BendixKing IN-862A System RDR-2100 - Manual (Page 14)

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Effective Date: 9/98 RDR 2100 Pilot's Guide: Rev 1
Theory of Operation
In this scenario the weather cell might be at 100 nm, the altitude might
be 40,000 feet, and the appropriate tilt angle is approximately -3
degrees. Notice that the beam is centered on the rain but it also inter-
sects the ground. The angle the beam makes with the ground is called
the grazing angle. When this angle gets greater than about 2 degrees
the ground reflections that return to the radar become very significant. A
later section called “Tilt Management” discusses this difficult topic and
makes some suggestions to help make weather/ground distinction.
The following diagrams show the beam width relationship with 10 inch,
12 inch and 18 inch antennas. For illustrative purposes the aircraft are
shown at approximately 40,000 feet and the tilt is set at zero degrees.
Radar Beam Illumination
with 10 Inch Antenna
Radar Beam Illumination
with 12 Inch Antenna
Radar Beam Illumination
with 18 Inch Antenna
RDR 2100 PG 3/12/07 3:45 PM Page 10