EASA Part-66 B1 vs B2 Licence: Mechanical vs Avionics Explained
When pursuing your EASA Part-66 licence, one of the most important decisions you will make is choosing your category. The two main certifying categories are B1 (mechanical — covering structure, systems, and engines) and B2 (avionics — covering electrical and electronic systems), each leading to a different scope of work, exam pathway, and career profile. Most engineers pursue one category first, but understanding each on its own is essential. This guide breaks down the differences to help you choose the right path for your future.
Skylicence Europe Team
EASA Part-66 exam preparation specialists — helping engineers earn their Aircraft Maintenance Licence since 2025
Understanding the B1 and B2 Categories
The EASA Part-66 licensing system, governed by Regulation (EU) No 1321/2014, Annex III, recognises two main certifying categories for most of the fleet. The B1 category authorises the holder to certify mechanical work — the aircraft's structure and all non-electronic systems, including engines. The B2 category authorises work on the electrical and electronic systems — avionics, instruments, communication and navigation, autopilots, and digital systems. An engineer who holds both holds the dual B1/B2 licence, a rare and highly valued combination.
It is also possible — and increasingly common — to earn categories sequentially. Many engineers start with one category, gain experience, and add the second later by passing the additional modules and assessment. However, most employers strongly prefer engineers who hold a full certifying category, and the experience requirement (5 years for B1.1 and B2, reducible to 3 with a recognised technical diploma) is proportionally efficient.
B1 Category (Mechanical)
The B1 category covers the aircraft's physical structure, its mechanical systems, and its propulsion installation. B1 engineers are the general practitioners of structural and systems maintenance — they work on everything from fuselage skins and flight controls to landing gear, hydraulics, engines, and cabin environmental systems. B1 is divided into four subcategories: B1.1 (aeroplane turbine), B1.2 (aeroplane piston), B1.3 (helicopter turbine), and B1.4 (helicopter piston).
What B1 Engineers Do
- Perform scheduled inspections (daily, weekly, phase, and base checks) on airframes and their systems
- Troubleshoot and repair mechanical systems including landing gear, brakes, flight controls, and hydraulic systems
- Perform sheet metal, composite, and structural repairs on fuselages, wings, and control surfaces
- Maintain engines and propellers — from piston engines on trainers to turbofans on airliners
- Sign the release to service (CRS) for mechanical work within the scope of their category
Modules Required for B1
A B1.1 licence requires 13 module exams: the fundamentals (M1 Mathematics, M2 Physics, M3 Electrical Fundamentals), M4/M5 (electronic and digital basics), M6 Materials and Hardware, M7 Maintenance Practices, M8 Basic Aerodynamics, M9 Human Factors, M10 Aviation Legislation, plus the aeroplane-specific M11 Aeroplane Aerodynamics Structures and Systems, M14 Propulsion, M15 Gas Turbine Engine, and M17 Propeller. The pass mark for every module is 75%.
Career Outlook and Salary
B1 engineers are in high demand across all sectors of European aviation. General aviation, airlines, charter operators, and MROs all need B1 certifying staff. Entry-level licensed salaries range from €30,000 to €45,000, with experienced engineers earning €45,000 to €65,000. Type-rated B1 engineers at major airlines can earn €70,000 or more.
B2 Category (Avionics)
The B2 category focuses on the electrical and electronic systems of the aircraft — avionics: communication and navigation equipment, instruments, radar, autopilots, flight management computers, and integrated digital systems. B2 engineers are the specialists who keep the electronic brain of modern aircraft running safely and reliably.
