Module 10 of the EASA Part-66 basic knowledge syllabus provides the regulatory foundation for aircraft maintenance certifying staff. It covers the legal framework governing civil aviation in the European Union, with particular emphasis on the regulations that directly govern the certification, performance, and release of maintenance work.
For the B3 category (light helicopters and small non-complex aeroplanes with a maximum take-off mass not exceeding 2,725 kg), this module ensures that certifying staff understand:
The structure of EU aviation regulations and the hierarchy of legal documents
The specific requirements of Part-66 (licensing of maintenance personnel)
The requirements of Part-145 (approved maintenance organisations)
The requirements of Part-M (continuing airworthiness)
The privileges, responsibilities, and limitations of a B3 licence holder
The procedures for certification of maintenance and release to service
The reporting obligations and occurrence reporting systems
This module is examined at knowledge levels 1, 2, and 3 depending on the subtopic. Level 3 (detailed theory) applies to the core responsibilities of certifying staff, the conditions for issuing a Certificate of Release to Service (CRS), and the privileges of the licence.
2. The Regulatory Framework
2.1 The Hierarchy of EU Aviation Legislation
The European Union aviation regulatory system operates on a hierarchical structure:
17.The Basic Regulation — Regulation (EU) 2018/1139 (formerly Regulation (EC) No 216/2008) establishes the European Union Aviation Safety Agency (EASA) and sets the overarching legal framework for civil aviation safety in the EU.
18.Implementing Regulations — These are binding legal acts that implement the Basic Regulation. The most relevant for maintenance personnel are:
Regulation (EU) No 1321/2014 — the continuing airworthiness regulation, containing:
Annex I (Part-M) — continuing airworthiness requirements for aircraft
Annex II (Part-145) — requirements for maintenance organisations
Annex III (Part-66) — requirements for the licensing of maintenance personnel
Annex IV (Part-147) — requirements for maintenance training organisations
Regulation (EU) No 748/2012 — the initial airworthiness regulation, containing Part-21 (certification of aircraft and related products, parts, and appliances)
25.Acceptable Means of Compliance (AMC) and Guidance Material (GM) — These are non-binding documents issued by EASA that provide acceptable methods of demonstrating compliance with the regulations. Alternative methods may be used if they are shown to be equivalent.
26.Certification Specifications (CS) — Technical standards used for the certification of products, parts, and appliances.
2.2 Key Definitions
Term
Definition
**Certifying staff**
Personnel authorised to sign a Certificate of Release to Service (CRS) after maintenance
**Certificate of Release to Service (CRS)**
The document attesting that maintenance has been performed correctly and the aircraft is airworthy
**Continuing airworthiness**
All processes ensuring that an aircraft complies with its approved design and is safe for operation
**Maintenance**
Any one or combination of overhaul, repair, inspection, replacement, modification, or defect rectification
**Life-limited part**
A part with a mandatory replacement interval defined in the approved maintenance data
**Type rating**
The specific aircraft type(s) for which a licence holder has completed training and is authorised to certify
3. Part-66 — Licensing of Maintenance Personnel
3.1 The Aircraft Maintenance Licence (AML)
Part-66 (Annex III to Regulation (EU) No 1321/2014) establishes the requirements for the issue, renewal, and privileges of the Aircraft Maintenance Licence.
Key provisions of Part-66.A.10 (Application and validity):
The AML is issued by the competent authority of an EU Member State
The licence has unlimited validity — it does not require periodic renewal
The licence may be revoked, suspended, or limited by the competent authority if the holder fails to meet the requirements
The licence remains valid provided the holder continues to meet the experience requirements
Minimum age requirement: An applicant for an AML must be at least 18 years of age (Part-66.A.5(a)).
