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Thread: AFCS Communication Error

  1. #1
    Senior Member Andy's Avatar
    Join Date
    Dec 2019
    Glendale, AZ

    Default AFCS Communication Error

    FX-3 with G3X Touch and AFCS option -

    Soon after engine start observed Message - "Network communication error - check wiring" and AFCS FMA message "AFCS COMMUNICATION ERROR". Both messages persisted until G3X system was re-booted by cycling Master and IBBS. This message pair has been seen only once in about 90 hours operation.

    Data log review shows the fault was annunciated at the end of AFCS PFT which is initiated when servos are first powered (Avionics bus energized and Servo switch is also on). Autopilot status shows a longer than normal PFT state then
    Fail/Servo communication fault/00000001 00000000, then FAIL.

    The status message "Fail/Servo communication fault/00000001 00000000" is not very informative as it's exactly the same message that is seen when G3X boots with servos not powered. (Every time the airplane is powered from cold)

    The data log shows engine RPM and Volts-1 stable before AFCS PFT begins so PFT failure cannot be attributed to abnormal voltage during engine start.

    I'm inclined to think this is a nuisance fault but if there really is a servo or wiring issue I'd like to fix it.

    Has anyone else seen this fault? If so, how often, and what was the resolution?

    Last edited by Andy; 12-17-2020 at 05:00 PM.

  2. #2
    Administrator Pete D's Avatar
    Join Date
    Jan 2010
    Yakima, WA

    Default Re: AFCS Communication Error

    I haven't seen this issue before. Maybe double check the connectors on the servos and make sure the thumb screws are all tight? Possibly the vibration from start up caused a momentary connection issue if it was slightly loose? Just guessing.
    Pete Dougherty
    R & D Shop Manager
    Cub Crafters Inc

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