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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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737-300/400/500MAINTENANCE MANUAL
11. VHF NAV Transfer Relays
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A. Two stepping-type transfer relays are installed in rack E3-4. When the VHF NAV transfer switch is in the NORMAL position, the captain is on system No. 1 and the first officer is on system No. 2. Placing the VHF NAV transfer switch to BOTH ON 2 position momentarily energizes transfer relay No. 1 and the relay steps to the BOTH ON 2 position. Positioning the VHF NAV transfer switch back to the NORMAL position, again momentarily energizes transfer relay No. 1 and the relay steps back to the normal position. The first officer's transfer relay is controlled in the same manner as the captain's by positioning the VHF NAV transfer switch to BOTH ON 1.
12. Flight Instrument Accessory Unit (AIRPLANES WITH A FLIGHT INSTRUMENT
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ACCESSORY UNIT)
A. A flight instrument accessory unit is located in electronic equipment rack E1-2. The unit contains relays and a printed circuit for signal conditioning and interface between the navigation systems and the flight instruments. In addition, the unit contains numerous relays, time delay gates, a circuit interrupter and other components used for interconnecting the DFCS system.
B. The flight instrument accessory unit circuits associated with the VOR/ILS navigation system consist of the diodes across the coils of the transfer relays; four relays for inhibiting the VOR/ILS self-tests when the autopilot is operating in an approach mode and the ground return for energizing ILS relays No. 1 and No. 2; and two DME agility mode relays for inhibiting the RDDMI VOR bearing displays when the DME and FMC systems are operating in the agility mode.
13. Integrated Flight System Accessory Unit (AIRPLANES WITH AN INTEGRATED
_______________________________________ FLIGHT SYSTEM ACCESSORY UNIT)
A. An integrated flight system accessory unit is located in electronic equipment rack E1-3. The unit contains solid state relays, solenoid operated relays, and printed circuits for signal conditioning and interface between the navigation systems and the flight instruments. In addition, the unit contains numerous relays, time delay gates, a circuit interrupter and other components used for interconnecting the DFCS system.
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34-31-02
ú ú 06 Page 10 ú Mar 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
B. The integrated flight system accessory unit circuits associated with the VOR/ILS navigation system consist of the diodes across the coils of the transfer relays; six solid state relays, four relays for inhibiting the VOR/ILS self-tests when the autopilot is operating in an approach mode and two to control the ground return for energizing ILS relays No. 1 and No. 2; and two solenoid operated mode relays for inhibiting the RDDMI VOR bearing displays when the DME and FMC systems are operating in the agility mode.
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