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#2 C-12 heading flag


ahgambler
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I've got a problem with the heading flag coming into view from 240 degrees to 300 degrees on the c/p HSI only. It happens in mag and dg but only if going from N clockwise, N counterclockwise the flag stays out of view .Swapped the pilot and co pilot hsi and gripe remains on c/p side and only the #2 system.Cleaned all nav switching relays,compared signal, pwr, and grounds to the #1 system and results when compared were the same. Components that have been swapped: c12 amps, directional gyro, digital controller, heading coupler, flt directors comp. Thank you for taking the time to read this...stuck in C12 heading hell

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  • 2 weeks later...

Using gripe points to a Navy or Marine bird. You didn't give any info on the aircraft year or model. USAF aircraft have the SCNS systems on them. Is this in all heading modes? Not sure what your control panel looks like. I have seen bent pins on the HSI connector cause strange problems.

I would also find the terminals for the compass card inputs in the junction box and loosen/tighten them.

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I don't know if this changed or not but years ago we used to have problems now and then with the C-12 compasses. The issue then was the access panel for the flux valve. Then the panel required brass screws screws instead of steel. Sometimes they would get a brass screw get stripped and mistakenly replaced with steel. But, then again that was a long time ago.

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I don't know if this changed or not but years ago we used to have problems now and then with the C-12 compasses. The issue then was the access panel for the flux valve. Then the panel required brass screws screws instead of steel. Sometimes they would get a brass screw get stripped and mistakenly replaced with steel. But, then again that was a long time ago.

Yea, just because the screw fits, doesn't mean the aircraft can wear it.

Ramstein had a bird that had a whiskey compass problem. It took them few days to find a couple incorrect screws installed in the pilot's window next to the compass. But, something like that shouldn't have any affect on your flag. Are you just using the controller to spin the compass around to see this, or are you using a MAD simulator? Give me an idea of year group so can check some diagrams.

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Hello,I want to first thank everyone for you help and input. The herc is a F model 148893. We looked at the flux panel screws and they are all non-magnetic,we also had the terminals off in the radio j box and in the flt dir j box to compare signal,looking for lose of volt,grounded wires. With both Hsi's selected with the #2 c-12 only and moving the compass with the digital controller only the c/p HSI gets the off flag and its only between the headings 240-300 clockwise from N and the flag nevers appears counterclockwise from N. I also dont get why its only 70 degrees of the 120 degree leg. The heading Monitor voltage stays constant @ 26 volts even with heading flag in view. With INS 1 and 2 or cdnu selected the heading flag stays out of view. The flag is will only come into view with tacan 1 and2 ,vhfnav 1 and 2. and ara-63. We had to take the A/C to compass rose for annual swing,we installed new flux valve with no change in gripe.We also slaved in a new compass compenstator. Gripe remains.

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This aircraft does have the Compass Select switch right?

Disconnect each RMI and BDHI one at a time you may not have a "compass" problem you may have an indicator problem. The resolver in a single indicator may be dropping your heading signal. Dont remember the exact problem but do remember I had a BDHI that was causing a similar issue. Good luck!

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OK, now I'll act like a real idiot. Keep in mind I haven't been on an aircraft in 3 years. I see no mention of an OFF flag on the HSI in either the Flight Director or C-12 compass checkouts. Where exactly is this OFF flag on the HSI?

This is the HSI that I am familiar with.

I'm not even sure what an F model is. I assume it is similar to our E and Hs with the Standard Flight Director system and the C-12 gyro.

.

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