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Aero Precision provides military aviation aftermarket solutions for c-130

Lkuest

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Lkuest last won the day on August 14 2018

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core_pfieldgroups_3

  • core_pfield_11
    Went to LRAFB in November 2002 working as an engine specialist on the flightline at the 314 AMXS/Blue AMU. In May 2011, started working as an FTD instructor at Yokota AFB, Japan. Arrived back at 314 AMXS/Blue in 2014.
  • core_pfield_12
    LRAFB
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    C-130H Propulsion

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  1. I agree with NATOPS, once the engine shuts down, any fluid pressure from the still-spinning pumps will go directly to the increase-pitch side of the dome via the feather valve and feather actuating valve until the pumps can no longer supply 100 PSI. Then the blades stop changing pitch. Since the internal seals for each propeller are worn differently, it's difficult to nail down a specific degree when you transition through that pressure. Also, as you are flying, airflow is still trying to spin the propeller beyond what it would be during a ground run. I doubt you will get all the way to feather, but you should get far enough to make sure propeller drag isn't dangerous. Think of the propeller as an air brake which either absorbs or transmits airflow energy. If the airflow is inadequate to continue spinning the propeller, then the propeller resistance to airflow is naturally going to be low. I am unfamiliar with the flight manuals, so purely from a maintenance standpoint I also want to emphasize that you will still have 28vdc attempting to actuate the propeller feather solenoid, so once the blades stop changing pitch, the propeller feathering circuit may still be energized, both overheating the circuit as well as sucking DC voltage if that bus is powered. Check your flight manual to see if you need to manually pull the feather override button up if the propeller blades stop changing pitch, but are not all the way in feather.
  2. I recommend your military request technical data upgrades. I've never even seen a 1C-130B-2-4, so I have no idea what information I could add to help you troubleshoot your problem. With updated technical data, you might be able to do this on your own. As with most fluctuations, it is much easier to recommend a maintenance action if I was able to see all the engine instruments. Just about anything can cause a torque flux, and "all wiring" is a pretty broad statement.
  3. I would be interested to know what kind of troubleshooting manuals you have available to you.
  4. I agree with pjvr. What you are describing is a throttle misalignment below crossover, for which there is no limit. If everything else is within limits, there isn't a problem. If you are still really concerned about this, you could check for air leaks, but you should also have lower torque and slower starts. You could also adjust the TD Valve and/or Fuel Control, but ONLY if the rich/lean check shows rich AND you have warm start temperatures and well within normal start times. Otherwise, it sounds like the TD system is doing its job well, and stops controlling when it's supposed to stop controlling.
  5. If TIT, Fuel Flow, and Torque are all low together with no change in RPM, whatever is causing the problem is definitely fuel related. Have you run an electrical check on all wiring? Some of the electricity goes through the LH engine wiring harness, and there is a J3 lead that can cause problems. You might also hook up the TD Amp test set and shake the wiring around to try to duplicate. You should also pull the lid off the junction box next to the TD Amp and see if anything looks out of place.
  6. Was RPM doing anything, and if so, which direction in relation to TIT? Also, were torque and TIT low together, or opposite each other?
  7. As a maintainer, I've seen this a few times, both with engine running and during static pitch changes. Also, with the throttle in any position, as well as reversing with the condition lever in feather. I've never had an aircraft from my unit reverse in flight during the 200,000+ flight hours worth of malfunctions I've either worked or got turnover for, but I do believe this eventuality is covered in simulator training.
  8. This really needs more detail. Try to describe the malfunction in detail so we can get a mental picture of what's going on. Torque dropped for only 2 seconds. Which 2 seconds? At the beginning of the 5 seconds that RPM was low? At the end of it? If torque and RPM dropped together, it would indicate air as a likely cause. If Torque stayed high when RPM dropped, then that would indicate a propeller malfunction, and TIT happened to shoot up due to the SCV opening at 94%. If TIT shot up only after RPM dropped to 94%, that would further indicate the propeller as the cause. If TIT shot up before RPM dropped, then that would point to an air malfunction. How did the engine recover? Did you turn off bleed air, adjust the TD switch, or did it come back on it's own? Is there a history? How many hours are on the compressor? You're also missing fuel flow, which might help indicate a fuel or TD system malfunction. You might also include much TIT and Torque moved, as well as the pressure altitude and outside air temperature. A very slight TIT increase might indicate it was fuel related because once the SCV opens, the TIT should shoot up a lot. A large TIT increase should eliminate fuel system as the cause. A SCV malfunction is usually only good for about 5000 in-lbs of torque at power and around sea level, but I'm sure the power loss could get much more severe at high altitude or hot conditions and engine wear level. There's just too many variables for us to be truly helpful with the little information that was provided.
