Part 66 General Aviation Maintenance Licences

Category A2 applies to piston‑engine aeroplanes.

Holders of an A2 licence may certify minor scheduled line maintenance and simple defect rectification tasks, as authorised by their organisation.

This category is typically used for:

• Routine line maintenance tasks
• Task trained authorisations for specific simple tasks
• May only certify for work personally performed
• Can be extended to other licence categories

Category A4 applies to piston‑engine helicopters.

Holders of an A4 licence may certify minor scheduled line maintenance and simple defect rectification tasks, as authorised by their organisation.

This category is typically used for:

• Routine line maintenance tasks
• Task trained authorisations for specific simple tasks
• May only certify for work personally performed
• Can be extended to other licence categories

Category B1.2 applies to piston‑engine aeroplanes.

Holders of a B1.2 licence may perform and certify:

• Maintenance on aircraft structure
• Powerplant and mechanical systems
• Electrical systems
• Minor avionics work requiring only simple tests

Category B1.2 is commonly used in general aviation maintenance organisations, including those supporting multiple aircraft types.

Holders of a B1.3 licence may perform and certify:

• Maintenance on aircraft structure
• Powerplant and mechanical systems
• Electrical systems
• Minor avionics work requiring only simple tests

Category B1.3 is commonly used in helicopter maintenance organisations, including those supporting multiple rotorcraft types.

A B1.3 licence holder may apply to the CAA for additional type ratings within the scope of turbine‑engine helicopters. Where appropriate, this may require completion of relevant type training and examinations.

A B1.3 licence holder endorsed with the appropriate group ratings may also apply to extend privileges to other rotorcraft within the same category, subject to compliance with Part‑66 requirements and any applicable limitations.

Holders of a B1.4 licence may perform and certify:

• Maintenance on aircraft structure
• Powerplant and mechanical systems
• Electrical systems
• Minor avionics work requiring only simple tests

Category B1.4 is typically used in maintenance organisations supporting light piston‑engine helicopters, often in general aviation environments.

A B1.4 licence holder may apply to the CAA for additional ratings within piston‑engine helicopter types. Dependant on the type ratings held, further training or assessment may be required.

A B1.4 licence holder with appropriate experience and endorsements may also seek to extend their privileges in line with Part‑66 requirements, subject to any limitations applied to the licence.

Category B2 applies to avionic and electrical systems on all aircraft types, including general aviation aircraft.

Holders of a B2 licence may certify:

• Avionic and electrical systems
• Electrical and avionic tasks in powerplant and mechanical systems which only require simple tests to prove serviceability
• Minor scheduled line maintenance and defect rectification on specific task trained authorisations issued by a Part 145 for personally performed maintenance within the specific Part 145 organisation limited to a rating endorsed on the B2 licence.
• Category B2 does not include a Category A

This category is typically used by specialists supporting avionics maintenance in general aviation environments.

The holder of a B2 licence with given aircraft ratings may apply for a B2L licence in order to include a different aircraft rating if the applicant only wants to demonstrate compliance with the experience requirements for certain system ratings.

Category B2L applies to electrical and avionic systems on aircraft, except those in aircraft Group 1.

The licence is limited to the specific system ratings endorsed on the licence, such as:

• Communication and navigation
• Instruments
• Autoflight
• Surveillance
• Airframe systems (electrical and avionic tasks within the powerplant and mechanical system only requiring simple tests to prove serviceability)

Category B2L may be used in general aircraft maintenance organisations when a full B2 licence is not required.

Category B3 applies to piston‑engine, non‑pressurised aeroplanes with a maximum take‑off mass of 2000 kg or below.

The maintenance privileges are similar to those of Category B1.2, but limited to aircraft within this weight category.

A B3 licence does not require individual type ratings as the rating is 'piston-engine non-pressurised aeroplanes of 2000 kg MTOM and below'. It will normally be issued with any of the following limitations, which shall be endorsed on the licence for aircraft construction methods that the applicant has not demonstrated experience upon.

• wooden-structure aeroplanes,
• aeroplanes with metal-tubing structure covered with fabric,
• metal-structure aeroplanes,
• composite-structure aeroplanes.

A B3 licence holder endorsed with the rating ‘piston engine non-pressurised aeroplanes of 2000 kg MTOM and below’, may apply to the CAA for a fully rated licence in subcategories L1 and L2, with the same limitations as the B1.2/B3 licence held.

