REQUIRED_NODES_MISSING
Applicable alarms (1)
Likely outcomes — click to expand
Based on 23 missions where this alarm fired in the last 90 days as of 2026-10-13
Grounding vs discrepancy (of 2 ZERP issues filed on these missions)
Aggregated from fleet operations and refreshed daily. Individual outcomes may vary by site and configuration.
Background
Section titled “Background”This alarm means the distro hover configuration checker did not detect one or more required hover nodes.
This is commonly accompanied by one or more *_MISSING alarms that identify the affected hover corner.
Distro A only receives hover identity traffic in one direction around the hover ethernet ring. Because of that, a broken link or damaged flex can make a healthy downstream node appear missing to the checker. Depending on which link is down, multiple hover nodes may appear missing.
Baraza or flight logs may still show hover identity messages for those nodes because the compute path receives traffic in both directions around the ring. For this alarm, use the distro alarm set together with the hover identity topics and hover / tail link status messages to identify whether the failure is a true missing node or a ring-link issue.
See DISTRO HOVER CONFIGURATION CHECKER for a description of how the diagnostic works.
Signals to check in Baraza
Section titled “Signals to check in Baraza”First check the hover identity topics:
/hover_port_fwd.identity/hover_port_aft.identity/hover_stbd_fwd.identity/hover_stbd_aft.identity
If one of these identity topics is missing, the issue is likely local to that hover motor unit, its harness, or its power / connection path.
If all four identity topics are present but REQUIRED_NODES_MISSING is still active, check the link-status signals below. The most useful fields are the fully qualified alarms.PORT_A_LINK_FAULT / alarms.PORT_B_LINK_FAULT, port_a_link_monitor_status / port_b_link_monitor_status, and port_a_link_alarm_reason / port_b_link_alarm_reason fields on the listed topics.
HOVER_PORT_FWD_MISSING
Section titled “HOVER_PORT_FWD_MISSING”- Identity topic:
/hover_port_fwd.identity - Clockwise link status:
/hover_port_fwd.comm_status.port_b_link_monitor_status/hover_port_fwd.comm_status.alarms.PORT_B_LINK_FAULT/distro_b.comm_status.port_ring_link_monitor_status/distro_b.comm_status.alarms.PORT_RING_LINK_FAULT
- Counter-clockwise link status:
/hover_port_fwd.comm_status.port_a_link_monitor_status/hover_port_fwd.comm_status.alarms.PORT_A_LINK_FAULT/tail_bridge.comm_status.port_a_link_monitor_status/tail_bridge.comm_status.alarms.PORT_A_LINK_FAULT
HOVER_PORT_AFT_MISSING
Section titled “HOVER_PORT_AFT_MISSING”- Identity topic:
/hover_port_aft.identity - Clockwise link status:
/hover_port_aft.comm_status.port_b_link_monitor_status/hover_port_aft.comm_status.alarms.PORT_B_LINK_FAULT/tail_bridge.comm_status.port_b_link_monitor_status/tail_bridge.comm_status.alarms.PORT_B_LINK_FAULT
- Counter-clockwise link status:
/hover_port_aft.comm_status.port_a_link_monitor_status/hover_port_aft.comm_status.alarms.PORT_A_LINK_FAULT/hover_stbd_aft.comm_status.port_b_link_monitor_status/hover_stbd_aft.comm_status.alarms.PORT_B_LINK_FAULT
HOVER_STBD_AFT_MISSING
Section titled “HOVER_STBD_AFT_MISSING”- Identity topic:
/hover_stbd_aft.identity - Clockwise link status:
/hover_stbd_aft.comm_status.port_a_link_monitor_status/hover_stbd_aft.comm_status.alarms.PORT_A_LINK_FAULT/hover_port_aft.comm_status.port_b_link_monitor_status/hover_port_aft.comm_status.alarms.PORT_B_LINK_FAULT
- Counter-clockwise link status:
/hover_stbd_aft.comm_status.port_b_link_monitor_status/hover_stbd_aft.comm_status.alarms.PORT_B_LINK_FAULT/hover_stbd_fwd.comm_status.port_a_link_monitor_status/hover_stbd_fwd.comm_status.alarms.PORT_A_LINK_FAULT
HOVER_STBD_FWD_MISSING
Section titled “HOVER_STBD_FWD_MISSING”- Identity topic:
/hover_stbd_fwd.identity - Clockwise link status:
/hover_stbd_fwd.comm_status.port_a_link_monitor_status/hover_stbd_fwd.comm_status.alarms.PORT_A_LINK_FAULT/distro_a.comm_status.port_ring_link_monitor_status/distro_a.comm_status.alarms.PORT_RING_LINK_FAULT
- Counter-clockwise link status:
/hover_stbd_fwd.comm_status.port_b_link_monitor_status/hover_stbd_fwd.comm_status.alarms.PORT_B_LINK_FAULT/hover_stbd_aft.comm_status.port_a_link_monitor_status/hover_stbd_aft.comm_status.alarms.PORT_A_LINK_FAULT
Troubleshooting Steps
Section titled “Troubleshooting Steps”Related pages
Section titled “Related pages”graph TD
is-draft-required-nodes-missing-active{"<small><b>Step 1</b></small><br/>Question: Is REQUIRED_NODES_MISSING active on..."}
power-cycle-the-vehicle-and-send-a{"<small><b>Step 2</b></small><br/>Question: Power cycle the vehicle and send a pr..."}
the-aircraft-may-return-to-service["<small><b>Step 3</b></small><br/>Action: The aircraft may return to service."]
