PRIMUS
r
880 Digital Weather Radar System
A28- 1146- 102- 00
Radar Facts
5-35
WEATHER DISPLAY CALIBRATION
Ground based radar observers of the National Weather Service (NWS)
currently use video integrator processor (VIP) levels in reporting
thunderstorm intensity levels. These radar echo intensity levels are on
a scale of one to six. Refer to Section 6 of FAA Advisory Circular
AC- 00- 24B for additional details.
To assist the pilot in categorizing storms in accordance with VIP levels,
the indicator display colors represent calibrated rainfall rates in WX and
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 affect radar 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 level that does not
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 flying in familiar surroundings, verify that landmarks can
still be painted at the same distances.
Any loss in performance results in the system not painting the reference
target at the normal range.
Summary of Contents for Primus 880
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