Selection of the map function causes system
parameters to be optimized on the three lowest ranges
to improve resolution and identification of small forgets
at short ranges. The reflected signal from various
ground surfaces is displayed as magenta, yellow, or
cyan (most to least reflective).
The radar system consists of three units:
indicator, receiver/transmitter, and antenna. The
indicator is mounted in the cockpit and contains all the
receiver/transmitter is located on the radio rack. The
antenna, which is fully stabilized for aircraft pitch and
roll, is in the avionics compartment in the nose of the
Refer to Figure 3C-22.
(1) INT / OFF. Rotary control used to turn
system on and off, and to adjust (intensity) of display.
STARTUP, STBY, and 100 will be displayed.
(2) Display Area. Displays visual indication,
in color, of rainfall intensity with range marks and
(a) Mode Field. Selected function is
displayed as STBY, WX, CYC, MAP, or TEST. WAIT
is displayed until the initial RT warm-up period has
(b) Auxiliary Field. Color bar relates
displayed colors to signal reflectivity levels 1, 2, and 3
displayed beneath color bar.
1 For WX, CYC, and TEST, color bar
is green, yellow, and red. For MAP, color bar is cyan,
yellow, and magenta.
2 VAR replaces 1, 2, 3 in WX and
MAP when GAIN control is not in detented PRESET
3 FRZ is displayed as a blinking word
when freeze function is selected.
(c) Target Field. Blank unless target
alert is enabled causing letter T in red rectangle to be
displayed. Flashing alert symbol TGT in a red
rectangle is displayed when red-level target is
detected within the target alert sector.
(d) Range Mark Numerics. Five labeled
range marks are displayed on each range. The fifth
range mark label is larger serving to identify the
selected range. Range and azimuth marks and
numerics are displayed in cyan for WX, CYC, and
TEST; in green for MAP.
(3) 10 / 25 / 50 / 100 / 200 / 300. Momentary
push buttons used to select one of six ranges. For
each selected range, five range marks are displayed.
At system startup, 100-mile range is automatically
selected. Internal memory for range push buttons is
(4) TILT. Rotary control used to select tilt
angle of antenna beam with relation to earth (with
stabilization on) or with relation to airframe (with
stabilization off). Clockwise rotation tilts beam upward
downward 0 to 10.
(5) AZ MK. Slide control used to either
display or not display azimuth markers at 30 intervals.
(6) STAB. Slide control used to turn antenna
stabilization on or off.
(7) TGT ALRT. Slide control used to turn
target alert function on or off. When enabled, letter T
in red rectangle is displayed to identify that target alert
function is active. Target alert is active only when
radar gain is calibrated; i.e., in WX with GAIN PRESET
and in CYC or TEST. The symbol TGT in a red
rectangle is displayed and flashes once each second
whenever a red-level target is detected within the
target alert section (range from 60 to 160 nm and
within 7.5 of aircraft heading). Target alert is
deactivated automatically if MAP is selected or if
variable GAIN is used, but is reactivated automatically
when operating controls are restored to valid alert