identify-the-affected-hover-corner["<small><b>Step 4</b></small><br/>Action: Identify the affected hover corner fr..."]
in-baraza-check-whether-all-four["<small><b>Step 5</b></small><br/>Action: In Baraza, check whether all four hov..."]
if-the-affected-hover-identity["<small><b>Step 6</b></small><br/>Action: If the affected hover identity topic ..."]
if-all-four-hover-identity-topic["<small><b>Step 7</b></small><br/>Action: If all four hover identity topics are..."]
correct-any-installation-issue["<small><b>Step 8</b></small><br/>Action: Correct any installation issue, resea..."]
run-an-ota-to-update-firmware-and["<small><b>Step 9</b></small><br/>Action: Run an OTA to update firmware and hov..."]
send-a-preflight-mission-again-did{"<small><b>Step 10</b></small><br/>Question: Send a preflight mission again. Did p..."}
the-aircraft-may-return-to-service-2["<small><b>Step 11</b></small><br/>Action: The aircraft may return to service."]
escalate-to-p2-firmware-motors-on{{"<small><b>Step 12</b></small><br/>Escalation: Escalate to P2 Firmware Motors On Call."}}
continue-troubleshooting-using-the["<small><b>Step 13</b></small><br/>Action: Continue troubleshooting using the al..."]
is-draft-required-nodes-missing-active -->|Yes| power-cycle-the-vehicle-and-send-a
is-draft-required-nodes-missing-active -->|No| continue-troubleshooting-using-the
power-cycle-the-vehicle-and-send-a -->|Yes| the-aircraft-may-return-to-service
power-cycle-the-vehicle-and-send-a -->|No| identify-the-affected-hover-corner
identify-the-affected-hover-corner --> in-baraza-check-whether-all-four
in-baraza-check-whether-all-four --> if-the-affected-hover-identity
if-the-affected-hover-identity --> if-all-four-hover-identity-topic
if-all-four-hover-identity-topic --> correct-any-installation-issue
correct-any-installation-issue --> run-an-ota-to-update-firmware-and
run-an-ota-to-update-firmware-and --> send-a-preflight-mission-again-did
send-a-preflight-mission-again-did -->|Yes| the-aircraft-may-return-to-service-2
send-a-preflight-mission-again-did -->|No| escalate-to-p2-firmware-motors-on
style is-draft-required-nodes-missing-active fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style power-cycle-the-vehicle-and-send-a fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style the-aircraft-may-return-to-service fill:#dcfce7,stroke:#22c55e,color:#14532d
style identify-the-affected-hover-corner fill:#dcfce7,stroke:#22c55e,color:#14532d
style in-baraza-check-whether-all-four fill:#dcfce7,stroke:#22c55e,color:#14532d
style if-the-affected-hover-identity fill:#dcfce7,stroke:#22c55e,color:#14532d
style if-all-four-hover-identity-topic fill:#dcfce7,stroke:#22c55e,color:#14532d
style correct-any-installation-issue fill:#dcfce7,stroke:#22c55e,color:#14532d
style run-an-ota-to-update-firmware-and fill:#dcfce7,stroke:#22c55e,color:#14532d
style send-a-preflight-mission-again-did fill:#dbeafe,stroke:#3b82f6,color:#1e3a5f
style the-aircraft-may-return-to-service-2 fill:#dcfce7,stroke:#22c55e,color:#14532d
style escalate-to-p2-firmware-motors-on fill:#fef3c7,stroke:#f59e0b,color:#78350f
style continue-troubleshooting-using-the fill:#dcfce7,stroke:#22c55e,color:#14532d Hover or focus a block to preview it. Select the block to keep the preview open.
REQUIRED_NODES_MISSING active on /distro_a.power_status?*_MISSING alarm./hover_port_fwd.identity, /hover_port_aft.identity, /hover_stbd_fwd.identity, and /hover_stbd_aft.identity.Resolution note
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