Differential Pressure Alarms
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Applicable alarms (4)
DIFFERENTIAL_PRESSURE_DISAGREEMENT_DETECTEDDIFFERENTIAL_PRESSURE_FUSION_REJECTEDDIFFERENTIAL_PRESSURE_INPUT_INVALIDDIFF_PRES_TIMED_OUT
Likely outcomes — click to expand
Based on 463,651 missions where this alarm fired in the last
90 days
(for DIFF_PRES_TIMED_OUT) as of 2026-10-13
Grounding vs discrepancy (of 3,331 ZERP issues filed on these missions)
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 97
Frequently replaced parts
| Part | P/N | Removals |
|---|---|---|
| SERVO, ASSY, UNIVERSAL, P2 | 20398 | 929 |
| HOVER MOTOR ASSY, CCW MOTOR, ZIP, P2 | 19607 | 638 |
| TAIL ASSY STBD(RH), PRE-EV2, ZIP, P2 | 21840 | 582 |
| PRE-PREG TAIL ASSY PORT(LH), 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
Section titled “Background”These alarms indicate that differential-pressure data is invalid (DIFFERENTIAL_PRESSURE_INPUT_INVALID), is persistently rejected by the wind estimator (DIFFERENTIAL_PRESSURE_FUSION_REJECTED), or disagrees with the aircraft model (DIFFERENTIAL_PRESSURE_DISAGREEMENT_DETECTED). The legacy DIFF_PRES_TIMED_OUT alarm can indicate missing or invalid data, or fusion rejection.
Likely causes include air-data blockage, weather effects, sensor issues, or abnormal mixed-motor or hover-motor behavior. Follow the steps below to distinguish input-health problems from air-data or aircraft-performance issues.
Troubleshooting Steps
Section titled “Troubleshooting Steps”graph TD
identify-differential-pressure-alarm{"<small><b>Step 1</b></small><br/>Question: Which differential-pressure alarm is ..."}
check-concurrent-sensor-alarm{"<small><b>Step 2</b></small><br/>Question: Does DIFFERENTIAL_PRESSURE_SENSOR_UN..."}
follow-unreliable-sensor-guide("<small><b>Step 3</b></small><br/>Reference: Follow Suspect Compute A Air Data Co...")
inspect-air-data["<small><b>Step 4</b></small><br/>Action: Inspect the air data system and nose ..."]
check-high-drag-validator["<small><b>Step 5</b></small><br/>Telemetry: Load the failed maintenance validator..."]
did-the-high-drag-validator-fail{"<small><b>Step 6</b></small><br/>Question: Did the high drag validator fail?"}
perform-high-drag-inspection["<small><b>Step 7</b></small><br/>Action: Perform the High Drag Zip Inspection..."]
check-weather{"<small><b>Step 8</b></small><br/>Question: In Baraza, open the affected flight's..."}
check-weather-map{"<small><b>Step 9</b></small><br/>Question: Check the weather at the aircraft loc..."}
weather-transient-blockage["<small><b>Step 10</b></small><br/>Action: This likely indicates a transitory ai..."]
escalate-zip-controls{{"<small><b>Step 11</b></small><br/>Escalation: Escalate to P2 Zip Controls On Call."}}
identify-differential-pressure-alarm -->|DIFFERENTIAL_PRESSURE_INPUT...| inspect-air-data
identify-differential-pressure-alarm -->|DIFF_PRES_TIMED_OUT without...| check-concurrent-sensor-alarm
check-concurrent-sensor-alarm -->|Yes| follow-unreliable-sensor-guide
check-concurrent-sensor-alarm -->|No| inspect-air-data
inspect-air-data --> check-high-drag-validator
check-high-drag-validator --> did-the-high-drag-validator-fail
did-the-high-drag-validator-fail -->|Yes| perform-high-drag-inspection
did-the-high-drag-validator-fail -->|No| check-weather
perform-high-drag-inspection --> check-weather
check-weather -->|true — at least 1 mm| weather-transient-blockage
check-weather -->|false — less than 1 mm| escalate-zip-controls
check-weather -->|null or missing| check-weather-map
check-weather-map -->|Yes| weather-transient-blockage
check-weather-map -->|No| escalate-zip-controls
style identify-differential-pressure-alarm fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style check-concurrent-sensor-alarm fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style follow-unreliable-sensor-guide fill:#f3e8ff,stroke:#a855f7,color:#581c87
style inspect-air-data fill:#dcfce7,stroke:#22c55e,color:#14532d
style did-the-high-drag-validator-fail fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style perform-high-drag-inspection fill:#dcfce7,stroke:#22c55e,color:#14532d
style check-weather fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style check-weather-map fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style weather-transient-blockage fill:#dcfce7,stroke:#22c55e,color:#14532d
style escalate-zip-controls fill:#fef3c7,stroke:#f59e0b,color:#78350f Hover or focus a block to preview it. Select the block to keep the preview open.
1 question
Which differential-pressure alarm is present?
2 question
Does
DIFFERENTIAL_PRESSURE_SENSOR_UNRELIABLE also appear in the alarm list? 3 reference
Follow Suspect Compute A Air Data Comms Issue to troubleshoot
DIFFERENTIAL_PRESSURE_SENSOR_UNRELIABLE. 4 action
Inspect the air data system and nose cone. Look particularly for blockages or debris in the pitot tube and static ports, or for any damage/abnormalities that might interfere with sensor readings.
For EV2, use the following guides:
UMM 53.1.7.a Inspect Nose Cone – General
UMM 42.4.1.a Inspect Angle of Attack Vane
For EV3, use the following guides:
UMM 53.1.8.a Inspect Nose Cone
UMM 42.3.1.a Inspect Angle of Attack Vane
If no issue is found, proceed to the next section of this guide.
For EV2, use the following guides:
UMM 53.1.7.a Inspect Nose Cone – General
UMM 42.4.1.a Inspect Angle of Attack Vane
For EV3, use the following guides:
UMM 53.1.8.a Inspect Nose Cone
UMM 42.3.1.a Inspect Angle of Attack Vane
If no issue is found, proceed to the next section of this guide.
5 telemetry
Load the failed maintenance validator results for the affected mission. Look for the fixed-wing high drag maintenance validator,
high_drag_fixed_wing_maintenance/fixed_wing_drag_and_torque. Enter the mission identifier above to load failed maintenance validator results.
6 question
Did the high drag validator fail?
7 action
Perform the High Drag Zip Inspection. If no issue is found, return here and continue to the next step in the guide.
8 question
In Baraza, open the affected flight's metadata and inspect
What is the value?
weather.mrms.whole_flight.precip_accumulation_3h_before_takeoff_ge_1mm_mrms. This field is true when MRMS recorded at least 1 mm of precipitation at the aircraft location during the three hours before takeoff, false when it recorded less than 1 mm, and null when the metric is unavailable.What is the value?
9 question
Check the weather at the aircraft location and flight time by visiting the Weather Domain Awareness precipitation map. The time and site location can be adjusted using the slider and dropdown menu indicated in the screenshot:
Were there any reports of precipitation at the site region of the affected flight?
Were there any reports of precipitation at the site region of the affected flight?
10 action
This likely indicates a transitory air-data blockage due to weather. It is safe to try flying the zip again, but the issue is likely to repeat if weather conditions stay the same.
11 escalation
Escalate to P2 Zip Controls On Call.
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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