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.
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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.
B.  Apply electrical power.
C.  Position flight director controller switches and controls (P7 panel) as follows: MODE SEL - HDG All Others - OFF Course Counter - 000 Heading Control - Position HSI heading marker under lubber line.
D.  Verify that autopilot P7 panel is disengaged.
E.  Position HSI transfer switches (P7 panel) to RADIO.
F.  Position /RMI VOR/ADF switches (P1 and P3 panels) to VOR.
G.  Position DME mode selector on VHF NAV control panels (P8 panel) to STBY.
H.  Position VHF NAV transfer switch (P5 panel) to NORMAL.
I.  Position COMPASS transfer switch (P5 panel) to NORMAL.
NOTE:  Throughout the trouble shooting NORMAL position of transfer switch implies captain on 1 and first officer on 2.
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VOR/ILS NAVIGATION SYSTEM - ADJUSTMENT/TEST
EFFECTIVITY
GJ ALL EXCEPT B-2509 and B-2510
1.  VOR/GS Navigation System Test
A.  Equipment and Materials
(1)  Ramp and Bench Test Set - Collins Type 972Q-4, or Instrument Flight Research Type NAV-401L
B.  Prepare to Test System
(1)  
Provide electrical power and energize panels P6 and P18.

(2)  
Check that circuit breakers for following systems are closed: compass, flight director, instrument, interphone, and VOR/ILS navigation systems.

(3)  
Position VHF NAV transfer switch to NORMAL. Check that captain's HSI nav data source annunciator indicates 1 and first officer's indicates 2.
　
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