Category L applies to specific light aircraft types, including sailplanes, balloons, airships and some light aeroplanes.

A category L aircraft maintenance licence shall permit the holder to issue certificates of release to service and to act as L support staff in a similar manner to a Category B licence however within a smaller scope of privileges as defined by 66.A.20 Privileges and 66.A.45 Endorsement with aircraft ratings.

The Category L subcategories are:

L1C – Composite sailplanes

Applies to sailplanes constructed primarily from composite materials.

L1 – Sailplanes

Applies to non‑powered sailplanes, including non‑composite types.

L2C – Composite powered sailplanes and composite ELA1 aeroplanes

Applies to composite powered sailplanes and composite aeroplanes within the ELA1 definition.

L2 – Powered sailplanes and ELA1 aeroplanes

Applies to powered sailplanes and ELA1 aeroplanes. This subcategory overlaps most closely with general aviation aeroplanes.

L3H – Hot‑air balloons

Applies to hot‑air balloons only.

L3G – Gas balloons

Applies to gas balloons only.

L4H – Hot‑air airships

Applies to hot‑air airships.

L4G – ELA2 gas airships

Applies to gas airships that meet the ELA2 definition.

L5 – Gas airships (other than ELA2)

Applies to gas airships outside the ELA2 definition and normally requires specific type ratings.

The holder of a B1.2 or B3 licence with the appropriate type ratings may apply for licences in the L1 and L2  subcategories under the following conditions:

• A B1.2 licence endorsed with the Group 3 rating or in category
• A B3 endorsed with the rating ‘piston engine non-pressurised aeroplanes of 2000 kg MTOM and below’,
• Any limitations on the B1.2 or B3 licence will be reflected on an Category L1 or L2 issued.

Category B2L applies to electrical and avionic systems on aircraft, except those in aircraft Group 1.

The licence is limited to the specific system ratings endorsed on the licence, such as:

• Communication and navigation
• Instruments
• Autoflight
• Surveillance
• Airframe systems (electrical and avionic tasks within the powerplant and mechanical system only requiring simple tests to prove serviceability)

Category B2L is often used in light aircraft maintenance organisations where a full B2 licence is not required.

When an applicant wishes to get the privilege to issue certificates of release to service and to act as support staff for electrical and avionics tasks within powerplant and mechanical systems, he/she should apply for the rating ‘airframe system’ on the B2L licence. The reason is that the ‘airframe systems’ rating is the only rating which covers completely the electrical and avionics tasks of the powerplant and mechanical systems of the aircraft.

Category C applies to certification following scheduled base maintenance. The privileges apply to the aircraft in its entirety and the issuance of a certificate of release to service, following the completion of all maintenance completed by category B1, B2, B2L, B3 and L, support staff, as appropriate, following base maintenance and those staff have signed the maintenance tasks under their respective specialism.

The principal function of the category C certifying staff is to ensure that all required maintenance has been called up and signed off by the category B1, B2, B2L, B3 and L support staff, as appropriate, before issue of the certificate of release to service.

Only category C personnel who also hold category B1, B2, B2L, B3 or L qualifications may perform both roles in base maintenance.

Category C licences are issued as either complex or other than complex (non-complex). 

ELA1 aircraft means the following manned European light aircraft:

• an aeroplane with a maximum take-off mass (MTOM) of 1200 kg or less that is not classified as complex motor-powered aircraft;
• a sailplane or powered sailplane of 1200 kg MTOM or less;
• a balloon with a maximum design lifting gas or hot air volume of not more than 3400 m3 for hot air balloons, 1050 m3 for gas balloons, 300 m3 for tethered gas balloons;
• an airship designed for not more than four occupants and a maximum design lifting gas or hot air volume of not more than 3400 m3 for hot air airships and 1000 m3 for gas airships;

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ELA2 aircraft means the following manned European Light Aircraft:

• an aeroplane with a Maximum Take-off Mass (MTOM) of 2000 kg or less that is not classified as complex motor-powered aircraft;
• a sailplane or powered sailplane of 2000 kg MTOM or less;
• a balloon;
• a hot air ship;
• a gas airship complying with all of the following characteristics:
  • 3 % maximum static heaviness,
  • non-vectored thrust (except reverse thrust),
  • conventional and simple design of structure, control system and ballonet system, and
  • non-power assisted controls;
• a Very Light Rotorcraft;

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