Yes, MRO-specific turnaround KPIs can be aligned with ISO 22400 concepts, but it is a translation and modeling task, not a direct one-to-one mapping. You are effectively expressing MRO turnaround behavior (TAT, visit cycle times, AOG exposure) using ISO 22400’s way of structuring equipment, operations, states and time categories.
What ISO 22400 actually provides
ISO 22400 defines a framework for manufacturing KPIs, including:
- Standard entities: equipment, work units, work centers, production orders, operations.
- Time categories: operating, scheduled downtime, unscheduled downtime, standby, etc.
- Common performance views: availability, effectiveness, responsiveness, quality rate, etc.
It does not define MRO-specific indicators like turnaround time (TAT) per tail number or AOG risk, but it gives you a consistent way to decompose and measure time and events.
Typical MRO turnaround KPIs that can align with ISO 22400
Most MRO KPIs can be expressed using ISO 22400 concepts with careful modeling:
- Turnaround Time (TAT) / Visit Duration
Map the start/end of a “maintenance order” (or visit) to ISO 22400 production order timings and break the total into ISO time categories: operating time (work being performed), waiting (for parts, engineering, approvals), planned downtime (scheduled checks), and unplanned downtime (rework, findings).
- Induction-to-Teardown / Teardown-to-Repair / Repair-to-Release cycle times
Model each phase as an operation or operation segment. ISO 22400 timing concepts apply to each operation, so cycle-time KPIs can be expressed as operation duration and wait time between operations.
- Hangar / Bay Utilization
Treat each bay or dock as an “equipment” or “work center” and use ISO availability and utilization concepts: scheduled time vs actual operating time vs idle or blocked time.
- Findings and induced work impact on TAT
Use ISO 22400’s breakdown of planned vs unplanned activities. Induced work can be modeled as unplanned operations added to the original production order, and their time contribution measured explicitly.
- Rework and quality-related delays
Align with ISO time categories for rework and scrap. Even though MRO quality metrics may be tailored to regulatory and airline program terms, the time they consume fits ISO 22400’s loss-tree style thinking (e.g., rework as a specific class of non-productive time).
- Material- and engineering-hold time
Model these as specific standby or waiting states associated with the “equipment” (bay) or the maintenance order. ISO 22400 supports the concept of waiting time; you must define clear rules for when an order is “waiting for parts” vs “waiting for engineering” vs actually in work.
Where alignment is more approximate
Some MRO KPIs sit partly outside ISO 22400’s native focus on production:
- AOG risk and exposure
ISO 22400 can help with internal responsiveness and lead time, but “AOG risk” is a fleet- and schedule-level concept. You will likely need an external model that uses ISO-derived cycle times and variability as inputs rather than a pure ISO KPI.
- Contractual or program-specific SLAs
SLAs that include penalty windows, partial credits, or complex definitions of “clock stop” often extend beyond simple start/end timestamps. ISO 22400 time categories help you structure the underlying data, but the SLA logic usually remains custom.
- Configuration and maintenance lineage KPIs
Metrics about configuration changes per visit, SB/AD compliance velocity, or maintenance lineage complexity tie more to asset history and traceability than to ISO 22400’s production focus. You can still use ISO time concepts for “how long did it take,” but the configuration dimension is outside ISO’s core scope.
Practical alignment steps in brownfield MRO environments
In a real MRO stack with legacy MRO software, ERP, MES-like systems, and point tools, alignment depends heavily on data quality and integration maturity.
- Define what “the unit” is for KPIs
Decide whether you treat the unit of analysis as the aircraft visit, the work package, the maintenance order, or the bay. ISO 22400 expects clarity about “production unit”; without this, mappings become inconsistent across sites and systems.
- Map your existing states to ISO 22400 time categories
Most MRO systems already track status codes (e.g., IN WORK, AWAITING PARTS, ENGINEERING HOLD, QA HOLD). Create a mapping to ISO categories like operating, planned downtime, unplanned downtime, standby. This is usually the most contentious step and should go through change control.
- Align events and timestamps
Ensure that key MRO events (induction, bay-in, maintenance start, maintenance complete, bay-out, release to service) are consistently timestamped across systems. ISO 22400 concepts are only useful if the event data is reliable and traceable.
- Implement a common time accounting model
Use an ISO 22400-aligned “time accounting” layer that sits above individual systems. It can consume events from MRO software, ERP, MES, and planning tools, then compute standardized durations and categories, without forcing a full system replacement.
- Document KPI definitions and governance
For each MRO turnaround KPI, maintain a controlled definition that states how it maps to ISO 22400 entities and time categories, including explicit treatment of clock start/stop rules, holds, partial work, and rework. Treat these as controlled documents under your QMS.
- Validate before using for compliance or contracts
If ISO 22400-aligned KPIs will feed regulatory reports, internal audits, or customer-facing dashboards, validate the calculation logic and data flows. In regulated aerospace MRO, this typically requires test datasets, comparison to legacy reports, and documented verification.
Constraints and tradeoffs
- No automatic compliance benefit
Aligning KPIs to ISO 22400 does not, by itself, improve audit outcomes or prove compliance. It mainly improves internal consistency and comparability across sites and programs.
- Brownfield integration complexity
Legacy MRO and ERP systems may not expose all required timestamps or state changes cleanly. You may need middleware, data warehouse logic, or MES overlays to derive ISO-style KPIs without replacing core systems, which is often not feasible due to downtime, validation, and re-qualification burdens.
- Site- and program-specific variations
Different hangars and programs may have meaningfully different process states and coding practices. A single ISO 22400 mapping is possible, but it usually involves compromise and local change management.
- Partial alignment is still useful
It is reasonable to keep some KPIs as explicitly “MRO-specific” and not force a clean ISO 22400 mapping, while still using ISO-based time accounting as the foundation for most turnaround metrics.
How this typically works in aerospace MRO
In aerospace MRO, operators commonly:
- Keep existing MRO and ERP systems for work control and finance.
- Add an execution or analytics layer that normalizes states and timestamps into an ISO 22400-like model.
- Define turnaround KPIs (TAT, on-time release, bay utilization, induced work impact) using that normalized model.
- Maintain KPI definitions and mappings under document control so that audits and customers can see how times are derived and aggregated.
This coexistence approach avoids the cost and risk of replacing core MRO systems, while still giving you ISO 22400-aligned, comparable metrics across fleets and facilities.
