A28-1146-102-00
Radar Facts
5-35
WEATHER DISPLAY CALIBRATION
Groundbased radarobservers oftheNationalWeatherService(NWS)
currently use video integrator processor (VIP) levels in reporting
thunderstorm intensity levels. Theseradar echointensity levels areon
a scale of one to six. Refer to Section 6 of FAA Advisory Circular
AC-00-24Bfor additional details.
Toassistthepilotincategorizingstormsinaccordance withVIPlevels,
theindicatordisplaycolorsrepresentcalibratedrainfallratesinWXand
preset calibrated gain. The relationship between the 4-color
calibrations and the VIP levels is shown in table 5-11.
As covered in the RCT description, intervening attenuating rainfall
reduces the calibrated range and the radar can incorrectly depict the
true cell intensity.
The radar calibration includes a nominal allowance for radome losses.
Excessive losses in the radome seriously affectradar calibration. One
possible means of verification is signal returns from known ground
targets. It is recommended that you report evidence of weak returns to
ensure that radome performance is maintained at a levelthat doesnot
affect radar calibration.
To test for a performance loss, note the distance at which the aircraft’s
base city, a mountain, or a shoreline can be painted from a given
altitude.When flyingin familiarsurroundings,verifythat landmarkscan
still be painted at the same distances.
Anylossinperformanceresultsinthesystemnotpaintingthereference
target at the normal range.
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