Part 145 Maintenance Organisation Exposition (MOE)

Development, Revision, Gap Analysis & Authority Acceptance for EASA Part 145 & UK Part 145 Approved Maintenance Organisations

The Maintenance Organisation Exposition is the defining document of a Part 145 Approved Maintenance Organisation. For the competent authority, it is the evidence that the AMO understands its obligations and has the procedures in place to discharge them. For the maintenance engineers, certifying staff and management who use it every day, it is the operational reference for how the organisation conducts its approved maintenance activities. A well-constructed MOE satisfies the authority and functions as a genuine operational tool. A poorly constructed one — whether inaccurate, built on an unadapted template, or allowed to fall behind the organisation’s operational reality — fails both tests simultaneously.

Aerospace and Aviation Consulting Services (AACS) provides specialist development, revision and review of Maintenance Organisation Expositions for AMOs operating under EASA Part 145, UK Part 145, and equivalent national airworthiness frameworks. Our MOEs are designed to be practical, structured, and fully integrated into day-to-day maintenance operations — not documentation assembled to satisfy the initial approval application and then shelved. We write what the organisation actually does, in procedures that certifying staff can follow and that authority inspectors will find accurately reflected in the operation.

The MOE is scrutinised at every authority oversight audit. Discrepancies between the MOE and how the organisation actually operates — whether in its quality procedures, its certifying staff authorisation processes, or its contracted maintenance arrangements — are findings that place the approval at risk. The most dangerous MOE is not the one that is obviously inadequate: it is the one that was accurate when approved and has not been maintained since.

Who We Support     Line maintenance organisations  │  Base maintenance facilities  │ Component and avionics workshops  │  Engine overhaul organisations  │  AMOs seeking initial Part 145 approval  │  Established AMOs extending their approval scope  │  AMOs whose MOE has fallen behind their operational reality  │  AMOs responding to authority MOE findings  │  Operators establishing in-house Part 145 capability  │ General aviation and helicopter maintenance organisations  │  Defence and military maintenance organisations with civil Part 145 approval

WHY THE MOE IS THE FOUNDATION OF PART 145 COMPLIANCE

Part 145.A.70 requires every Approved Maintenance Organisation to establish and maintain a Maintenance Organisation Exposition that sets out the procedures, means and methods of the organisation. Compliance with its contents is a prerequisite for obtaining and retaining the maintenance organisation approval certificate. The UK CAA’s guidance on MOE construction references CAP 2375 — the UK Part 145 MOE Guidance — and the associated compliance checklist SRG1775. These documents define the expected structure and content in detail. An MOE that does not meet this standard will not be approved.

Beyond the approval requirement, the MOE serves a practical operational purpose. The Accountable Manager’s statement in the MOE is a personal commitment to compliance. The certifying staff authorisation framework documented in the MOE defines the boundaries within which engineers are authorised to sign for completed work. The maintenance procedures in the MOE govern how every maintenance task on every approved aircraft type must be accomplished. And the quality and compliance monitoring procedures in the MOE are the mechanism through which the organisation identifies and corrects departures from those standards.

The MOE is not an approval document. It is an operational one. An MOE that is produced for the authority and not used in the maintenance environment creates a dangerous divergence between the documented system and the real one. When an incident occurs, when the authority audits, or when a customer conducts a supplier assessment, that divergence becomes the finding. AACS builds MOEs that are written to be used — which is also why they satisfy the authority.

