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  • Mark replied to the topic Kapton Wiring in Wiring
    Different aircraft. Same forward left sidewall.
    Previous comments to people about issue..... ignored.
    Any aircraft flying with Kapton wiring are ticking time-bombs.
    What's it going to take before the problem is addressed?
      
      
      
     
      
     
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  • Mark created a new forum post in How "Not" To Do It
    IDG power phase wire. This is a "one aught" or 1/0 gauge wire..... in other words "big".

    The wire had shorted to ground. The Generator Control Unit sensed this as a differential fault and it disconnected the main generator contactor and removed voltage from the excitation field coil of the IDG.

    There's a reason it shorted to ground..... When four extra feet are just left flopping inside the pylon! Pretty shitty maintenance if you ask me.

    Pylon right. You can see the wire all the way near the top coming through a gap in a cross-member structure area. The other (properly run) wires are behind that opening.
      
      
      
     
      
      
      
    Pylon left.....
      
      
      
     
      
      
      
    What more can be said?????
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  • Mark created a new forum post in ATA 76 Engine Controls
    (A previous fault dealing with this system can be found  here .)

    We had a Engine Fuel Valve (or what is called a Fuel Conditioning Unit) that was not extending to its full length when the fuel lever was placed in the "Run" position.
      
      
      
     
      
      
      
    The piston should extend about 4"  to allow the MEC (Main Engine Control or as some people call it..... Fuel Control) to start the engine. The piston will stay extended during the entire engine run cycle.
      
      
      
     
      
      
      
    The complete system consists of the fire handle, run/cutout switch, and the conditioner itself. If the fire handle is down, all control is through the switch.

    Power to extended comes in on pin 8 of the conditioner, 7 to retract. The initial ground to start movement is pin 9. As soon as the actuator starts to move, a internal switch swaps that ground to 7 to extend, 8 to retract.

    The switch just reverses polarity going to pins 7 and 8 depending on what position it’s in.

    During the start cycle, if the actuator moves out a small amount and stops..... either the internal switch in the conditioner is bad or the ground path on pin 7 is high or open.

    For our problem with this aircraft, we had a fuel run/cutoff switch that had 300+ ohms on the ground path out of pin 7 of the conditioner. If the switch was flipped vigorously, the ground path was less than 20 ohms and the piston would extend fully.
      
      
      
     
      
      
      
     
    A better image can be found  here .  
      
      
    If you look at the prints you'll see that with the fire handle pulled, the switch is by-passed. Power is sent directly to pin 7 and ground on pin 8 to retract the actuator and shut off the engine.
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  • Mark is now following Gemar155
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  • Mark created a new forum post in Troubleshooting Tips
    I've seen three types of fire/overheat detection systems used on corporate to commercial sized aircraft.

    Systron-Donner systems are used extensively on GE engines. I've seen them on Pratts also.

    I've explained how they work  here .

    The easiest way to identify a Systron is the white circle terminal connection point.
      
      
      
     
      
      
      
    GE CF6-80A engines use three equal resistance elements. 4.5K each - 1.5K total in parallel.
      
      
      
     
      
      
      
    Kidde detection systems are hooked up in a series circuit. An example of one is explained  here .
      
    A couple images of Kidde systems.....
      
      
      
     
      
      
      
     
      
      
      
      
    The connector and crimp die for the image above.
      
      
      
     
      
      
      
     
      
      
      
    Finwal detectors are usually single probes. I've seen these used on Gulfstream aircraft for duct overheat and APU fire systems.
      
      
      
     
      
     
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  • Swage crimps for shield ground connections.
      
      
      
     
      
      
      
     
      

      
      
     
      
     
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