The Part-66 B1 licence is the qualification most people mean when they talk about becoming a licensed aircraft engineer. It covers the mechanical side of an aircraft, from the structure and engines to the hydraulics, fuel and electrical systems, and it is the category behind most line and base maintenance certifying roles on aeroplanes and helicopters. This guide explains what a B1 engineer can certify, how B1.1, B1.2 and B1.3 differ, which modules each sits and how long the papers are under EASA and UK CAA rules, the experience you need and what it costs.
Part-66 Prep is an independent study aid, not EASA, the UK CAA or a Part-147 organisation. For the other categories, see the Part-66 licence categories guide; the rule text is Part-66 (Annex III) in Regulation (EU) No 1321/2014 for the EU and the retained UK Part-66 for the UK.
What a Part-66 B1 licence lets you do
Under 66.A.20, a B1 licence holder may issue certificates of release to service, and act as B1 support staff in base maintenance, for work on:
- aircraft structure;
- the powerplant (engines and, where relevant, propellers);
- mechanical systems such as flight controls, landing gear, hydraulics, fuel and air conditioning;
- electrical systems;
- avionic systems, but only where the task needs simple tests to prove serviceability and no troubleshooting.
Each B1 subcategory also includes the matching category A subcategory, so a B1.1 holder can certify the minor scheduled line maintenance and simple defect rectification an A1 holder can.
A licence on its own is not enough to sign. You also need a certification authorisation from your employer, for example a Part-145 or Part-CAO organisation, a type rating for complex (group 1) aircraft, and recent experience: six months of relevant maintenance in the last two years. Our free licence categories note sets out the privileges for every category side by side.
Key fact: The B1 is the mechanical licence and the B2 the avionics licence. A B1 can do simple avionic tests; a B2 can troubleshoot avionic systems but doesn't include category A. The B1 vs B2 comparison helps you choose.
B1.1, B1.2, B1.3 and B1.4: the subcategories
| Subcategory | Aircraft | Typical work |
|---|---|---|
| B1.1 | Aeroplanes with turbine engines | Airliners, business jets, turboprops |
| B1.2 | Aeroplanes with piston engines | Light aircraft, training fleets, older piston twins |
| B1.3 | Helicopters with turbine engines | Offshore, air ambulance, police and corporate helicopters |
| B1.4 | Helicopters with piston engines | Light training and private helicopters |
B1.1 is by far the most common choice, because airline and large maintenance organisation jobs need it. B1.3 suits people heading for helicopter operators. B1.2 has a shorter experience requirement and suits general aviation, though work on complex piston aircraft and some types needs more than B1.2 alone.
This site covers B1.1, B1.2 and B1.3. B1.4 uses the same modules as B1.3, with Module 16 (piston engine) in place of Module 15.
A note on B1.E (EASA only)
Regulation (EU) 2025/111, applicable from 13 February 2026, adds an EASA subcategory B1.E for aeroplanes with electric power plants (maximum take-off mass below 5,700 kg) and a new Module 18 Electric power plant, with a transitional endorsement for B1.1 and B1.2 holders until 13 February 2028. EASA now has 18 modules. The paper sizes for Module 18 have not been confirmed, and this site covers Modules 1 to 17 with no Module 18 questions yet. The UK has consulted (RMT 0201) on similar changes; the CAA plans to make the law in 2027, mostly in force in 2029 with a four-year transition.
B1 modules and paper sizes: EASA and UK CAA
Every B1 subcategory sits Modules 1 to 10, then its own aircraft and engine modules. Questions are three-option multiple choice, about 75 seconds each, with a 75% pass mark. This table gives questions per paper as EASA / UK CAA.
