bandwidth is widened to enhance the identification of
stabilization system is designed to maintain the
antenna beam at the selected tilt angle relative to the
earth's surface. The stabilization system uses the
aircraft vertical gyros as a reference and is comprised
of electronic amplifiers in the Receiver/Transmitter
interconnected with electromechanical components in
(7) Level Flight. Trim aircraft for straight and
level flight in smooth, clear air, over level terrain.
Select a 50-mile range and set STAB to off.
Rotate tilt control upward until all ground returns
disappear and then rotate tilt downward until ground
returns just begin to appear. After several antenna
sweeps, check to see that ground returns are equally
displayed. If returns are only on one side of the radar
screen or uneven across the radar antenna mounting
and should be corrected before proceeding. Repeat
this procedure until a balanced display is achieved.
stabilization off, select stabilization ON and tilt upward
once again to remove all returns. Rotate tilt downward
and check for even displays of ground returns. If this
test indicates improper display, possible errors in the
radar stabilization circuits or aircraft gyro exist.
It is typical of a precessing aircraft gyro to
cause ground returns to first appear on
one side of the display, then have them
shift to the opposite side of the display.
apparent with respect to flight control
established in level flight, rotate the TILT control
upward in 1 increments until ground returns just
disappear, then rotate an additional 2 upward.
Place the aircraft in a standard rate turn to the
right. Note the radar display. It should be free of
If returns display on the right side of radar
indicator, the radar system is understabilizing. Targets
on the left side of radar display indicate the system is
In prolonged turns, gyro precession may occur
which will be tracked by the stabilization system and
appear as undesirable ground targets on the indicator.
e. Maximum Permissible Exposure Level
(MPEL). Heating and radiation effects of weather
radar can be hazardous. Personnel should remain at
a distance greater than R from the radiating antenna in
order to be outside of the envelope in which radiation
exposure levels equal or exceed 10 mW/cm2. Refer to
Figure 3B -141. The distance (radius R) of the MPEL
boundary is calculated for the radar system on the
basis of radiator diameter, rated peak-power output,
and duty cycle.
3B-33. TRANSPONDER (APX-100).
For information on the APX-100 Transponder,
refer to Chapter 3, Paragraph 3-5.