Intro to Part 66
The aviation industry is one of the most safety-sensitive domains globally, requiring strict regulatory oversight over every facet of operation, including aircraft maintenance. Within the European Union, this oversight is governed by Regulation (EU) No 1321/2014, particularly Annex III, commonly referred to as Part 66.
This regulation sets out the requirements for the issuance of aircraft maintenance licences, qualifications of personnel, and the privileges and limitations attached to each licence category.
Part 66 categorises aircraft maintenance licences into various classes: Category A for minor scheduled line maintenance and simple defect rectification; Category B1 for mechanical systems; Category B2 for avionics; Category B3 for non-pressurised piston-engine aeroplanes; and Category C for base maintenance certification.
These licences ensure that maintenance activities are performed by individuals with the appropriate technical competence and knowledge base.
However, as aircraft technology has evolved, particularly with the rapid emergence of electric and hybrid-electric aircraft, there has been a growing regulatory gap. Until recently, Part 66 primarily addressed aircraft with piston or turbine engines.
This left the emerging sector of electrically propelled aircraft in a state of uncertainty. To address this, the European Commission, informed by EASA's Opinion No. 04/2024, introduced the new B1.E licence category through Commission Implementing Regulation (EU) 2025/111.
Addition of B1.E
The inclusion of the B1.E licence subcategory marks a pivotal regulatory evolution in European aviation legislation. The B1.E licence is the first to be tailored specifically for aeroplanes equipped with electric power plants.
The new category addresses the need for a distinct certification path to deal with the unique challenges and maintenance requirements posed by electric propulsion systems, which differ substantially from conventional piston or turbine engines.
The change is a forward-looking measure designed to support the safe and sustainable integration of new air mobility solutions into the European airspace.
With increasing investment in electric vertical take-off and landing (eVTOL) vehicles, small commuter aircraft, and training aircraft powered by electric propulsion, there is an urgent need for engineers who are trained, assessed, and authorised to maintain these aircraft types.
This addition was published in the Official Journal of the European Union on 24 January 2025 and will come into full regulatory effect from 13 February 2026. The transition period allows organisations and engineers to prepare for compliance with the new requirements.
What is the B1.E licence for? Aircraft type, weight etc.
The B1.E licence is specifically designed for aeroplanes that:
- Are powered exclusively by electric propulsion systems
- Have a maximum take-off mass (MTOM) of 5,700 kg or less
- Are not classified as complex motor-powered aircraft under Regulation (EU) No 1321/2014
Typical aircraft covered under the B1.E licence include light electric training aircraft, electric commuter aircraft for regional routes, and potentially certain models of eVTOL aircraft if they meet the criteria. These aircraft are generally simpler in their propulsion architecture but incorporate advanced energy management and battery systems that require dedicated training and handling procedures.
Key components subject to maintenance under the B1.E licence include:
- High-voltage electric motors
- Lithium-based or alternative battery systems
- Fuel cells (if applicable, though these may be excluded if they fall into a different subcategory)
- Power distribution and management systems
- Engine monitoring and diagnostic systems specific to electric propulsion
Because of the high voltages and energy densities involved, safety protocols for B1.E engineers are notably different from those required for conventional engines. Maintenance tasks must factor in the risks of electric shock, thermal runaway, and battery degradation.
Relevance to the aviation industry and environmental goals
The introduction of the B1.E category aligns closely with the EU’s broader environmental objectives, including the European Green Deal and the “Fit for 55” legislative package.
Electrically propelled aircraft emit no carbon dioxide during operation and produce significantly less noise than their combustion counterparts, making them ideal candidates for urban air mobility and short-haul flights in environmentally sensitive regions.
From an industry perspective, the B1.E licence supports a skilled workforce capable of maintaining these emerging aircraft technologies, thereby reducing barriers to entry for electric aircraft in commercial operations.
Furthermore, the regulatory clarity encourages investment in new airframes and propulsion systems, as manufacturers and operators now have a defined maintenance certification framework within which to operate.
How to gain a Part 66 B1.E licence
For new entrants to the profession who wish to attain a B1.E licence, the following steps are required:
Basic training and licence extensions
The B1.E licence requires the same core modules as B1.1, but some topics are covered at a lower level. For example, Module 11 includes less detail on fuel systems, which is instead addressed in Module 18 through battery storage and energy systems.
Module 18 replaces Module 15 and is delivered entirely at Level 3. It focuses on the design, operation, maintenance, and troubleshooting of electric propulsion systems, preparing engineers to support electric and hybrid-electric aircraft technologies.
- 18.1 Fundamentals
- 18.2 Engine performance
- 18.3 Engine construction
- 18.4 Electric energy system
- 18.4.1 Batteries and accessories
- 18.4.2 Fuel cells and accessories
- 18.4.3 Power distribution systems
- 18.4.4 Electronic engine control
- 18.5 Engine indication systems
- 18.6 Power plant installation
- 18.7 Engine monitoring and ground operation
- 18.8 Engine storage and preservation
How to extend an existing B1.1, B1.2 or B2 licence across to a B1.E
Recognising the significant overlap in knowledge and skills between existing licence holders and those required for B1.E, EASA has provided a simplified pathway for engineers already holding B1.1 (turbine), B1.2 (piston), or B2 (avionics) licences.
