3.3 Type Ratings, Type Training, OJT & Practical Experience

3.3 Type Ratings, Type Training, OJT & Practical Experience

Quick Answer: Holding a basic EASA Part-66 licence in Category B1, B2, or C does not allow an engineer to certify commercial air transport aircraft without an Aircraft Type Rating Endorsement. Under Part-66.A.5, aircraft are divided into four groups. Since Regulation (EU) 2025/111, Group 1 is defined by explicit criteria (aeroplanes above 5 700 kg, more than 19 passengers, minimum two pilots, turbojet or multiple turboprops, non-piston aeroplanes above FL290, or a non piston/turbine/electric power plant; helicopters above 3 175 kg, more than nine passengers, minimum two pilots, multi-engine, or a non piston/turbine/electric power plant; gas airships other than ELA2; non-conventional aircraft; and fly-by-wire aircraft) and requires individual type ratings earned through approved Part-147 theoretical training (Level 3, 75% pass mark) and practical training. Endorsing the first aircraft type rating within a licence category/subcategory additionally requires mandatory On-the-Job Training (OJT) in an approved Part-145 maintenance organisation covering at least 50% of the syllabus task list. Transitioning to aircraft variants requires approved differences training.

While a basic Part-66 licence validates an engineer's mastery of universal aeronautical principles, aircraft systems vary enormously between types. A Boeing 787 composite structure with 5,000 psi hydraulics and a distributed variable-frequency electrical system has little in common with a vintage Cessna 172 or a cable-controlled turboprop. Part-66 ensures air safety by requiring specific type rating endorsements before certifying staff can sign release documents for complex machines.

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Aircraft Grouping Framework (Part-66.A.5)

To establish proportional qualification standards, Part-66.A.5 categorises all civil aircraft into four distinct regulatory groups:

Group 1: Complex Aircraft and High-Performance Machines

Much older training material still describes Group 1 as “CMPA, multi-engine helicopters, above FL290 and fly-by-wire”. Regulation (EU) 2025/111 replaced that wording with explicit criteria. Group 1 is now composed of:

(i) Aeroplanes that are any of:

• certified for a MTOM exceeding 5 700 kg;
• certified for a maximum passenger seating configuration of more than 19;
• certified for operation with a minimum crew of at least two pilots;
• equipped with turbojet engine(s) or more than one turboprop engine;
• with a maximum certified operating altitude exceeding FL290 and powered with a power plant other than piston;
• with a power plant that is not piston, turbine or electric.

(ii) Helicopters that are any of:

• certified for a MTOM exceeding 3 175 kg;
• certified for a maximum passenger seating configuration of more than nine;
• certified for operation with a minimum crew of at least two pilots;
• equipped with multiple engines;
• with a power plant that is not piston, turbine or electric.

(iii) Gas airships other than ELA2.

(iv) Non-conventional aircraft.

(v) Aircraft equipped with fly-by-wire systems.

EASA may nevertheless reclassify an aircraft that meets one of these criteria into a subgroup of Group 2, 3 or 4 where its lower complexity justifies doing so.

The Group 1 Legal Rule: Individual aircraft type ratings are strictly mandatory for all Group 1 aircraft. A licence holder cannot hold a generic "large aeroplane" endorsement; the licence must explicitly read, for example, Airbus A318/A319/A320/A321 (CFM LEAP-1A / PW1100G) or Boeing 737-700/800/900 (CFM56).

Groups 2, 3, and 4: General Aviation and Sport Craft

• Group 2: Aircraft other than Group 1 belonging to the following subgroups:
  • Subgroup 2a: Single-engine turboprop aeroplanes.
  • Subgroup 2b: Single-engine turbine helicopters.
  • Subgroup 2c: Single-engine piston helicopters.
  • Subgroup 2E: Aeroplanes with an electric power plant (added by Regulation (EU) 2025/111).
• Group 3: Piston-engine aeroplanes other than Group 1 (typically all single and multi-engine light piston aeroplanes).
• Group 4: Sailplanes, powered sailplanes, balloons and airships, other than those in Group 1.

For Groups 2 and 3, Part-66 permits group ratings or manufacturer subgroup ratings (e.g., "Piper piston aeroplanes" or full "Group 3"), enabling an engineer to certify multiple light aircraft models without sitting individual factory courses for each model, provided appropriate practical experience is demonstrated.