  9. I'm assuming a BARV is a Bleed Air Regulator Valve, and when you say "accompanied of TIT", you mean TIT dropped with torque, and not increased. The TD Amp's job is not to maintain power, but to maintain temperature based on the throttle setting. If the TIT is low while the TD Amp is in AUTO, then there is an error with a signal being supplied to the TD Amp, or there is an error with the Amp itself, a setting or malfunction, When you lose air, you lose power for two reasons. Jet engines love more air, both to increase power through expansion, and also to keep the combustion chamber cool. If you lose air, you lose power immediately since there is less air to expand, but also the loss of cooling air causes an increase in TIT, and results in the TD Amp to pull fuel back. This all produces a loss of torque and fuel flow while maintaining TIT. I cannot emphasize this enough, before doing anything, ensure your indications are accurate! TIT to within 6 degrees of actual as measured with a test set and all thermocouples verified good and connected properly. Torque indicator recalibrated and set to within 50 in-lbs of actual. Swap the Fuel Flow gauge with a known good one for good measure, then reverify the problem. Why the engine goes to normal when the Regulator Valve gets turned off is interesting. If the TIT was to remain normal, I would say the Regulator Valve was mis-tuned and the TD Amp was doing its job. Since the TIT is also low, we know the TD Amp is not doing its job (above crossover only). Even if the Regulator was malfunctioning, the TD Amp is definitely having an issue. The fact that the valve affects the TD System operation means they may be connected electrically in some way, like the power/signal wires may be chafing together. If the fuel control was perfectly tuned and we suspected the TD Amp was just inop, we would see high TIT with bleed air open, not low TIT. To check if it is an electrical problem, check power going to the TD Amp using a TD Amp Test Set, then cycle the bleed air valve and see if the power at the Amp changes. There are two types of power going to the Amp, so check them both. If I misunderstood you, and the TIT is high during the malfunction, and not low, then you have a TD Amp malfunction AND a bleed air regulating valve balance issue causing you to lose 2500 in-lbs.
  10. Is the engine operating within limits? If so, disregard the differences as there is no limit for symmetrical operation in HSGI. Otherwise, you might consider checking rigging with the valve housing, or swap it with a known good valve housing, as long as the Fuel Control has already been eliminated. I know the prop causing fuel flow problems sounds weird, but I've had it cause stranger problems in HSGI.
  11. I'm sure if the boss wants it to get done, it will get done one way or another. Seriously though, it depends. If you're looking for justification for an argument, the 61-series job guides are meant to be used by the specialists, so if that's the tech data being used, the engine folks are doing it. If the 12-series job guides are being used, then it's APG doing the check. By concept, APG is in charge of all routine maintenance. In practice though, if an engine troop doesn't have work, he's doing it. If engine troops are busy, it could go either way. Not sure if it really matters who does it, as long as they do it right. I've seen a few APG folks grab the wrong color can, so do what your comfort allows you to do.
  12. I agree, all you can really do is a check first stage rotor blades, balance, and a good signature check. If all those are good, you might just be having bad luck. We've gotten quite a few that crack again and again, mostly due to poor weld repairs on the replacement supports. If the signature run is good, you might try installing a known brand-new case and see if it still cracks. Of note, the rear bearing support case wasn't originally designed to mount a tailpipe, so the extra length acts as a cantilever to amplify vibrations through the weak points. The support case is Allison, and the tailpipe is Lockheed. That's why vibration is the top cause, but also explains why you might have nothing wrong with the rotating assembly and still get cracks.
  13. Agreed. If you are ops checking the system, the chances are you have a malfunction somewhere in the indication or fuel/TD systems, or you wouldn't be ops checking it. If the malfunction is in the fuel/TD system, the situation is at least stabilized in-flight with the appropriate procedure. When you start adding variables to a stable situation, such as enabling and disabling the system with various bleed air loads and throttle positions, you can make things much worse, such as a power surge/overtemp or an engine flameout, or any sudden power change in-between. On the ground, neither are dire events when the aircraft is safely parked.
  14. Have you tried the switch that tells the Geneva lock to close? It can be tempermental. I've had the same problem before in ground stop. Hitting the quadrant did the trick in my case, which means switch, but it could outright fail as well. There's a lot of wiring and components in the system, so I'd recommend hunting the problem down using a wiring schematic if it isn't the switch.
  15. How does the starter break? Does it shear, seize, or otherwise fail to engage? There's a couple simple possibilities, but you'll have to forgive the suggestions if they seem too accusatory. Your installation method may be incorrect, such as running the starters with shipping fluid instead of engine oil, or even running the starters dry. Some people don't realize that starters without dipsticks may still need to be drained and serviced if there is a fill port on the left side. Another simple possibility may be your supplier building defective starters. either could possibly cause the starters to sieze. Certain part numbered starters use a friction seal that exerts resistive friction against a thrust assembly. If the friction seal is worn, damaged, or incorrect, it will allow the starter to freespin, and possibly shell out under high RPM. There is a procedure in USAF tech data to test the friction seal. Another simple cause may be a clogged return line from the starter back to the starter control valve. This would cause the starters to shear excessively due to too much torque being exerted through the starter shaft shear point. Of course, a damaged propeller brake can cause the starter to shear as well. The key will be to check the engine start times. If the engine starts quickly and shears, it's getting too much air. If engine starts tend to be slow, the prop break and/or gearbox may be failing internally. The worst possibility though would indeed be vibration. Since the starter is in the center of all the RGB harmonics, it tends to get quite a beating if the engine isn't quite right. If you run an engine signature and come up good, you may just have a run of defective starters, and I would recommend installing a starter you know to be reliable. I have seen an engine vibrate so much that it shook the starter nuts loose, and the starter ended up hanging on by just two nuts. The starter was still good though, so that might give you an indication of how much vibration one can take, but that of course may have more to do with the style of starter more than anything. I wouldn't suspect torquemeter shaft unless either a signature run/torquemeter runout confirms it, or your torquemeter pickup has evidence of grinding on it. You can test the power section for internal binding by releasing the prop brake using the air adapter and manually turning the engine over to listen for any abnormal noises. Rubbing blades would usually manifest as sparks shooting out of the tailpipe at night though, and internal engine failure should show up as significant oil quantity or pressure loss. I'm sure I'm missing something if someone else would like to chime in.
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