Part-66 Licence Categories Explained

Part-66 licence categories decide what an aircraft maintenance engineer may certify. Your category sets the modules you sit, the experience you need and the jobs you can do, so it is the first decision on the way to an aircraft maintenance licence (AML). This hub explains every category and subcategory, what each lets you certify, how aircraft groups and type ratings work, which modules each category sits under EASA and UK CAA rules and how much experience each needs, and links to a full guide for each category.

Part-66 Prep is an independent study aid, not EASA, the UK CAA or a Part-147 organisation. The categories are set by 66.A.3 and their privileges by 66.A.20 of Part-66, in Regulation (EU) No 1321/2014 for the EU and in the retained UK Part-66 for the UK. Both systems use the same categories.

The Part-66 licence categories at a glance

Category	Subcategories or ratings	Aircraft	In short	Guide
A	A1 turbine aeroplanes, A2 piston aeroplanes, A3 turbine helicopters, A4 piston helicopters	as named	Minor line maintenance and simple defect rectification	Category A licence
B1	B1.1 turbine aeroplanes, B1.2 piston aeroplanes, B1.3 turbine helicopters, B1.4 piston helicopters	as named	Structure, engines, mechanical and electrical systems	B1 licence
B2	none	all aircraft	Avionic and electrical systems	B2 licence
B2L	system ratings: com/nav, instruments, autoflight, surveillance, airframe systems	all except group 1	Avionics within the ratings held	B2L licence
B3	none	piston, non-pressurised aeroplanes of 2,000 kg MTOM or less	B1-style privileges on light aeroplanes	B3 licence
C	none	aeroplanes and helicopters	Release of the whole aircraft after base maintenance	covered below

There is also category L for light aircraft (sailplanes, powered sailplanes, balloons, airships and some light aeroplanes), with its own syllabus. This site doesn't cover L.

Key fact: Under EASA rules, Regulation (EU) 2025/111 (applicable from 13 February 2026) added subcategory B1.E for aeroplanes with electric power plants below 5,700 kg and a new Module 18, so EASA now has 18 modules. Module 18 paper sizes are not confirmed, and this site covers Modules 1 to 17 with no Module 18 questions yet. The UK has consulted on similar changes (RMT 0201), with the law planned for 2027 and most of it in force in 2029.

What each category can certify (66.A.20)

Category A

An A licence holder can issue a certificate of release to service (CRS) for minor scheduled line maintenance and simple defect rectification, but only for tasks listed on the certification authorisation issued by their employer, and only for work they did themselves. Category A holders don't hold type ratings; their organisation trains them on each task.

Category B1

B1 covers structure, powerplant, mechanical and electrical systems, plus avionic tasks that need only simple tests and no troubleshooting. B1 holders can also act as support staff in base maintenance, and each B1 subcategory includes the matching A subcategory.

Category B2 and B2L

B2 covers avionic and electrical systems, and electrical or avionic tasks within powerplant and mechanical systems that need only simple tests. With task training, a B2 can also do minor scheduled line maintenance and simple defect rectification within their ratings, but B2 does not include an A subcategory. B2L gives the same kind of privileges limited to electrical systems and the avionic systems covered by its ratings, on aircraft outside group 1.

Category B3

B3 gives B1-type privileges (structure, powerplant, mechanical and electrical systems, simple avionic tests) for piston-engine, non-pressurised aeroplanes of 2,000 kg maximum take-off mass or less.

Category C

C lets the holder release the whole aircraft after base maintenance. B1 and B2 support staff make sure every task in the check has been done; the C certifier signs for the aircraft as a whole.

Our free licence categories note puts all of this in one table. If you are torn between the two main options, read the B1 vs B2 comparison.

Aircraft groups and type ratings (66.A.5 and 66.A.45)

The category says what you may certify; the group and ratings say on which aircraft.

Group	Aircraft	Rating needed for B1, B2 and C
1	Complex motor-powered aircraft, multi-engine helicopters, non-piston aeroplanes certified above FL290, fly-by-wire aircraft, gas airships other than ELA2	Individual type rating
2	2a single turboprop aeroplanes; 2b single turbine helicopters; 2c single piston helicopters (with some exceptions EASA classifies)	Type, manufacturer subgroup or full subgroup rating
3	Piston-engine aeroplanes outside group 1	Type or full group rating
4	Sailplanes, powered sailplanes, balloons and airships outside group 1	B2 only: full group rating

B2L uses subgroup and group ratings for groups 2 to 4, and B3 has a single rating for its class of aeroplane. Category A has no ratings on the licence. Type ratings are gained through approved type training, plus on-the-job training for your first type in a category. The Part-66 type ratings guide explains the process.

Which modules each category sits

Every B category sits Modules 1 to 10; category A sits the same set without Module 4. The aircraft and engine modules follow the subcategory. Under UK CAA rules the split modules apply: B3 sits 7B, 9B, 11C and 17B, and everyone else sits 7A and 9A.

