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

Lkuest

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Everything posted by Lkuest

  1. Tenten, I understand your frustration, but there really is no hope in logically understanding the system without looking at the schematic. Doing so allows you a much greater understanding of why the system behaves the way it does under all conditions. In this specific case, it is important to understand that the TD Valve brake does not get energized in order to engage, it actually is energized into the "released" position. If the TD Valve brake solenoid loses power, it moves the the "applied' position, locking in the fuel correction. In this case, if you were to move the TD switch to the "locked" position, this energizes the brake lock relay, which is meant to cut the power going from the brake lock relay switch to the TD Valve brake solenoid. It just so happens that, below 66 degrees, the coordinator also sends power to the TD valve brake solenoid, thus, the brake is still "energized" into the released position. Why select locked below crossover then? Because when the Brake Lock relay becomes energized, it sends power to the limit selector relay, telling the TD Amp to ignore Bias and Slope and to only start pulling fuel once the TD system reaches the max limit, which on a -15 engine is 1077. Once you advance the throttle above 66 degrees, the power no longer comes from the coordinator to release the TD Valve brake solenoid, and lock the brake. So, is the brake locked? Nope. The electronic fuel correction light is on below crossover due to being below the 66 degree switch, but remains on while advancing throttles above crossover because the brake lockout relay is already energized by the below 66 degree switch, which not only provides its own circuit once energized below crossover, but also powers the electronic fuel correction light, and also the TD Valve brake solenoid, keeping the TD Valve brake released. In short, placing the TD Control Switch to "Locked" below crossover accomplishes nothing other than providing overtemp protection, and the brake is not locked at any time, no matter the throttle position. If the brake lockout relay is energized by the coordinator below 66 degrees before going to "locked", it always powers the TD valve brake to release. You must allow the coordinator to go above the 66 degree switch in order to prevent the brake lockout relay from energizing before the brake lock relay. You do this by first putting the TD switch to "Auto", advance above crossover, then go to "Locked". This prevents the brake lockout relay from keeping itself energized, and removes all possible power sources from the TD Valve brake solenoid, allowing it to apply and lock fuel correction. Now, for your second question, if the system were to be locked above crossover, and the throttle were moved below crossover, would the brake hold below crossover? The answer is, yes. If the brake lock relay becomes energized without the brake lockout relay first becoming energized, the brake lock relay prevents the 66 degree switch from ever receiving power, thus it cannot power the TD valve brake solenoid to release it. It also does not have power to energize the electronic fuel correction light. This is why the light stays off below crossover once the TD system is locked above crossover. How can you "reset" the system? Downspeed the motor. This allows the 94% switch to energize the brake lockout relay, restoring power to the 66 degree switch and the TD Valve brake solenoid to the released position. Or, you could just put the TD switch back to Auto, which restores power to the brake lockout relay. Then, you'd have to advance the throttle above 66 degrees to deenergize the brake lockout relay in order to lock the TD valve again.
  2. Tenten, Below crossover, the brake lock function is locked out through the brake lockout relay, so as pjvr states, going to locked below crossover would only have overtemp protection and nothing more. This same relay kicks in when you overtemp in locked, and that's why the fuel correction light stays on after overtemp. Potentially, you could have a 100 rich and 70 lean engines on opposite wings cause issues with pulling the throttles back unevenly, but you still have that problem because the props don't exactly all pitchlock at the same blade angle anyway, so the procedure may be just as effective regardless of what throttle position you flip the switch to locked. I prefer going to locked above crossover just to eliminate variables, but both procedures may give you the same information for the op check.
  3. ​I agree this can be an indicator of fuel control health, but please don't take it for more than it is. Even if the engine will low speed, you never know if the fuel governor is correctly set anyway without doing the correct ops check, so the LSGI operation is of low value as an indicator you have overspeed protection. Maintenance performs the ops check every HSC and ISO, so you should be covered. Sure, something could break in-between, but it's not as simple as that. The flyweights that tell the governor it is overspeeding are the same flyweights that assist the speed servo valve to increase fuel flow during engine starting, so if that mechanism were malfunctioning, you would likely see more severe issues with fuel flow. The only fuel governor components not needed by the speed servo valve are a spring and a shaft. The only true ops check for fuel cutoff is to do a fuel governor/pitchlock check. If the you are willing to tail swap for an engine that fails to low speed, you should be prepared to allow maintenance to do an official ops check of the fuel control to prevent a tail swap, especially when the LSGI solenoid is exempted on the MESL. In my experience, the entire LSGI system is infinitely less reliable than the fuel governor system. By all means, call maintenance out, but please, let us do an official ops check before refusing the aircraft.