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Approved Part-147 Aircraft Type Training (Appendix III)

For Group 1 aircraft, gaining a type rating endorsement requires completing an approved course delivered by an EASA Part-147 Approved Maintenance Training Organisation. Appendix III to Part-66 dictates that type training must comprise two integrated parts: the theoretical element and the practical element.

Theoretical Element: Knowledge Levels 1, 2, and 3

Theoretical type training is stratified into three distinct depth levels:

• Level 1 (General Familiarisation): Brief overview of the airframe, systems, and powerplant. Enables maintenance personnel to identify major components and understand basic safety precautions.
• Level 2 (Ramp and Transit): Basic operational overview, systems layout, component locations, servicing, and line defect troubleshooting.
• Level 3 (Detailed Technical Knowledge): In-depth, master-level engineering instruction. Covers detailed system descriptions, component internal operation, schematics, removal/installation techniques, built-in test equipment (BITE) diagnostics, and complex troubleshooting procedures.

Level 3 Requirement: For Category B1 and Category B2 licence endorsements, theoretical training must be conducted to Level 3 standard. Category C base engineers also require Level 3 depth for avionics and mechanical systems, but focus on the overarching airworthiness release perspective.

Theoretical Examination Standards

Upon completing theoretical instruction, candidates sit a formal closed-book examination:

• Questions must be multiple choice with three options.
• The passing standard is strictly 75% for each phase and overall.
• Candidates are examined on every ATA chapter covered in the course syllabus.

Practical Element Standards

Theory alone is insufficient. Candidates must complete an approved hands-on practical training element in a workshop or line/base maintenance environment. Appendix III to Part-66 does not fix a single calendar duration in the rule text; the practical element must cover a representative selection of tasks for the type and be assessed. Treat any specific month figure you see in commercial course brochures as that provider's programme length, not a regulatory minimum. The practical element trains the engineer in:

• Using special tools and test equipment.
• Performing component replacements (e.g., flight control actuators, fuel pumps).
• Interrogating BITE and running operational system tests.
• Locating and inspecting EWIS harnesses, structural fittings, and safety locking devices.
• Practical assessment is performed by qualified practical assessors using standardized assessment sheets.

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On-the-Job Training (OJT) for Initial Type Endorsement

The most rigorous practical phase in an aircraft maintenance engineer's career is On-the-Job Training (OJT), governed by Section 6 of Appendix III to Part-66.

The First Type Rating Trigger

Candidates frequently confuse general practical experience with OJT. OJT is legally mandatory for the endorsement of the FIRST aircraft type rating within a given licence category or subcategory.

For example:

• When a newly licenced B1.1 engineer applies for their first type rating (e.g., Airbus A320), OJT is mandatory.
• When that same engineer later applies for their second type rating (e.g., Boeing 737) within the B1.1 subcategory, formal OJT is not mandatory (only the Part-147 theoretical and practical elements are required).
• However, if that engineer later qualifies for a Category B2 licence and applies to endorse the Airbus A320 on their B2 licence, OJT is once again mandatory, because it represents their first type rating within the B2 category.

Part-145 Environment and Task Syllabus Selection

OJT must be conducted inside an approved Part-145 maintenance organisation whose exposition (MOE) includes approved OJT procedures. The organisation must draft a detailed OJT programme tailored to the specific aircraft type, which must be formally approved in advance by the Competent Authority.

The 50% Representative Task Threshold

Under AMC to Part-66 Appendix III, the OJT task list cannot simply consist of routine daily fluid checks. The programme must:

1. Include tasks across a balanced cross-section of line and base maintenance.
2. Cover scheduled servicing, component replacement, defect rectification, troubleshooting, rigging, and operational testing.
3. Cover at least 50% of the representative tasks listed in AMC to Appendix III applicable to the aircraft type and category.

Every task must be executed under the direct supervision of a designated OJT mentor/supervisor who signs the candidate's OJT logbook. Upon completion, a designated assessor (an experienced, independent certifying engineer) conducts a comprehensive practical assessment of the candidate's competence, verifying maintenance data comprehension, safety culture, and mechanical skill.

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Differences Training

Airlines frequently modernise their fleets by acquiring re-engined or updated variants of an existing aircraft type. Transitioning an engineer who holds an existing type rating to a derivative variant does not require repeating a full initial type course. Instead, the engineer completes Differences Training.

