GNSS_A_DEGRADED and GNSS_B_DEGRADED
Applicable alarms (2)
Likely outcomes — click to expand
Based on 897,538 missions where this alarm fired in the last
90 days
(for GNSS_A_DEGRADED) as of 2026-10-13
Grounding vs discrepancy (of 5,893 ZERP issues filed on these missions)
Top work orders
- EV3: Inspect Aircraft after Droid Left Behind (DLB) · MAINTENANCE_ACTION 212
- Troubleshoot Hover Motor Resistance on Aircraft · INSPECTION 77
- EV2: Troubleshoot Electrical Contacts on Aircraft and Droid · INSPECTION 72
- Reset Droid Lid · TROUBLESHOOTING 57
- EV2: ZCO-2026-08-03 Lower Foam Wear Pad Retrofit (FRCO-286 / SB-2026-023) · UPGRADE_RETROFIT 35
Frequently replaced parts
| Part | P/N | Removals |
|---|---|---|
| SERVO, ASSY, UNIVERSAL, P2 | 20398 | 983 |
| CCW HOVER MOTOR ASSY, EV3 ZIP, P2 | 19607 | 834 |
| ASSY, SPOOL AND LINE, DOCKING FIN, AIRCRAFT, P2 | 48477 | 770 |
| PRE-PREG TAIL ASSY STBD(RH), ZIP, P2 | 21840 | 765 |
| PRE-PREG TAIL ASSY, AL, PORT(LH), ZIP, P2 | 31280 | 728 |
Aggregated from fleet operations and refreshed daily. Individual outcomes may vary by site and configuration.
Background
Section titled “Background”This alarm occurs when the Aircraft is unable to observe the “typical” number and quality of GNSS satellites. In flight, it triggers a DOCK_ASAP to avoid flying with reduced redundancy, whereas in preflight it will block launch to prevent launching in an unsafe condition.
These events can be either environmental in origin (for example, a truck driver with a jamming device passing by), or specific to the Aircraft. Environmental causes are typically transient whereas Aircraft-related problems are generally persistent.
Aircraft causes can occur if any of the following hardware components are damaged:
- The GNSS antenna
- The coaxial cable between the antenna and the compute board
- The connector at the compute board
- The GNSS receiver module
- The serial link between the GNSS receiver and the Orin compute
The following software components are involved in handling this data:
- The GNSS driver (
gnss.service) - The PointOne “FusionEngine” (a child of
gnss.service) - The “slow” navigation stack (
navigation.service)
Troubleshooting Steps
Section titled “Troubleshooting Steps”graph TD
has-this-alarm-happened-multiple-times{"<small><b>Step 1</b></small><br/>Question: Has this alarm happened multiple time..."}
there-is-likely-interference-in-the-env["<small><b>Step 2</b></small><br/>Action: There is likely interference in the e..."]
was-the-alarm-set-in-flight{"<small><b>Step 3</b></small><br/>Question: Was the alarm set in flight?"}
check-for-previous-failure-and-reboot["<small><b>Step 4</b></small><br/>Action: This alarm should only cause the Airc..."]
was-there-a-previous-failure-and-reboot{"<small><b>Step 5</b></small><br/>Question: Before the current alarm, do you see ..."}
power-cycle-aircraft-and-return-to-service["<small><b>Step 6</b></small><br/>Action: Power cycle the Aircraft/procedure..."]
the-tail-antennas-need-maintenance["<small><b>Step 7</b></small><br/>Action: The tail antennas need maintenance. C..."]
has-this-alarm-happened-multiple-times -->|Yes, 3 or more times across...| there-is-likely-interference-in-the-env
has-this-alarm-happened-multiple-times -->|No, it is an isolated incid...| was-the-alarm-set-in-flight
there-is-likely-interference-in-the-env --> was-the-alarm-set-in-flight
was-the-alarm-set-in-flight -->|Yes. The alarm occurred in ...| check-for-previous-failure-and-reboot
was-the-alarm-set-in-flight -->|No. The alarm occurred in p...| the-tail-antennas-need-maintenance
check-for-previous-failure-and-reboot --> was-there-a-previous-failure-and-reboot
was-there-a-previous-failure-and-reboot -->|No, there was no earlier fa...| power-cycle-aircraft-and-return-to-service
was-there-a-previous-failure-and-reboot -->|Yes, there was an earlier f...| the-tail-antennas-need-maintenance
style has-this-alarm-happened-multiple-times fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style there-is-likely-interference-in-the-env fill:#dcfce7,stroke:#22c55e,color:#14532d
style was-the-alarm-set-in-flight fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style check-for-previous-failure-and-reboot fill:#dcfce7,stroke:#22c55e,color:#14532d
style was-there-a-previous-failure-and-reboot fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style power-cycle-aircraft-and-return-to-service fill:#dcfce7,stroke:#22c55e,color:#14532d
style the-tail-antennas-need-maintenance fill:#dcfce7,stroke:#22c55e,color:#14532d Hover or focus a block to preview it. Select the block to keep the preview open.
Consider a pause in operations to that service area if disruptive to customer experience, however vehicles are still clear to fly.
- GNSS A: EV2: use Work Order Template 24 and specify the STARBOARD tail. EV3: use Work Order Template 672 and specify the PORT tail.
- GNSS B: EV2: use Work Order Template 24 and specify the PORT tail. EV3: use Work Order Template 672 and specify the STARBOARD tail.
Resolution note
This plaintext block is ready to paste into the Resolution Note field on the ZERP issue you're working. The permalink below gives engineering review access to the full step-by-step timeline including any back-navigation; share it if the case needs a deeper look.
Permalink:
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