Validator: winch/max_nis_encoder
Applicable alarms (1)
Likely outcomes — click to expand
Based on 0 missions where this alarm fired in the last 90 days as of 2026-10-13
Aggregated from fleet operations and refreshed daily. Individual outcomes may vary by site and configuration.
Background
Section titled “Background”The winch firmware maintains an estimate of the motor state such as rotor angle and phase currents. It then compares that state with what it measures and normalizes the error by how confident it was in its estimated state. This is NIS (normalized innovation squared). Values of NIS greater than one (1) indicate that measurements disagree with predictions more than expected, potentially indicating damaged, degraded, or miscalibrated hardware. Values of NIS smaller than one (1) indicate that measurements disagree with predictions less than expected, commonly arising from low noise conditions or mis-modelling of the measurement noise.
The winch encoder NIS typically sees average values of about one (1) while spinning quickly and values as low as 0.01 while stationary. Maximum values during a flight are typically around 1.5 to 1.8. If you were linked to this page by a validator, the winch you are troubleshooting likely has maximum NIS values above average.
Troubleshooting Steps
Section titled “Troubleshooting Steps”graph TD
is-the-winch-otherwise-holding-torque-n{"<small><b>Step 1</b></small><br/>Question: Is the winch otherwise holding torque..."}
recalibrate-the-winch-the-most-common-c["<small><b>Step 2</b></small><br/>Action: Recalibrate the winch. The most commo..."]
check-to-see-if-the-problem-has-been-re["<small><b>Step 3</b></small><br/>Action: Check to see if the problem has been ..."]
is-the-value-of-nis-encoder-from-step-2{"<small><b>Step 4</b></small><br/>Question: Is the value of nis_encoder from st..."}
escalate-to-p2-firmware-motors-on-call{{"<small><b>Step 5</b></small><br/>Escalation: Escalate to P2 Firmware Motors On Cal..."}}
the-aircraft-can-return-to-service["<small><b>Step 6</b></small><br/>Action: The Aircraft can return to service."]
look-for-any-other-errors-and-address-t["<small><b>Step 7</b></small><br/>Action: Look for any other errors and address..."]
is-the-winch-still-not-holding-torque{"<small><b>Step 8</b></small><br/>Question: Is the winch still not holding torque?"}
the-aircraft-can-return-to-service-2["<small><b>Step 9</b></small><br/>Action: The Aircraft can return to service."]
escalate-to-p2-firmware-motors-on-call-2{{"<small><b>Step 10</b></small><br/>Escalation: Escalate to P2 Firmware Motors On Cal..."}}
is-the-winch-otherwise-holding-torque-n -->|Yes| recalibrate-the-winch-the-most-common-c
is-the-winch-otherwise-holding-torque-n -->|No| look-for-any-other-errors-and-address-t
recalibrate-the-winch-the-most-common-c --> check-to-see-if-the-problem-has-been-re
check-to-see-if-the-problem-has-been-re --> is-the-value-of-nis-encoder-from-step-2
is-the-value-of-nis-encoder-from-step-2 -->|Yes| escalate-to-p2-firmware-motors-on-call
is-the-value-of-nis-encoder-from-step-2 -->|No| the-aircraft-can-return-to-service
look-for-any-other-errors-and-address-t --> is-the-winch-still-not-holding-torque
is-the-winch-still-not-holding-torque -->|The winch IS now holding to...| the-aircraft-can-return-to-service-2
is-the-winch-still-not-holding-torque -->|No, the winch is NOT holdin...| escalate-to-p2-firmware-motors-on-call-2
style is-the-winch-otherwise-holding-torque-n fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style recalibrate-the-winch-the-most-common-c fill:#dcfce7,stroke:#22c55e,color:#14532d
style check-to-see-if-the-problem-has-been-re fill:#dcfce7,stroke:#22c55e,color:#14532d
style is-the-value-of-nis-encoder-from-step-2 fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style escalate-to-p2-firmware-motors-on-call fill:#fef3c7,stroke:#f59e0b,color:#78350f
style the-aircraft-can-return-to-service fill:#dcfce7,stroke:#22c55e,color:#14532d
style look-for-any-other-errors-and-address-t fill:#dcfce7,stroke:#22c55e,color:#14532d
style is-the-winch-still-not-holding-torque fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style the-aircraft-can-return-to-service-2 fill:#dcfce7,stroke:#22c55e,color:#14532d
style escalate-to-p2-firmware-motors-on-call-2 fill:#fef3c7,stroke:#f59e0b,color:#78350f Hover or focus a block to preview it. Select the block to keep the preview open.
The most common cause of high encoder NIS is loss of calibration, e.g. because the screws holding the winch PCB to the winch motor weren’t sufficiently tightened which allowed the board to slip. Tighten the screws and recalibrate according to SB-2025-024, parts A and C.
- If implemented as a missions, the results can be checked in Baraza by looking at
estimator.nis_encoder in the /winch.debug message. Alternatively, this field is plotted near the bottom in the winch diag template.- If using Hawkeye, the value can be plotted by selecting
/winch.debug.estimator.nis_encoder.nis_encoder from step 2 exceeding 2.0 at any point?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.
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