3.2 Licence Categories
Part-66 defines several licence categories. The B3 category is specifically for:
Light helicopters (maximum take-off mass not exceeding 3,175 kg)
Small non-complex aeroplanes (maximum take-off mass not exceeding 2,725 kg)
The B3 licence covers the entire aircraft, including the airframe, engines (piston/reciprocating), electrical systems, and avionics systems. It does not cover turbine engines — for turbine-powered aircraft, a different category (B2 or B1 with appropriate subcategory) is required.
Mandatory examination modules for B3 (Part-66 Appendix I):
Module
Subject
Module 1
Mathematics
Module 2
Physics
Module 3
Electrical Fundamentals
Module 4
Electronic Fundamentals
Module 5
Digital Techniques / Electronic Instrument Systems
Module 6
Materials and Hardware
Module 7
Maintenance Practices
Module 8
Basic Aerodynamics
Module 9
Human Factors
Module 10
Aviation Legislation
Module 11
Aeroplane Aerodynamics, Structures, and Systems
Module 12
Helicopter Aerodynamics, Structures, and Systems
Module 13
Aircraft Aerodynamics, Structures, and Systems (not applicable to B3)
Module 14
Propulsion (piston engines)
Module 15
Gas Turbine Engine (not applicable to B3)
Module 16
Piston Engine (not applicable to B3)
Module 17
Propeller (not applicable to B3)
Note: Module 15 (Gas Turbine Engine) is not a mandatory requirement for the B3 category. Module 14 (Propulsion) covers the piston engine requirements for B3.
3.3 Privileges of the B3 Licence
Part-66.A.20 defines the privileges of the licence holder:
The B3 licence authorises the holder to certify maintenance (issue CRS) on aircraft covered by the B3 category
The holder may also supervise maintenance performed by unlicensed personnel
The holder must have the appropriate type rating for the specific aircraft type
Type ratings for B3: Unlike some other categories, B3 type ratings are granted for specific aircraft types (e.g., Robinson R22, Cessna 172). The holder must complete type training and pass the relevant examination to obtain a type rating.
3.4 Requirements for Exercising Licence Privileges
Part-66.A.20(e) specifies that to exercise the privileges of the licence, the holder must have:
At least 6 months of relevant maintenance experience in the preceding 2 years, OR
Met the requirements for refresher training as determined by the competent authority
This requirement ensures that certifying staff maintain current knowledge and practical competence.
3.5 Suspension and Revocation
If a licence is suspended or revoked (Part-66.A.20(b)), the applicant may regain it by:
Completing a refresher training course as determined by the competent authority
Passing the applicable examinations
This ensures that the certifying staff member demonstrates current knowledge before the licence is reinstated.
3.6 Responsibilities of the Licence Holder
The licence holder is personally responsible for:
Ensuring that all maintenance certified has been performed in accordance with approved data
Ensuring that the aircraft is airworthy and safe for operation
Ensuring that all required documentation is complete before issuing a CRS
Maintaining their own competence and recent experience
Reporting any defects or occurrences that could affect the safe operation of the aircraft
4. Part-145 — Approved Maintenance Organisations
4.1 Scope and Applicability
Part-145 (Annex II to Regulation (EU) No 1321/2014) establishes the requirements for organisations performing maintenance on aircraft and components. A Part-145 approval is required for:
Maintenance of aircraft used for commercial operations
Maintenance of components (unless performed by the aircraft owner under specific conditions)
Any maintenance performed by an organisation that issues an EASA Form 1
4.2 Personnel Requirements (Part-145.A.30)
The maintenance organisation must ensure that:
All personnel performing maintenance are trained and qualified for the tasks assigned
Certifying staff hold the appropriate Part-66 licence and type rating
Unlicensed personnel may perform maintenance only under the direct supervision of certifying staff or appropriately qualified personnel
Task-specific training is provided and recorded
Direct supervision means that the supervisor must be present and able to provide immediate guidance and inspection of the work. Merely checking the final result after the work is completed does not constitute direct supervision.
