D. Weather radar system on/off control is provided by the WXR switch/indicator on the EFIS control panels. In addition, the EFIS control panels enable the weather or map displays on the captain's and first officer's navigation displays (ND's) (AMM 31-61-00, Integrated Display System).
E. The weather radar system consists of two identical systems, only one of which operates at one time. Two identical receiver/tranmitters (R/T) are installed on the equipment rack (E30) in the forward equipment center as shown in Fig. 1. A waveguide switch connects the selected R/T to the antenna through the waveguide. The antenna is a flatplate array radiating antenna with two identical drive systems. A dual system control panel controls operation of the weather radar, providing R/T selection, mode selection, system self-test, receiver sensitivity adjustment (GAIN), and tilt angle selection.
F. The receiver/transmitter generates and transmits high energy radio frequency (rf) pulses which are radiated by the antenna. A small portion of the radiated energy is reflected back to the airplane by moisture laden clouds or by major terrain features. The reflected signals are received by the same antenna, processed by the R/T unit and displayed on the navigation displays. The transfer of the RF energy between the R/T unit and the antenna takes place via the waveguide. Stabilization of the antenna in pitch and roll is provided by the inertial reference system (IRS).
G. Predictive Windshear General Operation
(1)
Windshear is a threat to the airplane during takeoff and in the early phase of climbout as well as during the final phases of approach. The predictive windshear circuits are activated automatically in the receiver/transmitter during the takeoff or approach phases of flight whether the weather radar system is on or not.
(2)
In addition to the equipment listed above, on the control cabin ceiling there are two speakers that are used by the predictive windshear system for audio warning and caution messages to the flight crew. Equipment location is shown in Fig. 1.
(3)
During normal ground maintenance the weather radar system on/off control is provided by the WXR switch/indicator on the EFIS control panels. The EFIS control panel also enables the weather or map displays on the captain's and first officer's navigation displays (ND's) (AMM 31-61-00, Integrated Display System). On the receiver/transmitters with predicitive windshear, the weather radar circuit breakers must be open when engine runs associated with maintenance are performed to prevent inadvertent weather radar system turn-on.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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MAINTENANCE MANUAL
(4) On airplanes with predictive windshear, PWS aural test commands are annunciated on the cabin loudspeakers for takeoff and approach modes of operation. For a complete test sequence for the various lights, displays and annunciations refer to the System Self Test.
H. The left weather radar system operates from bus No. 3 115-volt ac 400-Hz, single-phase power and the right system uses bus No. 2 115-volt ac 400-Hz, single-phase power.
I. The weather radar system has a built-in operator-actuated test pattern for fault identification. The operator-actuated test causes the injection of test signals, which are used to generate a test pattern on the navigation displays allowing the operator to adjust the display prior to flight and to ascertain correct operation of all system components.
2. Control Panel
_____________
A. The weather radar control panel is located on aft electronics control panel P8.
B. The control panel has a system transfer (SYS) toggle switch, a rotary mode selector switch, a antenna TILT mode select toggle switch, a rotary antenna TILT control, and a rotary receiver GAIN control.
(1)
The system transfer switch allows selection of the left or right system also controls primary power to the selected system.
(2)
The rotary mode selector switch allows selection of TEST, WX, WX/TURB and MAP modes of operation.
(3)
The antenna TILT mode switch allows selection of MANual or AUTOmatic operation of the antenna tilt. During MANual operation, tilt is controlled by the rotary tilt control on the WXR Control Panel. In AUTOmatic operation, the antenna tilt is controlled electronically using inputs from the Enhanced Ground Proximity Warning System (EGPWS).
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