  4. Ronc, Have you seen this problem with the new gaskets, or was it with the old copper ones? I haven't had any problems with the acceleration bleed pad gaskets since we went to the new material, so I'd be interested if you've had issues with the new material. I have seen many bleed pad gaskets blown out when they were copper though. Many times all we saw was either a low power engine, or copper laying around the bottom of the nacelle.
  5. Could be a long shot, but you might consider an overheat detector might be lying to you. Also, if you can't pinpoint a specific clamp, you might just re-torque all of them for good measure and see if the problem goes away. Just as NATOPS1 says, I've had good luck troubleshooting air leaks by noting the difference between a bleed down with the problem motor and a bleed down with all of the other motors. In this case, that might pinpoint which side of the check valve your leak is on. Also, depending on your circumstances, an infrared camera could work wonders on a job like that. I understand you're not at home station, but if your plane isn't flying anywhere, an infrared camera might be part of your requested supplies kit. It will most definitely help you pinpoint those little leaks.
  6. I was agreeing with Ramrod about the interval too, 15 days. In your case though, It might be more appropriate to address it from a standpoint of leakage limitations. As long as your tec's are checking the propeller thoroughly for leaks, I wouldn't worry about "trace/evidence" unless the engine is ingesting enough hydraulic fluid to become noticeable in the Air Conditioning. The propeller control is allowed to leak 1 drop every 45 seconds, whether operating or static. Nothing else is allowed to leak, unless it's freezing outside, in which case, warm the propeller up first before doing a fluid leak inspection. Sometimes, when people "X" the props, some fluid might stream out. This is normal due to accumulation from minor seepage collecting in the rear spinner, then suddenly being released by the drain holes located half-way between the blades on the rear spinner.
  7. I agree with Ramrod. The key is that, when you check using the atmospheric sump, you are checking the servicing level in a similar way to how the aircrew operate the prop, that is, with a pressure and scavenge pump running. The barrel and pressurized sump both overflow into the atmospheric (beta feedback shaft and sump relief valve), so if you have the right amount of fluid in the atmospheric, your prop should be serviced properly in the barrel and pressurized sump. This requires that #1 blade point to the top. The problem is when the pitchlock regulator orifice cups become clogged and doesn't properly fill the barrel. The pressurized sump will always be full, and the atmospheric will always be empty. The pressurized sump is inaccurate because it is not an accurate reflection of how much fluid is in the barrel. Maintainers find the pressurized sump comforting because they like to think the prop is telling them exactly how many quarts are required instead of servicing the atmospheric sump 5cc at a time.
  8. I'm going to go with Flight Idle & Beta Shaft.
  9. Forgive me, but it is very difficult to troubleshoot a problem this complex without being there in-person, so please feel free to disagree with me on anything. It sounds like you have so far swapped the TD Amp, TD Valve, Coordinator, Speed Sensitive Control, Relay Box, TD Null Relay, Thermocouples, Y-Lead, T-Block, thermocouple harnesses, and J3 lead from Amp to TD Valve. The only things left are the Left-Hand Wiring Harness (Spider Box), or wiring between the TD Amp, J-Box, and Firewall. The last thing I would recommend is swap engines between #2 and #3 and see if the problem stays or moves. It's a big job for just diagnosing, but it would tell you if aircraft wiring is the cause, or if the engine is defective. If the problem stays with the engine, you may have a new part that is bad. It may seem like a big job to do on just the suggestion from someone on the internet, but you've already done everything else that causes this. Do you have any engineering support from Lockheed to help you?
  10. It seems the only thing you have not yet swapped to another engine is the Speed Sensitive Control. Let me see if I read your problem correctly. You advance the throttle up to flight idle, and I am guessing #2 engine is higher in TIT than the other 3. Then, you advance the throttle up to crossover, and TIT becomes 840. You move the throttle up above crossover, and the TIT becomes 790, but then TIT goes back up by itself. Do I have this correct? Does the light pop back on when temperature shoots back up, or does the light stay off all the time above crossover? Is there any other malfunction, such as the TD Valve Brake Check, Temp Control Check, Temp limiting? Does this still happen with the A/C Instrument and Engine Fuel Control Invertor in the opposite position (D/C instead of A/C, or A/C instead of D/C)? What is your Auto Start temp? What is your Null Start Temp? When TIT moves up, does torque and fuel flow also increase?
  11. Well, if it's not the J3 lead, the cables between the coordinator and the Amp, or the Relay Box, then I'm thinking it is an issue with the power being supplied to the Amp. There is also a Temp Control Relay you might swap with #3 to see if that's causing it. It is located inside the cargo compartment. Just follow the wiring schematic to figure out where it is if you can't find it. Also, if the fuel control is failing, it may just be becoming too rich for the TD valve to take enough fuel. If this were the case, the fuel control would be more than 100 rich.
