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

pjvr99

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Posts posted by pjvr99

  1. So there we were, an engine giving 104% performance, 29.85"Hg air pressure,

    and 20°C OAT. Engage the pitchlock, push the throttle to take off. Watch the

    overspeed at 105% rpm, fuel flow at 1500pph, torque around 10000"lb.

    Next moment fire warning light flashes on, fuel flow shoots to 2000pph, torque

    rising rapidly, and rpm on the way down. Then everything goes back to pitchlock

    settings, ....... and again the fire warining, and fuel and torque rise, rpm drop, and

    back again.

    Fighting the instinctive throttle back to prevent overtorque/flame-out situation while

    pitchlocked, yet still trying to analyze the situation, I finally opted for feather shut-

    down.

    Lots of extremely wide eyes in the control, I find myself thinking "double rum and

    coke would be good about now", and realizing that I'm in the Magic Kingdom. So

    reset everything, cool down the engine and start up again. Everything all happens

    again except this time there is no response on the throttle when I tried to throttle

    back. Another feather shut down!!

    Decided that because the engine had been standing unpreserved for a looonnnggg

    time, it must be the fuel control governor that [email protected] out. One FCU change later

    and we try again. Initial pitchlock check good - joy!! 20 minutes later (and another

    feather shutdown), I'm shaking from adrenaline overload.

    After consulting with the prop shop brains trust, the decision was made to replace

    the valve housing. Again everything checked good, with 3 back-to-back pitchlocks

    successful. Work through an entire run sheet, and get to the pitchlock step again,

    back to square one!!!

    Slaved in a spare prop main control conduit - no change! Started investigating the

    test cell cables and junction boxes. Finally found the 'sync box' of the test cell had

    a burnt component. The main control and the fire detector leads run in the same

    harnass. So I'm guessing damaged wires inside the harnass shorted between the

    prop control and the fire circuit.

    Disabled the fire circuit and replaced the prop control box, now everything is

    working as advertised. My arms, however, feel like I've been wrestling bears or

    something .......

  2. Difference in torque at FI when throttle is moved from GI to FI, and

    when moved from above FI back to FI. Difference should be a

    minimum of 500"lb (200"lb on some special variants). Sometimes a

    failure will be indicated by no difference, while the torq may hold for

    a few seconds when coming back to FI, before dropping off. Also in

    static operation, no hesitation at LPS angle is noted on protractor

    when unfeathering to GI or Reverse

  3. Anything in mist form with an air/fuel ratio of about 15/1 will burn. MIL-PRF-83282 is

    supposed to be less flammable than MIL-H-5606. Least flammable is really sh!tty

    stuff used by Boeing, known as SKYDROL

  4. I once got a center right window that the heating elements had broken. I set

    it up at my local shooting range with some paper targets behind it. 5 shots

    with a 9mm P, 3 with a .45ACP, a 2 with a .357 Desert Eagle didn't penetrate,

    but made me think seriously about being crew. The paper targets behind were

    shredded!!! Hail and birdstrikes shouldn't be too much of an issue, as mostly

    the window will either deflect or the whole panel will be pushed in; small diameter

    high energy objects turn the inner layer into a shrapnel storm of note.

  5. RPM is determined by the prop governor. Throttle position around 55° - 60° on the

    coordinator is where the prop will hold RPM at 100%. Below that the blade angle is

    mechanically determined by throttle position, and RPM is merely a function of fuel

    flow vs blade angle. New strong engines tend to run around 97% - 97.5% at GI,

    while older weaker engines tend to 96%. FI is around 96.5% on new engines, while

    older engines go to 95%. Top-of-Beta is +-0.5% lower on older engines than on new.

    There is nothing I know of to change this, given all engine and prop rigging, and

    blade angles are correct. It does happen from time to time that RPM's at these

    positions are lower than expected, but bear in mind your limitations:

    TO 1C-130H-2-71JG-00-1 71-00-02

    Normal ground idle RPM: 94% - 102%

    Flight idle RPM : 92.5% - 100.5%

  6. Sometimes a crew change also makes the problem go away :-)

    There is a LOT of things that can cause a pulling problem, props 'n engines often being

    the first accused. Take a good look at the MLG: shelf brackets, torque link, guides,

    rails, etc.