4.3 Certification of Maintenance (Part-145.A.50)
Part-145.A.50 establishes the requirements for the certification of maintenance:
A Certificate of Release to Service (CRS) must be issued after any maintenance is completed
The CRS may only be issued by authorised certifying staff
The certifying staff member must have personally performed or directly supervised the work
The maintenance must have been performed in accordance with approved data
The aircraft must be airworthy and safe for operation
Key principle: The CRS is not a mere formality — it is a legal attestation of airworthiness. The certifying staff member who signs the CRS takes personal responsibility for the maintenance performed. This responsibility is personal and cannot be transferred to the organisation.
Conditions for issuing a CRS:
93.All required maintenance has been properly carried out
94.The maintenance was performed in accordance with approved data
95.The certifying staff member has control over the maintenance performed
96.The certifying staff member has personally performed or directly supervised the work
97.No defects remain that would affect the safe operation of the aircraft
98.All required documentation is complete
4.4 Tools and Equipment (Part-145.A.40)
The maintenance organisation must ensure that:
All tools and equipment are controlled and calibrated
Tools are appropriate for the tasks being performed
The correct tools are used for each task
Important principle: The maintenance data specifies torque values and other parameters in specific units. Using tools calibrated in different units introduces a risk of error and is not acceptable unless the approved data explicitly permits alternative units. The certifying staff must use the specified tools.
4.5 Maintenance Data (Part-145.A.45)
The organisation must ensure that:
All applicable maintenance data is available and current
Maintenance is performed in accordance with the approved data
Any deviations from the approved data require prior approval
Approved data includes:
The manufacturer's maintenance manual (AMM), structural repair manual (SRM), and component maintenance manual (CMM)
Airworthiness Limitations Section (ALS) of the Instructions for Continued Airworthiness
Service bulletins and airworthiness directives
Data approved by the competent authority
4.6 Occurrence Reporting (Part-145.A.60)
Part-145.A.60 requires that:
Any defect, malfunction, or occurrence that could affect the safe operation of an aircraft must be reported
Reports are made to the competent authority through the organisation's reporting system
Reports are also made to the quality manager in accordance with the organisation's procedures
This is a key safety responsibility of certifying staff. Failure to report a significant defect is a violation of Part-145 and could lead to enforcement action.
5. Part-M — Continuing Airworthiness
5.1 Scope and Applicability
Part-M (Annex I to Regulation (EU) No 1321/2014) establishes the continuing airworthiness requirements for aircraft. It applies to:
All aircraft registered in an EU Member State
All aircraft operated by EU operators
5.2 Responsibilities of the Owner (Part-M.A.201)
The owner of an aircraft is responsible for:
Ensuring that the aircraft is maintained in an airworthy condition
Ensuring that any defect that could affect safety is rectified before flight
Ensuring that maintenance is performed in accordance with the approved maintenance programme
Ensuring that all applicable airworthiness directives are complied with
The owner may contract a Part-145 organisation or a Part-M Subpart F maintenance organisation to carry out the work, but the ultimate responsibility remains with the owner.
5.3 The Maintenance Programme (Part-M.A.302)
The maintenance programme must:
Be approved by the competent authority
Be based on the manufacturer's recommendations
Include all mandatory requirements (e.g., airworthiness limitations)
Be reviewed and updated as necessary
Important principle: Any change to the maintenance programme, including extending inspection intervals, requires approval by the competent authority. The CAMO cannot unilaterally change the programme. The approval process may involve a reliability analysis or other evidence demonstrating that the safety level is maintained.
A Continuing Airworthiness Management Organisation (CAMO) may be contracted to manage the continuing airworthiness of an aircraft. The CAMO is responsible for:
Developing and managing the maintenance programme
Ensuring that maintenance is performed by an appropriate organisation
Tracking airworthiness directives and service bulletins
Maintaining the aircraft's maintenance records
A written maintenance contract must be in place between the owner/operator and the CAMO (Part-M.A.201). This contract must define the responsibilities and scope of work.
