Remote Weapon Station (RWS)

Rationale: Vehicle Commander (RWS Operator), Urban Patrol Engagement scenario: the fundamental operational need is eliminating crew exposure during weapon operation, which is the leading cause of upper-body casualties in mounted operations.

Rationale: Vehicle Commander (RWS Operator), Urban Patrol Engagement scenario: operator detects RPG threat on rooftop via thermal, confirms with day camera. Dual-mode sensor with PID range drives engagement decision quality and reduces friendly fire risk (H-004).

Rationale: Vehicle Commander (RWS Operator), Urban Patrol Engagement scenario: auto-tracks target prior to firing 3-round burst at 200m. Manual tracking from a moving vehicle is impractical for the engagement timelines in urban asymmetric warfare.

Rationale: Tactical Commander, Urban Patrol Engagement scenario: commander receives authorization before arming weapon. ROE compliance requires explicit engagement authority in the fire control chain.

Rationale: Tactical Commander, Urban Patrol Engagement scenario: tactical commander receives sensor imagery via data link to authorise engagement per ROE. Without shared imagery the commander cannot make informed fire decisions.

Rationale: Dismounted Infantry, Emergency Stop scenario: uncommanded motion detected, drives de-energised and braked within 200ms. Dismounted personnel in the turret danger zone are the highest-risk stakeholder for H-002 (crushing/striking).

Rationale: Dismounted Infantry, IED Strike Control Loss and Emergency Stop scenarios: weapon must be safed immediately when control is compromised. Addresses H-001 (uncommanded discharge), H-006 (loss of control), and H-007 (software fault).

Rationale: Weapons System Maintainer, Field Maintenance Barrel Change scenario: armourer changes barrel in 15 min, inspects feed, reloads. Maintenance must be achievable in the field without specialist equipment.

Rationale: Weapons System Maintainer, Field Maintenance scenario: safety interlocks enforced, no traverse past maintenance limits, access panels unlocked only in maintenance mode. Protects maintainer from H-002 (turret motion) while working in the hazard zone.

Rationale: Vehicle Crew (Driver/Loader), Urban Patrol Engagement scenario: crew affected by recoil, vibration, noise. Recoil isolation prevents structural damage to crew station equipment and injury to occupants.

Rationale: Vehicle Crew (Driver/Loader), Field Maintenance scenario: loader replenishes ammunition and clears stoppages. Ammunition handling must not require crew exposure during active operations.

Rationale: Vehicle Commander (RWS Operator), Degraded Sensor Operation scenario: thermal crossover renders TI ineffective, system falls back to day camera with manual tracking. Phit >= 0.5 at 200m represents minimum suppressive capability; below this threshold, the system cannot reliably neutralise an RPG threat. Quantified threshold derived from SYS-REQ-011 degraded engagement analysis.

Rationale: Vehicle Commander (RWS Operator), IED Strike Control Loss scenario: IED damages cable harness, control link lost, hardware safety auto-safes weapon within 500ms. Addresses H-006 directly — armed weapon with no operator is catastrophic.

Rationale: RWS System Integrator (OEM), Field Maintenance scenario and IED Strike scenario: LRU replacement needed after encoder fault or battle damage. Through-life supportability requires modular design with standard tooling.

Rationale: RWS System Integrator (OEM), regulatory stakeholder: hazard register identifies H-001, H-003, H-007 as SIL 3 (catastrophic uncommanded discharge, failure to safe, software fault) and H-002, H-004, H-005, H-006 as SIL 2. Certification requires demonstrated compliance.

Rationale: Environment as stakeholder, operating constraints: temperature and vibration extremes define the envelope within which all functions must perform. Failure to operate at temperature extremes leaves vehicles without weapon capability in theatre.

Rationale: Environment as stakeholder, Ingress Protection constraint: turret is exposed to rain, dust, mud, and temporary immersion during fording. Electronics failure from ingress causes loss of weapon capability in the field.

Rationale: Derived from STK-REQ-001 and STK-REQ-003. Urban engagement scenario requires high first-round hit probability at typical urban combat ranges from a moving platform. 0.7 Phit is the minimum for effective suppression against an RPG threat.

