*
The mode, tilt, and gain messages show

*
The FMCF range shows.

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777 AIRCRAFT MAINTENANCE MANUAL

WXR SYSTEM -ND RANGE DISAGREEMENT

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WXR SYSTEM -SYSTEM SELECT AND SYSTEM ON/OFF

System Select
When you select the left or right WXR system at the WXR panel, an RT ENABLE goes to switch S1 in the same WXR RT to enable the RT to operate. 28v dc from the keep-alive power supply goes from the selected RT through the system select switch in the WXR panel to the waveguide switch. The 28v dc energizes the waveguide switch relay to connect the selected RT to the WXR antenna.
System On
To make the WXR system operate, do either of these:
*
Push the WXR switch on an EFIS control panel

*
Push the LSK for WXR on the EFIS OPTIONS page on the CDU.

When you do this, the AIMS cabinets supply a ground level discrete through the WXR panel through switch S1 of the RTs. This ground level discrete lets 28v dc power go from the keep-alive power supply to energize the relay to close switches S2 and S3 if S1 is energized by the WXR control panel system select switch. The 28v dc keep-alive power supply sends power through switch S2 to energize the WXR CP power supply. 115v ac goes through switch S3 to energize the RT power supply and the WXR antenna drive.
Certain conditions cause the predictive windshear (PWS) function to turn the WXR system on automatically. When this happens, the ground signal to switch S1 comes from the PWS card in the selected RT, instead of the AIMS cabinets.
System Off
To make the WXR system go OFF, do either of these:
*
Push the WXR switch again

*
Push the WXR LSK on the EFIS OPTIONS page again.

This removes the ground level discrete from the AIMS cabinet. If more than one WXR switch is on, push all of the switches again.
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WXR SYSTEM -SYSTEM SELECT AND SYSTEM ON/OFF

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WXR SYSTEM -WXR RT FUNCTIONAL DESCRIPTION

General
The selected left or right WXR RT makes RF pulses and sends them over a waveguide to the antenna. The antenna transmits pulses and receives the return signals and sends them to the selected RT. The RT processes the return signals to make display data that shows on the NDs. The WXR display on the NDs shows the weather patterns in front of the airplane.
Control Inputs
The EFIS CP or CDU sends the WXR system ON/OFF and the WXR range selection data to the onside AIMS cabinet.
The AIMS cabinet sends this control data on its ARINC 429 general purpose data bus #2 to:
*
The CONTROL BUS 1 input of the onside WXR RT

*
The CONTROL BUS 2 input to the off-side WXR RT.

The WXR panel sends control data on CONTROL BUS 0 to the WXR RT. The WXR panel sends this data:
*
Gain, tilt, and mode of operation

*
Ground return suppression

*
Turbulence detection selection.

Antenna Control
Each AIMS cabinet gets attitude data for antenna stabilization from the air data inertial reference system (ADIRS). An AIMS cabinet sends this attitude data to:
*
The onside attitude input of the onside RT

*
The offside attitude input of the offside RT.

If the attitude data from the AIMS cabinet fails, an ADIRS invalid analog discrete goes to the onside WXR RT. The RT then uses the offside attitude data.
Maintenance Interface
Test start commands from the CMCF in the AIMS cabinet go into the RT on a ARINC 429 maintenance (MAINT) DATA IN data bus. The WXR RT sends WXR system status and maintenance data to both AIMS cabinets on the MAINT DATA OUT data bus.
Central Processor Unit
The RT has a central processor unit (CPU) that uses the control data to control the operation of the RT and the antenna drive. The CPU sends some of these control signals such as range, gain, and operational mode to the transmitter circuits. Also, the CPU makes the scan and elevation signals from the ADIRS attitude data. It sends these scan and elevation signals to the antenna assembly for antenna stabilization. The CPU also gets antenna position monitor signals from the antenna assembly.
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WXR SYSTEM -WXR RT FUNCTIONAL DESCRIPTION

Oscillator/Transmitter Circuits
　
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