The gold-rush-like race to bring a transformative urban air mobility (UAM) dimension to air transport with a new generation of electric aircraft has attracted entrepreneurs and innovators from beyond the mainstream aerospace industry. While their fresh thinking may well be just what aviation needs two decades into the 21st century, it is apparent that some of those behind the new wave of start-up companies are not at all accustomed to the highly regulated nature of an industry that has to put safety first.
Many of the new companies developing electric vertical takeoff and landing (eVTOL) aircraft have committed to aggressive, fast-tracked development timelines that seem to take little account of how long traditional aircraft programs generally take to get to market. This has prompted skepticism, especially considering that leading aviation regulators have only recently begun to define how they intend to conduct the process for certifying and approving the new aircraft. The prospect of aircraft being operated autonomously has added an even greater layer of complexity for what could prove to be a watershed period in the history of aviation regulation.
Many of the new companies developing eVTOL aircraft have committed to aggressive, fast-tracked development timelines that seem to take little account of how long traditional aircraft programs generally take to get to market.
However, this uncertainty hasn’t deterred some of the pioneers from seeking to push the regulatory boundaries to accelerate the development process for their new products. For instance, China’s EHang has convinced the Civil Aviation Administration of China (CAAC) to allow it to begin provisional operations with its 216 Autonomous Aerial Vehicle under a pilot program. The company claims to have delivered 38 of the aircraft, even though it is far from clear on what basis, and when, the new type will be certified.
Regulations Getting Clearer
There are now signs that the regulatory landscape could be set to get clearer in 2020, with more detailed regulatory guidance regarding certification standards for eVTOL aircraft flying in the UAM environment expected.
In July 2019, the European Union Aviation Safety Agency (EASA) led the way with a widely welcomed announcement of its new Special Condition for VTOL regulatory framework that will form a basis for certifying the new class of aircraft (see below).
EASA’s U.S. counterpart, the Federal Aviation Administration (FAA), has yet to publish a detailed equivalent to this regulatory structure but has, for now, indicated that it expects eVTOL aircraft to follow a broadly similar path to that mapped out under its revised Part 23 rules for light aircraft.
This initial guidance is expected to focus on the aircraft themselves, but there is far more to the regulatory equation than just type certification. In a 2018 report, the Mitre Corporation identified 13 separate areas that will need some sort of regulatory component or consideration to bring an integrated UAM system to fruition. They include eVTOL airworthiness, certifying autonomous flight, air traffic control, detect-and-avoid capability, operating rules, information and communication networks, operational oversight, related ground infrastructure, oversight and enforcement, security, public acceptance, environmental impact, and personnel.
The task at hand is both daunting and complex. It is complicated by increased scrutiny facing global aviation regulators, particularly the FAA, in the wake of the Boeing 737 Max airliner fatal accidents of 2018 and 2019 and accusations that the U.S. agency allowed the manufacturer to have excessive leeway over the type certification process.
Meanwhile, both CAAC and EASA have provided initial guidance in 2019. In the U.S., top FAA officials have indicated that the template for small eVTOL certification—aircraft that seat up to nine passengers or less and weigh less than 7,000 pounds—will track closely with the revised Part 23 light aircraft certification standards adopted by the FAA and EASA. This provides an alternative to having to meet the mainstream Part 25 standards for fixed-wing aircraft or Part 27 standards for helicopters. The AW609 tiltrotor, which has been in development for almost 20 years by Italian manufacturer Leonardo Helicopters, is being certified under the separate Part 21.17 standards (introduced for aircraft that don't fit existing criteria) that are based on intended use and risk associated with operations. This involves having to meet a mix of Part 25 and Part 27 requirements.
The FAA's new Part 23 standards (designated as 14 CFR Part 23 Amendment 64) went into effect in August 2017 and apply to airplanes weighing 19,000 pounds or less and with 19 or fewer passenger seats. The new standards replace “prescriptive requirements with performance-based standards coupled with consensus-based means of compliance (MOC) methods for specific designs and technologies,” according to the FAA. They consist of 71 performance-based regulations that can be met by more than one MOC.
