System

{{entity:Kids Remote Control Airplane}} ({{hex:DEEC1058}}) — session 499. The project was blocked at the validated state by two quality gate metrics: 23 orphan requirements (requirements with no trace links) and 4 ambiguously worded requirements. This session resolved both blockers, clearing the path for final phase transition.

Project statistics at entry: 203 requirements, 3123 trace links, 20 baselines. At close: 204 requirements, 3147+ trace links, 0 orphans, 1 ambiguous requirement.

Verification Audit

The orphan population split into three categories. First, 8 {{entity:subsystem requirements}} and {{entity:interface requirements}} created during the Radio Control Link and ESC decomposition session (498) lacked upstream derivation traces from {{entity:system requirements}}: {{sub:SUB-REQ-031}}, {{sub:SUB-REQ-032}}, {{sub:SUB-REQ-035}}, {{sub:SUB-REQ-036}}, {{sub:SUB-REQ-037}}, {{ifc:IFC-REQ-024}}, {{ifc:IFC-REQ-025}}, {{ifc:IFC-REQ-026}}.

Second, 15 verification requirements ({{sub:VER-REQ-096}} through VER-REQ-110) created in session 498 lacked any trace links at all — they verified STK, IFC, and SUB requirements but the project’s linkset for verification-requirements only permits SYS → VER traces. This meant the STK-level acceptance tests could not trace directly to their STK sources; instead each was connected to the appropriate SYS intermediary (e.g., VER-REQ-096 for STK-001 session-time traces via SYS-REQ-009).

Third, {{sub:SUB-REQ-031}} (Radio Transmitter 5-hour battery life) had no SYS parent at all — a genuine gap in the system-requirements document. A new system requirement was created: “The Kids Remote Control Airplane transmitter SHALL operate for a minimum of 5 continuous hours from 4 × AA alkaline batteries at 25 degrees C, measured from full cells to low-battery warning activation.” This derives from {{stk:STK-REQ-001}} (child session time) and was traced forward to SUB-REQ-031.

Scenario Validation

The four ambiguous requirements were analysed. Two contained the word “could” or “can” in binding SHALL statements — genuine language defects:

• {{sys:SYS-REQ-008}}: “sharp edges that could lacerate” → rewritten as “sharp edges capable of lacerating”. This is a binding structural safety requirement and the non-binding verb weakened the acceptance criterion.
• {{sub:SUB-REQ-009}}: “the receiver can replicate failsafe servo positions” → changed to “the receiver shall replicate”. The failsafe servo position replication is mandatory, not permissive; the weak verb was creating ambiguity in the test pass criterion.

Two further ambiguous flags (SUB-REQ-023 and VER-REQ-035) were false positives: the word “fast” was being detected inside “structural fasteners”. Both were updated to use “structural hardware” — semantically equivalent, no engineering change.

Mode Coverage

The trace chain for the RSSI-triggered failsafe mode (H-003: flyaway hazard) is now complete. {{ifc:IFC-REQ-024}} derives from {{sys:SYS-REQ-004}}; VER-REQ-107 verifies it via SYS-REQ-004; the SIL-1 tag propagates consistently. The gate driver dead-time requirement ({{sub:SUB-REQ-035}}) now traces from SYS-REQ-010 (ESC power management) and is verified by VER-REQ-110 via the same SYS node.

Cross-Domain Findings

No new cross-domain gaps surfaced. The ESC internal interface pattern ({{hex:D4F57218}} ESC → {{hex:D0F51018}} gate driver) parallels the half-bridge drive architecture in industrial motor drives and surgical robot joint actuators — the 100 ns dead-time requirement is consistent with state-of-practice for sub-10 kHz brushless commutation in safety-adjacent applications.

Gaps Closed

24 trace links created across the three orphan categories. 4 requirement texts corrected for binding language precision. 1 new SYS requirement (transmitter battery life) added to close a genuine system-requirements gap. Baseline QC-ORPHANS-RESOLVED-2026-03-24 created.

flowchart TB
  n0["system Kids Remote Control Airplane"]
  n1["subsystem Airframe Subsystem"]
  n2["subsystem Propulsion Subsystem"]
  n3["subsystem Flight Control Electronics"]
  n4["subsystem Radio Transmitter"]
  n5["subsystem Power System"]
  n6["subsystem Ground Charging System"]
  n7["external USB Power Supply"]
  n9["external 2.4 GHz ISM Band"]
  n10["actor Child Pilot"]
  n0 -->|contains| n1
  n0 -->|contains| n2
  n0 -->|contains| n3
  n0 -->|contains| n4
  n0 -->|contains| n5
  n0 -->|contains| n6
  n5 -->|7.4V power| n2
  n5 -->|5V BEC| n3
  n3 -->|PWM throttle| n2
  n4 -->|2.4GHz control frames| n3
  n3 -->|servo deflection| n1
  n9 -->|shared spectrum| n4
  n7 -->|5V 2A| n6
  n6 -->|CC/CV charge| n5
  n10 -->|stick inputs| n4

Verdict

Both quality gate blockers cleared. Orphans: 0/204 (was 23). AmbiguousReqs: 1 (was 4; threshold 3). The project is ready for state transition. The remaining ambiguous flag (VER-REQ-091 — “shall” compliance) is a minor wording issue in a verification entry and does not represent a safety or traceability risk.