Part-66 Category A Licence (A1 to A4) Guide

The Part-66 category A licence is the line mechanic's licence: it lets you sign the certificate of release to service for simple, routine jobs you have done yourself. It is often the first licence an apprentice gets, and it is included in every B1 licence. This guide explains what category A holders can and cannot certify, the four subcategories, the modules and paper sizes under EASA and UK CAA rules, the experience you need and how category A leads to B1.

Part-66 Prep is an independent study aid, not EASA, the UK CAA or a Part-147 organisation. The rules are in Part-66 (Annex III to Regulation (EU) No 1321/2014) for the EU and in UK Part-66 for the UK; privileges are in 66.A.20 and experience in 66.A.30. For an overview of every category, see Part-66 licence categories.

What a category A licence lets you certify

A category A aircraft maintenance licence permits the holder to issue a certificate of release to service (CRS) after minor scheduled line maintenance and simple defect rectification, within the limits of the tasks on their certification authorisation. Two limits make it very different from B1 or B2:

1. Only listed tasks. The licence is not enough on its own. Your maintenance organisation must issue a certification authorisation that names the tasks you may certify, after task training and an assessment.
2. Only your own work. A category A certifier may certify only tasks they personally performed. You cannot sign for a colleague's job.

Typical category A tasks are the routine line jobs that keep an aircraft flying between checks, such as wheel or brake unit changes, replacing lights, and replenishing fluids. EASA guidance material for maintenance organisations gives examples, but the actual list is set by each organisation for its aircraft and procedures, so two A1 mechanics at different operators can hold quite different authorisations.

Key fact: Category A does not cover troubleshooting or work that needs anything beyond simple tests. A defect that needs fault-finding, or a task that is not on your authorisation, goes to a B1 or B2 certifier.

Where category A holders work

Most work in line maintenance: on the ramp at airports, at outstations, and on transit and daily checks for airlines and line maintenance contractors. The A licence suits the pace of line work, where a mechanic with the right authorisation can release an aircraft after a simple job without waiting for a B1. People with an A licence also work in base maintenance, where their certification privileges matter less but the licence shows progress towards B1.

Pay is often asked about. It varies by employer, location, aircraft type, shift pattern and overtime, and no authority publishes figures, so check current job adverts for the roles you are interested in rather than relying on a quoted average.

The four subcategories: A1, A2, A3 and A4

Subcategory	Aircraft	Matching B1 subcategory
A1	Turbine-engined aeroplanes	B1.1
A2	Piston-engined aeroplanes	B1.2
A3	Turbine-engined helicopters	B1.3
A4	Piston-engined helicopters	B1.4

Choose the subcategory that matches the aircraft you work on or plan to work on. Most airline line maintenance is on turbine aeroplanes, so A1 is by far the most common choice; A3 suits helicopter operators. Part-66 Prep covers all four A subcategories for practice, because the A papers are the same for A1 to A4 in each module the subcategory sits.

Category A modules and paper sizes

Category A sits a reduced set of modules at lower knowledge levels than B1, and the papers are shorter. Module 4 is not required at all.

Which modules each subcategory sits

Module	A1	A2	A3	A4
1, 2, 3, 5, 6, 7, 8, 9, 10	yes	yes	yes	yes
4 Electronic fundamentals	no	no	no	no
11A Turbine aeroplane	yes	—	—	—
11B Piston aeroplane	—	yes	—	—
12 Helicopter	—	—	yes	yes
15 Gas turbine engine	yes	—	yes	—
16 Piston engine	—	yes	—	yes
17A Propeller	yes	yes	—	—

Paper sizes for category A: EASA vs UK

Questions and minutes per paper, from Appendix II. The pass mark is 75% throughout.

Module	EASA	UK CAA
1 Mathematics	16 / 20 min	16 / 20 min
2 Physics	32 / 40 min	32 / 40 min
3 Electrical fundamentals	20 / 25 min	20 / 25 min
5 Digital techniques / EIS	20 / 25 min	16 / 20 min
6 Materials and hardware	52 / 65 min	52 / 65 min
7 Maintenance practices	76 / 95 min + 2 essays	72 / 90 min + 2 essays (7A)
8 Basic aerodynamics	24 / 30 min	20 / 25 min
9 Human factors	28 / 35 min	20 / 25 min + 1 essay (9A)
10 Aviation legislation	32 / 40 min	32 / 40 min + 1 essay
11A Turbine aeroplane (A1)	108 / 135 min	108 / 135 min
11B Piston aeroplane (A2)	72 / 90 min	72 / 90 min
12 Helicopter (A3, A4)	100 / 125 min	100 / 125 min
15 Gas turbine engine (A1, A3)	60 / 75 min	60 / 75 min
16 Piston engine (A2, A4)	52 / 65 min	52 / 65 min
17A Propeller (A1, A2)	20 / 25 min	20 / 25 min

Added up, the multiple-choice totals are:

Subcategory	Papers	EASA questions	UK CAA questions	Essays (EASA / UK)
A1	12	488	468	2 / 4
A2	12	444	424	2 / 4
A3	11	460	440	2 / 4
A4	11	452	432	2 / 4

Under UK rules, the CAA treats an essay passed at category A level as a pass at category B level, so a Module 7, 9 or 10 essay passed for A does not have to be repeated when you move to B1. The EASA vs UK CAA guide explains why the two systems differ.

