providing electrical bonding is through the mounting screws,
which attach to a backing plate inside the aircraft skin. Remove any interior paint in
the area where the backing plate is placed to assure a good ground. Coat this area
with alodine to minimize corrosion. To test the electrical bonding of the blade to the
aircraft, a reading of .003 ohms between the antenna basplate and ground should be
achieved.
6.8.5 MECHANICAL INSTALLATION
Typical antenna installations require either an #8-32 or #10-32 stainless steel
mounting screw. Length will vary based on each particular installation requirement.
REFER TO INSTALLATION DRAWING before drilling holes in aircraft skin to determine
proper size.
Some designs require a pan head screw, others a counter sunk screw is required.
Personally inspect the mounting area of the antenna you are installing to confirm the
proper screw type requirement.
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