Electric vertical takeoff and landing aircraft differ from traditional aircraft in several main aspects and regulators worldwide are accelerating development of requirements specific to eVTOL or fine-tune existing regs to the new technology. Mario Pierobon, PhD, outlines the parallel efforts in key regions.

  • Electric propulsion, propulsion-controlled trajectory and small-aircraft FBW are key technical differences
  • 'Special Conditions' as a certification gap-filler

EVTOL aircraft have unconventional configurations. The European Union Aviation Safety Agency (EASA) explains, “We have, for example, multi-copters, tilt-rotors, and vectored thrust. None of the current regulations is adapted to these configurations. Moreover, they are all fitted with fly-by-wire (FBW) flight control systems. Even if this is not new in itself, as most recent large aircraft all have FBW systems, it is new in the small aircraft domain. There are, in addition, the challenges associated to size and energy consumption. FBW systems are also of a new nature as the propulsion is often the means to control the trajectories while propulsion and trajectory control are independent systems in traditional aviation. The integration of these systems is also more advanced.”

The main difference between eVTOL from conventional aircraft is their distributed electric propulsion system and its associated energy storage system (batteries), according to ANAC (Agência Nacional de Aviação Civil), the civil aviation authority of Brazil. “There is also a fundamental difference on the expectation that lower operating costs and noise footprint will enable a much larger number of operations,” says ANAC.

Indeed, electricity as the energy source is quite new. “It needs to be handled with care, together with the high degree of automation of these small aircraft. Lastly, the operations and for some applications like air taxi, flight over traditionally not authorised airspace is a challenge”, says EASA. “All these novelties – and the list is not exhaustive – are currently not accounted for in the traditional aviation regulatory framework. This is the reason why specific regulation needs to be defined in all domains, including airworthiness, flight crew licencing, and operations.”

FAA: We’ve Got This

In the United States, the Federal Aviation Administration can certify new technologies such as eVTOL through its current regulations, the FAA affirms. “When tailoring existing rules to an applicant’s new concept, the FAA determines the certification requirements for the eVTOL’s design, production, airworthiness, and operation. Some certifications could require the FAA to issue special conditions or additional airworthiness criteria, depending on the type of project. Determining qualifications for these aircraft is an ongoing process.”

Similarly in Canada, Transport Canada does not have ready-made standards for eVTOL aircraft. “The aircraft certification framework under the Canadian Aviation Regulations (CAR 521) does, however, allow Transport Canada to certify new and emerging technologies for which standards do not exist or are still under development. This is done by developing Special Conditions – Airworthiness to bridge the gap and address where the standards have not kept up with the pace of technology,” says Transport Canada.

Under EASA, the regulatory framework of eVTOL aircraft is being set up now. On the aircraft certification side, EASA published in July 2018 the special condition (SC) VTOL. “This SC is setting performance-based requirements for eVTOL certification. It is so far limited to aircraft with a MTOW of less than 3,175 kg and fewer than 9 passengers. A safety continuum has been embedded into the SC-VTOL depending on the type of operations,” says EASA. “For operations within a city or for commercial transport of passengers, the ‘enhanced’ category has been created, with a level of safety similar to large transport aircraft. This is to specifically address air taxi operations that are not general aviation type of operations and where an extended number of vehicles will be produced to transport a large volume of passengers. For other types of operations, such as non-commercial passengers, special operations or leisure flights, we have broken down the safety continuum according to the number of passengers.”

In 2019 and 2020, EASA published the first set of means of compliance (MoC Phase 1) as well as the SC E-19 on electric and hybrid propulsion system (EHPS). “In 2021, we published the final release of MoC Phase 1 and MoC Phase 2 for public consultation. We are currently consolidating the comments received and expect to release the MoC Phase 2 final version” in the first half of 2022, EASA estimates. “In parallel, we are working with EUROCAE, in the WG-112 to develop standards not addressed by EASA proposed MoCs.”

On the operational side, EASA is currently developing a notice of proposed amendment (NPA), which should also be published in 2022, and which will address all operational requirements to enable eVTOL aircraft to fly, including such as aspects as operations, crew licencing, maintenance, and vertiport guidance. “In the air traffic management ATM space, we are developing U-Space aspects to enable safe integration of these aircraft into airspace and with other airspace users. So, really, all regulatory frameworks are being adapted. This is quite a challenge in such a short timeframe,” says EASA.

In Brazil, eVTOL regulations are also being considered from a holistic perspective encompassing all aspects including aircraft design, production, maintenance, operations, training, infrastructure, air services, and air traffic management, according to ANAC.

The UK CAA notes, because of the broad range of eVTOL designs in development, regulatory approaches need to consider the specifics of each case: balancing robust guidance with flexibility, to determine the right risk-based solutions.

Risk-Mitigation Strategies

Type certification is one of the safety steps for an aircraft to be certified for flying inside Canadian airspace, highlights Transport Canada. “In addition, we have released a drone strategy to 2025 to identify priority areas of work that will enable remotely piloted aircraft – or drone – operations of increasing complexity. While not all eVTOL aircraft are remotely piloted, many are being designed with the objective of being fully autonomous,” says TC.

ANAC is considering and assessing all safety risks from a holistic perspective. “The risks may be substantially different based on individual design characteristics as well as proposed operational scenarios. These are addressed based on performance-based criteria that enable an adequate and proportional approach to each specific case evaluated,” says ANAC.

Beyond the certification aspects, there are many other factors related to safety, security and consumer protection which need to be understood, according to the UK CAA. “Specific safety risks will depend on the operations being undertaken by the aircraft. We can begin to identify these through detailed case studies and looking at a holistic safety management approach to address these,” the UK CAA says.

While safety risks on the technological aspects are addressed via the certification process, safety risks are also stemming from the operations, according to EASA. “Robust operation risk management will be key. SMS and information security management system (iSMS) should be included and will provide some mitigations. High operation oversight will also be key. But we will not reinvent the wheel. Some of the operational mitigations implemented today in traditional aviation will also be adapted,” says EASA.

The FAA is using a safety-risk management system to identify, analyse and mitigate hazards while safely integrating new operations. “We plan to apply existing airworthiness standards for Advanced Air Mobility aircraft, like eVTOLs, where the risks posed are similar to manned aircraft. We will use our proven methods for ensuring the safety of complex systems,” says the FAA.

Flipping the EIS Switch

As to when eVTOL aircraft will start to operate, the FAA affirms that determining qualifications for these aircraft is an ongoing process.

According to the UK CAA, the industry has suggested that the first commercial operations of eVTOL could happen as soon as 2024. “Entry into service will require training and other operational aspects to be defined. We are exploring the feasibility of such proposals from a regulatory development perspective,” the UK CAA says.

With today’s knowledge and without major development issues, 2024/2025 could be a good estimate for when eVTOL aircraft will start to operate, affirms EASA. “Regulations will indeed cover training and operations. They should be ready by then. However, should this not be the case, we could still provide some exemptions or alternative paths to enable the first operations,” says EASA.

Companies are expecting to start operating eVTOLs in Brazil by around 2025. “We are working closely with involved parties (manufacturers, operators, other public agencies, etc) so that these operations can begin as soon as there is evidence that risks have been identified and properly addressed,” concludes ANAC.