THE REGULATORY FRAMEWORK

Regulatory Instrument	MOE Obligation
Part 145.A.70 — MOE Requirement	The primary obligation. Every AMO must establish and maintain an MOE. The initial issue must be approved by the CAA. Amendments must be managed in accordance with procedures set out in the MOE itself. The MOE must remain an up-to-date description of the organisation at all times.
AMC1 145.A.70(a)	Provides the acceptable outline layout for a compliant MOE. Where an organisation uses a different format, the exposition must still contain all required content. The UK CAA’s ORS9 Decision No. 38 sets out the current UK-applicable AMC.
GM 145.A.70(a)	Guidance Material confirming the purpose of the MOE: to set forth the procedures, means and methods of the organisation. Compliance with MOE content assures compliance with Part 145 requirements. Personnel must be familiar with the parts of the MOE relevant to their tasks.
CAP 2375 — UK Part 145 MOE Guidance	The UK CAA’s specific guidance document for MOE construction under UK Part 145. The reference document for all UK Part 145 AMOs. Used alongside the compliance checklist SRG1775 to structure and validate MOE content.
SRG1775 — Compliance Checklist	The UK CAA’s compliance checklist for Part 145 MOE approval. Used by the authority to assess whether the MOE meets all required content areas. AACS uses this checklist as a quality assurance tool throughout MOE development.
EASA Regulation (EU) No 1321/2014 — Part 145	The primary EASA regulation for AMO approval. Sets out the approval conditions, personnel requirements, facilities and equipment standards, and MOE content requirements for all EASA Part 145 AMOs.
AMC & GM to Part 145 (EASA)	Acceptable Means of Compliance and Guidance Material published by EASA defining how the regulatory requirements are to be met in practice. AMC compliance is the expected standard at EASA authority oversight.
Part 145.A.85 — Changes to Organisation	Requires the AMO to notify the CAA of any proposal to make changes to the organisation, including facilities, equipment, tools, procedures, work scope, certifying staff and airworthiness review staff. These changes require corresponding MOE amendment.
Part 145.A.65 — Compliance Monitoring	The compliance monitoring and quality system requirements must be documented in the MOE. The quality function described in MOE Part 1 must be genuinely independent of the maintenance activities it audits.
Part-M / Part-CAMO Interface	Where the AMO contracts services to or from a CAMO, the interface procedures must be documented in MOE Part 2. The authority assesses whether the documented interface accurately reflects the contractual and operational relationship.

THE MOE STRUCTURE — WHAT EACH PART MUST CONTAIN

The MOE is structured in four main parts, each with specific regulatory content requirements under AMC1 145.A.70(a) and the UK CAA’s CAP 2375 guidance. AACS develops each part from the ground up for the specific AMO — not assembled from templates, not adapted from a previous client’s document.

MOE Part	Section Title	Key Content Requirements
Part 0	General Organisation	Scope of approval, Accountable Manager statement, management responsibilities, organisational structure chart, personnel numbers and qualifications, list of approved locations, scope of work description
Part 1	Management Procedures	Certifying staff and support staff management, competence assurance, continuation training, quality and compliance monitoring system, safety management, authority liaison, document and record management procedures, amendment procedures
Part 2	Maintenance Procedures	Aircraft and component acceptance, maintenance planning, accomplishment of maintenance tasks, certifying staff authorisation framework, completion of maintenance records, return to service procedures, maintenance data control, technical records management, CAMO interface procedures, contracted maintenance procedures
Part 3	Quality System Procedures	Quality policy and objectives, internal audit programme design and schedule, finding classification and corrective action procedures, supplier approval and control, contracted maintenance oversight, sub-contracted work procedures, corrective action effectiveness review
Part 4	Appendices	Approval certificate, example forms and records, list of contracted maintenance organisations, list of approved component suppliers, certifying staff authorisation list (may be maintained as a separate controlled document)

CORE MOE DEVELOPMENT & REVISION SERVICES

Initial MOE Development for Part 145 Approval

For organisations seeking their initial Part 145 approval, the MOE is the centrepiece of the certification process. The competent authority will examine it in detail — assessing whether the procedures described are genuinely capable of producing compliant maintenance, whether the certifying staff authorisation framework is correctly structured, whether the compliance monitoring system is independent and properly designed, and whether the Accountable Manager’s statement reflects a genuine organisational commitment rather than a boilerplate declaration.