  7. To add to Lkuest, check magnetic plugs on RGB and P/S. Also do a fuel governing & pitchlock

    check - unstable fuel flow, rpm would indicate a fuel control failure. If you're going to try

    another flight or FCF, close the bleed air valve and see if the problem persists.

    A very long time ago, I had an engine that had a torque flux below X-over. The engine was sent

    to overhaul, but when it came back it still did the same thing .... but worse. The next time it

    came back with the report of a problem with the towershaft bearing. What was happening, it

    was intermittently missing a tooth on the gearing, and the speed valve was popping open. Above

    x-over, the TD system was strong enough to smooth out the problem. I only knew about the speed

    valve opening because I heard an intermittent hiss during a man-on-stand check.

    As Lkuest says, there is any number of things independently or in conjunction, that could cause

    this. Let us know what you find.....

  8. A shredded rag attached to safety wire for checking bleed air leaks in the nacelle always worked for me...

    True, also spraying the suspect area(s) with NDI penetrant developer will

    give you a good idea without the risk of a man-on-stand check

  9. I was around then a know the said ACFT and crew well. Chief Vail was a family friend . Summit 38 was a tragic loss. If anybody WIKI's the Summit 838 accident there are a few inaccurate pieces in that write up. Not fun being at the wrong end of a accident investigation board. Anybody that would like to know more just ask.

    Can't seem to find it, so I'm asking ...... Maybe start a separate thread ......

  10. If it hot starts only in Auto, you most definitely have a wiring, or TD Amp problem;

    Wrong!! A messed up TD valve has done this to me before. Cost going back over 5 TD amps to verify they were

    actually good. For the same price, sticky FCU bellows can have you chasing you tail

    Someone here said the 130 will make a liar out of you; it's true.

    It just did! If your 5th & 10th bleed valves are closed, you should hit 810° at about 35% rpm in AUTO, at which point

    the engine will bog down if the TD system is strong. Alternately, if you are in NULL, you'll be passing 900°C before you

    could get the condition lever to STOP or FEATHER.

    Don't be fooled by the obvious - double check EVERYTHING, look at (and see) what your gauges are telling you

  11. Trev,

    If the nozzle is coked or damaged in some way, the fuel blows back through the nozzle. It is a shroud that

    allows air to mix with the fuel before injecting into the combustion can. This 'blowback' occurs in the diffuser,

    and therefore easily taken into the 14th stage bleed ducts

    Invert aircraft - error will go away :rofl:

  12. As brothers mentioned that a “Compressor Tight Engine” is one possible cause of the defect. (engine failed to rotate during air start).

    The question for brothers having experience on “Tight Engines” is; such engine; dose it show some indications during ground check?

    Such as:

    1- Repeated failure to rotate during start, when still hot.

    2- Repeated starter failure.

    3- Above 100% efficiency.

    6- Visual evidence of “Rubbing” on the compressor blades tips (fifth & tenth stages compressor check).

    7- Rubbing noise during “hand rotation” when engine still hot; etc…

    For the sake of knowledge, comments will be appreciated.

    1010

    Over the years had a number of high performers up to 113%, but none of the problems you

    mentioned. We simply followed the seal break-in procedure in TO 2J-T56-56 SWP 058 03 Sect 13

  13. I have recently had a rash of extremely high AUTO starts, AUTO T/O TIT, and fails NORMAL LIMITING check. All

    are using solid state amplifiers. TD amp is driving the valve to PUT condition. I have also had an instance where

    the Y-box leadset was damaged. Y-box shows everything on the numbers, but on startup AUTO TIT is 830°C,

    take off will happily go past 1083° with the throttle still well short of the stop. NORMAL LIMITING check just

    overtemps with no TIT cut-back. RICH/LEAN check shows a 50 - 60°C lean

    Before I figured out what the problem was, I recalibrated the cells indication system, installed my thermocouple

    swap-over relay, and generally spent a lot of time chasing my tail. Also slaved in various relay boxes, J3 leads,

    on one occasion a coordinator, and another occasion a TD VALVE, and even thermocouples, t/c harnesses, T-blocks,

    and y-lead.

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