- Experience logbook to be completed on relevant electric propulsion aircraft under 2000kg MTOW. For B1.1 and B1.2 only 6 months experience is required. For B2’s you would require 12 months experience.
- Undertake module 18 as stated below, 76 questions with a pass mark of 75%
Extending a B1.E Licence to B1.1
Module 18 is a newly introduced unit focused on electric propulsion systems, covering their design, operation, maintenance, and troubleshooting. It is delivered entirely at Level 3 and includes a wide range of subjects such as engine construction, electric energy systems (batteries, fuel cells, power distribution, and electronic control), engine indication systems, and ground operation procedures.
Module 18 has been developed primarily as a bolt-on to existing B1.1, B1.2, or B2 licences, rather than as a standalone qualification.
There are notable differences in both content and complexity between B1.E and other licence categories. For example, fuel systems included in Module 11 are not required for B1.E but are essential for B1.1 and B1.2. As a result, extending a B1.E licence to other categories requires completing additional modules:
- To extend from B1.E to B1.1: Modules 11 and 15
- To extend from B1.E to B1.2: Modules 11 and 16
- To extend from B1.E to B2: Modules 4, 5, 13, and 14
This structure means that progressing from B1.E to a broader licence type often involves more effort than the reverse. Therefore, it is generally more advantageous to begin with a B1.1, B1.2, or B2 licence and later add B1.E as a supplementary qualification, rather than using B1.E as a starting point for an aviation maintenance career.
Practical experience
Part 66 allows the practical experience from previously held categories to be partially credited toward B1.E, especially when the engineer has recent experience working on similar aircraft. A minimum of six months additional experience may be required if the systems differ substantially.
Licence amendment
Once the difference training and experience requirements are met, the engineer can apply for the B1.E endorsement on their existing licence. This ensures that experienced professionals can adapt their qualifications efficiently without duplicating previously acquired competencies.
First type and OJT
The latest regulatory changes do not mention On-the-Job Training (OJT) requirements. With this in mind, obtaining an additional licence category, such as B1.E, would require OJT for the first type endorsement, just as it is required when adding the B2 category to an existing B1.1 licence.
Safety and operational considerations
Electric aircraft maintenance introduces unique safety considerations not present in traditional aircraft. High-voltage battery systems present risks such as:
- Arc flash incidents
- Battery thermal runaway
- Electrocution hazards
- Chemical exposure
The B1.E curriculum therefore includes robust safety training, including the use of personal protective equipment (PPE), isolation protocols, and emergency response procedures for battery fires or leaks.
Maintenance personnel must also be trained in interpreting data from battery management systems (BMS) and integrating software updates or firmware revisions, tasks not traditionally associated with other maintenance roles.
Future developments and regulatory outlook
The B1.E licence is expected to evolve alongside the technology it supports. As hybrid-electric aircraft and larger electric airframes enter the market, there may be scope for expanding the B1.E privileges to higher MTOM categories or introducing additional endorsements for hybrid propulsion systems.
Additionally, the B1.E category sets a precedent for the integration of other non-conventional aircraft into the regulatory framework, including hydrogen-powered aircraft, tilt-rotors, and vertical-lift systems. The creation of a clearly defined training and certification path will likely accelerate the adoption of such technologies across the continent.
Introduction of B1.E effect on part 147 training centres
With the February 2026 implementation date approaching, it is likely that many Part 147 training organisations are now scrambling to stay ahead of the curve. As of now, there is little indication that any centres have fully rolled out training for the new B1.E category.
With Module 18 introducing entirely new subject matter focused on electric propulsion, the pressure is mounting. Developing a compliant syllabus, sourcing expertise, and securing regulatory approval in time is no small task.
In addition to delivering full B1.E programmes, training centres must also prepare to offer differences training for existing B1.1, B1.2, and B2 licence holders. This adds further complexity. Unless action is taken soon, many may find themselves racing the clock to meet compliance requirements before the deadline.
Conclusion
The establishment of the B1.E licence subcategory within Part 66 represents a crucial milestone for the aviation industry. It responds proactively to the changing landscape of aircraft propulsion and ensures that safety standards remain rigorous as new technologies are introduced.
By offering both a clear path for new entrants and a conversion route for experienced engineers, the B1.E category facilitates the growth of a competent workforce ready to maintain the aircraft of tomorrow.
As electric and hybrid-electric aircraft gain prominence, the B1.E licence will be central to ensuring the safe, sustainable, and innovative evolution of air transport across Europe and beyond.
To read the full regulation change click here
Companies to watch: RollsRoyce, ZeroAvia, Vertical Aerospace, Electron, Volocopter, Scylax, Pipistrel, Heart Aerospace, VoltAero, Jetson, Vaeridion.