FreeFlight 2101 I/O PLUS, Installation And Checkout Manual

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Page 2-2
Revision E
May 31, 2006
FreeFlight 2101 I/O Approach Plus GPS Navigation System
2.3.3 GPS Antenna Installation
The GPS antenna, the antenna gasket (-21kit only) and two 90° TNC connectors are provided in the installation kit.
Straight TNC connectors are also available from FreeFlight. Proper antenna installation is critical to both the
performance of the system and the aircraft's structural integrity.
CAUTION
Use of the GPS antenna (P/N 81194) for IFR installations in aircraft equipped with satellite communication
equipment should be tested to ensure no interference exists between the SATCOM equipment and the GPS
antenna.
2.3.3.1 Location
In order to receive transmissions from GPS satellites, the GPS antenna must be in line-of-sight. Therefore, the
most important factor in GPS antenna installation is determining which location on the fuselage affords the least
amount of airframe blockage. Always mount antenna on the top of the fuselage, never on the underside. Also,
mount the antenna so that the mounting holes are perpendicular to the line of flight. Select a mounting location
at least three (3) feet away from any transmitting antenna.
On fixed wing aircraft, the best mounting location is usually above the cabin, near the front and as close to the
center line as possible.
2.3.3.2 Location Considerations on Rotorcraft
As in fixed wing aircraft, the primary factor in rotorcraft GPS antenna site selection is to minimize airframe
blockage. Two other guidelines to be considered in placing the antenna on rotorcraft are listed in order of
importance below:
A. Install as far from the main rotor hub as possible. At a given RPM, the linear velocity of the blade
increases as the distance from the rotor hub increases. Since the blade blocks the line-of-sight GPS
satellite signal, the effect will be reduced further away from the rotor hub.
B. If under the blade, get as far below the blade as possible to minimize signal distortions from the blade
edges, which decrease as the distance from the blade increases.
2.3.3.3 Wiring
The installation agency is responsible for the fabrication of the cable to the specifications outlined in Section 1.5.2
of this document. Take care when routing the cable to avoid kinking and sharp bends. If the antenna cable is
routed through bulkheads, be sure to install protective material to avoid chafing. Figure 2-3 illustrates a proper
cable termination.
2.3.3.4 Installation
CAUTION
Before drilling aircraft fuselage and/or mounting adapter holes to receive the GPS Antenna, make certain
the hole pattern for the antenna is oriented with respect to its forward direction.
2.3.3.4.1 16248-11 Antenna
After a suitable mounting location is identified, position and affix the adhesive-backed mounting template
supplied with the antenna. The mounting holes may be drilled through the template at 0.22 inch through or
threaded at 10-32 UNF 2-B, refer to Figure 2-5. The connector hole is 1.25 inch diameter. Be sure to remove
the mounting template prior to installing the antenna.