The quality of the initial MOE submission determines how long the certification process takes and how many revision cycles the authority requires before granting approval. An MOE built on genuine regulatory knowledge and an accurate understanding of the organisation’s actual structure and procedures accelerates the process. One adapted from a template, or copied from another AMO’s document, generates comment cycles and — more dangerously — creates inaccuracies that persist into the approved organisation.

AACS initial MOE development services include:

• Facility, scope and capability assessment — understanding the organisation’s physical environment, approval class and rating requirements, certifying staff establishment and maintenance activities before writing a single paragraph
• Approval scope definition — confirming the precise scope of approval sought (aircraft types, engine types, components, specialist services) and ensuring the MOE accurately describes the capability that scope implies
• Full Part 0 development — organisational structure, Accountable Manager statement, management responsibilities, personnel framework and approved locations
• Full Part 1 development — certifying staff management, continuation training, compliance monitoring system design and documentation, safety management integration, authority liaison and document control procedures
• Full Part 2 development — the complete maintenance procedures framework: aircraft and component acceptance, maintenance planning, task accomplishment, certifying staff authorisation and limitations, technical records, return to service and CAMO interface
• Full Part 3 development — the quality system procedures including audit programme design, finding classification and corrective action, supplier approval and contracted maintenance oversight
• Part 4 appendices — all required supporting documentation including example forms and the initial certifying staff authorisation list
• Authority pre-application meeting preparation — preparing the Accountable Manager and Quality Manager for the pre-application engagement with the competent authority
• Authority comment and finding response management — drafting technically accurate responses to authority queries and managing revision cycles through to MOE approval

MOE Revision — Scope Change, Regulatory Change & Organisational Change

An approved MOE is not a static document. Part 145.A.85 requires the AMO to notify the competent authority of changes to the organisation that affect the approval — and any such change requires corresponding MOE amendment. The same obligation applies when the regulatory framework changes: EASA and UK CAA regulatory revisions, AMC/GM updates and CAP amendments must be reflected in the MOE, not left to accumulate until the authority finds them at oversight.

The categories of change that commonly require MOE revision include:

• New aircraft type rating additions — the certifying staff type training requirements, tooling implications, maintenance data provisions and any new procedures specific to the new type must all be reflected in the MOE
• New approval classes or ratings — expanding from line to base maintenance, adding component or avionics workshop capability, obtaining specialist service approvals including NDT, welding or composite repair
• New base or line stations — additional locations require MOE amendment to reflect the management structure, certifying staff and facilities at the new site
• Certifying staff establishment changes — additions, deletions or changes to authorisation scope within the certifying staff list
• Contracted maintenance arrangement changes — additions or removals from the list of contracted organisations; changes to the procedures governing those contracts
• CAMO relationship changes — new CAMO contracts or changes to existing interface arrangements require corresponding MOE Part 2 procedural updates
• Regulatory framework changes — UK CAA post-Brexit Part 145 amendments, EASA regulatory revisions, CAP 2375 updates and new AMC/GM requirements
• Quality and compliance monitoring system changes — revisions to the internal audit programme, finding classification criteria or corrective action procedures

AACS revision services include:

• Scope of change assessment — identifying exactly which MOE sections require amendment for the proposed change and what the revision must contain
• Targeted section revision — revising only the affected sections while confirming that no cross-references or dependent procedures in other parts require consequential amendment
• Full MOE revision review — where the document has accumulated multiple unaddressed changes, a structured review and revision of all affected sections
• Regulatory change impact assessment and implementation — identifying what specific regulatory changes require the AMO to do and drafting the corresponding MOE amendments
• Authority notification management — managing the CAA notification or approval process for changes that require authority acceptance before implementation

MOE Gap Analysis & Independent Review

An independent MOE gap analysis from AACS provides AMOs with an external assessment of their exposition against current Part 145 requirements and their actual operational reality — the assessment that identifies what an authority inspector would find, before they find it. The most common gap is not missing content: it is content that was accurate when the MOE was approved and has not been updated to reflect how the organisation has evolved since. This divergence between documentation and practice is the single most consistently identified finding category in UK CAA and EASA Part 145 oversight.