  12. I see you mention all TD System components were swapped with #3. Did you also swap the TD Valve?
  13. Most likely the 62nd name will transfer to what is currently the 48th, because of the heritage. That's the story I got anyway.
  14. Does your synchrophaser run directly off the Essential AC Bus, or through a constant voltage transformer? You must make sure the Synchrophaser pin 34 is receiving a steady 115VAC/400Hz power source. If you source of power is dirty or malfunctioning, this could be the cause. If the issue happens in-flight only, I have heard a stray signal from calling on the radio can cause problems, so try to run again, and use the radio. Also, I have heard of the bottom strobe light causing a synchrophaser issue. During the ground run, I would recommend running all equipment your pilots use so that you can duplicate this problem. Once you duplicate it, turn off one system at a time until the problem goes away. If you can confirm the power voltage is ok, I would recommend taking a synchrophaser from another aircraft that you know is OK, and putting it in this bad aircraft temporarily and see if it can fix the problem. Sometimes, we get new parts that are bad.
  15. That's a new one on me. If the pulse generator circuit was bad on #2 propeller, it would make the #1,3,4 prop RPMs drop from 100% to 0% (can only follow 2 %). When you switch master to #3, #2 prop RPM only should rise, thinking it is trying to increase from 0%. Since both masters are dropping, and the outboards are not, I think the problem is wiring. This is assuming all other propeller checks are good (throttle anticipation w/in 5 seconds, and no RPM difference between mechanical and normal, pitchlock check). I suggest verifying all propellers are set to a Mechanical RPM of 100%, +-0.2%, then perform a reindex and try again. If the problem persists, I believe the problem is between the essential DC bus, the master select switch, and the synchrophaser. If the master select switch is shorted internally so that a master is always selected, it will cause a problem such as this. If the propellers do not pitchlock, you may have a problem with the Essential A/C bus voltage going to the synchrophaser. The A/C power is used as a reference signal, and further amplified once error signals are given to the synchrophaser to decide how far to make the speed bias servo motor move. If the A/C power is dirty, the synchrophaser will do crazy things.
  16. Does it only do this in the flight range of power, or all the time? In Mech Gov or Normal Gov? Synchrophasing on or off? When RPM goes up, then down, what do the other indicators do? The same direction, or opposite? The best possibility is both Tach Gen spline holes are worn excessively. At worst, your reduction gearbox tach generator drive gears might be worn out. Both Tach Gen pads are geared into the same idler gear, so possibly the idler gear bearings are wearing out, or even the Hydraulic Pump gear bearings too, as it drives the idler gear. If you have a vibration signature program, I suggest doing a vibration signature readout of the gearbox to check the bearings for wear. Another possibility might be wiring near the Reduction Gearbox causing intermittent contact as the engine torques within the QEC at power. I would also swap RPM indicators with another engine, because swapping indicators doesn't cost anything.
  17. You might be on to something there. The 1C-130J-01 makes reference to the -185L(A) pn 3800599-1, which cross-references nicely with the 1C-130H-2-49GS-00-1 APU installed in the AFSOC birds.
  18. The GTCP85-185L is the APU used on the AFSOC U/W-model gunships, and the Talon-II. It weighs about 40 pounds more than the standard APU, and some operating limitations are different. Also, it has an electronic 3-speed switch. The 49GS has more info, and the limits are in the typical 49JG.
  19. The way I phrased my reply was a roundabout way of making the exact points you just made. I am aware of the Talon I with an APU, as well as why it's the only one. You try to fix the problem permanently and you keep hitting brick walls, whether you're trying to get the system to work as advertised, or simply upgrading to a new APU, which won't happen due to the extreme modifications required to both wheel well fairings. The bottom line is you just can't expect a GTC to work as advertised. I agree that it is supposed to work without a boost pump, but if it flames out when a small amount of dirt gets on the filter, it is simply just poorly designed from the start. If an item isn't even slightly over-engineered for its use, then it's intentionally designed to be repaired regularly. I can't tell you how many GTC's I've found without a filter installed because the flight engineers kept pressing the issue and refused to address the fact that there's a serious flaw in the design. Maintainers can't fix that with a filter change, only system design engineers can. Lockheed can write whatever they want on the sales brochure, but if it is physically incapable of running without a boost pump, then you're right, it's no longer a self-contained airframe. It is what it is. I don't feel the need to notify Lockheed of their issue. If they haven't heard enough about the GTC over the last few decades to consider it's inadequacies, then someone's asleep at the wheel. Either that or just wanting to sell the newest model. I can't imagine why anyone would try to defend a machine such as the GTC with a reliability so abysmal it's almost legendary, if not plainly laughable. As for the problem at hand from the original post, I felt I put enough in my post to suggest parts to change to give it the benefit of the doubt, as well as to set the expectations low enough to explain why changing those parts may not fix the problem in the long-run. If it does, great. If not, it is what it is. Change a GTC or three and it still may not fix the problem. I think that experience speaks for itself.