5.5 Airworthiness Limitations
Life-limited parts have mandatory replacement intervals defined in the approved maintenance data (typically in the Airworthiness Limitations Section of the Instructions for Continued Airworthiness). These limits:
Are mandatory and cannot be extended without an approved design change
Are approved by EASA or the State of Design
Must be tracked and complied with
A crack in a critical component (e.g., a main rotor blade) renders the aircraft unairworthy. Extensions are only possible through a modification approved by EASA or the State of Design.
6. Part-21 — Design and Production Approval
6.1 Scope and Applicability
Part-21 (Annex I to Regulation (EU) No 748/2012) establishes the requirements for the certification of aircraft and related products, parts, and appliances. It covers:
Type certification
Production certification
Airworthiness certification
Approval of design changes and repairs
6.2 Approval of Repairs (Part-21.A.433)
When a repair is not covered by existing approved maintenance data:
The repair design requires approval in accordance with Part-21
The approval may be issued by EASA or by a Design Organisation Approval (DOA) holder with the appropriate scope
The certifying staff member cannot approve the design — they can only certify the embodiment of the repair using approved data
The OEM may provide data, but the approval must come from a Part-21 design organisation or the competent authority
Key principle: A certifying engineer may only certify maintenance after ensuring that all required maintenance has been properly carried out in accordance with approved data. Any repair not covered by approved data requires approval from the competent authority or use of data approved by the competent authority.
7. The Certificate of Release to Service (CRS)
7.1 Purpose and Legal Significance
The CRS is the document that:
Attests that maintenance has been performed correctly
Confirms that the aircraft is airworthy and safe for operation
Is a legal attestation of airworthiness
Establishes personal responsibility of the certifying staff member
7.2 Conditions for Issuing a CRS
The certifying staff member may issue a CRS only when all of the following conditions are met:
179.All required maintenance has been properly carried out — including all scheduled inspections and any defect rectification
180.The maintenance was performed in accordance with approved data — no deviations from the approved data are permitted
181.The certifying staff member has personally performed or directly supervised the work — signing a CRS for work not performed or supervised is a violation
182.The certifying staff member holds the appropriate licence category and type rating — experience alone or supervision does not substitute for the required licence
183.The aircraft is airworthy and safe for operation — no known defects that could affect safety remain
184.All required documentation is complete — including maintenance records and any applicable forms
7.3 Personal Responsibility
The certifying staff member who signs the CRS:
Takes personal responsibility for the maintenance performed
Is responsible for ensuring that all required inspections are completed
Is responsible for the airworthiness of the aircraft
Cannot transfer this responsibility to the organisation
May be subject to enforcement action (including licence revocation) for violations
Critical point: If a defect is found after a CRS has been issued that was present before the CRS was issued but was not detected during the inspection, the certifying staff member who signed the CRS is primarily responsible.
8. Maintenance Personnel — Qualification and Supervision
8.1 Licensed vs. Unlicensed Personnel
Licensed personnel (certifying staff):
Hold a Part-66 licence with the appropriate category and type rating
Are authorised to issue CRS
May supervise unlicensed personnel
Unlicensed personnel (trainees/mechanics):
May perform maintenance tasks
Must work under the direct supervision of certifying staff or appropriately qualified personnel
Do not have the authority to issue CRS
8.2 Requirements for Task Performance
Part-145.A.30 requires that:
Personnel performing maintenance are trained and qualified for the tasks assigned
The B3 licence is a base qualification — the organisation must provide task-specific training and authorisation
The certifying staff member is responsible for ensuring that the person performing the task is competent
Type ratings are required for certifying staff, not necessarily for mechanics, but task training is mandatory
8.3 Direct Supervision
Direct supervision means that the supervisor:
Must be present and able to provide immediate guidance
Must be able to inspect the work
Must have control over the maintenance performed
Merely checking the final result after the work is completed does not constitute direct supervision.