Exam tip: The longest category A papers are Module 11A (108 questions) for A1 and Module 12 (100) for A3 and A4. Under EASA rules both may be split into two partial exams; ask your exam centre how it runs them.

Module pages for category A candidates

Each module page has the per-category table, a walkthrough of the sub-modules and free papers:

• Foundations: Module 1, Module 2, Module 3, Module 5 and Module 6.
• Practices and rules: Module 7 (with the essays), Module 8, Module 9 and Module 10.
• Aircraft and engines: Module 11 (11A for A1, 11B for A2), Module 12 (A3, A4), Module 15 (A1, A3), Module 16 (A2, A4) and Module 17 (A1, A2).

Practise at category A size: Module 7 paper 1 and Module 11A paper 1, or start from the category A practice hub.

Experience for a category A licence

Category A has the shortest basic experience requirement in 66.A.30, the same as B1.2, B1.4 and B3.

Background	Practical maintenance experience required
No relevant previous technical training	3 years
Skilled worker in a relevant technical trade	2 years
Part-147 approved basic training course for category A	1 year

At least one year must be recent experience on the subcategory you apply for, and all of it must be within the 10 years before the application. The UK CAA says it does not currently recognise any course as meeting the skilled-worker reduction, so in practice UK applicants use the 3-year or Part-147 route. Experience is recorded in a logbook (the CAA uses CAP 741). The experience requirements guide explains what counts.

From category A to B1

A B1 licence includes the matching A subcategory, so B1.1 includes A1 and B1.3 includes A3. Many engineers take A1 first and add B1.1 later, or apply for B1 directly. To move up you need:

1. Module 4, which category A does not sit.
2. The B1 papers for the other modules. B1 papers are longer and examined at higher knowledge levels: Module 6 is 52 questions for A and 80 (EASA) or 72 (UK) for B1; Module 11A is 108 for A1 and 140 for B1.1; Module 15 is 60 for A and 92 for B1. Ask your authority or Part-147 organisation whether a category A pass counts towards the B1 module or whether you need to sit the B1 paper.
3. More experience. B1.1 and B1.3 need 5 years (2 after a Part-147 B1 course), against 3 years for A. For an addition to an existing licence the recent experience may be shorter than one year, but at least 3 months.

The Part-66 B1 licence guide and how to become a B1 engineer cover that path in detail. If you are deciding between going straight to B1 or getting A first, consider whether your employer will use A privileges on the line, and how much time you have for the extra B1 modules.

Planning your category A exams

Neither EASA nor the CAA sets an order for the modules, and every pass counts towards a licence application for 10 years, so you can spread them over your experience period. A sequence that works for many category A candidates:

1. Modules 1, 2 and 3 first. They are short at category A size (16, 32 and 20 questions) and everything later builds on them.
2. Modules 8, 9 and 10 next. Short, largely self-contained, and good early passes. Under UK rules, Modules 9 and 10 each include an essay, so practise writing before you book.
3. Modules 5 and 6. Module 5 at category A covers displays, computer terminology, ESD and typical systems only; Module 6 is 52 questions of materials and hardware.
4. Module 7. The longest of the foundation papers at 76 (EASA) or 72 (UK) questions plus two essays. Sit it once you have hangar experience to draw on.
5. Your aircraft and engine modules last: 11A or 11B, or 12, then 15 or 16, and 17A for aeroplanes.

If you already plan to go on to B1, consider sitting the B1-size papers from the start for the modules both categories share, so you only sit each module once. Check with your authority or Part-147 organisation how a B1 pass is credited towards category A before you decide.

Applying for the licence

Once you hold the modules and the experience, you apply to your competent authority: the UK CAA for a UK licence, or the authority of an EU member state for an EASA licence. As of October 2026 the CAA charges £455 per category or subcategory for the grant of a UK Part-66 licence (CAA scheme of charges, ORS5 No 446); EU authorities set their own fees. The CAA publishes the process on its engineer licensing pages, and EASA answers common questions in its Part-66 FAQs. The licence is valid for 5 years and is then renewed.

Your study plan

1. Take the free category A diagnostic: 20 questions across the A modules.
2. Read the licence categories study note to confirm A1, A2, A3 or A4 is right for you.
3. Start with Modules 1, 2 and 3, then fit in Modules 8, 9 and 10, using each module's free quick practice and paper 1 from the category A hub.
4. Before Module 7, read the Module 7 page and practise essay structure.
5. Book each module once you score 85% on three different papers at category A size, and choose EASA or UK CAA rules on every paper's start screen.