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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. For several weeks flight and ground crews have been pecking away at a problem where engine torque, fuel flow 

    and TIT increase when engine anti-icing is turned on. We're not talking 100"lbs of torque here, its over 4000"lb

    and/or 300 to 500 pph of fuel. Every conceivable component from FCU, speed valve, anti-icing side valves, and

    the whole TD system has been replaced at least once with no change.


    Last week the engine was finally removed and sent to test cell. Engine was started, runs great, makes good power,

    but when anti-icing is turned on there is a massive surge of torq and fuel which the TD barely contains. I had the 

    to see what happens in NULL - instant soil-the-underwear moment as torq jumps from 12500"lb to almost 18000"lb,

    fuel goes 1600pph to 2000pph, and TIT from 900°C to 1040° ......


    I have a small flapper installed over the inlet duct anti-icing vent so we can see when the anti-icing valve opens. This

    device was working as intended, meaning a/icing on flapper flaps, but ...... massive torq, TIT and FF increases.


    We eventually shut down the engine without any real idea of how to proceed with troubleshooting. Then I started

    thinking: what if, somehow, a/icing air is getting into the FCU CIT or CIP lines .... Some examination of diagrams

    led me to the CIP inlet in the compressor inlet housing. A/icing air is pumped into the same strut  as the CIP

    fitting. If the fitting is corrode, cracked or loose, you'd be dumping 100psi air onto the CIP bellows.


    Long story short, a really skinny guy was sent up the 'S'-duct and CIP fitting was replaced. VOILA! A/icing no

    longer causes massive increases in torq, ff, and TIT

    • Like 1
  2. 2 things will happen here:

    1- you will lose the commercial (civilian) certification for the D22

    2- you will have no fuel flow indication.


    The T56 engine uses a 28v DC power supply for the ff transmitter and indicators, while 

    the D22 uses a 115v 400hz power supply. The wiring and connectors are completely



    In my opinion this would be a completely wasted excercise, not to mention the expense

    of recertifying the D22 again

    • Like 1
  3. Probably want to keep APU shut down when taxing on dirt or unprepared strips. Having

    said that, the intake screen holes are big enough to let in small gravel and stones which

    can and will damage the compressor when it is started again ....

  4. OK. big scavenge problem. How is oil temperature?


    Pull off lower E-duct from 14th stage. check the #2 & #3 bearing lines visible for oil staining. After

    that check #2 & #3 bearing lines to the external scavenge pump that they are not blocked.


    Heve you changed main oil pump yet?

  5. What is the difference in indicated oil quantity with engine running at 100% rpm and indicated oil qty

    immediately when engine is shut down (no rotation)?


    During ascent/descent are the oil pressures steady, or is there a fluctuation? Is there any fluctuation

    on the ground?


    Did the engine go across test cell before going back to aircraft?


  6. Lockheed Service News V18 #3 contains a brilliant explanation of causes and troubleshooting

    of oil dumping. It was later made into a service bulletin. I suspect you may be looking at RGB 

    scavenge failure


  7. Do you mean a rise from 'before light out', meaning less than 800 and correcting to 800 to 840 after light

    out: yes, it is good. The ONLY, let me repeat that, ONLY requirement is a correction of 800 to 840. There

    is the rare occasion when the mechanical and electronic schedules are the same and no correction occurs.

    If this happens you need to do a proper TD system check.

  8. Not much to be done there. Airfield safety should be taking care of birds thru keeping grass verges short, falcons, etc. Nothing a crew can do

    once they're committed to land or take off


  9. Thank you. based on this and your previous mentioning the shift

    to another engine, it sounds like you have a rollback, a problem

    with the synchrophaser. Check out synchrophaser, sych rack, and

    also run synch box tester. sometimes the problem can be a false

    signal generated by a seemingly good valve housing. also check

    all 4 prop pulse generators.

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