Comprehensive Failure Modes and Effects Analysis with severity ratings, detection methods, and risk mitigation strategies for mission assurance.
| ID | Subsystem | Failure Mode | Effect | Sev | Occ | Det | RPN | Mitigation |
|---|---|---|---|---|---|---|---|---|
| FM-001 | Propulsion | Thruster motor failure | Loss of maneuverability | 8 | 3 | 4 | 96 | Redundant thrusters, auto-surface |
| FM-002 | Propulsion | Propeller entanglement | Reduced thrust, motor damage | 6 | 4 | 5 | 120 | Prop guards, current monitoring |
| FM-003 | Navigation | IMU drift exceeds limit | Position uncertainty grows | 5 | 5 | 3 | 75 | Acoustic beacon updates |
| FM-004 | Navigation | DVL bottom-lock loss | Velocity estimate degraded | 5 | 4 | 2 | 40 | Model-based prediction |
| FM-005 | Power | Battery cell failure | Reduced capacity, imbalance | 7 | 2 | 3 | 42 | BMS monitoring, cell balancing |
| FM-006 | Power | Battery depletion | System shutdown | 9 | 3 | 2 | 54 | Low-power warning, auto-abort |
| FM-007 | Communication | Acoustic link loss | Cannot receive commands | 6 | 4 | 3 | 72 | Autonomous mission, timeout abort |
| FM-008 | Hull | Water ingress | Electronics damage | 10 | 2 | 3 | 60 | Leak sensors, watertight compartments |
| FM-009 | Hull | Pressure seal failure | Flooding, loss of vehicle | 10 | 1 | 4 | 40 | Regular inspection, drop weight |
| FM-010 | Navigation | Depth sensor failure | Cannot maintain depth | 7 | 2 | 2 | 28 | Redundant pressure sensor |
Risk Priority Number (RPN) = Severity × Occurrence × Detection
RPN > 100: Critical - Immediate action required | RPN 50-100: High - Action recommended | RPN < 50: Acceptable with monitoring