34-31-00
ú ú 02B Page 1 ú Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
F. Frequency selection is controlled from the control panel. The GS portion of the unit becomes operative only when a localizer frequency is selected. Localizer frequencies extend from 108.10 to 111.95 MHz, with 40 channels spaced at 50 kHz on the odd tenths megahertz and the odd tenths megahertz plus 50 kHz. Glide slope frequencies range from 329.15 to 335.0 MHz and are paired with the localizer frequencies as shown in Fig. 2. VOR frequencies also spaced at 50 kHz, extend from 108.00 to
117.95 MHz except for the localizer frequencies.
G. In VOR operation, two signals (30 Hz REF and 30 Hz VAR) as radiated by a VOR ground station are processed by the navigation unit to produce the station bearing, VOR deviation and TO/FROM signals. In LOC operation, the deviation signal is produced by a comparison of the amplitude difference between two tone modulated signals (90 Hz and 150 Hz) as radiated by a runway localizer transmitter. Portions of these signals are summed to produce the warning flag signals. The GS deviation and warning flag signals are produced in much the same manner as the LOC deviation and warning flag signals.
H. When both systems are operating at the same LOC frequency, LOC and GS deviation signals, along with control signals (GS super flag and ILS 28V dc which are used for switching) are fed to the comparator warning unit in the navigation warning system. Here a comparison is made of any discrepancy existing between the LOC and GS deviation information as fed from each system, and on it exceeding a certain predetermined value, the appropriate warning light will light (AMM 34-29-00).
2. Navigation Unit_______________
A. Two navigation units (VOR/ILS receivers) are installed in electronic equipment rack E3-4. The receivers employ 2-out-of-5 binary switching for frequency selection. These units process VOR, localizer and glide slope signals and provide output of ground station bearing and to-from, course deviation, and warning flag valids for flight instrument displays, DFCS, GPWS and the instrument warning system.
B. Collins 51RV-4( ) Receiver
(1)
Each receiver contains circuit boards and an interconnect unit. The circuit boards consists of VOR/LOC and glide slope receiver assemblies with associated instrumentation, digital instrumentation and self-test circuit board assemblies, an RMI driver and a power supply.
(2)
The chassis provides the mounting surfaces for connectors, support for two swing-out mounting frames, and a center mounting board.
(3)
The center mounting board consists of a removable printed circuit board that contains the power supply, audio amplifier, and RMI driver circuits.
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A 737-300/400/500MAINTENANCE MANUAL
VOR/ILS Navigation System Component Location
Figure 1 (Sheet 1)
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A 737-300/400/500MAINTENANCE MANUAL
VHF NAV CONTROL PANEL
HSI TRANSFER SWITCH VHF NAV TRANSFER SWITCH
VOR/ILS Navigation System Component Location
Figure 1 (Sheet 2)
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