| Module | B1.1 | B1.2 | B1.3 |
|---|---|---|---|
| 1 Mathematics | 32 / 32 | 32 / 32 | 32 / 32 |
| 2 Physics | 52 / 52 | 52 / 52 | 52 / 52 |
| 3 Electrical fundamentals | 52 / 52 | 52 / 52 | 52 / 52 |
| 4 Electronic fundamentals | 20 / 20 | 20 / 20 | 20 / 20 |
| 5 Digital techniques | 40 / 40 | 40 / 20 | 40 / 40 |
| 6 Materials and hardware | 80 / 72 | 80 / 72 | 80 / 72 |
| 7 Maintenance practices (+2 essays) | 80 / 80 | 80 / 80 | 80 / 80 |
| 8 Basic aerodynamics | 24 / 20 | 24 / 20 | 24 / 20 |
| 9 Human factors | 28 / 20 + essay | 28 / 20 + essay | 28 / 20 + essay |
| 10 Aviation legislation | 44 / 40 + essay | 44 / 40 + essay | 44 / 40 + essay |
| 11A Turbine aeroplane | 140 / 140 | – | – |
| 11B Piston aeroplane | – | 100 / 100 | – |
| 12 Helicopter | – | – | 128 / 128 |
| 15 Gas turbine engine | 92 / 92 | – | 92 / 92 |
| 16 Piston engine | – | 76 / 72 | – |
| 17A Propeller | 32 / 32 | 32 / 32 | – |
| Total multiple-choice questions | 716 / 692 | 660 / 612 | 672 / 648 |
| Essays | 2 / 4 | 2 / 4 | 2 / 4 |
So a B1.1 candidate answers 716 multiple-choice questions over 13 papers under EASA rules, and 692 plus two extra essays under UK rules. The longest single paper is Module 11A at 140 questions and 175 minutes; under EASA rules a paper over 90 minutes may be split into partial exams, and one over 180 minutes into three. The Part-66 modules guide explains what each module covers.
Module pages for B1 candidates
Each module page has the full paper table, a walk-through of every sub-module and free practice:
- Shared modules: Module 1, Module 2, Module 3, Module 4, Module 5, Module 6, Module 7, Module 8, Module 9 and Module 10.
- Aircraft modules: Module 11 for B1.1 (11A) and B1.2 (11B), Module 12 for B1.3.
- Engine and propeller modules: Module 15 for B1.1 and B1.3, Module 16 for B1.2, Module 17 for B1.1 and B1.2.
Practice hubs by subcategory: B1.1, B1.2 and B1.3. Each lists every module with the free quick practice and paper 1.
Exam tip: The B1.2 UK Module 5 paper is half the EASA size (20 questions against 40). If you sit UK exams, set the start screen to UK CAA rules so your practice papers match.
Experience you need for a B1 licence
Passing the modules is half of it. Under 66.A.30 you also need practical maintenance experience on operating aircraft before the licence is issued:
| Route | B1.1 and B1.3 | B1.2 (and B1.4) |
|---|---|---|
| No previous relevant technical training | 5 years | 3 years |
| Skilled worker in a relevant technical trade | 3 years | 2 years |
| Part-147 approved basic training course | 2 years | 1 year |
At least one year must be recent experience on the subcategory you are applying for, and the experience must fall within the 10 years before you apply. 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 durations (CAA licence application page). UK applicants record their experience in a CAP 741 logbook. The experience requirements guide explains what counts.
How long a B1 licence takes
No authority publishes a typical timescale, because it depends on your route:
- Part-147 full-time or apprenticeship route: a Part-147 basic course for B1.1 or B1.3 has a minimum of 2,400 hours of training (2,000 for B1.2) under Part-147, then the reduced experience of two years (one for B1.2). Schools set their own timetables, so ask them how long their course runs.
- Self-study route: you sit the modules at an exam centre while working, and need five years of experience for B1.1 or B1.3 (three for B1.2). Many people pass the modules within that time.
- Already in the trade: if you have years of relevant hangar experience, the modules are often what holds you back. The self-study guide covers planning them around shifts.
Remember that module passes count for an application for 10 years, so you don't have to sit everything in one go. The how to become a B1 engineer guide walks through each route step by step.
Type ratings for B1 engineers
The B1 licence is the basic licence. To certify on complex aircraft in group 1, such as airliners and multi-engine helicopters, you need an individual type rating for each type, gained through approved type training and, for your first type in the subcategory, on-the-job training. For simpler group 2 and group 3 aircraft, group or subgroup ratings are possible. Group 3 and B1.2 ratings can carry limitations, for example on composite or wooden structure, until you show the relevant experience. See the Part-66 type ratings guide.
Where B1 engineers work
B1 engineers work wherever aircraft are maintained under Part-145, Part-CAO or Part-ML rules. Typical employers include:
- Line maintenance at airports, for airlines or contract maintenance providers: turnarounds, daily and weekly checks, defect rectification and releasing aircraft for the next flight, often on shifts that include nights.
- Base maintenance in hangars: heavy checks, modifications and structural repairs, where B1 engineers act as support staff alongside a category C certifier.
- Helicopter operators for B1.3 holders: offshore transport, air ambulance, police and corporate fleets.
- General aviation for B1.2 holders: flying schools, light aircraft maintenance organisations and private owners, including independent certifying work under Part-ML.
- Engine and component shops, manufacturers and defence contractors, where licensed engineers often work in planning, technical services or quality roles.
