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Thread: In flight EFIS Failure.

  1. #1

    Exclamation In flight EFIS Failure.

    One problem led to another today.

    I had high oil temps, and I wanted see if recycling my AF3500 in flight would have any effect on the oil temp readings. I pulled the breaker on the efis, and strangely my oil temp dropped 10 degrees. (putting the breaker back in caused the temps to go back up).

    I still wanted to recycle the power on the EFIS, but pulling the breaker and/or turning off the avionics master switch just caused the EFIS to go on battery without the usual "I'm going to shutdown soon" messages that you get on the ground. (Now I see in the manual that auto-shutdown doesn't trigger when there's a/s or rpm, nice.)

    I couldn't recall the exact pattern to reset by holding buttons 2+3+4 for 3 seconds. Instead, I was trying to hold down button 1 or button 1+2. Something I did resulted in the unit going into what looks like a continual rebooting sequence. I can't be sure of the exact operation that caused it, but the AF3500 went into a loop and would not come out. It continued on in this state for another hour+ of flight time. It did NOT stop even after landing and shut down. It was still doing the reboot sequence when I left the airport. Eventually the battery will be dead, and I'll see if it comes back to life. Dunno.

    I have a video from my phone of this happening if that helps. Is this a known problem? While my actions triggered this, the device seemed to be in a completely unrecoverable state. My panel has suitable backups, so I was fortunate enough to be able to continue the flight to a safe landing.

    Thanks,

    Don

  2. #2
    Advanced Flight Systems, Inc.
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    Don,

    What type of system do you have (s or non-s CPU)? Can you tell us your serial number? To turn a unit off after master power has been removed, press and hold button 2, 3, 4, or 5. Button 1 provides a hardware path to apply power to the unit via the battery. Pressing button 1 along with other buttons can cause unpredictable results. Please help us know more about your unit so we can help diagnose the issue and get it resolved for you.


    Most likely the cause of the oil temp changing from internal battery and aircraft power is not having a good ground wire to the EFIS case ground screw or a bad engine case ground wire. Do you have a ground wire connected to the case ground screw on the back of the EFIS?

    What version of software were you running?
    Last edited by Trevor Conroy; 10-11-2010 at 10:34 AM.
    ---
    Trevor Conroy
    Technical Support
    Advanced Flight Systems
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  3. #3
    Quote Originally Posted by Trevor Conroy View Post
    Don,

    What type of system do you have (s or non-s CPU)? Can you tell us your serial number?
    I have a non-s system. I'll follow up with SN.

    Quote Originally Posted by Trevor Conroy View Post
    To turn a unit off after master power has been removed, press and hold button 2, 3, 4, or 5. Button 1 provides a hardware path to apply power to the unit via the battery. Pressing button 1 along with other buttons can cause unpredictable results. Please help us know more about your unit so we can help diagnose the issue and get it resolved for you.
    So I did try holding down [5] by itself, and that did not work. I did not try [2+3+4] as per the manual - a case of RTFM on my part. No joke on the "unpredictable" result thing.

    I spoke to another AF3500 owner who said he used button [3] to recycle power in flight...

    Quote Originally Posted by Trevor Conroy View Post
    Most likely the cause of the oil temp changing from internal battery and aircraft power is not having a good ground wire to the EFIS case ground screw or a bad engine case ground wire. Do you have a ground wire connected to the case ground screw on the back of the EFIS?
    I don't have a ground wire running to that screw. I'll take care of this immediately. I'm not too hopeful this will make any difference because I have checked for continuity with that screw to ship ground before, and it was fine (grounded through mounting). I'll double-check and install the ground wire regardless.

    Quote Originally Posted by Trevor Conroy View Post
    What version of software were you running?
    The last update file I applied was "AF3000V70104-MV12-AV40", some time back.

    Thanks for the reply.

  4. #4
    Advanced Flight Systems, Inc.
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    I don't have a ground wire running to that screw. I'll take care of this immediately. I'm not too hopeful this will make any difference because I have checked for continuity with that screw to ship ground before, and it was fine (grounded through mounting). I'll double-check and install the ground wire regardless.
    As an aside and benefit to others: This is a HUGE problem with many customers who have fluctuating oil temp/pressure/fuel psi readings. Due to a poor engine ground, the alternator uses our sensor as a ground which causes major problems with sensor readings. Mounting screws are a poor ground and should not be relied on. Just because a multi-meter says there is continuity between the engine and firewall, for example, doesn't mean there is an adequate one. A 26AGW wire would show a low resistance reading on a multi-meter, yet is completely unacceptable for an engine ground (where there should be large braided ground straps from the engine to engine mount and/or firewall).
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    Trevor Conroy
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  5. #5
    I "misremembered" about the ground wire. Lesson: don't trust the memory so much when you're over 40. It's installed, and I double-checked continuity. My panel originally came from a panel shop without that ground wire, but I noticed the omission and installed it long ago. Note that I have never had any fluctuating reading issues with fuel, pressure, etc. Only in the past 40-50 hours have I had periodic oil temp issues. I've replaced the probe and more recently the vernatherm. So it was with a new probe and new vernatherm that I noticed that pulling the breaker on the AF3500 causes a magically instant 20 degree immediate change in oil temp.

    Unfortunately, I guess I'm back to the drawing board on trouble-shooting oil temp.
    At least I can avoid the funky reboot failure, though you guys should eventually try to fix that.

  6. #6
    Advanced Flight Systems, Inc.
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    What happens to oil pressure when you turn off the Alt Field switch mid-flight?
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    Trevor Conroy
    Technical Support
    Advanced Flight Systems
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  7. #7
    Oil temperature, not pressure. The Oil temp goes to a normal reading when I disable the ALT. Again, on many flights, the oil temp just stays on 187. The other day it was reading 230, with all other cht/egt temperatures normal to low. I disabled ALT, and the temps dropped to 180.

  8. #8
    Advanced Flight Systems, Inc.
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    Excellent, that isolates the problem. Your alternator is using our sensor as a ground path through your engine to the electrical system. You will need to install a large gauge wire from your engine to the mount and firewall and ground bus to ensure your alternator has a low resistance path (that can handle 60 amps of current).
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    Trevor Conroy
    Technical Support
    Advanced Flight Systems
    Support@Advanced-Flight-Systems.com

  9. #9
    Junior Member
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    Trevor,
    That wire should be able to handle the current that the starter motor draws. That would be quite a bit more than the alternator puts out.

  10. #10
    Advanced Flight Systems, Inc.
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    That is a great point!
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    Trevor Conroy
    Technical Support
    Advanced Flight Systems
    Support@Advanced-Flight-Systems.com

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