747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航1(148)

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 B.  The VOR/ILS navigation system determines airplane bearing with respect to ground-based VOR stations and airplane position with respect to a selected VOR radial, or to an ILS approach path. This data is provided to the autopilot/flight director (A/P-F/D) system and to displays on the captain's and first officer's instrument panels.
 C.  Airplane magnetic bearing to the VOR ground station signals received is determined by the VOR portion of the system. The ILS portion of the system provides lateral and vertical deviation information with respect to a radio beam positioned above runways for landing guidance.
 D.  Power is applied to the VOR/ILS system through circuit breakers located on overhead circuit breaker panel P7 and P126 as shown in following illustrations.
 2.  VHF NAV Control Panel
_____________________
 A.  Each VHF NAV control panel on the pilots' lightshield panel P10 consists of two concentric frequency selector knobs, a frequency indicator, a test switch, and an on-off, VOR/ILS and DME function selector (Ref 34-55-00). On LH 011-099, the function selector is not installed on the VHF NAV control panels. On LH 014-050, 061-081 and 084-099, VOR/DME and UP/LT TEST switches are installed on each VHF NAV control panel.
 B.  The control panel provides manual VOR or localizer frequency selection. The glide slope receiver is automatically tuned when a localizer frequency is selected. Frequency control is in the 108.00- to 117.95-MHz range. ILS frequencies are odd tenth MHz between 108.00 and 112.00 MHz. All other frequency steps are VOR stations.
 C.  The large outer knob of the two concentric knobs provides frequency selection in the units, tens and hundreds range. The inner knob provides frequency selection in fractions (tenths and hundredths of a MHz).
 D.  The frequency indicator displays the operating frequency of the VOR or localizer circuits of the VOR/ILS receiver.
 E.  The TEST switch provides a self-test capability for the VOR functions of the VOR/ILS receiver and associated displays.
 EFFECTIVITY
 AF 101-120, 123-154,  CONFIG 1 172-173, 191-194; GN ALL;  01 Page 1 LH ALL AND MD ALL  Sep 25/94

34-31-00

 F.  On LH 014-050, 061-081 and 084-099, the UP/LT TEST switch provides a self-test capability for the ILS up/left functions of the VOR/ILS receiver and associated displays. The UP/LT test is also used by the AFCS for testing the AP/FD LRCU's.
 3.  VOR/ILS Receiver
________________
 A.  Three VOR/ILS receivers are installed on shelves E1-2 and E1-3 in the main equipment center. All interconnections are made through multipin connectors on the rear of the chassis. A test connector is also mounted on the rear of the unit for testing and fault analysis.
 B.  BENDIX RNA-26C Receiver
 (1)  
An omnibearing indicator which displays VOR bearing is visible through an opening in the front panel. The right side of the main frame assembly contains the omnibearing indicator (OBI), power supply, localizer circuits, VOR circuits, localizer integrity monitor. The VHF receiver and the glide slope receiver are mounted on the other side of a vertical support wall that also serves as a heatsink for some of the power transistors.

 (2)  
Connection to the main frame is accomplished through a multipin connector on the receiver that mates with a connector on the mounting.

 C.  Bendix RNA-34A Receiver
 (1)  
Each receiver contains planar construction-type circuit boards and an interconnect unit. The circuit boards consist 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. These assemblies process VOR, localizer and glide slope signals and provide outputs to drive deviation, flag and to-from flight instrument displays.

 (2)  
The chassis provides the mounting surfaces for connectors, hinged front and side panels, and a center mounting frame.

 (3)  
The hinged front panel supports an RMI driver board and the receiver power supply. The exterior surface of the panel also serves as a heat sink for the power supply.

 (4)  
The hinged left and right side panels and the center mounting frame support the remaining VOR/ILS circuit boards and interconnecting circuits.

 4.  VOR Antenna
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 A.  The VOR antenna is a dual, pedestal-mounted, V-type unit, supplying the VOR/ILS receivers with rf received form the VOR stations. The antenna is located beneath the vertical fin cap and has independent outputs connected to the two VOR/LOC antenna switches for distribution to the receivers. The antenna is protected by lighting diverter strips on the outside of the fiberglass fin tip.
　
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