Pay and conditions vary with employer, region, licence and type ratings held, and shift allowances, so we don't quote salary figures. Job adverts from employers you would like to work for are the most reliable guide to current rates.
What a B1 licence costs
Costs depend on your route and your authority. UK CAA charges as of October 2026, from the CAA scheme of charges:
| Item | UK CAA fee |
|---|---|
| Licence grant, per category or subcategory | £455 |
| Module exam at a CAA venue, per attempt | £60 |
| B1.1 or B1.2: 13 modules passed first time | £780 in exam fees |
| B1.3: 12 modules passed first time | £720 in exam fees |
| Adding a type rating | £183 |
| Licence renewal every 5 years | £455 |
Part-147 organisations set their own exam and course prices, and EU authorities set their own fees. Course fees for a full basic course are far larger and vary widely. The licence cost guide breaks the total down by route.
The B1 licence in Ireland and the EU
In Ireland and every other EU state, a B1 is an EASA Part-66 licence issued by that country's competent authority, and the exams follow the EASA standard from Regulation (EU) 2023/989: no essays outside Module 7 and up to three attempts per module in any 12 months. A UK licence does not give EASA privileges and an EASA licence does not give UK privileges, so choose the system of the country where you plan to work. The EASA vs UK CAA guide covers the differences.
Your study plan
- Take the free B1.1 diagnostic (or the B1.2 or B1.3 version from its hub) to see where you stand across all your modules.
- Start with Modules 1, 2 and 3, then fit in short papers such as Modules 8, 9 and 10 for early passes.
- For each module, read the free first note, do quick practice daily and sit the free paper 1 at your system's size.
- Leave the long aircraft and engine papers (11A, 11B or 12, and 15 or 16) until your basics are solid.
- Book each exam once you score 85% on three different papers. Pro unlocks papers 2 to 10, the mixed papers and every note for all three B1 subcategories.
10 free Part-66 B1.1 practice questions with answers
Try each one, then open the answer. For the timed experience use the free diagnostic.
1. A machine has a velocity ratio of 5 and an efficiency of 80 %. What is its mechanical advantage?
- A. 6.25
- B. 0.16
- C. 4
Show answer
C. 4
MA = efficiency × VR = 0.8 × 5 = 4.
2. Critical fatigue areas on control cables are where the cable:
- A. passes over pulleys or through fairleads
- B. runs straight through open bays
- C. is painted for identification purposes
Show answer
A. passes over pulleys or through fairleads
Areas where the cable bends or rubs (pulleys, sleeves, fairleads) and within about 1 ft of a swaged fitting are prone to wire breakage and are inspected closely.
3. Why does a feathering propeller on a light twin have start locks (high-pitch latches)?
- A. To prevent the blades going into reverse on the ground
- B. To lock the blades at maximum pitch during take-off
- C. To stop the blades feathering when the engine stops, easing restart
Show answer
C. To stop the blades feathering when the engine stops, easing restart
Oil is lost at shutdown, so the spring/air charge would feather the blades. Spring-loaded latches engage below about 600-800 rpm, holding the blades in low pitch so the engine is not heavily loaded at the next start.
4. The average value of a sine wave taken over one half-cycle is
- A. 0.5 × peak value
- B. 0.637 × peak value
- C. 0.707 × peak value
Show answer
B. 0.637 × peak value
The mean of a half-cycle of a sine wave is 2/π ≈ 0.637 of the peak. Over a full cycle the average is zero.
5. A 'basic T' layout refers to the arrangement of
- A. the four engine display pages on the EICAS
- B. the flight deck circuit breaker panels
- C. airspeed, attitude, altitude and heading instruments
Show answer
C. airspeed, attitude, altitude and heading instruments
The basic T places attitude in the centre, airspeed on the left, altitude on the right and heading below; EFIS preserves this arrangement.
6. CG positions calculated by fuel management computers are usually expressed as:
- A. a percentage of the aircraft length
- B. a percentage of the mean aerodynamic chord (% MAC)
- C. a distance from the nose landing gear
Show answer
B. a percentage of the mean aerodynamic chord (% MAC)
For transport aircraft the CG is given as % MAC. This relates it to the wing's aerodynamic centre, so limits can be compared easily. Station numbers in inches or metres may be used in loading calculations.
7. On a stress-strain graph for a metal, the straight initial portion shows that stress is:
- A. proportional to strain
- B. independent of strain
- C. inversely proportional to strain
Show answer
A. proportional to strain
Within the elastic limit stress/strain is constant (Hooke's law); its gradient is Young's modulus.
