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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. Just saw this post, so here's my 2cents. A15 ff xmtr (big black metal block) tends to read higher than charts

    indicate at lower throttle setting. D22A xmtr (small silver can) appears to be more accurate. My test cell runs

    both types of engine. I can only surmise this is due to the way each transmitter works.


    A15 when engine is powered up, you can hear a clicking noise coming from the xmtr. On occasion when we

    experienced fuel/acceleration problems , this clicking noise was erratic or even absent. The D22 xmtr, is a simple

    in-line turbine driving a pulse generator

  2. TC2, I wish I could give you a positive answer and shout out "EUREKA! We have it!" But alas we are going thru the

    same thing right now. My guys are changing TD valve as a 2nd to last resort, as even my good amp is not performing

    to spec. DC voltage I am happy with at 26.6v,and both hobart and /60 GPU ouputting 115v 400hz.


    The only other suggestion i can make at this time is to swap over your indicator and amplifier leads on the T-block

    and see what happens. There should not be more than 6°C difference at take off. We have found several thermocouple

    harnesses bad in this way over the last year or so

  3. Over several years I have found this problem on most of the solid state amps. In my test cell, I have a Bendix amp that I use for

    troubleshooting TD system problems. I have no idea what causes the solid states to do this. My test cell generally runs off

    the base 400hz generators and i have a large rectifier for the dc supply

  4. Well that was easy .... glad to assist :-)

    Several years ago, the computer system on my cell crashed completely. As an interim

    measure I installed regular aircraft guages and direct reading guages untill we received

    the new system. I made the installation dual, so even if the computer fails during a run,

    all indication continues uninterrupted. You may want to do similar on your cell

  5. In over 500 engines on test cell, I have only ever seen 1 engine in high zone. My calculator shows

    you should have a normal zone of 95.1 to 102.6. You need to check your test cell guages and transducers,

    as a start, and also check your thermocouples for correct TIT output. As a rule-of-thumb check, 75degrees

    on coordinator is very close to 900TIT for a T56/501 engine

    To check thermocouples, you need to find a way to switch over the IND/AMP wires at the T-block. I have

    a relay that I switch during the run (for safety reasons, I do this with TD switch in NULL) - a change of

    more than 6degrees C indicates a problem with TIT indication system

  6. I like the idea of a scoop valve problem. I had one some time ago that would open as the CDP passed 105psi. The odd fuel

    flow also supports a loss of air theory

    Another possibility is one that has come up more often recently, where the TD valve is stuck in "TAKE" condition -

    yellow-box checks good, but has a hard time making take-off power/TIT.

    Cross-over 'cutback' is something that has been taken out of context. Basically, if the FCU is slightly rich at this part of the

    schedule, fuel and TIT will be trimmed back when the system goes from normal-limiting to normal controlling. Bare in mind

    normal limiting is the same as null, except you have overtemp protection. For the same price a lean FCU can have a fuel/TIT

    spike as you go from limiting to controlling. Bottom line: only requirement at crossover is TIT must stabilize between 800°C

    and 840°C.

  7. so with your mil-spec b5 stand jacked up to to work top/prop panel area you discover you need

    another tool ....... I guess you need to lower the stand completely, then go down on hands and

    knees, leaning over the edge of the stand to reach your colleague (who has in the mean-time

    decided to grace you with his presence)handing the tool to you ......... guess it will save a life or

    limb somewhere ........... :-)

    p.s.: don't overbalance ......

    p.p.s.: how the hell are you going to get that

    generator up there to change it ...??

  8. Nothing wrong with it as far as I can see, its just running right at the bottom of its limit. Only thing i would be concerned about is what is going to happen when you come back from power to low pitch stop, as you normally lose 1 - 1.5% rpm

  9. We use the HP48GX calculator. Itcalculates almost identical values as the old slipsticks, and we

    also have a DOS pc version calculator which comes up with same results as HP. I have a copy of the

    excel spreadsheet, but dont use it as the results vary too much from the other 3 methods.

    Even my own attempts at making a spreadsheet calculator are more accurate (but not enough to

    use it as anything more than a reference)

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