777 AIRCRAFT MAINTENANCE MANUAL
WXR SYSTEM -RECEIVER-TRANSMITTER
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WXR SYSTEM -RT MOUNT
Purpose
The purpose of the WXR RT mount is to:
*
Hold the RT
*
Connect the RT to the airplane wiring
*
Connect the RT to the waveguide
*
Supply airplane cooling air to the RT.
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777 AIRCRAFT MAINTENANCE MANUAL
WXR SYSTEM -RT MOUNT
EFFECTIVITY BEJ ALL 34-43-00
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WXR SYSTEM -ANTENNA ASSEMBLY 1
Antenna Assembly
The antenna assembly includes:
*
The flat plate WXR antenna
*
The antenna pedestal.
Flat Plate Antenna
The flat plate antenna transmits RF pulses from the WXR RT, and receives the pulses as they reflect off precipitation formations.
The flat plate antenna is an array of radiation slots. The RF pulses radiate from each of the slots and combine to make a pencil beam 3.6 degrees high and 3.4 degrees wide. The antenna weighs 6.5 lb (3 kg) and is 23 inches wide.
Antenna Pedestal
The antenna pedestal contains these items:
*
Electrical connectors
*
Stepper motors to drive the horizontal scan and vertical elevation scan
*
Antenna position monitors
*
Disable switches.
The antenna pedestal receives 115v ac power from the WXR RT. The antenna pedestal has two sets of power supplies and electronics. One set drives the antenna with the left RT selected. The other set drives the antenna with the right RT selected.
There is a horizontal scan stepper motor to drive the antenna +/-90 degrees of the airplane centerline. There is also a vertical elevation scan stepper motor to drive the antenna +/-40 degrees up or down (this includes the +/-degrees for manual tilt selection from the WXR control panel). The stepper motors use 26v dc for operation.
There is a zero position monitor and an incremental monitor for each motor. These monitors send antenna horizontal scan and elevation scan position feedback to the WXR RT. There are elevation and azimuth scales that permits a visual measurement of the tilt and scan angles.
There is a horizontal scan and elevation scan disable switch on the antenna pedestal to permit you to remove power to the scan and elevation stepper motors. Use these switches to inhibit movement of the antenna during maintenance. The switches do not stop RF transmissions from the WXR RT.
A torque spring inside the antenna pedestal counter balances the weight of the antenna. When you remove the antenna, the torque spring moves the elevation drive into the upper position.
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777 AIRCRAFT MAINTENANCE MANUAL
WXR SYSTEM -ANTENNA ASSEMBLY 1
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WXR SYSTEM -ANTENNA MOUNT ASSEMBLY
General
The antenna drive unit attaches to the antenna mount assembly with four antenna mount bolts.
The mount assembly attaches to a support assembly with five mount assembly bolts.
The support assembly attaches to the forward pressure bulkhead with six support assembly bolts.
Training Information Point
The support assembly and mount assembly are aligned at the factory.
NOTE: Do not loosen the mount assembly bolts or the support assembly bolts. The support assembly and mount assembly are aligned at the factory. If the bolts are accidently loosened or if the base is loose or not aligned, special alignment procedures must be done by a Boeing specialty team. Contact Boeing Seattle
A.O.G. Office, Technical Assistance Team.
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777 AIRCRAFT MAINTENANCE MANUAL
WXR SYSTEM -ANTENNA MOUNT ASSEMBLY
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WXR SYSTEM -RF SWITCHING
Purpose
The WXR waveguide switch, switches the WXR antenna between the left and right WXR RTs.
Description
The WXR waveguide switch has three rigid waveguide sections attached to it that go to the:
*
Left WXR RT
*
Right WXR RT
*
WXR antenna pedestal.
