EFFECTIVITY
GJ ALL EXCEPT B-2504 AND B-2505
5C8 VOR/ILS Navigation System SchematicJun 20/85 Figure 3 (Sheet 1) 34-31-0 Page 9/10 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

EFFECTIVITY

K83069
5C8 VOR/ILS Navigation System SchematicJun 20/85 Figure 3 (Sheet 2) 34-31-0 Page 11/12 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

L35021
5C8 VOR/ILS Navigation System SchematicFeb 20/86 Figure 3 (Sheet 3) 34-31-0 Page 13/14 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

EFFECTIVITY
CA ALL EXCEPT B-2501
THRU B-2503

K76949
5C8  VOR/ILS Navigation System Schematic 
Jun 20/85  Figure 3 (Sheet 4)  34-31-0 
Page 15 

BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

O.  Interface of the navigation systems is shown in Fig. 3. RF signals from the VOR or GS antenna are fed to their respective nav receivers. Heading generated in the compass system is also sent from the compass coupler or the RMI's to the nav receivers. Using these signal inputs, the receiver processes the signals used by the navigation system. With the navigation transfer switch in NORMAL position, the signal output of nav receiver No. 1 controls the warning flags and GS and course deviation displays in the captain's ADI and HSI, and the single (narrow) pointer in the RMI. Signals from nav receiver No. 1 also go to the autopilot, flight director, ground proximity warning and instrument warning systems. NAV receiver No. 2 and the first officer's ADI, HSI, and RMI operate in a similar manner. When the navigation transfer switch is in BOTH ON 2 position, the captain's and the first officer's ADI, HSI, and RMI receive their inputs from nav receiver No. 2. When the nav transfer switch is in BOTH ON 1 position all instruments indicate nav receiver No. 1 outputs.
5C8 
34-31-0 Page 16  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Jun 20/85 

VOR/ILS NAVIGATION SYSTEM - TROUBLE SHOOTING
EFFECTIVITY

GJ ALL EXCEPT B-2509 and B-2510
1. General
A.  The following trouble shooting procedures are based on performance of the system self-test using VOR/ILS navigation system 1. Trouble shooting system 2 can be accomplished using the same procedures with the substitution of first officer for captain and wide (No. 2) bearing pointer for narrow (No. 1) bearing pointer. The procedures are presented in tree-type format. The test steps are connected to show the OK condition path. When all steps in the OK condition path check out, the system is operable.
B.  When a test step does not check out, follow the NOT OK line to the box containing the trouble symptom and continue to follow a single line by analyzing the results of each test step until the required corrective action is determined. Perform the specified corrective action; then repeat the step at which the failure was encountered.
C.  All trouble shooting procedures are based on the assumption that wiring is OK and that electrical power is available. If the corrective action in the procedure does not correct the problem, check wiring using the wiring diagram.
2.  Trouble Shooting Tips
A.  The malfunctions associated with the VOR/ILS navigation system can generally be divided into four groups: VOR/LOC deviation, glide slope deviation, VOR bearing and flag warning. First check for power to the defective system and establish that power is available.
B.  Verification of a navigation unit malfunction can usually be accomplished by observing for presence of flag warnings in the indicators and by self-test of the VOR/ILS navigation system. In the event of flag warnings, use the VHF NAV transfer switch to transfer to the opposite system for component isolation.
C.  To trouble shoot a VOR bearing malfunction, for example, if the VOR bearing displays are different when both systems are tuned to the same station, interchange the navigation units. If the problem follows, replace the malfunctioning navigation unit. If the problem remains in the same system, check the VOR/LOC antenna installation for corrosion at antenna feed cable connections and for physical damage to the cables and the antenna.
NOTE:  A nonsymmetrical ground station signal can also cause different bearing and deviation displays when tuned to the same frequency.
5C8
Jun 20/85 34-31-0 Page 101
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
3. Prepare for Trouble Shooting

A.  Verify that all applicable VOR/ILS, compass, flight instrument and instrument transfer circuit breakers on panels P6 and P18, are closed.
　
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