Operations / Reliability & Maintenance
Reliability & Availability (MTBF / MTTR) MTBF, MTTR
How long equipment runs between failures, how long it is down, and what fraction of the time it is actually available.
The fork, why two teams get different numbers
MTTR is the landmine: mean time to REPAIR (wrench time only) versus mean time to RESTORE/RECOVER (detection + wait-for-parts + repair + test).
In the Metric Library
- The full fork, both definitions worked all the way through
- The trap that makes the number lie, on a real export
- Every formula variant, spelled out
- The reconciliation anchor, what to tie it to and when to refuse
Reference: reliability engineering convention (Ao vs Ai) · MIL-HDBK-338 style definitions · APICS/ASCM maintenance terms