Regulatory Triggers and Technical Scope

Differences training is required under Part-66 Appendix III when transitioning between:

• Aircraft sharing a common type certificate but possessing substantial differences in powerplants, airframe design, flight deck systems, or operational characteristics.
• Classic Examples: Airbus A320ceo (CFM56/V2500) to Airbus A320neo (CFM LEAP-1A / PW1100G); Boeing 737 Next Generation (-700/800) to Boeing 737 MAX (-8/9); Boeing 777-200 to Boeing 777-300ER.

Differences training must address both theoretical and practical elements covering the specific deltas between the variants. Once the differences course and assessments are completed, the Competent Authority updates the licence endorsement to reflect the new variant or engine type.

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Group and Subgroup Ratings for Groups 2 and 3

Unlike commercial air transport operators flying Group 1 aircraft, general aviation maintenance facilities service dozens of diverse light aircraft models. Requiring a separate Part-147 factory course for every single piston model would paralyze light aviation.

Under Part-66.A.45, the Competent Authority endorses manufacturer subgroup ratings or full group ratings for Groups 2 and 3 upon demonstration of appropriate practical experience:

• Full Group 3 Rating: Endorsed on Category B1.2 or B3 licences, granting privileges across all piston-engine aeroplanes, provided the applicant demonstrates practical experience on a representative cross-section of at least 3 distinct aircraft types representing the group.
• Group 2 Subgroups: An engineer demonstrating practical experience on single-engine turbine helicopters can gain a Subgroup 2b rating covering multiple models from that manufacturer.

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Aircraft Grouping and Type Rating Requirements Matrix

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Practical Maintenance Scenario: Fleet Introduction and First Type Endorsement

A European regional airline operating ATR 72 turboprops (Group 1 aircraft) hires a recently licenced Category B1.1 engineer who holds a basic Part-66 AML without any type endorsements.

Regulatory Steps to Certification Authorisation:

1. Theoretical Type Training: The engineer attends an EASA Part-147 approved ATR 72-600 theoretical course for six weeks, covering all systems to Level 3 standard. The engineer passes all theoretical examinations with scores of 75% or higher.
2. Practical Training Element: The engineer completes an approved Part-147 practical training course (hands-on aircraft servicing, engine run-up procedures, propeller rigging, BITE checks).
3. On-the-Job Training (OJT): Because this is the engineer's first aircraft type rating on their B1.1 licence, the engineer must complete an approved OJT programme in the airline's Part-145 hangar. The engineer logs tasks covering at least 50% of the AMC syllabus tasks over several months, supervised by senior B1.1 certifying staff.
4. Final Assessment & Endorsement: A designated assessor conducts a final evaluation. The engineer submits EASA Form 19 with the training certificates and OJT logbook to their National Aviation Authority, which endorses ATR 42/72 (PW120) on their Part-66 licence.
5. Subsequent Type Acquisition: Two years later, the airline acquires Airbus A320 aircraft. The engineer attends an A320 Part-147 theoretical and practical course. Because this is their second type rating in the B1.1 subcategory, formal OJT is not mandatory, allowing streamlined endorsement upon passing the Part-147 course assessments.

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Exam Tips & Regulatory Traps

• The Group 1 Criteria: Since Regulation (EU) 2025/111 the FL290 criterion is qualified: an aeroplane with a maximum certified operating altitude above FL290 is Group 1 only if it is powered with a power plant other than piston. A piston aeroplane certified above FL290 is not caught by that limb. Also remember the three limbs candidates forget: gas airships other than ELA2, non-conventional aircraft, and the helicopter criteria (>3 175 kg, >9 pax, min 2 pilots, multi-engine, or a non piston/turbine/electric power plant).
• First Type Rating OJT: OJT is only mandatory for the first type rating in that licence category/subcategory. If an exam question asks: "A B1.1 engineer holding an A320 rating adds a B737 rating. Is OJT required?" The answer is no.
• OJT Task Percentage: The required syllabus coverage for an approved OJT logbook is at least 50%, not 75% or 100%.
• Theoretical Depth: Level 1 is general familiarisation, Level 2 is ramp/transit, and Level 3 is detailed technical knowledge (mandatory for Category B1 and B2 type endorsements).