Airborne Color Weather Radar; Weather Radar Basics - Garmin G1000 Cockpit Reference Manual

10.7 AIRBORNE COLOR WEATHER RADAR

Weather Radar Basics

Antenna Beam Illumination
It is important to understand the concept of the
antenna beam illumination. The radar beam is much like
the beam of a spotlight. The farther the beam travels, the
wider it gets. The radar is only capable of "seeing" what is
inside the boundaries of the beam.
Altitude (x1000 ft.)
80
0
0
190-00708-00 Rev. A
Antenna at Zero Tilt
9°
15 30
Figure 10-26 Radar Beam from 10 inch Antenna
Figure 10-27 Radar Beam in Relation to the Curvature of the Earth
Garmin G1000 Cockpit Reference Guide for the Socata TBM 850
Figure 10-26 depicts a radar beam' s characteristics.
The figure illustrates vertical dimensions of the radar
beam, although the same holds true for the horizontal
dimensions. In other words, the beam is as wide as it is
tall. Note that it is possible not to see areas of precipitation
on the radar display because of the antenna tilt setting.
With the antenna tilt set to zero in this illustration, the
beam overshoots the precipitation at 15 nautical miles.
The curvature of the earth can also be a factor, especially
at range settings of 150 nautical miles or more ( Figure
10-27).
18,000 ft.
18,000 ft.
45 60
Range (nautical miles)
SECTION 10 – HAZARD
AVOIDANCE
Max Power at Beam Center
75
320 nm
90
10-17