Frequently Asked Question

Reliability evidence

Reliability planning connects mission profile, failure mechanisms, environment, duty cycle, maintenance assumptions, and acceptable risk. Life tests should use representative failure mechanisms; accelerated tests require a justified acceleration relationship. Track failure modes individually so an aggregate pass does not hide a systematic defect.

R(t) is reliability at time t and λ is a constant failure rate in the simplified model.

Worked example

If λ = 2×10^-5 per hour, MTTF is 50,000 h and R(10,000) = e^-0.2 = 0.819. Use the model only when its assumptions match the failure behavior.

Engineering check

For Reliability Prediction, Life Testing, and Growth, maintain traceability from requirement to risk, design output, evidence, and approval. Record the configuration, acceptance criterion, test or analysis conditions, open actions, and residual risk. A method is not complete when the document is filled in; it is complete when the evidence supports the decision and affected controls are updated.

Traceability note

For Reliability Prediction, Life Testing, and Growth, maintain a visible link between the requirement, design or process characteristic, risk entry, planned evidence, measured result, and approval record. Identify the configuration and revision used, record deviations and open actions, and state who accepts residual risk. When evidence changes, update the affected requirement, risk analysis, verification or validation plan, and manufacturing control rather than editing only the summary status.