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UK – EU Transition, and UK Civil Aviation Regulations

To access current UK civil aviation regulations, including AMC and GM, CAA regulatory documents, please use this link to UK Regulation. Please note, if you use information and guidance under the Headings, the references to EU regulations or EU websites in our guidance will not be an accurate information or description of your obligations under UK law. These pages are undergoing reviews and updates.

Part 145 Maintenance Organisation Approval holders provide maintenance services in accordance with Regulation (EU)1321/2014 as retained (and amended in UK domestic law) under the European Union (Withdrawal) Act 2018

This page includes details and links to regulation, policy and guidance. It will provide approval holders resources to ensure they remain compliant with not only the regulations but also UK policy.

Guidance material provides interpretation or amplify in greater detail certain areas or aspects of regulation and/or policy to allow an approval holder to fully implement quality systems which remain compliant and perform well.

Alerts and notifications

Tailored news, notifications and alerts from the CAA, including alerts issue in the last 12 months are available though SkyWise.


  • Maintenance Organisation Exposition (MOE) should be constructed using user guide UG.CAO.00024 and associated CAA guidance. Background information regarding policy of Initial/Changes to Airworthiness Organisation Expositions
  • Part 145 Loss of Capability - Part 145 organisations the actions that may be taken by the CAA where it is identified that an organisation is temporarily unable to fulfil the Part 145 requirements for a particular product, part, appliance or process listed on its approval certificate.
  • Part 145 Occasional and Temporary Line Stations - Sets out what the CAA considers as a Part 145 occasional or temporary line station, how they may be established and the periods of time that they may remain in place.
  • Acceptance of maintenance tasks carried out by pilots - Part 145 caters for certain maintenance tasks to be carried out by a suitably qualified pilot. AMC to Part 145.A.30(j)4 lists various items which a qualified pilot may be issued an Authorisation to carry out. Tasks which relate to section 2(i)e require specific agreement from the competent authority
  • Part 145 Maintenance Staff Employment Status - to enable Part-145 organisations to establish the employment status of staff engaged on zero hours contracts for the purposes of Part 145.A30(d). This Information Notice provides guidance to enable Part-145 organisations to establish the employment status of staff engaged on zero hours contracts and those engaged indirectly for the purposes of Part 145.A30(d).
  • Part 145 Applicability of AMC2 145.A.50(d) and Certification of Used Aircraft Components - clarifies the use of AMC2 145.A.50(d) so that the competent authority, installers and operators have confidence that used aircraft components have been satisfactorily removed from the aircraft, inspected, assessed and tested, as necessary, before being recertified and made eligible for installation on an aircraft registered in an EASA Member State.

There have been various interpretations of the requirements which at times have led to organisations not being fully prepared or capable of providing the scope of work that they have applied for or have been approved to provide.

The purpose of this policy note is to remove ambiguity about what the UK CAA expects of an organisation applying for Part 145 approval or wishing to continue to hold Part 145 approval.

Facilities (145.A.25)

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.


Close Facilities (145.A.25)

Maintenance Data (145.A.45)

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.


Close Maintenance Data (145.A.45)

Tooling and Equipment (145.A.40)

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.

Close Tooling and Equipment (145.A.40)

Certifying staff and Manpower Resources (145.A.30, 145.A.35)

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.


• 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.
Close Certifying staff and Manpower Resources (145.A.30, 145.A.35)

Maintenance Organisation Exposition (145.A.70)

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 User Guide UG.CAO.00024 and the associated CAA guidance. Background information regarding policy of Initial/Changes to Airworthiness Organisation Expositions

Close Maintenance Organisation Exposition (145.A.70)

Line Maintenance

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;

Close Line Maintenance

Major repairs and/or major modifications;

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.

Close Major repairs and/or major modifications;

Related Information


Close Guidance

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