NO_CLOCK_SYNC
Applicable alarms (1)
Likely outcomes — click to expand
Based on 844 missions where this alarm fired in the last 90 days as of 2026-10-13
Grounding vs discrepancy (of 9 ZERP issues filed on these missions)
Aggregated from fleet operations and refreshed daily. Individual outcomes may vary by site and configuration.
Background
Section titled “Background”The system does not have a valid time source. It may not have GNSS fix, or access to the internet if it is docked. Preflight times out with NO_CLOCK_SYNC.
Troubleshooting Steps
Section titled “Troubleshooting Steps”Proceed to the next step.
graph TD
inspect-the-gnss-antenna-for-steps-see{"<small><b>Step 1</b></small><br/>Question: Inspect the GNSS antenna. For steps, ..."}
replace-the-antenna-for-steps-see["<small><b>Step 2</b></small><br/>Action: Replace the antenna. For steps, see: ..."]
power-cycle-the-aircraft-for-steps-see{"<small><b>Step 3</b></small><br/>Question: Power cycle the Aircraft. For steps, ..."}
return-the-aircraft-to-service("<small><b>Step 4</b></small><br/>Reference: Return the Aircraft to Service.")
escalate-to-embedded-linux-oncall{{"<small><b>Step 5</b></small><br/>Escalation: Escalate to P2 Embedded Linux On Call."}}
inspect-the-gnss-antenna-for-steps-see -->|Yes| replace-the-antenna-for-steps-see
inspect-the-gnss-antenna-for-steps-see -->|No| power-cycle-the-aircraft-for-steps-see
power-cycle-the-aircraft-for-steps-see -->|Yes| return-the-aircraft-to-service
power-cycle-the-aircraft-for-steps-see -->|No| escalate-to-embedded-linux-oncall
style inspect-the-gnss-antenna-for-steps-see fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style replace-the-antenna-for-steps-see fill:#dcfce7,stroke:#22c55e,color:#14532d
style power-cycle-the-aircraft-for-steps-see fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style return-the-aircraft-to-service fill:#f3e8ff,stroke:#a855f7,color:#581c87
style escalate-to-embedded-linux-oncall fill:#fef3c7,stroke:#f59e0b,color:#78350f Hover or focus a block to preview it. Select the block to keep the preview open.
- UMM: Remove Aft GNSS Antenna
- UMM: Install Aft GNSS Antenna
Resolution note
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