TM 55-1510-221-10
Section IV.
TRANSPONDER AND RADAR
3-31. WEATHER RADAR SET (AN/APN-215).
a. Description. The weather radar set fig.
3-25) provides a visual The weather radar set (fig.
3-25), provides a visual 120° around the nose of the
aircraft, extending to a distance of 240 nautical
miles. The presentation on the screen shows the
location of potentially dangerous areas, such as
thunderstorms and hailstorms, in terms of distance
and azimuth with respect to the aircraft. The radar
is also capable of ground mapping operations. The
weather radar set is protected by a 5-ampere
RADAR circuit breaker located on the overhead cir-
cuit breaker panel (fig. 2-26).
b. Controls/Indicators and Functions.
(1.) GAIN control. Used to adjust radar
receiver gain in the MAP mode only.
(2.) STAB OFF switch. Push type on/off
switch. Used to control antenna stabilization signals.
(3.) Range switches. Momentary action
type switches. When pressed, clears the screen and
increases or decreases the range depending on switch
pressed.
(4.) TILT control. Varies the elevation
angle of radar antenna a maximum of 15 degrees up
or down from horizontal attitude of aircraft.
(5.) 60° switch. Push type on/off switch.
When activated, reduces antenna scan from 120° to
60 degrees.
(6.) TRACK switches. Momentary action
type switches. When activated, a yellow track line
extending from the apex of the display through top
range mark appears and moves either left or right,
depending on the switch pressed. The track line
position will be displayed in degrees in the upper
left comer of the screen. The line will disappear
approximately 15 seconds after the switch is
released. It will then automatically return to “0“
degrees.
(7.) HOLD switch. Push type on/off
switch. When activated, the last image presented
before pressing the switch is displayed and held. The
word HOLD will flash on and off in the upper left
comer of the screen. Pressing the switch again will
update the display and resume normal scan opera-
tion.
(8.)
Function switch. Controls operation of
the radar set.
(a.) OFF. Turns set off.
(b.) STBY. Places set in standby
mode. This position also initiates a 90-second
warm-up delay when first turned on.
(c.) TEST. Displays test pattern to
check for proper operation of the set. The transmit-
ter is disabled during this mode.
tion.
(d.)
ON. Places set in normal opera-
(9.) MODE switches. Momentary action
type switches. Pressing and holding either switch
will display an information list of operational data
on the screen. The data heading will be in blue, all
data except present data will be in yellow, and pres-
ent selected data will show in blue. The three
weather levels will be displayed in red, yellow, and
green. If WXA mode has been selected, the red bar
will flash on and off. If the switch is released and
immediately pressed again, the mode will increase
or decrease depending on switch pressed. When
either top or bottom mode is reached, the opposite
switch must be pressed to further change the mode.
(10.)
NAV switch. If pressed with the INS
operating and the weather radar operating in a
weather depiction mode, the screen will display INS
waypoints that are located within the range dis-
played and within the degree of coverage left or right
of the present heading of the aircraft.
(11.) BRT control. Used to adjust screen
brightness.
c.
Weather Radar - Normal Operation.
Do not operate the weather radar set
while personnel or combustible materials
are within 18 feet of the antenna reflector
When the weather radar set is operating,
high-power radio frequency energy is
emitted from the antenna reflector, which
can have harmful effects on the human
body and can ignite combustible materi-
als.
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