Topic-icon ATA 34-24, Standby Attitude ILS Indication

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3 months 4 days ago - 3 months 4 days ago #575 by Mark
767-200 with the ILS (Instrument Landing System) function of the standby horizon inoperative. The deviation bars along with associated flags in view no matter what position control switch was in.



The ILS indication is controlled via the Static Inverter/ILS Processor unit located on the E1-4 shelf. This unit is located next to the Center Multi-Mode Receiver. (The MMR's have two functions, GPS and ILS.)



The Center MMR feeds ILS information to both the Static Inverter/ILS Processor and the Center EFIS SGU with a single 429 data bus output.

With the indicator switch on the "Off" position, both bars and both flags should be biased out of view. In the "ILS" position with a valid ILS signal, the flags should be out of view and the bars should indicate actual left/right-up/down information.

To verify the operation of the Center MMR, either the Captain's or F/O's EFIS switch can be placed in the "Alternate" position and a test run on the ILS Control Panel. (The test should display "up/left then down/right. The EADI mode select should be placed into "Approach" for this test to show.)



In the ILS position, the Standby Horizon deviation bars should mimic the bars on the EADI selected to the Alternate EFIS SGU.

In the case of this particular problem, the issue turned out to be the Static Inverter/ILS Processor Unit itself. All outputs had failed.

The Standby Horizon does not control any functions for the indication. Flag voltage and bar deviation signals all come from the Inverter/Processor unit. Having all four failed in the "Off" position would tend to say the box is bad vs the indicator.





767-200 SSM 34-24-01
AWM 34-24-11
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Last edit: 3 months 4 days ago by Mark.

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3 months 1 day ago #576 by Mike Forti
That's great info I will remember that one, thanks Mark!!

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