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Thread: Where do PFD / MFD take Zulu time from?

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  1. #1

    Where do PFD / MFD take Zulu time from?

    I observed that the Zulu time on all my screens is off by5h 33min.
    The plane is in the hangar and was parked there for 3 weeks without GPS reception.
    The IFD440 shows the correct time.
    1) Where does the AF-5000 get the time from?
    2) Why does it loose the time and the IFD440 not?

    Kind Regards

  2. #2
    The AF-5000 gets its time from the GPS almanac. The EFIS does not have an internal clock battery, rather, the EFIS backup battery is also the clock battery. If the TCW backup battery is ever disconnected, completely discharged, or the ATO fuse on the battery blows for any reason, then the EFIS will lose count of time.

  3. #3
    Thank you Jonathon. So once power is supplied and gps reception is available it would aufomatically pick up the correct Zulu time, correct?

  4. #4
    Correct. It is automatic but it does take 12.5 minutes to download the GPS almanac.

  5. #5
    The backup battery fuse has been burnt. I replaced it and I will have to check if the issue is now gone.

    Kind Regards
    Last edited by Michael; 10-23-2022 at 11:40 PM.

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