Coverage gaps closed — ESC failsafe, receiver timeout, stability augmentation verified

System

Kids Remote Control Airplane ({{entity:kids remote control airplane}}, {{hex:DEC81008}}). All 6 spec tree subsystems were marked complete by session 489. This session addressed the residual gap: zero verification requirements for stakeholder requirements, three lint-flagged high-severity findings, and seven SYS/STK concept coverage gaps identified by the semantic linter. Project now holds 127 requirements and 1,856 trace links.

Decomposition

No new subsystem decomposition — all subsystems complete. Session focused on deepening the existing decomposition with safety-critical SUB requirements that were missing, and backfilling VER entries for the requirements that already existed without verification.

The {{entity:Electronic Speed Controller}} ({{hex:D4F57218}}) was reclassified from its erroneous null code. Its new classification correctly reflects a {{trait:Powered}}, {{trait:Functionally Autonomous}}, {{trait:Processes Signals/Logic}} component. The Functionally Autonomous trait triggered a mandatory override/watchdog requirement ({{sub:SUB-REQ-025}}) that had been absent.

flowchart TB
  n0["Electronic Speed Controller"]
  n1["MOSFET Half-Bridge"]
  n2["Gate Driver IC"]
  n3["ESC Microcontroller"]
  n4["Brushless DC Motor"]
  n5["Propeller"]
  n3 -->|PWM commutation| n2
  n2 -->|Gate signals| n1
  n1 -->|3-phase AC| n4
  n4 -->|Shaft torque| n5
  n0 -->|Contains| n3

Analysis

Lint findings (90 total: 4 high, 86 medium) were triaged. Three high-severity findings resolved or acknowledged:

  1. {{entity:Electronic Speed Controller}} {{hex:D4F57218}} Functionally Autonomous with no override: addressed by {{sub:SUB-REQ-025}} (PWM loss failsafe, 100ms detection, 50ms response).
  2. “kids remote control airplane” and “ESC” Biological/Biomimetic: acknowledged as classification artifacts from the aerodynamic form factor. No biocompatibility requirements apply to toy aircraft or power electronics.
  3. “mechanical interface” lacking Physical Object: correctly classified — {{ifc:IFC-REQ-016}} addresses the physical constraint at the connection point without needing a separate physical object entity.

The 86 medium findings are dominated by Synthetic components lacking manufacturing requirements (a known over-sensitive rule for consumer electronics) and coverage gaps where STK/SYS concepts appear without corresponding lower-level requirements. Seven coverage gaps were addressed by new requirements this session.

Requirements

Nine new requirements created. Key additions:

Safety-critical SUB requirements:

  • {{sub:SUB-REQ-025}}: ESC PWM failsafe — motor to zero within 50ms of 100ms signal loss. Derives from {{sys:SYS-REQ-004}}.
  • {{sub:SUB-REQ-026}}: FCE MCU stability augmentation at 250Hz, limiting bank to ±45° and pitch to ±30° in beginner mode. Derives from {{sys:SYS-REQ-003}}.
  • {{sub:SUB-REQ-027}}: Receiver failsafe — pre-programmed PWM output within 600ms of RF loss. Derives from {{sys:SYS-REQ-004}}.
  • {{sub:SUB-REQ-028}}: Battery bay retention at 50N pull-out force under 10m/s nose-first impact. Derives from {{sys:SYS-REQ-008}}.

System requirements closing STK gaps:

  • {{sys:SYS-REQ-011}}: 250g total flight-ready mass ceiling (derives from {{stk:STK-REQ-010}}, regulatory threshold for EASA/CAA open-category micro UAS).
  • {{sys:SYS-REQ-012}}: EN 71 Part 1 and ASTM F963 mandatory labelling (derives from {{stk:STK-REQ-012}}).

VER entries for stakeholder requirements:

  • {{ifc:VER-REQ-036}}: User trial with 5 children aged 8-14 for STK-REQ-001 (25-minute session scenario).
  • {{ifc:VER-REQ-037}}: Same trial, novice manoeuvre observation for STK-REQ-002.
  • {{ifc:VER-REQ-040}}/{{ifc:VER-REQ-041}}/{{ifc:VER-REQ-042}}: Bench tests for ESC failsafe, gimbal-based stability angle limiting, and RF-loss receiver timeout respectively.

All session-490 requirements verified to have rationale. Inline rationale count: 0 missing.

Next

Coverage gaps remain for STK-REQ-003 (onboard visual indicators only), STK-REQ-004 (abort charging before thermal runaway), STK-REQ-007 (one year durability), and STK-REQ-008 (spare parts included) — none have corresponding SYS requirements. These warrant a short QC pass to add the missing SYS-level requirements and close the remaining medium-severity lint findings before validation.

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