Base maintenance is the in-depth work on the aircraft. It takes place in a hangar, with the aircraft out of service for days or weeks. It involves hundreds or thousands of tasks, dozens of technicians, large volumes of material and constant coordination between planning, production, stores, quality and the customer.
In this article we explain what sets base maintenance apart from line maintenance, how a hangar check is organised, and why digitalisation is no longer optional.
Base maintenance vs line maintenance
Each organisation defines the exact boundary in its MOE, within the scope approved by the authority. In general, the differences are these:
| Aspect | Line maintenance | Base maintenance |
|---|---|---|
| Location | Ramp, parking stand | Hangar |
| Duration | Minutes or hours | Days or weeks |
| Aircraft status | In service, between flights | Out of service |
| Typical scope | Transit, daily, weekly, some A-checks, defects | C-checks, structural inspections, modifications, major repairs |
| Teams | Small, per shift | Large, multidisciplinary |
| Planning | Highly dynamic, tied to operations | A project with input and output dates |
Under EASA Part-145, an organisation needs a specific base maintenance approval, with suitable facilities (a hangar able to house the aircraft, workshops, stores) and category C certifying staff, supported by B1 and B2 staff.
What base maintenance includes
- C-checks and equivalent heavy checks, according to the operator's maintenance programme.
- Structural inspections, including corrosion (CPCP) and fatigue-related tasks.
- Modifications: service bulletins, STCs, cabin changes, avionics upgrades.
- Structural repairs according to the Structural Repair Manual (SRM) or approved data.
- Airworthiness directives that require deep access.
- Painting, configuration changes and preparation for aircraft transfer between operators.
Key processes in a hangar check
1. Defining the work package
Everything starts with the work package: the list of tasks the customer (usually the operator's CAMO) requests for the check. It includes maintenance programme tasks, ADs, service bulletins, modifications and specific customer requests.
The MRO reviews the package, confirms it holds the applicable maintenance data and prepares the quotation. This is where the first risk appears: a poorly analysed package leads to surprises in cost and turnaround time.
2. Hangar slot planning
The hangar is a finite resource. Each bay has its own dimensions, equipment and calendar. Hangar planning decides which aircraft goes into which bay, when it arrives and when it leaves. A delay on one check affects the next one.
3. Detailed task planning
The package is broken down into task cards. Each task card has an estimate of hours, a trade (structures, avionics, powerplant, cabin), preconditions (access panels open, systems deactivated) and associated materials and tools.
Good planning sequences tasks by zone and by dependency. Opening a panel once for five tasks is far more efficient than opening it five times.
4. Resource management
A check depends on four resources:
- People: by trade, shift and authorisation. Available hours are not enough; you need people authorised to certify each type of task.
- Materials: rotables, consumables, check kits. A part that arrives late blocks task closure.
- Tools and equipment: including type-specific tooling and equipment with valid calibration.
- Space: hangar bays, work platforms, workshop areas.
5. Execution and findings (NRCs)
During the check, findings appear: corrosion, cracks, wear beyond limits. Each finding generates a non-routine card (NRC). NRCs often account for a very significant share of the total hours on a heavy check, and they are the main source of schedule and cost deviations.
Each NRC needs a technical assessment, repair data, sometimes customer approval and, frequently, additional material.
6. Close-out and certification
At the end, certifying staff check that every task is complete and signed, that all materials are traceable, and that the maintenance data used is current. Only then is the CRS issued and the aircraft returned to the customer.
Why spreadsheets are not enough
Many organisations start with spreadsheets. That is understandable: they are flexible, familiar and cheap. But in base maintenance their limits appear quickly.
| Problem | Spreadsheet | Specialised software |
|---|---|---|
| Single source of truth | Copies by email, versions that diverge | One shared dataset in real time |
| Access control and sign-offs | Anyone can edit any cell | Role-based permissions, sign-offs linked to authorisations |
| Traceability | Hard to reconstruct who changed what | Full change history |
| NRCs | Added by hand, not linked to material or hours | Raised from the task card, with material and hours attached |
| Materials | Separate query to stores | Reservations and consumption linked to the task |
| Progress visibility | Manual reports, always out of date | Real-time check status |
| Audits | Searching for evidence in folders and files | Evidence available from the record |
The underlying issue is not the tool; it is the risk. A spreadsheet does not stop an unauthorised person from marking a task as complete. It does not warn you when a tool's calibration has expired. It does not link a finding to the part installed to correct it.
Benefits of digitalising base maintenance
Realistic planning
With historical data on actual hours per task, planning improves with every check. Quotations reflect reality more closely and turnaround times are met more often.
NRC control
NRCs are recorded on the spot, with photos, a reference to the originating task and an estimate of hours and material. The customer receives the information sooner and can approve faster. Invoicing for additional work is backed by evidence.
Cross-department coordination
Planning, production, stores and quality work from the same information. Stores sees which parts are needed tomorrow. Quality sees which tasks are waiting for an independent inspection.
Less paper, fewer errors
Digital task cards remove transcription. Digital sign-off, linked to the user and their authorisation, reduces certification errors.
Audit readiness
When an authority or customer audit arrives, the evidence is in the system: who did what, when, with which data, which tool and which material.
How to approach the transition
Digitalisation does not happen over a weekend. We recommend:
- Start with a well-defined process, such as NRC management or the task cards for one product line.
- Migrate master data carefully: aircraft, programmes, staff, authorisations, stock.
- Involve technicians from day one. If the tool does not work in the hangar, it does not work.
- Update the MOE and procedures to reflect the use of the system, and coordinate with the authority when required.
Conclusion
Base maintenance is a complex project with many moving parts. Managing it with spreadsheets is possible at small scale, but it limits growth and increases risk. Specialised software brings visibility, control and traceability to the entire check cycle.
SkyPlannerHub is a cloud ERP designed for aviation maintenance organisations, including hangar-based base maintenance. If you are assessing how to digitalise your checks, contact us and we will look at your specific case.