4-70Garmin G500 Pilot’s Guide 190-01102-02 Rev. EForewordSec 1SystemSec 2PFDSec 3MFDSec 4HazardAvoidanceSec 5AdditionalFeaturesSec 6Annun.& AlertsSec 7SymbolsSec 8GlossaryAppendix AAppendix BIndexIf the aircraft is above 29,000 feet, be cautious of any target return that getsto 30 NM or closer. This is likely a thunderstorm that has a top high enough thatthe aircraft cannot fly over it safely.If the aircraft altitude is 15,000 feet or lower, set the displayed range to60 NM. Closely monitor anything that enters the display.Also, after setting up the antenna tilt angle as described previously, groundreturns can be monitored for possible threats. The relationship between antennatilt angle, altitude, and distance is one degree of tilt equals 100 feet of altitudefor every one nautical mile.Vertical Change of Radar Beam (feet)Change in Antenna Tilt10 nm010002000300040001000200030004000-1°0°-2°-3°-4°+1°+2°+3°+4°Figure 4-61 Vertical Change in Radar Beam per Nautical MileTherefore, with the antenna tilt set so that the bottom of the beam is fourdegrees below parallel with the ground, a target return at 10 NM is approximately4,000 feet below the aircraft; at 20 NM, 8,000 feet; at 50 NM, 20,000 feet. Inother words, at this tilt setting, a ground return (such as a mountain peak) beingdisplayed at 10 NM would have a maximum distance below the aircraft of 4,000feet. If that ground target return moves to 5 NM, maximum distance below theaircraft will be 2,000 feet.This setup will provide a good starting point for practical use of the GWX 68.There are many other factors to consider in order to become proficient at usingweather radar in all situations.4.9.5 Weather Mapping and Interpretation4.9.5.1 Weather display InterpretationWhen evaluating various target returns on the weather radar display, thecolors denote approximate rainfall intensity and rates as shown in the tablebelow.
