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


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Posts posted by pjvr99

  1. To get back to the origional problem, my feeling is a wiring problem. Maybe a

    dry joint in a cannon plug at a pressure break, firewall, in a lead. Having reread

    the original post, he does says at all power settings ...... torq should not be

    used as a comparative reference as a 98% engine wil have much less torq than

    a 108% engine, especially once throttle is above x-over. If the TD systems on

    symmetrical engines are good, TIT should be near identical with throttles above

    x-over lined up. Fuel flows on engines should be very close, but may differ for

    a number of reasons. RPM should be 99.75% to 100.25%

  2. Haha, that's an easy one. Check your bleed valves. Close your engine bleed then check the engine anti-ice to see if you get a 24 degree rise. If you get less than 24 degrees TIT rise, lets say it only rises 18 degrees you have a stuck bleed valve, if you get no rise at all your anti-ice valve is stuck open or your bleeds are just stuck open.

    Check it in null too.

    Does it have oil cooler augmentation?

    Not true: bleed valves will not affect TIT rise at LSGI and NGI, below X-over, or in NULL. The

    24°C rise is created when scoop anti-icing and inlet anti-icing are functioning correctly. A lesser

    rise will indicate one or both a/icing side valves, and/or a/icing solenoid valve inop and/or scoop

    valve inop.

    Now: the only way to figure out what's happening is to do man-on-stand. Start engine, and at

    NGI, lightly touch fingers to side valve(s) and feel if they're hot: if so, valve(s) are open. If cool

    have cockpit open engine a/icing for a minute, and touch again. If still cool, valve(s) are closed.

    In either case the problem may lie with the side valves stuck open/closed, or with the solenoid

    valve which controls them being inop.

    A hand held over the scoop vent on the RHS of the inlet duct will tell you whether the scoop valve

    is functioning as required.

  3. I have very similar results in the test cell, and on the odd run I sit

    in on the aircraft. The only setting where it is out of the range is

    at LSGI. I have a suspicion that its cause is the way the fuel flow

    transmitter works, and the accuracy of the gauge.

    I do not believe this to be a crisis, as my indication is consistant in

    all engines with similar performance at similar atmospheric conditions

  4. A little new to these engines then? Okay, T-block is located on the upper left side of

    the combustion case - used to connect the two thermocouple harnesses together. Next,

    the Y-lead - takes the signal from the T-block through the fireseal, and then splits to connect

    to the TD amp, and back to the firewall for the indicator signal.

    T-block part no: 6840004

    Y-lead part no: 6847718

    By the way, what is an 'ECTM converter' .......?? Another question: are the throttles lined

    up above X-over?

  5. What about T-block and Y-lead? I realize this is a long

    shot (and difficult), try swapping the indicator and amp

    wires around on the T-block - only allowed 6·C difference

    at same throttle position. Also try disconnecting at firewall,

    gauge, and T-block, then do resistance checks between the

    chromel-alumel wires and also to ground. In all cases there

    should NOT be any continuity . . . .

    Something else to try, use your TD tester to shoot TIT signal

    to cockpit

    Good luck, let us know what you find

  6. 2J-T56-56 SWP 058 03 gives a table for starting times vs air temp. These times are commonly

    referred to as "on-speed", i.e. the time taken from starter button pressed, until RPM is stabilized

    at LSGI

  7. This one has the grey matter in a mess (more so than usual). For the numbers to change

    that radically, you need the TD and the FCU to work together. I'm wondering if there isn't

    a split pulley or tension regulator stirring the pot. Also take a good look (disassemble) the

    gimble assy at the coordinator.

    Also take a look at the CIP hoses for blockage, both upstream and downstream of the FCU,

    blow them out with compressed air

  8. The wire pairs for the reference and torque signals are shielded, and grounded on the torq

    indicator. A break between the shield and wire can cause a misread. Had the same thing

    late last year. We had disconnected the tm pickup cannon plug, and the Misc2 (?) cp and

    had a 20MOhm reading to ground on pin A of the tm cp, where it should have been open

    circuit. Hope this helps .......

  9. ..... the little motor in there simply isn't strong enough to overcome the brake?

    That's the operating theory, but every once in a while, the TD brake lock test

    passes, but fails TD system check by losing TIT and fuel flow when the switch

    is moved from AUTO to LOCKED with the anti icing on. Even though the brake

    may indicate LOCKED, the valve may still slip away to the NULL position ......

  10. During aircraft decent (landing)rpm fluctuate 99%-102%.normal flight rpm no fluctuate.td valve null,propeller mec gov position also fluctuate.tit,fuel flow,torque normal.

    Anyone can give solution.

    I'd hazzard a guess and go with NTS'ing. However, you're at flight idle/low pitch stop, so rpm will be below 100% (out of prop governing). Alternately, if there is no other indication, it may just be a bad tach generator ....

  11. 1500"lb difference should not be a problem, unless both engines had the same torque

    on previous flights. This difference is worth about 7.5% performance. If previously the

    same, I would hazard a guess at a scoop anti-icing valve failure - the numbers are

    fairly consistent, and a 50pph fuel flow difference would be hard to spot during take

    off ..... all of Lkuest statement is true

    On the scoop valve, I had one several years ago that worked great below

    about 850°C TIT. Above that, it would open and had me hunting a TD system

    malfunction for several hours.

  12. Filter 8psi

    FHS 12psi

    Cooler 10psi

    Filter outlet also should not exceed 30psi

    Now: older type oil coolers (full oval face) below 75°C give a differential of +-8psi, but

    happily rise to 18psi above 75°C. Newer type (square face) seldom have a differential

    of more than 8psi, but often have trouble keeping the oil temp below 85°C on very hot

    days. The question becomes 'do you go by the book, and reject cooler after cooler for

    high back pressure', or, 'get the back pressure right, but have high oil temp problems

    in ground range on hot days'?

    Bearing in mind, that high back pressure can lead to oil dumping at altitude. What I would

    suggest is get the engine onto the test cell, and check out the scavenge system; i.e. is

    the RGB and power section scavenging all the oil back from the various sections. Check the

    indicated difference in qty between running at 900°C and immediately after shutdown. Also

    check indicated qty at LSGI and NGI with the oil temp at normal running temperature. Check

    residual quantities in RGB and PS by draining and measuring immediately after shutdown. Make

    your decision from there ......

  13. Oil cooler the most likely culprit, but if the #2/#3 bearing pumps are not doing their job (or any

    of the other scavenge pumps), high oil temps do result. Easy way to check this - run engine

    at 900TIT and note oil qty, check the qty after shutdown with engine stopped. The difference

    should be less than 2 gallons. Old dirty oil has also been known to cause high oil temps

  14. Also APU FCU cannot compensate enough for altitude/temperature change. Even big

    commercial aircraft are limited to about 15000ft. It may run at higher altitudes but will

    flame out at the first application of load - even a shift in generator load can be too much

  15. What NATOPS1 says. Null/auto TIT, before/after light out TIT at X-over, and rich/lean TIT

    TO 2J-T56-56 SWP 060 00 Troubleshooting Table 57: Replace thermocouples.

    If this doesn't work, do an OHM's check on the coordinator potentiometer.

    Last, if this is an ABB or other solid state TD amp, have a go at swapping it out

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