What B2 Engineers Do
- Install, test, and certify communication and navigation systems (VHF, VOR, ILS, DME, GPS, transponders)
- Troubleshoot and repair instrument systems, autopilots, and flight management computers
- Work on electrical power generation and distribution, wiring, and bonding
- Load software and perform functional tests on integrated avionics systems
- Sign the release to service (CRS) for avionics work within the scope of their category
Modules Required for B2
The B2 licence requires the electronics-heavy module set: M1 Mathematics, M2 Physics, M3 Electrical Fundamentals, M4 Electronic Fundamentals, M5 Digital Techniques/Electronic Instrument Systems, M6 Materials and Hardware, M7 Maintenance Practices, M8 Basic Aerodynamics, M9 Human Factors, M10 Aviation Legislation, plus M13 Aircraft Aerodynamics Structures and Systems and M14 Propulsion. The pass mark for every module is 75%.
Career Outlook and Salary
B2 engineers are essential at airlines, MROs, and avionics shops — and the avionics specialist shortage is well documented as aircraft become more computerised. Salaries are competitive with B1 roles, typically ranging from €30,000 to €65,000 depending on experience and employer. B2 engineers with type ratings on modern fleets (A320neo, 737 MAX, A350, 787) and experience with integrated modular avionics are particularly well compensated.
Side-by-Side Comparison
| Factor | B1 (Mechanical) | B2 (Avionics) | Both (Dual B1/B2) |
|---|---|---|---|
| Focus Area | Structure + mechanical systems + engines | Electrical + electronic systems | Full aircraft |
| Module Exams | 13 modules (M11/M14/M15/M17 set) | 12 modules (M4/M5/M13 set) | Both sets (shared M1-M10) |
| Experience Required | 5 years (3 with diploma); B1.2: 4 (3) | 5 years (3 with diploma) | 5 years + additional modules |
| Salary Range | €30K–€70K+ | €30K–€65K+ | €40K–€85K+ |
| Key Skills | Structural, mechanical, engine theory | Electronics, digital systems, diagnostics | Broad, most versatile |
| Employer Demand | Steady, broad | High (avionics growth) | Highest (rare combination) |
How to Choose the Right Category for You
Your choice of category should be guided by three factors: your natural aptitudes, your career goals, and the opportunities available in your region.
Choose B1 If You
- Enjoy working with your hands on structures and systems — sheet metal, composites, landing gear, flight controls, engines
- Want to work in general aviation, corporate aviation, or MRO heavy maintenance
- Prefer variety in your daily work — no two days are the same for a B1 engineer
- Are drawn to inspection and structural repair work
Choose B2 If You
- Have a strong interest in electronics, digital systems, and software
- Enjoy troubleshooting complex faults using schematics, test equipment, and diagnostic software
- Want to specialise in the fastest-growing area of aircraft technology
- Prefer working in avionics bays, avionics shops, or bench environments
Choose Both (Dual B1/B2) If You
- Want the maximum career flexibility — the dual licence is rare and highly valued
- Plan to work at airlines, major MROs, or OEMs where full coverage is an advantage
- Want to sign off a wider scope of work and earn the certification premium
- Are willing to study for both module sets and complete both assessments
Can You Hold Both Categories?
Yes — and more engineers are doing it every year. Part-66 allows you to hold B1 and B2 on a single licence, and the dual B1/B2 engineer is the most versatile configuration in the industry. The fundamentals modules (M1-M10) are shared between the two sets, so the additional study burden is mostly the category-specific modules (M11/M14/M15/M17 for B1.1 vs M4/M5/M13 for B2).
The typical path is to earn one category first, then extend: the exam preparation overlaps significantly, and holding both increases your employability, allows you to certify a wider range of work, and commands a salary premium at virtually every employer.
Prepare for Your Category Exams with Skylicence Europe
Whatever category path you choose, Skylicence Europe has you covered. Our AI-powered platform provides targeted practice for the Part-66 module exams, organised by module and aligned with Part-66 Appendix I:
- For B1 candidates — The full B1.1/B1.2 module sets including M11, M14, M15, M16 and M17 with in-depth structures, systems, and propulsion content
- For B2 candidates — The electronics-heavy set including M4, M5 and M13 with full digital and instrument systems coverage
- For dual candidates — All 17 modules with complete Appendix I coverage and full exam simulations across all 8 licence categories
Start preparing for your category exams with Skylicence Europe →