Suspect Compute A Air Data Comms Issue

published Last Updated: Oct 9, 2026 HW: all

ABSOLUTE_PRESSURE_SENSOR_UNRELIABLE absolute pressure sensor unreliable DIFFERENTIAL_PRESSURE_SENSOR_UNRELIABLE differential pressure sensor unreliable TEMPERATURE_SENSOR_UNRELIABLE temperature sensor unreliable ABSOLUTE_PRESSURE_INPUT_TIMED_OUT absolute pressure input timed out RELATIVE_HUMIDITY_INPUT_TIMED_OUT relative humidity input timed out AMBIENT_TEMPERATURE_INPUT_TIMED_OUT ambient temperature input timed out DIFFERENTIAL_PRESSURE_INPUT_TIMED_OUT differential pressure input timed out ABS_PRES_TIMED_OUT abs pres timed out HUMIDITY_TIMED_OUT humidity timed out AMB_TEMP_TIMED_OUT amb temp timed out suspect-compute-a-air-data-comms-issue suspect compute a air data comms issue

Applicable alarms (10)

ABSOLUTE_PRESSURE_SENSOR_UNRELIABLEDIFFERENTIAL_PRESSURE_SENSOR_UNRELIABLETEMPERATURE_SENSOR_UNRELIABLEABSOLUTE_PRESSURE_INPUT_TIMED_OUTRELATIVE_HUMIDITY_INPUT_TIMED_OUTAMBIENT_TEMPERATURE_INPUT_TIMED_OUTDIFFERENTIAL_PRESSURE_INPUT_TIMED_OUTABS_PRES_TIMED_OUTHUMIDITY_TIMED_OUTAMB_TEMP_TIMED_OUT

Likely outcomes (463,289 missions, 3,326 issues) — click to expand

Based on 463,289 missions where this alarm fired in the last 90 days (for ABS_PRES_TIMED_OUT) as of 2026-10-13

Grounding vs discrepancy (of 3,326 ZERP issues filed on these missions)

Grounding 30.4% (1,011 of 3,326 issues) Discrepancy 69.6% (2,315 of 3,326 issues)

Top work orders

EV2: Inspect Aircraft after Droid Left Behind (DLB) · MAINTENANCE_ACTION 304
EV2/EV3 Diagnostics Test Without Motors · INSPECTION 205
Inspect Droid after Droid Left Behind (DLB) · MAINTENANCE_ACTION 166
Reset Droid after DLB · REPAIR 165
EV3: Inspect Aircraft after Droid Left Behind (DLB) · MAINTENANCE_ACTION 95

Frequently replaced parts

Part	P/N	Removals
SERVO, ASSY, UNIVERSAL, P2	`20398`	929
CCW HOVER MOTOR ASSY, ZIP, P2	`19607`	638
TAIL STBD, ZIP, P2	`21840`	582
TAIL, FIXED WING, PORT, ZIP, P2	`31280`	554
AFT MOTOR ASSY, ZIP, P2	`23548`	488

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

Background

These alarms indicate a sensor error or unavailable pressure, humidity, or temperature input from the nose-cone air data module on Compute A. A persistent communications problem after reboot may indicate a faulty air data flex. Historical timeout alarms can also include invalid values; a timeout alone does not prove a communications failure.

Troubleshooting Steps

graph TD
    reboot-vehicle["<small><b>Step 1</b></small><br/>Action: In Fleet Wrangler, open the Aircraft ..."]
    run-preflight-after-reboot-a["<small><b>Step 2</b></small><br/>Action: Wait for the reboot mission to comple..."]
    is-problem-resolved-after-reboot-a{"<small><b>Step 3</b></small><br/>Question: Did the **Run Health Checks** mission..."}
    return-to-service-after-reboot["<small><b>Step 4</b></small><br/>Action: Return the Zip to service."]
    replace-nose-cone["<small><b>Step 5</b></small><br/>Action: Assign and complete the nose-cone rep..."]
    run-preflight-after-replacement["<small><b>Step 6</b></small><br/>Action: After the replacement work order is c..."]
    does-preflight-pass-after-replacement{"<small><b>Step 7</b></small><br/>Question: Did the **Run Health Checks** mission..."}
    return-to-service-after-replacement["<small><b>Step 8</b></small><br/>Action: Return the Zip to service."]
    contact-embedded-linux-oncall{{"<small><b>Step 9</b></small><br/>Escalation: Escalate to P2 Embedded Linux On Call."}}
    reboot-vehicle --> run-preflight-after-reboot-a
    run-preflight-after-reboot-a --> is-problem-resolved-after-reboot-a
    is-problem-resolved-after-reboot-a -->|Yes| return-to-service-after-reboot
    is-problem-resolved-after-reboot-a -->|No| replace-nose-cone
    replace-nose-cone --> run-preflight-after-replacement
    run-preflight-after-replacement --> does-preflight-pass-after-replacement
    does-preflight-pass-after-replacement -->|Yes| return-to-service-after-replacement
    does-preflight-pass-after-replacement -->|No| contact-embedded-linux-oncall
    style reboot-vehicle fill:#dcfce7,stroke:#22c55e,color:#14532d
    style run-preflight-after-reboot-a fill:#dcfce7,stroke:#22c55e,color:#14532d
    style is-problem-resolved-after-reboot-a fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
    style return-to-service-after-reboot fill:#dcfce7,stroke:#22c55e,color:#14532d
    style replace-nose-cone fill:#dcfce7,stroke:#22c55e,color:#14532d
    style run-preflight-after-replacement fill:#dcfce7,stroke:#22c55e,color:#14532d
    style does-preflight-pass-after-replacement fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
    style return-to-service-after-replacement fill:#dcfce7,stroke:#22c55e,color:#14532d
    style contact-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.

1 action

In Fleet Wrangler, open the Aircraft asset view, select Mission Request, choose Reboot Zip (.15+), and click Submit. This reboots both computes and the stowed Droid.

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Topic history

2026-10-07 Susan Minne Bulk/mechanical change

Replace individual guide ownership with system technical contacts

Commit dca5a1a
2026-09-30 Jason Xu

Clarify air-data comms health checks and replacement work orders

Commit 07554b9
2026-09-29 Jason Xu

Link hardware-specific UMM air-data replacement procedures

Commit e40ecd5

Baseline import

Initial import into service_docs

Imported by Jason Xu on 2026-09-28

Update wind-estimator alarm guides and split air-data comms by compute

Commit fb09f88

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