Garmin G1000 King Air C90GT - Manual (Page 341)

190-00663-01 Rev. A Garmin G1000 Pilot’s Guide for the Hawker Beechcraft C90A/GT 327
HAZARD AVOIDANCE
SY
STEM
O
VER
VIEW
FLIGHT
INSTRUMENTS
EIS
AUDIO P
ANEL
& CNS
FLIGHT
MANA
GEMENT
HAZARD
AV
OID
ANCE
AFCS
ADDITIONAL
FEA
TURES
APPENDICES
INDEX
If the aircraft is above 29,000 feet, be cautious of any target return that gets to within 30 nautical miles. This is
likely a thunderstorm that has a top high enough that the aircraft cannot fly over it safely.
If the aircraft altitude is 15,000 feet or lower, setting the displayed range to 60 miles may be more helpful.
Closely monitor anything that enters the display.
Also, after setting up the antenna tilt angle as described previously, ground returns can be monitored for possible
threats. The relationship between antenna tilt angle, altitude, and distance is one degree of tilt equals 100 feet of
altitude for every one nautical mile.
Vertical Change of Radar Beam (feet)
Change in Antenna Tilt
10 nm
0
1000
2000
3000
4000
1000
2000
3000
4000
-1°
0°
-2°
-3°
-4°
+1°
+2°
+3°
+4°
Figure 6-49 Vertical Change in Radar Beam per Nautical Mile
Therefore, with the antenna tilt set so that the bottom of the beam is four degrees below parallel with
the ground, a target return at 10 nm is approximately 4,000 feet below the aircraft; at 20 nm, 8,000 feet;
at 50 nm, 20,000 feet. In other words, at this tilt setting, a ground return (such as a mountain peak) being
displayed at 10 nm would have a maximum distance below the aircraft of 4,000 feet. When the ground target
return moves to 5 nm, maximum distance below the aircraft is 2,000 feet.
This setup provides a good starting point for practical use of the GWX 68. There are many other factors to
consider in order to become proficient at using weather radar in all situations.
WEATHER MAPPING AND INTERPRETATION
WEATHER DISPLAY INTERPRETATION
When evaluating various target returns on the weather radar display, the colors denote precipitation intensity
and rates shown in the table.
Weather Mode Color Intensity
Approximate
Precipitation Rate
(in/hr.)
Black < 23 dBZ < .01.
Green 23 dBZ to < 32 dBZ .01 - 0.1.
Yellow 32 dBZ to < 41 dBZ 0.1 - 0.5
Red 41 dBZ to < 50 dBZ 0.5 - 2
Magenta 50 dBZ and greater > 2
Table 6-5 Precipitation Intensity Levels