TM 1-1520-218-10
3C-200
a. Description.
The
weather
radar/
Multifunction Display (MFD) system provides long and
short-range navigation maps, checklists, and weather
radar. The system contains two controllers. The MFD
controller provides for the selection and control of the
MFD format, modes, and waypoint designators. The
weather radar controller selects the radar modes and
adjustable quantities that may then be displayed on
the radar screen. The system consists of a
Receiver/Transmitter Antenna (RTA) (located in the
radome), a symbol generator (located on the bottom
shelf of the nose avionics compartment), the MFD
located in the center of the instrument panel, the MFD
controller, and the radar controller located on the
pedestal extension, Figure 2-6. The radar is operated
in conjunction with the multifunction display to provide
a composite display of weather and navigation
information. In the weather detection mode, the
system gives the pilot a color visual indication of storm
intensity.
Table 3C-106 shows the relationship between
the intensity levels displayed on the MFD and the
National Weather Service VIP levels. In this mode,
target returns are displayed at one of five video levels
(0, 1, 2, 3 or 4), with level 0 represented by a black
screen, because of weak or no returns. Levels 1, 2, 3,
or 4 are represented by green, yellow, red, and
magenta to show progressively stronger returns. In
ground mapping mode, video levels of increasing
reflectivity are displayed as black, cyan, yellow and
magenta.
b. Radar Control Unit (WC-650). The radar
control unit is located on the console and contains all
controls necessary for operating the radar system.
Refer to Figure 3C-147.
(1) Multifunction Display (ED-650). The
multifunction display indicator is an instrument panel-
mounted, full-color digital display system. Weather
display, ground mapping, and text functions are
provided. The inputs are displayed on the screen
together with range, mode, and status alphanumerics
to facilitate evaluation of the picture.
(2) Range Switches. The range switches are
two
alternate
action
push-button
switches,
one
placarded ¬ and the other placard ö, which are used
to select the radar operating range from 5 to 300 nm
full scale in the ON mode or 5 to 1000 nm full scale in
the flight plan mode. The ö push button selects
increasing ranges and the ¬ push button selects
decreasing ranges.
(3) Rain Echo Attenuation Compensation
Technique Switch and OFF Annunciator. This is a
momentary
alternate
action
push-button
switch,
placarded
RCT, which activates the rain echo
attenuation
compensation
technique
circuitry.
Selecting the RCT mode activates a cyan-colored
background field that indicates ranges at which the
radar receiver calibration has been exceeded. The
rain echo attenuation compensation technique is
active at all times in the WX mode to compensate for
attenuation of the radar signal as it passes through a
storm. This is accomplished by increasing the gain of
the receiver as weather is detected. An OFF
annunciator above the RCT switch indicates that the
RCT circuitry has been disabled.
Table 3C-106. Radar Display Levels Related to National Weather Service VIP Levels
VIDEO INTEGRATED PROCESSOR (VIP)
CATEGORIZATIONS
DISPLAY
LEVEL
RAINFALL
RATE
(MN/HR)
RAINFALL
RATE
(INCHES/HR)
STORM
CATEGORY
VIP LEVEL
RAINFALL
RATE (MN/HR)
(INCHES/HR)
MAXIMUM
CALIBRATED
RANGE (NM)
12-INCH FLAT-
PLATE
EXTREME
6
GREATER
THAN 125
4 MAGENTA
GREATER
THAN 52
GREATER
THAN 2.1
INTENSE
5
50-125 (2-5)
175
3 (RED)
GREATER
THAN 12
GREATER
THAN 0.5
VERY
STRONG
4
25-50 (1-2)
12-52
0.5-2.1
STRONG
3
12-25 (0.5-1)
175
2 (YELLOW)
4-12
0.17-0.5
MODERATE
2
2.5-12
(0.1-0.5)
175
1 GREEN
1-4
0.04-0.17
WEAK
0.25-2.51
(0.01-0.1)
175
0 BLACK
LESS
THAN 1
LESS THAN
0.04
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