TM 1-1510-225-10
3A-112
select the desired mode (Wx, WxA, or GND MAP) by
pressing the appropriate push-button switch.
The operation of scanning the antenna vertically
is referred to as taking a vertical slice.
Once vertical profile has been selected, the
desired profile azimuth angle may be changed in two-
degree increments by pressing and holding the
appropriate TRK switch. If the radar antenna is
already profiling, the antenna will move in two-degree
increments slicing in the direction determined by the
TRK switch, or a WAIT annunciation will be displayed
indicating that the radar antenna will perform the
desired slicing function as soon as the antenna returns
to the last selected profiling azimuth angle.
To terminate the vertical profile mode and return
to the normal mode (horizontal scan), press the VP
push-button switch. The radar system will retain its
existing weather mode and return to horizontal
scanning. A track line will be present on the screen for
15 seconds to indicate the location of the last profiling
azimuth angle.
(10) Gain Control. The manual gain control
knob becomes active when ground mapping mode
(GND MAP) is selected. In all other modes, gain is
internally set.
b. Weather Radar Normal Operation.
1. Radar mode selector switch – TST.
2. TILT/stabilization control – UP 7 (as
shown on tilt indicator on display). Check
for correct test pattern.
3. Radar mode selector switch – TST or
STBY. Taxi to a clear area where there
are no people, aircraft, vehicles, or
metallic buildings within approximately
100 yards.
4. Radar mode selector switch – ON. Wx
mode will be displayed in the 80-mile
range. Any targets (weather or ground)
will be displayed in green, yellow, red, or
magenta.
5. Range switches (EFIS control panel) –
Select 40 miles as maximum range.
6. WxA push-button mode selector switch –
Press and observe that the magenta
areas (if any) are flashing.
7. TILT control – Vary manually between UP
15 and DN 15 and observe that close-in
ground clutter appears at lower settings
and that any local rain appears at higher
setting.
8. Radar mode selector switch – TST or
STBY before taxi.
c. Weather Display Calibration. The radar
display has been calibrated to show five levels of
target intensity as shown in Table 3A-3. This table
shows the approximate relationship of aircraft weather
radar levels to the Video Integrated Processor (VIP)
levels used by the National Weather Service. These
levels are valid only when:
1. Wx or WxA mode is selected.
2. Displayed returns are within the STC
range
of
the
radar
(approximately
40 miles).
3. The returns are beam filling.
4. There are no intervening radar returns.
d. Tilt Management. Effective antenna tilt
management is the single-most important key for more
informative weather radar displays. Three prime
factors
must
be
kept
in
mind
for
proper
tilt
management.
1. The earth's curvature must be considered
in determining the location of the beam at
long distances.
2. The
center
of
the
radar
beam
is
referenced to the horizon by the aircraft's
vertical reference system.
3. Adjusting the antenna tilt control will cause
the center of the radar beam to scan
above or below the plane of the attitude
reference system.
A tilt setting that is too low will result in excessive
ground or sea return while a setting that is too high
can result in the radar beam passing above a weather
target.
For detecting weather targets at long ranges and
to allow adequate time for planning the proper
avoidance path, the tilt angle should be set for a
sprinkle of ground target returns on the display. By
slowly raising the tilt angle, weather targets will
emerge from the ground returns because of their
height above the ground. In order to minimize ground