Rationale: Derived from STK-REQ-001. Urban Patrol Engagement scenario: short engagement timelines in asymmetric warfare require rapid transition from surveillance to engagement. 8s is derived from typical RPG engagement timelines.

Rationale: Derived from STK-REQ-001. Omnidirectional threat environment in urban warfare requires full-hemisphere coverage. Slew rates derived from engagement timeline: 180° worst-case traverse in 3s to meet 8s detection-to-fire budget.

Rationale: Derived from STK-REQ-002. PID at 1500m (day) and 800m (night) requires 0.3 mrad IFOV per Johnson criteria (6 cycles on a 0.5m feature at 1500m). 50 mK NETD ensures thermal detection through moderate obscurants.

Rationale: Derived from STK-REQ-002. Ballistic computation requires accurate range data. ±5m accuracy at 3000m ensures fire control solution error is dominated by other factors (wind, propellant temperature), not range measurement.

Rationale: Derived from STK-REQ-003. Auto-tracking accuracy must keep the weapon within the target silhouette for the burst duration. 0.5 mrad RMS at 500m is 0.25m displacement — within a personnel target width.

Rationale: Derived from STK-REQ-004 and STK-REQ-007. Engagement mode transition requires two-action authorization per concept. Prevents accidental arming and supports ROE compliance chain. Addresses H-001 and H-007.

Rationale: H-001, H-003, H-007 drive SIL 3. Software alone cannot achieve SIL 3 PFD targets. A hardware interlock independent of the FCS software provides a diverse second channel that prevents discharge regardless of software state.

Rationale: Derived from STK-REQ-013. H-006 (loss of operator control while armed, SIL 2). IED Strike scenario: 500ms is the maximum acceptable time for an armed weapon to remain active without operator control. Hardware watchdog timer drives this independently of software.

Rationale: Derived from STK-REQ-006. H-002 (uncommanded turret motion, SIL 2). Emergency Stop scenario specifies 200ms brake engagement. Spring-applied brakes ensure fail-safe — loss of power results in braking, not free rotation.

Rationale: Derived from STK-REQ-012. Degraded Sensor Operation scenario: single sensor failure must not render the system combat-ineffective. 200m minimum range with day camera and manual tracking provides last-ditch engagement capability.

Rationale: Derived from STK-REQ-016. Initialization/BIT mode specifies 30-90s. Cold-start at -46°C is the worst case — lubricant viscosity, sensor warm-up, and electronics stabilisation are slowest. 90s ceiling ensures tactical readiness.

Rationale: Derived from STK-REQ-005. Tactical Commander needs real-time sensor imagery for engagement authorization. 15 fps minimum for situational awareness; 1 Hz position updates for blue force tracking integration.

Rationale: Derived from STK-REQ-010. Host vehicle interface specifies 25kN recoil load. Structural integrity and boresight retention under recoil are fundamental — loss of alignment during a burst makes subsequent rounds miss.

Rationale: Derived from STK-REQ-008. Field Maintenance scenario: 15-min barrel change, BIT confirms fix. The 5-min return-to-service includes boresight/calibration mode re-alignment after barrel change.

Rationale: Derived from STK-REQ-014. Operational availability requirement for deployed weapon systems. 400h MTBCF provides acceptable mission reliability over a 30-day deployment cycle. 60-min MTTR per STK-REQ-014 LRU replacement target.

Rationale: Derived from STK-REQ-016. EMC/EMI constraint: operation near radio transmitters and ECM. H-001 identifies EMI as a potential cause of uncommanded discharge — EMC compliance is safety-critical for the firing chain.

Rationale: Derived from STK-REQ-002. The Johnson criteria for positive identification require 6 cycles on the critical target dimension at the stated range. At 1500m, 6 cycles on 0.5m feature requires <=0.3 mrad IFOV (addressed by SYS-REQ-004). Stating the PID range explicitly in SYS ensures the sensor specification is traceable to the operational engagement requirement rather than only to a derived resolution metric. STK-REQ-002 identified that dual-mode sensors drive engagement decision quality and reduce friendly fire risk (H-004).