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Zipline Zipline Service Documentation

    Validator: winch_fatigue

    published Last Updated: Oct 9, 2026 HW: all
    Section titled “Related Search Phrases”

    This issue may also be described as SUSPECT_CRACKED_WIRE

    Background

    Section titled “Background”

    This validator is intended to preemptively detect a cracked phase wire in the winch while the zip is still functional, before it escalates into an in-flight alarm. A failure on this validator indicates hardware damage that requires maintenance, even if the mission was successful.

    A cracked wire manifests as an periodic open circuit (high resistance) on that phase, resulting in periodic increases in voltage as the controller attempts to account for this. This noisiness in the voltage setpoints is the signal that the validator is checking to detect this failure mode.

    Previously, this guide requested log review checking for imbalanced heating to confirm the cracked wire. However, the imbalanced heating leading to overtemperature is merely a correlated symptom and does not account for all cases of this failure. As we get better at detecting faulted winches before they have degraded as far, only looking at temperature logs becomes increasingly subjective and so is no longer used in the troubleshooting workflow.

    The following example plots of the WINCH OVERTEMPERATURE - Check for phase imbalance template are shown as a reference only. A cracked phase wire may still be present even if its logs don’t look exactly like these examples.

    Click to show examples Example 1: Degraded winch motor, cracked wire on the instrumented side

    One of the winch winding temperatures (orange on the middle plot) is noticeably lower than the other two and does not show the same shape for its temperature spike(s) This temperature imbalance occurs while the winch is actively moving (non-zero feedout rate on the lower plot). If the winch is not moving, imbalanced temperatures are not evidence of or against this failure mode. Winch phase imbalance example1

    Example 2: Degraded winch motor, cracked wire on the uninstrumented side

    One of the winch winding temperatures (red on the middle plot) is noticeably higher than the other two and is at least 10C above the next hottest winding during winch operation. Winch phase imbalance example2

    Example 3: Severely degraded winch motor, complete failure of broken phase

    This plot does not look imbalanced because the faulted phase is no longer sending temperature data - note how the there are only two temperature signals on the middle plot instead of three. Winch phase imbalance example3

    Example 4: Early-stage degradation

    This plot does not show the expected temperature imbalance. If it weren’t for the validator failure, it would be easy to conclude that there is nothing wrong with the hardware. However, on this zip’s next mission, the temperature signal matured into one that looked much more like Example 1. Perhaps this specific case could be a candidate for deferred maintenance when it becomes available, but in the meantime this is still a hardware failure that requires a part swap.

    Winch phase imbalance example4

    Troubleshooting Steps

    Section titled “Troubleshooting Steps”
    1 telemetry
    First, confirm that the validator has failed.

    Verify that the Alarm Report for the CRITICAL_WORKFLOW_ERROR alarm in the Zerp Auto Issue is displaying a check failure for winch_fatigue/SUSPECT_CRACKED_WIRE.

    Alternatively, load the failed maintenance validator results for the affected mission. Check whether the winch fatigue validator Firmware_zip_a_maintenance.winch_fatigue/SUSPECT_CRACKED_WIRE failed.

    Paste the mission identifier from the alarm report. Failed maintenance validator results load in place below.

    Enter the mission identifier above to load failed maintenance validator results.

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    Topic history
    1. 2026-10-07 Susan Minne Bulk/mechanical change
      Replace individual guide ownership with system technical contacts
      Commit dca5a1a
    2. 2026-09-24 Susan Minne Bulk/mechanical change
      chore: backfill aircraft owner identities batch 4
      Commit d9b2270
    3. 2026-09-23 Susan Minne Bulk/mechanical change
      docs: remove obsolete Confluence metadata
      Commit 2d5374e
    4. 2026-09-13 Susan Minne Bulk/mechanical change
      feat: add MX approval metadata to topics
      Commit 406a785
    5. 2026-09-09 Roseann Chan
      Removes outdated temperature guidance from winch fatigue validator
      Commit 7f94b38
    6. 2026-07-13 Roseann Chan
      Uses validators to detect crack wire in winch OVERTEMPERATURE guide
      Commit 1e2f697
    7. 2026-06-12 Susan Minne Bulk/mechanical change
      Update troubleshooting topics and escalation paths
      Commit 166da10
    8. 2026-06-08 Roseann Chan
      Update winch fatigue validator check naming
      Commit cd3ccbf
    9. 2026-05-28 Susan Minne
      Update troubleshooting flows
      Commit 843e8b8
    10. 2026-05-09 Susan Minne Bulk/mechanical change
      Fix high-confidence internal documentation links
      Commit a6593fc
    11. 2026-05-06 Gavin Edwards Bulk/mechanical change
      Remove redundant Engineer Owner table from topic body (#298)
      Commit 1619f07 PR #298
    Baseline import
    Initial import into service_docs
    Imported by Gavin Edwards on 2026-05-06
    Migrate 2 missing P0 topics from #305
    Commit e23e35a
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