The management, reliability, performance-assurance and continuous-improvement division of the handbook. Its purpose is not to perform maintenance — it determines whether maintenance was performed correctly, on time, whether the defect was actually eliminated, whether equipment is becoming more or less reliable, and what should change to improve future performance.
Audit philosophy: an audit should not simply ask "was the checklist filled in?" It should establish whether the maintenance system actually controlled the asset condition. A completed form without effective maintenance should not automatically be considered successful maintenance.
Division 25 runs the maintenance system itself through a fixed cycle, and examines every audited activity along the same requirement-to-outcome chain.
Grouped A–D — click any topic to expand its audit/analysis scope and what to check.
Review: due dates, completion dates, overdue/deferred/missed activities, repeat defects found during PM.
Special attention: repeat corrective maintenance on the same asset.
Purpose: identify whether emergency response can be improved.
Connects: the Inspection Handbook with the Maintenance Handbook — identifies findings not properly converted into maintenance actions.
Identify: whether spare shortages have caused maintenance delays.
Verify: the register accurately reflects the physical AGL system.
Allows: identification of high-failure equipment.
Objective: identify why the problem keeps returning.
Critical failures: receive a higher level of review.
Goes beyond: identifying the failed component — prevents repeatedly replacing the same part.
Increasing MTBF generally indicates improved reliability.
High MTTR may indicate: spare shortages, difficult access, poor diagnostics, lack of tools/competency, complex restoration.
Answers: did the maintenance actually improve asset condition and prevent recurrence?
High-cost assets: may require lifecycle review.
Feeds directly: into the spare strategy.
Feedback loop: Inspection Data → Failure Data → Risk → Inspection Frequency. Frequency changes must not fall below regulatory, manufacturer or airport-mandated minimums, and require documented risk assessment and approval.
Objective: effective maintenance, not simply more maintenance. Frequency changes must not fall below regulatory, manufacturer or airport-mandated minimums, and require documented risk assessment and approval.
Tool deficiencies that repeatedly delay maintenance should become improvement actions.
Note: poor-quality data can produce poor maintenance decisions.
Frequency: at least annually.
Two parallel workflows — one for scheduled auditing, one for significant or recurring failures.
Five requirement groups closed out on every audit.
Management KPIs tracked across the maintenance system.
| KPI | Purpose |
|---|---|
| PM Compliance | Measures scheduled maintenance execution |
| PM On-Time Rate | Measures schedule performance |
| Corrective Maintenance | Measures reactive workload |
| Emergency Maintenance | Measures unplanned critical workload |
| Backlog | Measures outstanding work |
| MTBF | Measures reliability |
| MTTR | Measures maintainability |
| Failure Rate | Measures deterioration/failure trend |
| Repeat Defects | Measures effectiveness of repairs |
| Maintenance Cost | Measures lifecycle burden |
| Spare Consumption | Measures component demand |
| Audit Findings | Measures compliance |
| Corrective-Action Closure | Measures improvement discipline |
The permanent feedback loop that converts the handbook from an instruction manual into a reliability system.
This makes Division 25 the highest-level management layer of the Maintenance Handbook, feeding lessons and reliability data back into Inspection, Preventive Maintenance, Predictive Maintenance, Condition-Based Maintenance, Planning and Training.
Quick answers about maintenance audit & continuous improvement, based on the topics in this division.
It is the management, reliability, performance-assurance and continuous-improvement division of the handbook. Its purpose is not to perform maintenance but to determine whether maintenance was performed correctly, on time, and effectively.
Division 25 (Maintenance Audit & Continuous Improvement) contains 40 topics in four groups: Group A Maintenance Audit (12 topics), Group B Failure Analysis (9 topics), Group C Reliability (9 topics) and Group D Continuous Improvement (10 topics).
An audit should not simply ask whether the checklist was filled in. It should establish whether the maintenance system actually controlled the asset condition, because a completed form without effective maintenance is not assurance.
Eight steps: Audit, Analyze, Identify Root Cause, Measure Reliability, Improve, Implement, Verify and Standardize. Each audited activity is examined along the chain of requirement, planning, execution, testing, record, defect closure and reliability outcome.
Five requirement groups on every audit: planning (plan, work order, priority, resources), execution (correct SOP and checklist, competent personnel, safety and LOTO followed), testing (required tests performed and recorded, instruments identified, valid calibration), documentation (complete record, components recorded, traceable test records, asset history updated) and effectiveness (defect eliminated, no immediate recurrence, repeat failure reviewed, corrective action effective).
The audit workflow runs from audit plan, document review, field verification and record verification through non-conformity or observation, root-cause analysis, corrective action, implementation, effectiveness verification and closure. The failure-analysis workflow, for significant or recurring failures, runs from failure and initial defect assessment through data collection, failure-mode identification, root-cause analysis, corrective and preventive action, implementation, monitoring and effectiveness verification.
Thirteen management KPIs: PM compliance, PM on-time rate, corrective maintenance, emergency maintenance, backlog, MTBF, MTTR, failure rate, repeat defects, maintenance cost, spare consumption, audit findings and corrective-action closure.
Through a permanent feedback loop: inspection, maintenance and testing generate failure and condition data, which feeds reliability analysis and root-cause analysis, leading to improvement, an updated strategy and improved asset reliability. Division 25 is the highest-level management layer, feeding lessons back into inspection, preventive, predictive and condition-based maintenance.
Maintenance audit and continuous improvement is more than preparing for an inspector's visit.
Build the technical knowledge to understand programme-level performance review, trend analysis across the asset base, and how audit findings feed back into a stronger maintenance strategy.
Audit with rigour. Learn from the data. Improve continuously.
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