System availability A = MTBF / (MTBF + MTTR) and annual downtime hours - the baseline uptime metric for critical marine equipment.
Formula
$$ A = \frac{MTBF}{MTBF + MTTR} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $MTBF$ | Mean time between failures | h | reliability history |
| $MTTR$ | Mean time to repair | h | maintenance data |
Sources
- IEEE 493 / MIL-HDBK-217.