Gap analysis services include:

• Full MOE assessment against current UK Part 145 requirements, CAP 2375 and AMC1 145.A.70(a) — identifying sections that do not meet current regulatory content requirements
• Operational accuracy review — assessing whether each MOE section accurately describes how the AMO currently conducts the activities it covers, including site visits where required
• Certifying staff authorisation review — confirming that the authorisation list and its scope accurately reflect the current certifying staff establishment and their individual authorisation limitations
• Maintenance data control assessment — reviewing whether the AMO’s maintenance data management procedures reflect how data is actually controlled and accessed
• Technical records review — assessing whether the technical records procedures described in the MOE accurately reflect how records are maintained and whether they meet the Part 145.A.55 standard
• Quality system effectiveness assessment — reviewing whether the compliance monitoring procedures described in the MOE are being implemented as documented and are generating genuine compliance intelligence
• CAMO interface accuracy review — confirming that the interface procedures in Part 2 accurately describe the current contractual and operational relationship with CAMO principals
• Prioritised corrective action plan — a structured, risk-ranked list of amendments required, with clear guidance on the urgency and sequencing of each correction

AMO Procedures Manual & Supporting Documentation

For larger AMOs, the MOE Part 2 maintenance procedures may be held in a series of separate procedures manuals cross-referenced from the main MOE document, rather than incorporated into the MOE itself. This is explicitly permitted under GM 145.A.70(a) and is common in base maintenance facilities, engine overhaul organisations and larger component workshops where the volume and complexity of maintenance procedures makes a single-document structure impractical. AACS develops and revises procedures manuals and supporting documentation for AMOs using this structure.

Services include:

• Maintenance procedures manual development — covering aircraft and component acceptance, maintenance planning, task accomplishment, technical records and return to service procedures as a standalone controlled document cross-referenced from the MOE
• Certifying staff authorisation manual development — the comprehensive authorisation document maintained separately from the MOE Part 4 appendix, including type authorisation scope, limitation records and continuation training requirements
• Supplier approval and contracted maintenance procedures manual — the documented framework for approving, auditing and managing contracted maintenance and component suppliers
• Maintenance data and technical records management procedures — the detailed procedures for controlling access to current approved maintenance data and managing technical records
• Document control framework — the revision management, amendment log, distribution and version control procedures that govern all controlled documents cross-referenced from the MOE

SMS Integration with the MOE

Part 145.A.200 requires AMOs to establish and maintain a Safety Management System, and the SMS framework must be documented in MOE Part 1. The relationship between the SMS and the compliance monitoring system — both of which are required to be documented in Part 1 — is a specific area of authority scrutiny. An SMS that is described separately from the compliance monitoring system, without clear integration between occurrence reporting, investigation findings and the compliance audit programme, does not meet the intent of the regulatory requirement.

AACS ensures that MOE Part 1 accurately describes a coherent, integrated quality and safety management framework — not two parallel systems that happen to share the same document section.

SMS/MOE integration services include:

• MOE Part 1 SMS framework documentation — the safety policy, safety objectives, hazard identification and risk management procedures, occurrence reporting system, safety performance monitoring and safety promotion framework documented within the MOE structure
• SMS and compliance monitoring integration design — ensuring that compliance findings feed into the SMS occurrence analysis process and that SMS safety data informs the compliance monitoring audit programme
• Just culture policy documentation — integrated into the MOE Part 1 occurrence reporting procedures
• Safety performance indicator documentation — the SPIs used to monitor maintenance safety performance, documented with their measurement methodology and review frequency
• SMS maturity assessment against MOE requirements — confirming that the SMS described in the MOE is the SMS the organisation is actually operating

Authority Engagement & Submission Management

The process of obtaining initial MOE approval, or of submitting significant MOE amendments for authority acceptance, involves structured engagement with the UK CAA or EASA that goes beyond submitting a document. The authority’s assessment of the MOE includes evaluation of whether the Accountable Manager and Quality Manager genuinely understand its contents and can demonstrate how the procedures described are implemented in practice. AACS supports AMOs through this process from first submission to final approval.