9. Defect Deferral and Maintenance Programme Compliance
9.1 Deferred Defects
A release to service may only be issued when all required maintenance has been properly carried out. A defect may be deferred only when:
The deferral is explicitly allowed by the approved maintenance data (e.g., MEL/CDL)
The deferral is permitted by the maintenance programme
The deferral is recorded in accordance with the organisation's procedures
Important principle: Verbal notification or substitution of materials without approval violates the approved maintenance data and Part-145 requirements.
9.2 Lubrication and Scheduled Maintenance
A lubrication task is part of the scheduled maintenance. If it cannot be completed:
The aircraft is not airworthy unless an approved deferral exists
The correct grease must be used — substitution without approval is not permitted
The certifying staff must not issue a CRS until the task is completed or an approved deferral is in place
10. Units of Measurement and Tooling
10.1 Correct Use of Units
The maintenance manual specifies torque values and other parameters in specific units (e.g., inch-pounds, Newton-metres, lb-ft). The certifying staff must:
Use the specified units as stated in the approved data
Use tools calibrated in the same units as specified
Not convert units unless the approved data explicitly permits it
Rationale: Using a torque wrench with different units than specified introduces a risk of incorrect torque application. The approved data does not permit deviation from the specified units.
10.2 Tool Control
Part-145.A.40 requires that:
All tools and equipment are controlled and calibrated
Tools are appropriate for the tasks being performed
Calibration is current and traceable
11. International and National Regulatory Interfaces
11.1 Applicability to EU-Registered Aircraft
Part-145 applies to maintenance of EU-registered aircraft performed by EU Part-145 organisations. The release to service is governed by:
Part-145.A.50 (for Part-145 organisations)
Part-M.A.801 (for Part-M Subpart F organisations)
The operator's nationality does not change the regulatory basis for the maintenance organisation's certification. ICAO Annex 6 sets international standards but does not override EU regulations for EU-registered aircraft.
11.2 EASA Form 1
The EASA Form 1 is the certificate of release to service for components. It certifies that the component has been maintained in accordance with approved data and is airworthy.
12. Common Relationships Between Concepts
The following relationships are fundamental to understanding the regulatory framework:
Licence → Privileges → Responsibility
The Part-66 licence grants the privilege to certify maintenance
With this privilege comes the personal responsibility for the airworthiness of the aircraft
The licence may be revoked or suspended if the holder fails to meet the requirements
Approved Data → Maintenance Performance → CRS
Maintenance must be performed in accordance with approved data
The certifying staff member must verify compliance with approved data
Only then may a CRS be issued
Supervision → Control → Certification
Direct supervision provides control over the maintenance performed
Control is a prerequisite for certification
The certifying staff member must have sufficient oversight and assurance of the work's quality
Maintenance Programme → Approval → Compliance
The maintenance programme must be approved by the competent authority
Any changes require authority approval
Compliance with the programme is mandatory
Defect → Rectification → Release
Any defect that could affect safety must be rectified before release
Rectification must use approved data
Deferral is only possible with explicit approval
13. Typical Exam Focus Points
When preparing for the Module 10 examination, pay particular attention to the following areas:
Personnel, certification of maintenance, tools, occurrence reporting
Regulation (EU) No 1321/2014, Annex III (Part-66)
Licensing of maintenance personnel
Licence requirements, privileges, experience, type ratings
Regulation (EU) No 748/2012, Part-21
Initial airworthiness
Approval of repairs and design changes
15. Conclusion
Module 10 establishes the legal and regulatory foundation for the professional practice of aircraft maintenance certifying staff. The B3 licence holder must understand not only the technical aspects of maintenance but also the legal framework that governs their work. The CRS is the central document that links the maintenance performed to the legal responsibility of the certifying staff member. Compliance with approved data, proper supervision of unlicensed personnel, and adherence to the maintenance programme are non-negotiable requirements.
The certifying staff member's signature on a CRS is a legal attestation of airworthiness that carries personal responsibility. Understanding the regulatory framework is not merely an academic exercise — it is essential for safe and lawful practice.