Category	Modules	Papers
A1 / A2 / A3 / A4	1, 2, 3, 5–10 plus 11A, 15, 17A (A1); 11B, 16, 17A (A2); 12, 15 (A3); 12, 16 (A4)	11 to 12
B1.1	1–10, 11A, 15, 17A	13
B1.2	1–10, 11B, 16, 17A	13
B1.3	1–10, 12, 15	12
B1.4	1–10, 12, 16	12
B2	1–10, 13, 14	12
B2L	1–10, Module 13 parts for each system rating, Module 14 for the instruments and airframe systems ratings	varies
B3	1–10, 11C, 16, 17B	13
C	B1 or B2 knowledge level (or a relevant degree route)	as B1 or B2

Adding all papers together gives very different workloads. Multiple-choice questions over the whole licence, EASA / UK CAA: B1.1 716 / 692, B1.2 660 / 612, B1.3 672 / 648, B2 684 / 652, B3 552 / 448. Essays add two under EASA rules (Module 7) and four under UK rules (Modules 7, 9 and 10). The Part-66 modules guide gives the size of every paper for every category.

Exam tip: When you add a category, you sit only what you are missing. A B1.1 engineer adding B2 typically needs Modules 13 and 14 plus the B2-level papers where the B2 paper is bigger, such as Module 4 (40 questions against 20) and Module 5 (72 against 40).

Experience required for each category (66.A.30)

Practical maintenance experience on operating aircraft is required before the licence is issued. The durations are the same in both systems:

Category	No relevant technical training	Skilled worker in a technical trade	Part-147 basic course
A, B1.2, B1.4, B3	3 years	2 years	1 year
B1.1, B1.3, B2	5 years	3 years	2 years
B2L	3 years	2 years	1 year, plus 3 months per added system rating
C	3 years using B1.1, B1.3 or B2 privileges on complex aircraft (including 12 months as base maintenance support staff), or 5 years using B1.2 or B1.4 privileges; degree routes also exist

At least one year must be recent experience on the category you apply for, and all of it must fall within the 10 years before your application. In the UK, the CAA currently recognises no course as meeting the skilled-worker reduction, so UK candidates use the no-training or Part-147 figures (CAA engineer licences). The experience requirements guide covers logbooks and what counts.

Common upgrade paths between categories

Few engineers stay with one category for their whole career. These are the paths people follow most often:

• A to B1. Category A shares most of its modules with the matching B1 subcategory, but at a lower level and with shorter papers. Moving up means sitting Module 4 and the B1-level versions of the shared modules where the B1 paper is bigger (for example Module 3 is 20 questions for A and 52 for B1), plus the experience for B1.
• B1 to B2, or B2 to B1. Many airline engineers hold both. The papers you add are the other category's own modules (13 and 14 for B2; 11A, 15 and 17A for B1.1) and the higher-level shared papers.
• B1.1 to B1.3, or similar. Changing between aeroplanes and helicopters, or turbine and piston, mostly means the aircraft and engine modules for the new subcategory.
• B1 or B2 to C. Experienced certifying engineers in base maintenance often add C. It needs no new module exams if you already meet the B1 or B2 knowledge level, but it does need the experience set out below.

Under UK CAA rules an essay passed at category A level counts at category B level, so it isn't repeated when you upgrade.

How to choose your category

A few practical questions settle it for most people:

1. What do you want to work on? Big aeroplanes point to B1.1 or B2; helicopters to B1.3; light aircraft to B1.2 or B3.
2. Mechanical or avionics? If you like engines, structures and hydraulics, B1. If you prefer wiring, computers and fault-finding on avionic systems, B2.
3. How fast do you need to certify something? Category A has a shorter experience requirement and fewer modules, so some apprentices start with A and build to B1.
4. What do local employers want? Job adverts and apprenticeship schemes near you show which categories are in demand.

The EASA Part-66 FAQs answer common questions on categories and adding them later.

Categories under EASA and UK CAA rules

The UK kept the same categories when it left the EASA system, so a UK B1.1 and an EASA B1.1 give the same kind of privileges. The licences are still separate: a UK licence does not give EASA privileges, and an EASA licence is not accepted for certifying UK-registered aircraft in a UK organisation. The exams differ in size and in essays, and the UK splits Modules 7, 9, 11 and 17 into A and B or C versions. If you may work in both systems, the EASA vs UK CAA guide explains what each licence needs.

Which categories this site covers

Part-66 Prep has papers for seven categories: A, B1.1, B1.2, B1.3, B2, B2L and B3. We don't have separate practice for:

• B1.4, because it uses the same modules as B1.3 with Module 16 in place of Module 15. Practise the B1.3 modules and Module 16 at B1.2 size, which matches B1.4 under EASA rules. Under UK rules, note that B1.4's Module 5 paper is 20 questions, the B1.2 size.
• C, because it has no module exams of its own: knowledge is met at B1 or B2 level.
• L, which has a separate syllabus.
• B1.E, because Module 18 paper sizes are not yet confirmed.

Category A appears as one category with every A module. On B2L, our Module 13 paper uses the full B2 size; the real B2L Module 13 is examined per system rating.

Your study plan

1. Pick your category using the guides above, and read its page: A, B1, B2, B2L or B3.
2. Take the free 20-question diagnostic for that category, for example the B1.1 diagnostic or the B2 diagnostic.
3. Choose your first module from the modules guide and use its free quick practice and paper 1.
4. Start recording your experience now, in a logbook your authority accepts, so the experience side keeps pace with your exams.