Mixed Motor Missing Feedback
Applicable alarms (2)
Likely outcomes — click to expand
Based on 856,009 missions where this alarm fired in the last
90 days
(for MIXED_MISSING_FEEDBACK) as of 2026-10-13
Grounding vs discrepancy (of 5,270 ZERP issues filed on these missions)
Top work orders
- EV3: Inspect Aircraft after Droid Left Behind (DLB) · MAINTENANCE_ACTION 215
- EV2: Replace Aft Motor Assembly on Aircraft · MAINTENANCE_ACTION 90
- Troubleshoot Hover Motor Resistance on Aircraft · INSPECTION 78
- 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 | 986 |
| CW/CCW HOVER MOTOR ASSY, ZIP, P2 | 19607 | 811 |
| ASSY, SPOOL AND LINE, DOCKING FIN, AIRCRAFT, P2 | 48477 | 782 |
| AFT MOTOR ASSY, ZIP, P2 | 23548 | 730 |
| PRE-PREG TAIL ASSY STBD(RH), ZIP, P2 | 21840 | 624 |
Aggregated from fleet operations and refreshed daily. Individual outcomes may vary by site and configuration.
Background
Section titled “Background”The GNC Zip Controller faulted the mixed motor because expected feedback messages were missing. This usually points to a hardware communication issue, though firmware or compute issues are possible if comms checks do not explain the alarm.
Troubleshooting Steps
Section titled “Troubleshooting Steps”graph TD
check-rs485-comms["<small><b>Step 1</b></small><br/>Telemetry: Check whether missing feedback is cau..."]
select-aircraft-build-version{"<small><b>Step 2</b></small><br/>Question: What is the aircraft build version?"}
inspect-mixed-harness["<small><b>Step 3</b></small><br/>Action: Assign Work Order Template 1100: EV2..."]
inspect-ev3-mixed-motor-hirose-connector["<small><b>Step 4</b></small><br/>Action: Assign Work Order Template 1118: EV3..."]
check-companion-alarms{"<small><b>Step 5</b></small><br/>Question: Was this Exec watchdog alarm set duri..."}
follow-motor-control-guide["<small><b>Step 6</b></small><br/>Action: Follow the troubleshooting guide for ..."]
escalate-firmware-platform{{"<small><b>Step 7</b></small><br/>Escalation: Escalate to P2 Firmware Platform On C..."}}
check-rs485-comms -->|Yes, poor comms are present| select-aircraft-build-version
check-rs485-comms -->|No, poor comms are not present| check-companion-alarms
select-aircraft-build-version -->|EV2| inspect-mixed-harness
select-aircraft-build-version -->|EV3| inspect-ev3-mixed-motor-hirose-connector
check-companion-alarms -->|Yes, MOTOR_CONTROL_FEEDBACK...| follow-motor-control-guide
check-companion-alarms -->|No, MOTOR_CONTROL_FEEDBACK_...| escalate-firmware-platform
style select-aircraft-build-version fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style inspect-mixed-harness fill:#dcfce7,stroke:#22c55e,color:#14532d
style inspect-ev3-mixed-motor-hirose-connector fill:#dcfce7,stroke:#22c55e,color:#14532d
style check-companion-alarms fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style follow-motor-control-guide fill:#dcfce7,stroke:#22c55e,color:#14532d
style escalate-firmware-platform fill:#fef3c7,stroke:#f59e0b,color:#78350f Hover or focus a block to preview it. Select the block to keep the preview open.
Load the plot below and look for signs that messages from the mixed motor were being missed or corrupted. Poor comms are present if either of these is true outside a power cycle:
- The message counter jump, shown as
message_sequence_number(delta), goes above 1.- The RX frame error count goes above 10.
Ignore jumps that happen during an aircraft power cycle. A power cycle usually looks like several signals resetting at the same time, and Show Alarms should show power-cycle or reboot activity nearby. If the message counter goes negative, use Show Alarms to zoom in on the part of the mission near this missing-feedback alarm before deciding.
Representative poor-comms example:
Does the plot show poor comms at the mixed motor?
- MOTOR_CONTROL_FEEDBACK_MIXED_UNAVAILABLE
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:
Session is too large to fit in a URL. Use Download session JSON to share the timeline out-of-band.
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