display, indicating that a storm target has been
(e) MAP. The MAP mode is used for
terrain mapping. Prominent ground features such as
lakes, bays, rivers, cities, coastlines, and offshore
drilling rigs can be clearly discerned and used as a
navigation cross-reference. The display colors are
changed in the MAP mode as follows: green to cyan,
yellow stays the same, red to magenta, and magenta
to blue. When using the MAP mode, the gain control
is used to adjust the prominence of ground features.
(2) RANGE Selector Control Knob. The
RANGE selector knob selects for displays, range at 5,
10, 20, 40, 80, 160, and 320 nm. This enables the
pilot to select the displayed distance for most weather
conditions that exist. There are four range calibration
rings on each range setting with numerical read-out of
their range in nautical miles. In addition to the range
rings, bearing markers are positioned dead ahead and
20° to either side of the aircraft heading for use in
judging the storm bearing and necessary heading
(3) TILT Control Knob. The TILT knob is
used to adjust the radar antenna angle ± 12°, relative
to the horizon. Proper tilt adjustment is one of the
most important factors in obtaining optimum use from
the weather radar. Too high an angle will pass the
majority of the radar beam above the storm cell,
particularly when the storm is a great distance away.
Too low an antenna tilt will clutter the indicator with
ground returns. The maximum distance at which
ground clutter can be obtained will depend greatly on
the terrain and aircraft altitude. The tilt setting is
displayed in the top right corner of the screen. When
the stab switch is in the ON position, the designation
TILT is replaced by STAB.
(4) BRIGHT / GAIN / MAX Control Knobs.
These knobs control display brightness and manual
adjustment of gain. Brightness of the display screen is
fully adjustable to compensate for a range of ambient
light levels, while automatically maintaining equal
brightness between the three colors displayed.
Likewise, the gain control can be manually adjusted in
both weather and ground mapping modes to provide
maximum flexibility in target interpretation. Whenever
the gain is varied from the preset maximum level, the
screen will annunciate VAR to remind the pilot to reset
the gain for standard intensity levels.
(5) OFF / STAB / ON Selector Switch. The
selector knob permits the pilot to select gyro-stabilized
control of the weather radar system. In the ON
position, the radars antenna scan is kept parallel to
the horizon and at the same relative tilt angle
previously selected. The display view is kept straight
and level, despite changes in aircraft pitch and roll,
thus preventing ground clutter from wiping out
potential weather targets.
c. Weather Radar System Operation.
Never operate the weather radar in the WX,
WXT, or MAP modes on the ground when
personnel are forward of the aircraft wing
and within 5 feet of the aircraft nose.
Failure to observe this warning may result
in permanent damage to the eyes and other
To increase the solid circuitry reliability, it
is recommended that the aircraft engines
be started before applying power to the
weather radar system.
(1) Turn On Procedure.
clockwise past detent to SBY position.
(2) Operating Procedure.
1. Mode Selector Switch TEST. Verify
that all four colors are present.
If TEST mode is bypassed and WX, WXT, or
MAP mode is selected, the display will light
up and the warmup annunciator in the
transmitter will become operational after
2. Mode Selector Switch SBY while
taxing and until clear of personnel,
then as required.
(3) Shutdown Procedure.
counterclockwise to OFF position.