  20. Change the GTC to an APU and you won't have this problem. Just a little story to illustrate my point, the GTC on 9812 refused to run without a boost pump since the 90's. The story I got was they were so tired of the problem getting written up that they added it to the PDM contract to investigate the issue. They did a flow test from the fuel source to the GTC and couldn't find the problem, even changing the fuel line itself all the way down to the GTC, and it still didn't fix the boost pump issue. They ended up just leaving the write-up in the info page of the forms. More recently, the leadership got tired of seeing it there, so they created a tiger team to fix the problem, reaccomplishing a lot of the work that has been done over the years, with no result. I personally changed 4 GTCs in that plane for various reasons, and we still could not find one that would run without a boost pump. The maintenance tech data states that you may need a boost pump to run the GTC, but for some reason, it never made it into the flight manual, even though the mountain of evidence shows the system design is inadequate to run without a boost pump. Air crew can press the issue all they want, but the end result will be unsavory maintainers just pulling the filter out to make them happy. If you truly want it fixed, change over to an APU and be done with it. Otherwise, just use the boost pump, and count your blessings when you can actually do a self-contained start. Sometimes, we have luck changing the filter, strainer screen, atomizer, and fuel cluster to fix this problem, but I don't think anyone will be able to get 100% of GTCs to run without a boost pump.
  21. With the Series III engines and below, the Air Force took all the odd-number designations, and the Navy took the evens. From my experience, the -15 fuel control NSN cross-references with the -14 engine, not the -16. I have seen some websites that show the -16 has an HP rating of 4910 SHP vs 4591 SHP for the -15 listed on other websites, but never the same website listing both -15 and -16 numbers. I've seen SHP ratings for the same engine be different depending on the website I was looking at at the time, so it doesn't mean much. Just the fact that the fuel controls are different may suggest a difference in fuel control tuning.
  22. Lkuest

    AMARG

    90-0161 was listed as crashed/ w/o in 2002 near Puerto Rico. 161 was lost in PR I wonder if they stored parts of it in AMARG as they have done in the past as with 63-7854 or if it was a typo? Here is the post. MC-130H 90000161 12/11/02 27 It has never shown on the inventory before but the post shows a date of arrival of 2002. 63-7854 was also in Area 27. Bob
  23. It is pretty impressive to see this kind of damage on the filter without the engine dumping oil overboard or venting internally. If this is caused by oil pressure, it is because the pressure going in is significantly more than the pressure coming out. There is a built-in bypass for this, so perhaps your bypass is ineffective or clogged, and someone "staked" the button to prevent it from indicating bypass. It would be best to wait for you to perform the scavenge backpressure test. Lockheed considers a pressure differential of 3-8 psi to be normal between the oil pressure going in and that coming out. The only other idea I have is to just blindly change the filter assemblies, to include the heads and bowls in order to eliminate all possibilities. You could also measure the length of the spring on the bottom of the filter and compare it to one that is not malfunctioning. Since it is happening to more than one engine, perhaps it is an error in installation, perhaps the cork gasket being installed incorrectly, or double-stacked.
  24. I'm definitely no expert on converting engines, but I'm pretty sure just about everything aft of the Diffuser, including the Y-Lead, is a different part number, with the exception of the Rear Bearing Support casing, Rear Bearing Assembly, Tailpipe, and T-Block. The fuel control will require replacement due to the different tuning internally for the extra fuel flow, but the TD Amp can just be re-adjusted to the new limitations. -7 to -15 conversions aren't too common because it is much easier to overhaul and re-use components than it is to order all new parts, but the US Coast Guard accomplished a set many years ago. See Lockheed Service News Bullitin Volume 26 No 1. The gist I got from it was the easiest way to do it is order a conversion kit directly from Rolls Royce tailored to your situation (some -7 engines may require a Gearbox or Compressor modification.)
  25. Install a micrometer so the measurement end of the tool is as far aft on the propeller shaft as you can get it. Put 81kg of downward and upward force on the end of the prop shaft. The micrometer should not move any more than .005" down, or .015" up. It must be overhauled if the limits are exceeded.
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