Services include:

• Pre-application meeting preparation — preparing the Accountable Manager, Quality Manager and other key personnel for the pre-application engagement that sets the tone for the entire certification or amendment process
• MOE submission management — structuring and presenting the MOE submission in the format and with the supporting evidence the authority expects
• Authority comment response — preparing technically accurate, clearly reasoned responses to each authority comment or finding on the MOE submission
• Revision cycle management — tracking the authority’s comment log, managing the revision cycle and ensuring that each revision accurately addresses the authority’s specific concerns
• MOE approval milestone management — tracking progress through the approval process and advising the AMO on what is required at each stage to maintain momentum towards approval
• Post-approval implementation advisory — supporting the organisation in transitioning from the approved documentation to operational reality — the step that determines whether the MOE functions as an operational tool or becomes a shelf document

Ongoing MOE Maintenance & Amendment Support

Most AMOs have a Quality Manager or Compliance Manager responsible for maintaining the MOE. What they frequently lack is the regulatory expertise to assess whether a proposed organisational change requires MOE amendment, what that amendment must contain, and whether it requires prior authority approval or can be incorporated under the AMO’s own amendment authority. The consequences of getting these judgements wrong are either unnecessary regulatory delay or unnotified changes that become findings at the next oversight visit.

AACS provides ongoing MOE maintenance support to AMOs seeking specialist expertise alongside their internal quality function:

• Amendment trigger assessment — advising whether a proposed organisational, operational or procedural change triggers a MOE amendment obligation and under which amendment category it falls
• Amendment drafting — producing the specific MOE section revisions required for the change, including all consequential amendments to cross-referenced sections
• Authority notification management — managing the CAA notification or acceptance process for changes that require authority involvement
• Annual MOE accuracy review — a structured annual review confirming that all sections of the MOE remain accurate and current, identifying any drift between the document and the operational reality
• Regulatory monitoring — tracking UK CAA and EASA regulatory developments that require MOE amendment, with early notification and amendment drafting support

Our Advisory Philosophy for MOE Development

AACS approaches MOE development with a single governing principle: the MOE must accurately describe how the organisation actually works — and the procedures it describes must be ones that the organisation is genuinely capable of following. A document that satisfies the authority but does not reflect operational reality creates compliance risk from the moment it is approved. A document that accurately reflects operational reality, and in which procedures are designed around how maintenance is actually conducted, satisfies the authority precisely because it is accurate.

  Every MOE is developed from an understanding of the specific organisation — its scope, its certifying staff, its facilities and its maintenance activities — not from a template adapted to look organisation-specific

  MOE procedures must be ones that operational staff will actually follow — procedures that do not reflect the operational environment will be worked around, creating divergence that the authority will find

  The certifying staff authorisation framework must accurately reflect who is authorised to certify what, within what limitations — this is one of the most closely scrutinised elements of every authority oversight visit

  The compliance monitoring system described in the MOE must be the compliance monitoring system the organisation is genuinely operating — not an aspirational framework that exists on paper

  SMS and compliance monitoring must be integrated in the MOE as a coherent framework — not two parallel systems that happen to share the same document section

  MOE amendments must be managed proactively — the document that was accurate at approval must remain accurate as the organisation evolves

  Authority findings on the MOE must be addressed at root cause — a finding response that amends a procedure without understanding why the procedure was inadequate will produce a recurrence

AACS-produced MOEs are accepted by competent authorities because they are built on genuine regulatory knowledge, accurate operational understanding and procedures that work in real maintenance environments. Every engagement is structured around the specific AMO, its approval scope and its operational reality — not a generic Part 145 documentation programme applied regardless of the organisation’s actual characteristics.

Speak to an AACS Specialist

If you are seeking initial Part 145 MOE development, revising an existing exposition, preparing for authority oversight, or responding to MOE findings, please contact us to discuss your requirements.