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737-300/400/500MAINTENANCE MANUAL
(k) Receiver/Transmitter Antenna Stabilization Functions
1) The ability of the weather radar system to provide a consistently accurate weather map depends upon the stability of the antenna and the attitude reference system. A stabilized antenna ensurses that successive sweeps of the antenna will scan the same sector of airspace regardless of changes in airplane pitch and roll.
2) The stabilized antenna (tilt control at 0 degrees) will sweep the same area at a constant height, equal to the airplane level. The tilt control is provided to enable the pilot's to set the antenna scan to sweep weather targets above or below the level of the airplane.
3) An ATT message will be present on the ND's if the following condition occurs: a) Loss of the IRU pitch and roll inputs.
(l)
Receiver/Transmitter System Monitoring Functions
1) Weather radar system monitoring consists of performance monitoring hardware and built in test equipment (BITE) software within the receiver/transmitter. The performance monitor continuously checks for proper transmitter power output and proper receiver operation. If either the transmitter or receiver is operating improperly a WXR, FAIL fault message will be displayed on status and fault lines 2 and 3 as shown in Fig. 7. The weather radar internal BITE continually check for proper operation of the control panel and antenna and valid IRU attitude input data to the receiver/transmitter. In addition serial data bus inputs to the receiver/transmitter are checked.
(m)
Input/output circuits provide the electrical interface circuitry for most of the receiver-transmitter rear connector signals. Many of these are routed through the central processing unit. Input/output circuits interface four 12-KHz serial data bus inputs, two 100-KHz serial data bus inputs, and three 1-MHz data bus outputs. Several discretes input are used, including the antenna feedback signals and installation program pins.
(7) EHSI Weather Radar Display Functions (Fig. 4)
(a)
The receiver/transmitter supplies both EFIS symbol generators with digital weather radar data. In the symbol generator, the digital data is converted to video data in a X-Y raster format. The signals are separated into analog deflection signals and digital video signals. The information is then routed to the EHSI's.
(b)
The EHSI separates the weather radar raster display from the EHSI stroke display symbol generator inputs. The two formats are processed separately. The EHSI then displays the weather radar data in a four color format in a low intensity raster format.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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737-300/400/500MAINTENANCE MANUAL
(8) EHSI Weather Radar Alphanumeric Displays (Fig. 5)
(a)
The selected range and range marks are positioned on the course line. Three range marks are placed on the line at equal distances. The range marks represent one-fourth of the selected range. One-half of the selected range (white numerics) is placed beside the center range mark. It equals one-half of the total display range selected on the EFIS control panel.
(b)
The range marks and range arcs are always displayed in the EFIS MAP mode. In the VOR and APP modes, the range marks and arcs are displayed only when weather radar data is also presented.
(c)
Weather radar mode, tilt and gain messages are not shown on the EHSIs. 1) Gain message VAR/MAP is displayed when the GAIN control is
in any position other than the calibrate position and the system is in the weather radar MAP mode of operation. 2) Antenna tilt messages of 0 to -15 or +15 are displayed.
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