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Aero Precision provides OEM part support for military aircraft operators across more than 20 aircraft

MillyD

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core_pfieldgroups_2

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    Mildred
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    Martindale

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  1. Hi Tiny, What we basically do on the ground is have SCNS on and we turn on TACAN and ILS/VOR and just tune them to a local station. With A/P engaged, we select LNAV/NLOC on the mode select panel - as soon as we depress that button we get a annunciator light on the Flight Progress Warning Unit Panel that goes from N/L ARM and immediately to N/L CAP. We have checked several of our other aircraft on pilots and copilots sides - all perform correctly. The plane I'm talking about is the only one that will not go into capture when we perform the aforementioned steps on the copilots side. Again - we do don't have an actual tech data driven test to follow. In the FI for the AN/AWY-1 autopilot it does have a fault tree for this scenario and it asks if the pilots AND copilots sides N/L CAP illuminate when we select LNAV/NLOC - we have to answer that as a NO. Then it asks if the pilots side annunciator illuminates - we answer that as a YES and it ends right there.………..it does not go into further info if the copilots light does not illuminate...……….whether or not we are actually capturing a signal is a mystery to us. When the capture light illuminates on the pilots side you can see and feel the control wheel move and stay on track. The copilots side doesn't have this result.
  2. Thank you Tiny. Over the years we have swapped out several parts and shot a lot of wiring with assistance from an engineer. It fails on the ground all the time no matter what we have done - copilots side with AP2 selected and NAV/LOV selected on the mode select panel always stays in N/L ARM - it never goes to capture. We used the IFR4000 and tested the glideslope, ILS and TACAN and all checks are good. We are in Great Falls, MT. We changed out the SCNS relay panel after swapping out a few NIRP relay's, just to rule out the panel after all else failed. As for stored faults - we don't see anything related on the TOPs panel for this issue and I'm not sure where else we would find a stored fault. The FI for the autopilot system is horrible to say the least. Even during the operational check it does not have the technician check this function of the system so it's pretty frustrating!! I sure appreciate your time and help, we will give those relays a try - can't hurt!!
  3. Thank you so much for your help TinyClark. We have not been able to find anything either regarding how this is supposed to work. Perhaps that is why the engineer could not answer our question. I will double check our troubleshooting diagrams that we used a long time ago, we may have already shot that wire, been a long time since we worked the issue. It's been sitting in the "K" write ups for almost 2 years. I too, am retiring the end of this year - and looking forward to it!! 38 years of service is LONG enough- ha ha!! Keep me posted if your contact has any further info. Thanks again, and look forward to hearing from you.
  4. We have a 74 model H1 with AN/AWY-1 single system autopilot, (Air Force Standard Flight Director, C12 Compass, single INU) that has had a perplexing discrepancy for a few years. With the FDMS switches in SCNS, AP2 selected on the FCP and LNAV/NLOC selected on the mode select panel the write up reads as follows "AP2 will not capture beam with SCNS selected". During the ops check with switches in the aforementioned positions the "N/L ARM" display on both pilot and copilot FPWU annunciators remain on and they never go to "N/L CAP". When AP1 is selected and all switches as listed, they system works as advertised and immediately the N/L CAP annunciator comes on. With that being said, the technicians have R2 the following components: AFCP (a couple of times), copilot HSI, ILS and TACAN receivers and TACAN adapters, Flight Director Computers, C12 Amps/gyros, the ENTIRE NIRP relay panel under the crew bunk, BICU, LEDEX relays on the SCNS relay panel in the hell hole, FDMS switch on the copilots side, shot multitudes of wiring that checks good to the FDMS, FCP, MSP, SCNS NIRP panel, flight directors computer #2, AFCP and even wires that didn't make sense but was directed by an engineer to shot them and all checked good. Very frustrating to say the least!! One of the biggest questions we have is this: Exactly what signal is it that the processor is looking for that enables the autopilot to go from L/ARM to L/CAP? Where is the signal coming from? We posed those questions to the engineer and never received an answer - he went off in left field and left us stumped...….If anyone on the forum has ever experienced something like this and can provide some tips and help, we would welcome any information you have. Thank You.
  5. 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!
  6. 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!
  7. Hi All, New to the C130 aircraft. Unit had fighters for years and now trying to gain helpful tips and info on guidance and control issues. Mainly AN/AWY-1 autopilot. We have older H1 models, single INU, C12 compass, standard flight director, etc. As we move through the conversion process and ops flies longer missions we have had several write ups on porpoise of aircraft with autopilot engaged on several aircraft. Being new to the airframe, limited training AND using the FI - we are extremely frustrated with the uselessness of the FI. The FI does not seem to address actual flight control issues - all it seems to address is "light" type problems, i.e. "is this light on, is that light on". Really? Is this the best they have out there for troubleshooting in flight problems? We hate to waste a bunch of time trying to reinvent the wheel and hope that someone out there on this forum has some useful info to help us troubleshoot actual inflight problems, debrief procedures, which we are no longer involved in, and how to go about duplicating issues on the ground. Naturally, our aircrews consist of experienced and inexperienced personnel. Aircraft all came from Little Rock with NO history data of prior maintenance, which really sucks. Any help would be greatly appreciated!!
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