As of July 2018, the FAA had accepted 63 industry consensus standards drafted by ASTM International (see below). However, significantly, this performance-based approach does not yet cover key elements of eVTOL aircraft, including autonomous systems, electric propulsion systems (EPS), and energy storage systems (ESS). As a consequence, companies developing aircraft powered by electric or hybrid-electric motors will have to work with FAA through the Issue Paper process and establish special conditions covering "novel or unusual" design features [AC-20-166A (5) (g)] to complete type certification, resolving issues such as crashworthiness for lithium-ion batteries. This could involve having to meet the Part 27 requirement to conduct a test in which the aircraft has to be dropped 50 feet to the ground to establish that the battery does not get damaged in the process. Type certification also entails having to meet Part 33 standards covering engines and Part 35 standards for propellers.
Setting Industry Consensus Standards
As for the Part 23 rewrite, the FAA would rely on industry consensus standards developed in part by organizations including various committees of ASTM International. Several ASTM committees are currently working to develop these standards and have completed or will complete this work soon. Other standards organizations also are working with the eVTOL industry, including the Radio Technical Commission for Aeronautics (RTCA), SAE International, the International Standards Organization (ISO), and EUROCAE, along with trade associations including the General Aviation Manufacturers Association (GAMA).
The FAA continues to rely on ASTM for standards used for the Part 23 rules. In 2018, it made available 63 MOCs based on 30 ASTM standards, including 46 from ASTM standards and the remainder a hybrid of ASTM standards and FAA changes.
According to Robert Garbett, chief executive of unmanned aircraft consultancy Drone Major Group, who is involved in ISO’s work to set standards, far more work remains to be done to establish standards that will cover all aspects of autonomous aircraft operations. In October 2019, he told the Vertical Flight Expo conference in the UK that the work of ISO and other bodies on operational standards has only recently begun and that it will take “at least three years” to complete. In his view, without a full set of widely accepted international standards, it will not be possible to achieve sustainable commercial operations with eVTOL aircraft.
Without a full set of widely accepted international standards, it will not be possible to achieve sustainable commercial operations with eVTOL aircraft.
Nonetheless, significantly, the FAA has an executive mandate to support the development of core technologies to enable eVTOL and UAM. On August 30, 2019, the U.S. Office of Management and Budget directed federal departments and agencies to give budget priorities to UAM-related technologies. The directive said these should include, “R&D to lower barriers to the deployment of surface, air, and marine autonomous vehicles with a focus on developing operating standards, integration approaches, traffic management systems, and defense/security operations.” It added that “Departments and agencies should prioritize R&D that enables electric vertical takeoff and landing and civil supersonic aircraft.”
Meanwhile, the ride-sharing service Uber, in concert with Safran, has developed a design for a concept for a four-passenger eVTOL urban air taxi and fabricated a full-size cabin mockup that they anticipate is likely to satisfy certification requirements for system redundancy, crashworthiness, and cabin safety. The concept vehicle is not intended for production, but merely to provide suggested best practices for design and functionality.
While as many as 200 companies are reported to be in the process of developing eVTOL designs, freezing a compliant design will be waiting on the regulations. By melding international consensus to use EASA’s revised CS-23 rules as a starting point (see below), regulators and industry are hoping to avoid the development of totally separate regulations regarding eVTOL and the inevitable time lag associated with such practice, given that the Part 23 rewrite spanned nine years between study and implementation. However, the need to build commercial-grade safety features and redundancies into eVTOL used for UAM means that not all elements of Part 23 will be appropriate for these aircraft. Certain features of eVTOL used for UAM undoubtedly will mandate stricter and more robust requirements that could impact the economic models and assumptions used to promote eVTOL. To date, these are the major related regulatory developments in China, Europe, and the United States.
China Proposes Risk-based System
In January 2019 the CAAC’s airworthiness department issued a document called “Guidance on UAV Airworthiness Certification based on Operational Risks.” The CAAC is expected to apply this guidance to UAM as well as it develops final regulations and standards, according to several companies working with the CAAC. The “guidance” centers around three principles:
- Orchestrating hierarchical certifications with different levels of operational risks.
- Extracting CAAC certification standards and regulations from industrial standards.
- Encouraging UAV companies to jointly participate in airworthiness management.
