Sep 25/94
(3)
Position switches and controls on weather radar control panel as follows:
(a)
GAIN control - AUTO
(b)
TILT control - 0
(c)
SYS switch - 1
(d)
AF 121, 122; SN 351;
Mode selector - WX or MAP
(e)
SN 352-399;
Mode selector - WX, TURB, or MAP
(4)
The R/T unit will generate the RF pulses for transmission and send them to the antenna via the waveguide. The reflected RF is returned to the R/T for processing (Fig. 2).
(5)
The video signal received by the radar receiver is digitized and fowarded to the indicator in binary format.
(6)
In the WX weather mode, targets are displayed in green, yellow and red according to the strength of the microwave pulses returning to the antenna.
(7)
AF 121, 122; SN 351; When the MAP mode is selected, the weather radar system operates in the terrain mapping mode. Rotating the GAIN control out of AUTO position toward MAX causes the noise and video in the display to increase. Varying the GAIN control setting in the map mode may increase the definition of certain types of terrain targets.
(8)
SN 352-399; In the TURB mode, normal weather detection is made and displayed in the same manner as the weather mode except targets (green yellow or red), within 40NM, containing turbulence will be displayed in magenta. Varying the GAIN control out of the AUTO position provides manual control of the weather video in the turbulence mode.
C. Functional Description
(1) Electrical Power and Power Control Circuits (Fig. 3)
(a)
AF 121-122; System 1 and 2 receiver/transmitters and indicators receive 115-volt, 400 Hz, ac power from circuit breakers on the P7 overhead circuit breaker panel. Receiver/transmitter No. 1 power supply is enabled when the mode selector on the weather radar control panel is in any position other than OFF and the system transfer switch is in position 1. The ON/OFF 1 or 2 (power enable) ground signal from the mode selector switch turns on receiver/transmitter power supply No. 1 or No. 2 which generate voltages for the R/T.
(b)
AF 121-122; Each indicator is enabled by the ON/OFF 1 or ON/OFF 2 discrete ground from the weather radar control panel. The indicator power supply is turned on when the indicator range switch is placed to an operating range. The range switch sends the power supply enable, or the ON/OFF discrete ground, to the indicator power supply.
EFFECTIVITY
AF 121, 122; SN 351-399 CONFIG 3 02 Page 10 Apr 25/9834-43-00
(c)
SN 351-399; System 1 and 2 receiver/transmitters and indicators receive 115-volt, 400 Hz, ac power from circuit breakers on the P7 overhead circuit breaker panel. Receiver/transmitter No. 1 is enabled as follows. The range switch on the captain's or first officer's indicator is set from OFF to any operating range. A control panel enable discrete ground is sent from the indicator to the mode selector switch in the weather radar control which generates the control bus 0 data to the R/T No. 1. Another discrete ground is sent from the mode selector switch thru the system transfer switch in position 1 as the power enable to the receiver/transmitter No. 1 power supply. When the system tranfer switch is in the 2 position the power enable discrete ground is sent to the R/T No. 2.
(d)
SN 351-399; Each indicator is turned on when the indicator range switch is placed to any operating range. A discrete ground is sent from the range switch to enable the indicator power supply.
(e)
The antenna receives 115-volt ac power supplied through the antenna stabilization and drive circuits in the R/T.
(f)
Voltages of 12 and 28 volts dc from R/T No. 1 or No. 2 are used by the control panel No. 1 or No. 2 power supplies and system transfer switch contacts. The No. 1 system 28 volts dc at the normally closed contacts of the system transfer switch is sent to the R/T microprocessor through the de-energized contacts of the waveguide switch. When R/T No. 2 is selected on the control panel, a discrete ground is sent to R/T No. 1 which stops transmission. The No. 2 system 28 volts de-energizes the waveguide switch to connect R/T No. 2 to the antenna and sends 28 volts dc to R/T No. 2 microprocessor to start rf transmission.
(2)
Weather Radar System Control Functions (Fig. 3)
(a)
Several control and data buses send ARINC 429 and 453 data between weather radar and interfacing systems as shown in Fig. 3. Control bus 0 from the control panel sends ARINC 429 system mode, gain and tilt data to the No. 1 and No. 2 R/Ts. Control Bus 1 and 2 from the indicators send range data to both R/Ts. Both receiver/transmitters send video information on ARINC 453 Data buses 1 and 2 to the captain's and first officer's indicators.
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本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航3(94)
