Safety and reliability engineers
Connect hazards, failure mechanisms and lifecycle evidence so that risk controls remain effective in the real product and its operating environment.
After this module, you should be able to:
- Frame hazards and reliability objectives at system level
- Trace risk controls into architecture and verification
- Challenge independence, common causes and diagnostic assumptions
- Use field information to maintain the assurance case
Safety and reliability are properties of operation.
The role examines how technical failures, misuse, environment, maintenance and external services can lead to harm or loss of function. It helps the team choose proportionate controls and assemble an argument that connects hazards to requirements, design features and evidence.
Keep the risk-control chain intact.
| Area | Question | Evidence |
|---|---|---|
| Hazard analysis | What conditions can cause harm, and through which sequences? | Hazard log and scenario analysis |
| Reliability model | Which failure mechanisms and mission profiles dominate? | FMEA/FMECA, fault tree or reliability model |
| Risk controls | What prevents, detects or limits each hazardous situation? | Safety requirements and allocation |
| Independence | Can one cause defeat both function and monitor? | Common-cause and independence analysis |
| Lifecycle feedback | How will complaints, incidents and drift revise assumptions? | Monitoring and escalation process |
Challenge diagnostic coverage
Ask which faults are detected, how quickly, under what operating conditions and by what independent means. A watchdog may detect lost execution but cannot prove that a plausible yet incorrect output has been identified.
Move continuously between scenarios and design.
- Define hazardous outcomes. Avoid starting with component failures alone.
- Build causal paths. Include software, users, environment and dependent services.
- Specify controls. State response time, independence and effectiveness.
- Allocate and trace. Connect controls to owners, interfaces and verification.
- Test assumptions. Inject faults and examine combinations and latent conditions.
- Monitor operation. Compare field evidence with predicted mechanisms and rates.
Worked hand-off: heater control
The safety engineer defines the hazardous over-temperature scenario and maximum safe response. Hardware provides an independent cut-off; firmware detects sensor plausibility and commands shutdown; systems engineering allocates timing; verification injects stuck sensors and failed outputs. Reliability analysis checks whether shared power or sensing defeats both layers.
Maintain a living assurance case.
Scenarios, causes, controls, status and residual risk.
Failure modes, dependencies, assumptions and mission profile.
Testable controls with ownership and traceability.
Independence, common causes and fault containment.
Analyses and tests that demonstrate control effectiveness.
Operational signals, trend thresholds and corrective action.
Common traps
Risk analysis is detached from design and change control.
Latent and common-cause failures are not examined.
A claimed diagnostic rate has no representative evidence.
Field data and product changes do not refresh the argument.
Further learning
- NASA Systems Engineering HandbookRisk, reliability and technical-process context.
- TEA-106 · Fault handling and safe statesDetection, containment, degradation and recovery.
Keep risk connected to engineering reality.
Strong assurance traces each important risk through concrete controls, credible independence and evidence that remains current throughout the lifecycle.