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MillyD

Pilot and Copilot ADI's on C130H 1974 Model

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We have an aircraft that has both pilot and copilots ADI's attitude spheres start showing 10 degrees of bank in straight and level flight approx. one hour into flight and getting progressively worse as flight continues. The FDMS has both sides in VG mode, pilot has VOR1 selected and copilot has SCNS selected. The airplane has the Air Force Standard Flight Director system, single INU, C12 Compass system and digital flight control system. We have swapped out both displacement gyros and system tests good on ground after running for 2 hours. This is a repeat write up after changing gyros. With the flight director being 2 separate systems we are scrambling trying to figure out what would cause both indicators to act the same (pilot ADI repeat switch was off). We are very new to the C130 and trying to learn and troubleshoot this new airframe! Any help and suggestions would be greatly appreciated!

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We have an aircraft that has both pilot and copilots ADI's attitude spheres start showing 10 degrees of bank in straight and level flight approx. one hour into flight and getting progressively worse as flight continues. The FDMS has both sides in VG mode, pilot has VOR1 selected and copilot has SCNS selected. The airplane has the Air Force Standard Flight Director system, single INU, C12 Compass system and digital flight control system. We have swapped out both displacement gyros and system tests good on ground after running for 2 hours. This is a repeat write up after changing gyros. With the flight director being 2 separate systems we are scrambling trying to figure out what would cause both indicators to act the same (pilot ADI repeat switch was off). We are very new to the C130 and trying to learn and troubleshoot this new airframe! Any help and suggestions would be greatly appreciated!

When I was crewing C-130E's with SCNS we experienced this same problem. If my memory has not failed me, it seems problems stemmed in the FDMS panel and the NIRP panel relays. The one thing that is not present on the ground that is present inflight is all the vibrations associated with the prop's. Those mini relays in the NIRP panel are known weak links and fail often, many times intermittent operation. In the FDMS panel it was wiring or the VG switch it's self, weak contacts and intermittent operation. Good luck. Tap or test the relays and check all your wiring at the FDMS panel and the VG switch.

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Thank you for your time and information. We did change out both displacement gyros last week as a most likely. Another repeat write up that I was just informed about was the #2 C12 compass system indicators start spinning uncontrollably 2 hours into flight. I was told by someone that magnetic objects near the #2 flux valve could cause this issue with both ADI's as signals go to the automatic flight control processor. We have C130H1 1974 models. The plane is currently at another location and landed with these repeat issues. We did not have a directional gyro for the c12 and changed out the amp/power supply as a most likely for that write up last week. So confusing - never dealt with this kind of problems on F16s and F15s!

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The Es and Early Hs both had problems with ADIs that were mechanically freezing in the roll function. I can't find any of my info on it, since most of it was in my e-mail, and that is long gone. I seem to remember that the NSN last 4 -3464 was a problem. Our wing wouldn't allow both ADIs having that number be installed on the same aircraft. Quite a few aircraft experienced DUAL ADI failure. This was a major PIWG and SSG item.

There was even a TCTO, 1C-130-1964

The purpose of this TCTO is to inspect/ensure only one each P/N 139602-01-01 ADI is installed per aircraft. Limiting one P/N 139602-01-01 ADI per cockpit will increase the reliability and reduce the risk of Dual ADI failures.

6610-00-068-3464

139602-01-01

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