Track MTBF growth and project cumulative test hours required to reach target MTBF.
What is Crow-AMSAA Reliability Growth modeling?
Standardized under IEC 61164 and MIL-HDBK-189, Crow-AMSAA models failure progression via a Non-Homogeneous Poisson Process (NHPP) Power Law: N(t) = λ · tβ. When β < 1 (growth rate α = 1 - β > 0), corrective engineering modifications are systematically eliminating failure modes, driving instantaneous MTBF upward: M(t) = t1-β / (λ · β).
Comma or newline separated cumulative operating hours
| # | Failure Time (h) | Cumulative MTBF (h) | Instantaneous MTBF (h) |
|---|---|---|---|
| 1 | 12 | 12 | 24.42 |
| 2 | 35 | 17.5 | 35.61 |
| 3 | 78 | 26 | 52.91 |
| 4 | 140 | 35 | 71.23 |
| 5 | 260 | 52 | 105.82 |
| 6 | 410 | 68.33 | 139.06 |
| 7 | 680 | 97.14 | 197.69 |
| 8 | 1100 | 137.5 | 279.81 |
During developmental testing or fleet commissioning, repair actions are accompanied by engineering redesigns. Standard constant-failure-rate (HPP) assumptions fail because the system is actively improving. The Crow-AMSAA NHPP power law model estimates the current instantaneous MTBF and predicts additional test hours required to demonstrate customer reliability targets.
Statistically verify whether wear-out is setting in or maintenance is improving reliability.
Reliability AnalysisEstimate failure characteristics, B10 life, and failure rate behavior (infant vs wear-out).
Reliability AnalysisDetermine statistical mission reliability and calculate required test duration or sample size.