Any Part 145 organisation must have facilities commensurate with the scope of work for which it is approved to provide.

Line Maintenance providers are expected to have an office, storage facilities and, for larger providers, possibly a workshop. These facilities must be airside or at the very least within a short drive.  The distance should be reasonable and appropriate for the activity being provided from the airside area. This is to ensure personnel from the organisation are not operating remotely from the approved facility.

Base maintenance providers must have a hangar which accommodates the aircraft types for which they are approved to maintain with offices, storage facilities and workshops as required. The aircraft type must be able to be completely enclosed by the facility.  It is not acceptable for the aircraft tail to be outside the hangar while performing base maintenance. Work may be performed outside the hangar subject to procedures being approved in the Organisations MOE.

Generic Maintenance data for each aircraft type within the requested or approved scope of work must be available at the organisation at all times. This data should be used in the initial approval stages to define tooling requirements and assist in the creation of the manpower plan.  It will define manpower requirements for each task. It will also need to be available during subsequent CAA audits. This helps to demonstrate the organisation's overall capability to perform maintenance.

The data does not have to be up to date at all times (although it needs to be controlled) and may be supplemented with customer supplied data specific to a particular model/fleet. Where customer supplied data is not used, a subscription service will need to be in place prior to commencement of any work. The organisation must have procedures in place that demonstrate how they control the data and ensure that it is up to date before use.

It is not acceptable for data to be supplied solely by the customer directly prior to an aircraft input.  This will not allow appropriate production planning to take place prior to any work being performed.

Organisations must have all tooling which is required to complete the maintenance tasks within their scope of work permanently available at their facilities. The exception to this requirement is where a task is only performed infrequently (as a guide, tasks that are performed at one in three of similar inputs) then the tooling can be acquired at the time the task is performed (through loan or pool arrangements).

The appropriate tooling for the scope of work may be supplied through a contract with an organisation that supplies, maintains and updates/replaces the tooling held by the Part 145 organisation is acceptable. The tooling should be provided on a permanent basis and its availability should not be dependent on a contract with an operator. It remains the responsibility of the Part 145 organisation to determine that the tooling is of the correct type and is in a condition that is suitable for use,

Each organisation must ensure it has sufficient staging and access equipment to gain access to all areas of the aircraft fall within the approved scope of work. Access equipment or staging should be of a suitable type to allow the maintenance task to be performed in an effective manner. Staging and access equipment should provide a stable working area where tools and materials can be located while performing the task to ensure that potential Human Factors issues are minimised.

All tooling and equipment must be controlled through a register and maintained or calibrated to Original Equipment Manufacturer (OEM) requirements/national standards. This includes servicing of Aircraft Jacks, Staging and Access Equipment.

Alternative or locally fabricated tools may only be used when there is an approved procedure in the Maintenance Organisation Exposition (MOE) that ensures an assessment of the suitability of alternative tooling has been is carried out, and that the use of the alternative tool has been properly validated. This is to ensure any such tools are of an equivalent specification, standard and accuracy as those specified in the applicable maintenance data provided by the OEM. 

The organisation shall have sufficient staff to plan, perform, supervise, inspect and quality monitor the activities which the organisation is approved to perform. This must be supported with a manpower plan which shows either:

• Planned vs Actual man-hours for work which is scheduled and has been completed at the organisation.

or

• Provides a capacity projection based on number of staff available and envisaged scope of work, including the assumptions made to develop the plan (such as number of staff needed to complete a check or number of persons to run a roster at a line station, typical level of defects and scheduled maintenance workload for a night stopping aircraft). This can then be used to establish the maximum capacity and scope of work the organisation can undertake.

The plan must take into consideration the following:

• Training, leave and an allowance for sickness etc.
• An efficiency level should be declared by the organisation. It is not feasible to be 100% efficient.  Human performance principles suggest that, a figure of 80% or less is more realistic when taking account of human factors.
• Resilience within the organisation: it is not possible to hold an approval based on one person's licence for aircraft where an A1 rating is required. The GM to 145.A.10 explains the limitations and permissible arrangements for organisations maintaining non-complex aircraft.
• Part 145.A.30(h) requires an organisation to have appropriate aircraft type rated certifying staff qualified in category C in accordance with Part-66, supported by sufficient aircraft type rated staff qualified as category B1 and B2 in accordance with Part-66. Organisations must be able to demonstrate their ability to maintain compliance, even when some staff are not available. This will ensure an aircraft's maintenance is not compromised or halted due to sickness or other non-availability of some staff.

The Maintenance Organisation Exposition (MOE) is integral to an organisation's ability to demonstrate its capability and compliance with Part 145. Statements that are open or ambiguous create the potential for misunderstanding, non-compliance with the regulation and could result in regulatory action, aircraft grounding or worse. The MOE must be fully reviewed on a regular basis by the organisation and by the CAA during the audit cycle. The procedures contained in an exposition should describe the detailed process that the organisation follows to comply with the applicable provision in the regulation. They should not simply be policy statements indicating that the organisation will comply with the relevant elements of the regulation when using a process/procedure.  

The exposition should kept up to date and follow the guidance set out in EASA UG UG.CAO.00024 and the associated CAA guidance. Background information regarding policy of Initial/Changes to Airworthiness Organisation Expositions  

Line Maintenance generally refers to minor, unscheduled or scheduled maintenance carried out on aircraft that includes:

• Unscheduled maintenance resulting from unforeseen events (e.g. trouble shooting, defect rectification).
• Scheduled tasks not exceeding the weekly check or equivalent specified in the approved aircraft maintenance programme.
• Scheduled checks that contain servicing and/or inspections that do not require specialised training, equipment, or facilities, and that have been assessed and accepted for inclusion in the line maintenance scope of work.
• Component replacement with use of external test equipment if required. Component replacement may include components such as engines and propellers, where environmental conditions are suitable.
• Maintenance performed on aircraft after a period of being out of service (such as aircraft in storage) when agreed in advance with the CAA.

• The need to access a hangar (even if the activity is permitted under a line maintenance scope of approval) considering the type of aircraft, the maintenance event type/complexity, the environmental and weather conditions.

It is not Line Maintenance when:

There are a significant number of different types of tasks to be carried out during a single input, even if when considered singularly they may still fall within the definition of line maintenance but together clearly require the use of  base maintenance production planning support and/or base maintenance release to service process (category C staff supported by B1/B2 support staff) in order to ensure that the maintenance ordered has been properly carried out before release to service.

Replacement of any major component where the related maintenance procedures clearly require the use of a hangar environment requiring special ground support equipment and/or structured production planning and/or complex and lengthy maintenance,

Any scheduled maintenance task which requires extensive disassembly of the aircraft and/or extensive in-depth inspection; 

Trouble shooting and/or Defect Rectification requiring special ground support usually relevant to base maintenance (e.g. special equipment, structured production planning, complex and lengthy maintenance).

A scheduled maintenance event, which in the planning phase has been already identified as significant in terms of duration and/or man-hours.

A work package requiring a complex team composition in terms of numbers and categories (avionic, structure, cabin, NDT, etc.) of staff involved per shift.

The management of the event by B1 and B2 support staff and the release by a C certifying staff.