(6)
The video signal received by the radar receiver is digitized and fowarded in binary format.
(7)
In the WX mode, normal weather returns are displayed in green, yellow and red at all ranges.
(8)
In the WX+T mode, normal weather detection is made and displayed in the same manner as the weather mode except targets (green, yellow, or red), within 50NM, containing turbulence will be displayed in magenta.
(9)
When weather radar MAP mode is selected, the radar system operates in the terrain mapping mode. Varying the GAIN control setting in the map mode may increase the definition of certain types of terrain targets. Rotating the GAIN control counterclockwise from MAX to MIN positions decreases the receiver gain.
C. Functional Description
(1) Electrical Power and Power Control Circuits (Fig. 4)
(a) The receiver transmitter receives single phase electrical power of 115v ac, 400 Hz, from the main power bus No. 2. Closing the 115v ac weather radar R/T circuit breaker sends a 28v dc interlock power signal from the R/T thru the control panel back to the R/T logic switch controlling relay K1. The R/T is turned on when one of the WXR power switches on the EFIS control panel is in the ON position. The control panel internal power is provided by +28v dc signal from the receiver/transmitter keep alive power supply. The antenna is powered by 115v ac through power control relay K1.
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A 737-300/400/500MAINTENANCE MANUAL
Weather Radar Scan Display and Antenna RF Beam Pattern
Figure 2
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A 737-300/400/500MAINTENANCE MANUAL
Weather Radar System Block Diagram
Figure 3
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737-300/400/500MAINTENANCE MANUAL
(2)
Weather Radar System Control Functions (Fig. 4)
(a)
The receiver transmitter acquires control data from the weather radar control panel, EFIS control panels, and inertial reference units. This data is either digital (ARINC 429) or discrete. The WXR power switch (EFIS control panel) and attitude data selection (IRS source select switch on the instrument switching panel) inputs are open/ground discretes. The WXR power switch ground discrete energizes the receiver transmitter main power supply. This in turn, provides operating power to the weather radar control panel, antenna, and receiver/transmitter for system turn on. The IRS source select switch provides an open discrete (in the NORMAL position) and a ground discrete (in the BOTH ON 2 position) to the data receiver/transmitters input circuits. This de-energizes (NORMAL) and energizes (BOTH ON 2) a relay to select between the No. 1 or 2 IRS's, respectively.
(b)
The range selection (EFIS control panel), attitude data (IRS), and system control data (weather radar control panel) are all digital. This data is transmitted to the receiver/transmitter via ARINC 429 digital data buses. The range selection and WXR power ON discrete from each EFIS control panel, independently controls its respective display. All other weather radar control data is common to both EHSIs. The receiver/transmitter processes each selected range separately.
(c)
Within the receiver/transmitter, the input control data is fed to the timing, control, and monitoring circuits and the antenna stabilization circuits. The timing, control, and monitoring circuits provide timing, control, and monitoring of all functions of the receiver/transmitter.
(3)
Weather Radar Control Panel Functions (Fig. 4)
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