8. Why are shake-proof tab lock washers used only once?
- A. They lose their spring action after heating
- B. They are cadmium plated and flake
- C. The tabs tend to break when bent a second time
Show answer
C. The tabs tend to break when bent a second time
Shake-proof lock washers with tabs bent against the nut can withstand higher heat than other safetying and suit high vibration, but should be used only once because the tabs tend to break when rebent.
9. A red disc missing from the fuselage indicator shows that the fire bottle:
- A. discharged due to overheat
- B. was fired by the crew
- C. is fully charged
Show answer
A. discharged due to overheat
The red (thermal) indicator is blown out when excessive heat causes the bottle's safety relief to vent overboard.
10. Which management action most directly supports a positive safety culture?
- A. Setting deadlines that cannot be met without taking shortcuts
- B. Visible commitment to safety and fair treatment of those who report errors
- C. Discouraging junior staff from asking questions of seniors
Show answer
B. Visible commitment to safety and fair treatment of those who report errors
Managers set the tone: by resourcing work properly, treating reporters fairly and acting on reports, they encourage staff to follow procedures and report errors. Poor management example quickly becomes the norm.
Frequently asked questions
+What is a B1 licence?
A B1 licence is the mechanical category of the Part-66 aircraft maintenance licence. It lets the holder issue certificates of release to service for maintenance on aircraft structure, powerplant, mechanical and electrical systems, and for avionic work that needs only simple tests, once their employer gives them a certification authorisation.
+What is the difference between B1.1, B1.2 and B1.3?
The subcategory sets the aircraft type: B1.1 is turbine-engined aeroplanes, B1.2 piston-engined aeroplanes, B1.3 turbine-engined helicopters and B1.4 piston-engined helicopters. Modules 1 to 10 are shared; each subcategory then sits its own aircraft and engine modules.
+Which modules do I need for B1.1?
B1.1 needs Modules 1 to 10, Module 11A (turbine aeroplane aerodynamics, structures and systems), Module 15 (gas turbine engine) and Module 17A (propeller). That is 13 papers, 716 multiple-choice questions in total under EASA rules and 692 under UK CAA rules.
+How long does it take to get a B1 licence?
With a Part-147 approved basic course, the minimum experience is two years for B1.1 and B1.3 and one year for B1.2. Without relevant training it is five years for B1.1 and B1.3 and three for B1.2. Exams can be taken alongside, so the experience is usually the limiting factor.
+How many exams are there for a B1 licence?
B1.1 and B1.2 have 13 module papers each and B1.3 has 12. Module 7 adds two essays under both systems, and UK CAA rules add one essay each in Modules 9 and 10.
+Does a B1 licence include category A?
Yes. Each B1 subcategory includes the matching A subcategory, so a B1.1 holder also has A1 privileges. B2 is different and does not include an A subcategory.
+Can a B1 engineer sign for avionics work?
Only for avionic tasks that need simple tests to prove serviceability, with no troubleshooting. Fault-finding and more complex avionic work belong to the B2 category.
+How much does a B1 licence cost?
Under UK CAA rules as of October 2026, the licence grant is £455 per category and each CAA module exam attempt is £60, so 13 B1.1 modules cost £780 in exam fees if every exam is passed first time. Part-147 courses, if you take one, cost far more and vary by school.
Study offline on your phone too
The Part-66 Prep: EASA & UK CAA app has the same questions plus a module board, essay coach, units drill and an attempt tracker for resit dates.
Keep reading
- Part-66 Licence Categories ExplainedEvery Part-66 licence category explained: A, B1.1 to B1.4, B2, B2L, B3 and C privileges, aircraft groups, modules per category and experience required.
- How to Become a B1 Licensed Aircraft EngineerHow to become a B1 licensed aircraft engineer: choose a subcategory, pass the modules, build experience, apply for the licence and get type rated.
- B1 vs B2: Comparing the Part-66 Mechanical and Avionics LicencesB1 vs B2 licence compared: privileges, the modules and paper sizes that differ, experience, adding the other category and which suits your career.
- Part-66 Module 11 Questions: Aeroplane Structures and SystemsPart-66 Module 11 questions for 11A, 11B and 11C: paper sizes per category, partial exams, every ATA sub-module explained and free timed papers.
- Part-66 Module 15 Gas Turbine Engine QuestionsPart-66 Module 15 gas turbine questions: 92 for B1.1 and B1.3, 60 for A1 and A3, all 22 sub-modules explained, worked thrust example and free paper.
- Part-66 Experience Requirements (66.A.30) ExplainedPart-66 experience requirements explained: 66.A.30 durations for every category, recent experience, what counts, logbooks like CAP 741 and the UK position.