TM 1-1510-262-10
(2) GAIN Control. The GAIN Control is used for manual gain control of the radar receiver. On the WXP,
this control is a 7-position switch. When placed in the CAL position, gain is preset to a value that allows the radar
receiver to calibrate its operation to the relectivity chart shown in Table 3-3. To aid the pilot in making correct
weather judgments, the GAIN Control may be adjusted to higher or lower gain settings. The higher settings (+1,
+2, +3 ) may be chosen to identify the lightest level of precipitation, while the lower settings (-1, -2, -3 ) may
be chosen to allow a more in-depth study of the most intense weather targets. Each of the minus settings (-1,
-2, -3 ) reduces receiver sensitivity below that of the CAL setting by approximately 6 dB, or one color level, per
setting. This results in a total reduction of approximately three-color levels when in the -3 position. Each of the plus
settings (+1, +2, +3 ) increases the system sensitivity through a combination of lengthening the transmitted pulse
width and increasing receiver gain. The effective gain increase can be as much as one color level when the target
is close (within approximately 65nmi). The effective gain is less than one color level at longer ranges (beyond
approximately 65nmi). The GAIN control can be used in the MAP, WX, WX+T , and TURB modes. The display
color of a target depends on the GAIN setting currently being used. With the GAIN control in the CAL position,
all detectable targets are shown in green, yellow, red and magenta in WX and WX+T modes, and in cyan, green,
yellow, and magenta in MAP mode (least effective to most relective). The selected GAIN is annunciated in the
upper left on the MFD. In the CAL position, G+0 may be annunciated on the MFD. The PAC feature is enabled only
when the GAIN control is set to the CAL position.
Although proper use of the GAIN control can provide added knowledge of the targets being dis-
played, the pilot should always return the GAIN control to the CAL position when inished analyzing
the display. Failure to do so may result in missing signiicant targets at any range when operating
in one of the minus settings (-1, -2, -3).
(3) TILT Control. The radar antenna is fully stabilized to compensate for aircraft pitch, and roll attitude
changes. The TILT control allows adjusting the vertical aim of the radar antenna from approximately 15 degrees
up from horizontal. When stabilization is on, the combination control range is from 30 degrees down to 30 degrees
up. (TILT functions when the antenna is stabilized as well as when it is unstabilized.) Tilt adjust resolution is 0.25
degrees when the TILT control is between +5 degrees and -5 degrees, and is 0.5 degrees outside the 5 degree
window. The hundredth s digit is rounded off, and the tilt is displayed at the left end of the half-range arc on the
MFD (i.e., +10.7, -5.3, etc).
3-29
