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Zipline Zipline Service Documentation

    PARACHUTE_DEGRADED

    published Last Updated: Oct 9, 2026 HW: all
    Applicable alarms (1)
    PARACHUTE_DEGRADED
    Likely outcomes (59 missions, 2 issues) — click to expand

    Based on 59 missions where this alarm fired in the last 90 days as of 2026-10-13

    Grounding vs discrepancy (of 2 ZERP issues filed on these missions)

    Grounding 0% (0 of 2 issues) Discrepancy 100% (2 of 2 issues)

    Frequently replaced parts

    Part P/N Removals
    PWR-DISTRO BOARD, ASSY, ZIP, P2 20817 5

    Frequently co-occurring alarms (% of the 59 missions above)

    CONTROL_FAILURE 89.8% of missions CAP_POWER_GOOD_FAILURE 88.1% of missions ANGLE_OF_ATTACK_INPUT_TIMED_OUT 54.2% of missions SOFTWARE_CONFIGURATION_EVALUATION_INCOMPLETE 52.5% of missions AMBIENT_TEMPERATURE_INPUT_TIMED_OUT 42.4% of missions

    Aggregated from fleet operations and refreshed daily. Individual outcomes may vary by site and configuration.

    Background

    Section titled “Background”

    PARACHUTE_DEGRADED is a general backup-power alarm in /distro_a.safety_status. Firmware sets it when the supercap state is outside its nominal charging, idle, or standby states, or when stack voltage is degraded in STANDBY. The alarm can block preflight, but does not identify the failed component. A first occurrence gets one full power cycle and preflight retry. An issue already raised in aircraft history moves to the more specific supercap checks without another power cycle. A recurrence after the retry escalates without further troubleshooting in this guide.

    Related squib faults have a separate Safety System Alarms guide. The EV3 Distro supercap ESR guide gives hardware-specific criteria for a failed distro_supercap/supercap_esr_range check and can direct a Distro replacement. An ESR alarm bit or PARACHUTE_DEGRADED alone does not establish that the Distro/PDB is unhealthy. Firmware Power owns diagnosis of other persistent supercap faults, and Service Engineering should coordinate any repair that diagnosis identifies. An Inspect PDB work order was suggested in SENG-108, but has not been confirmed as a standard response to PARACHUTE_DEGRADED.

    Troubleshooting Steps

    Section titled “Troubleshooting Steps”
    1 action
    Review this Aircraft's Zerp maintenance history and recent mission history for prior PARACHUTE_DEGRADED reports and power-cycle attempts.

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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
    Baseline import
    Initial import into service_docs
    Imported by Jake Federico on 2026-09-28
    Document PARACHUTE_DEGRADED triage for SENG-108
    Commit 40afeb2
    Suggest a change