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PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--03
REV 3
4-5
Normal Operation
To aid in target interpretation, targets are displayed in v arious colors.
Each color represents a specific target intensity. The intensity lev els
chosen are related to the National Weather Service (NWS) video
integrated processor (VIP) levels.
In the WX mode, the system displays five levels as black, green, yellow,
red, and magenta in increasing order of intensity.
If RCT is selected, the radar receiver adjusts the calibration
automatically to compensate for attenuation losses as the radar pulse
passes through weather targets on its way to illuminate other targets.
There is a maximum extent to which calibration can be adjusted. When
this maximum value is reached, REACT compensation ceases. At this
point, a cyan field is added to the display to indicate that no further
compensation is possible.
In the absence of intervening targets, the range at which the cyan field
starts is approximately 290° with a 12--inch antenna. For the 18-- and
24--inch antennas, the cyan field starts beyond 300 NM and therefore
will not be seen if there are no intervening targets.
The RCT feature includes attenuation compensation (Refer to Section
5, Radar Facts, of this guide for a description of attenuation
compensation.). Rainfall causes attenuation and attenuation
compensation modifies the color calibration to maintain calibration
regardless of the amount of attenuation. Modifying the color calibration
results in a change in the point where calibration can no longer keep the
radar system calibrated for red level t argets. The heavier the rainfall,
the greater the attenuation and the shorter the range where XSTC runs
out of control. Therefore, the range at which the cyan
background starts varies depending on the amount of attenuation. The
greater the attenuation, the closer the start of the cyan field.
The radar’s c alibration includes a nom inalallowance for radomelosses.
Excessive losses in the radome seriously affect radar calibration. One
possible means of verification are signal r eturns f rom k nown targets.
Honeywell recommends that the pilot report evidence of weak returns
to ensure that radome performance is maintained at a level that does
not affect radar calibration.
Target aler t can be selected in any WX range. The target alert circuit
monitors for hazardous targets within 7.5_ of the aircraft centerline.