7.  Antenna
_______
 A.  The antenna is mounted on the airplane bulkhead behind the radome in an unpressurized section of the airplane. It is used for both transmitting and receiving.
 B.  The antenna system consists of an azimuth drive motor, a tilt drive motor, an azimuth position synchro, an elevation position synchro, and a 30-inch planar array radiating element.
 C.  MANual operation of the TILT control at the control panel, up or down from the zero position, impresses a fixed angle on the stabilized/boresight zero position of the antenna planar array. Maximum compensating movement of the antenna is 45-degrees of combined pitch and roll plus or minus the TILT angle set at the control panel.
 D.  AUTOmatic operation of the TILT control at the control panel causes the R/T to use tilt data from the EGPWS to calculate antenna compensation. Optimum tilt angles are determined by the EGPWS based on altitude above the terrain and terrain conditions in the area. The AUTO-tilt data is integrated with the existing wind shear submodes during approach and take-off through 2300 feet. During these times, the weather scans alternate with the windshear scans. The AUTO-tilt function only controls tilt during the weather scan. The windshear scan algorithm is not changed when AUTO-tilt is enabled.
 E.  Elevation, EL and scan AZ switches are mounted on the antenna drive assembly to disable the respective movement of the planar array for maintenance purposes.
 8.  Display Load Resistors
______________________
 A.  Display load resistors are mounted below the P1 and P3 instrument panels. The resistors are connected to the right and left data bus inputs of the auxiliary EICAS display. The load resistors insure compatibility between the weather radar receiver/transmitter and the NDs and the auxiliary EICAS display.
 9.  Weather Radar Interfacing Systems (Fig. 2)
_________________________________
 A.  The weather radar system interfaces with the following systems:
 (1)  
Integrated Display System (AMM 31-61-00)

 (2)  
Landing Gear Multiple Use System/Components (AMM 32-09-00)

 (3)  
Inertial Reference System (AMM 34-21-00)

 (4)  
Flight Management Computer System (AMM 34-61-00)

 (5)  
Central Maintenance Computer System (AMM 45-10-00/001)

 B.  Integrated Display System (IDS)
 (1)  The components of the IDS that interface with the weather radar are the:
 (a)  
The captain's and first officer's EFIS control panels

 (b)  
The captain's and first officer's navigation displays (ND's).

 (c)  
Auxiliary EICAS display

 (d)  
The captain's and first officer's display transfer module.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
 (e)  EICAS display select panel
 (2)  
Electronic Flight Instrument System (EFIS) Control Panel

 (a)  
The EFIS control panels provide system on/off discretes to turn on the selected weather radar system and control signals for displaying weather radar range data on the NDs.

 (b)  
The captain's and first officer's EFIS control panels are located on the left and right sides of the pilots' lightshield, respectively.

 (3)  
Navigation Display (ND)

 (a)  The ND is a CRT that provides displays for several electronic systems. The captain's ND is located on the captain's instrument panel (P1). The first officer's ND is located on the first officer's instrument panel (P3). The following paragraphs describe the displays for the weather radar system: 1) The weather radar data is displayed on the NDs in a low
 intensity, raster format. The weather and turbulence data is displayed in a four-color format. Each color (green, yellow, red, and magenta) represents a range of moisture gradients. Position on the NDs of the displayed weather radar data corresponds to the actual storm position in relation to the airplane. Display position is also dependent on the selected range.
 2)  The ground map returns are displayed in a similar manner as the weather data in green, yellow and red. The colors represent the variations in the terrain.
　
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