The CAAC categorizes three levels of risk: low, medium, and high, and sees itself primarily involved in medium and high-risk operations wherein medium operations would trigger a CAAC review while high risk would include CAAC involvement.
EASA Issues Special Conditions
In July 2019, EASA issued its “Special Condition for Small-Category Vertical Takeoff and Landing Aircraft” (SC-VTOL). “Small category” is defined as an aircraft seating up to nine passengers and weighing up to 7,000 pounds.
SC-VTOL establishes two classes of eVTOL, “basic” for non-commercial operations and “enhanced” for commercial operations or those over urban areas. The enhanced rules are those that will apply for new aircraft including Volocopter's VoloCity and the Lilium Jet.
The basic class tracks the CS-23 (FAA Part 23) rules for normal category aircraft operations, while enhanced more closely follows the CS-25 (FAA Part 25) standard for transport category aircraft with regard to system redundancy. The special conditions also recognize SC-VTOLs are vertical aircraft and therefore borrow from existing regulations governing normal category (CS-27) and transport category (CS-29) rotorcraft.
By way of explaining its decision to focus on matching the level of regulation to operations, EASA noted in the published preamble to the special conditions that, “the current system safety objectives for CS-25 and CS-27/29 aircraft should be maintained as a minimum for the commercial air transport operations of passengers as well as for urban air mobility using VTOL aircraft to address the risks to persons on board and on the ground.” Early critics of EASA’s special conditions pointed out that for commercial eVTOL aircraft to be compliant, they must essentially demonstrate Part 29 rotorcraft safety standards, a move that would significantly increase vehicle cost and could flip the economic models used to promote UAM upside down.
Aside from aligning certification standards with vehicle usage, the special conditions depart from existing standards by imposing higher requirements based on propulsion type and the introduction of “novel technologies” and “new types of operations.” For example, EASA notes that because of an assumed need for “distributed propulsion,” some special conditions more closely mirror the certification requirements of CS-27 (normal category rotorcraft) as opposed to CS-23 (normal category airplane).
Accepting Industry Consensus
However, as the CAAC hints that it will accept “industrial standards” as a means of compliance, EASA also notes that “an applicant must comply with this special condition using means of compliance accepted by EASA, which may include consensus standards.” This implies that the industry could have quite a big say in determining how the required standards can be satisfied.
That was a view echoed by the head of the FAA’s aircraft certification office (ACO) at an industry conference in the summer of 2019. “The use of industry consensus standards gives us a huge benefit,” said Earl Lawrence, executive director of FAA’s Aircraft Certification Service. “We bring in the experts from any field from anywhere in the world who put down their thought on paper and say if you do it this way then it is the best way to address a particular design issue or approach. That is invaluable to the agency to have access to that brain trust.” Lawrence said the aircraft certification office is in the process of establishing an “industry consensus standards office” that will be focused on working with standards groups like SAE, ASTM, and Institute of Electrical and Electronics Engineers. Lawrence apparently agrees with EASA’s use of the new Part 23 with a risk-based approach when it comes to eVTOLs.
“The new Part 23 is not the answer to all of your problems, but it is a good example of where we want to move forward from a policy and regulatory standpoint,” he said, adding that inherent in the new Part 23 is a “risk continuum” based on the aircraft's/operation's likely activities. “We are committed to matching the level of regulatory oversight to the level of risk in your organization,” he said.
Currently, a variety of industry standards organizations are developing consensus standards with regard to eVTOLs. Major industry standards committees include AC (advisory committee) 377, autonomy in design and operations in aviation, comprised of ASTM members from committees including F38 (unmanned aircraft systems), F39 (aircraft systems), F44 (general aviation aircraft), and F46 (aerospace personnel). ASTM has formed another advisory committee, AC433, which will focus on eVTOL MOCs and that is charged with drafting a roadmap that identifies which new standards should be developed for eVTOLs and UAM and then sending that back to the member committees to develop them.
What’s the Bottom Line?
Lately, leading regulators have stepped up the level of engagement with the emerging eVTOL and UAM industry. However, plenty of work remains to be done and the next couple of years could yet see some twists and turns before clear, harmonized rules are established for every aspect of what it will take to safely operate the new aircraft.
The next couple of years could yet see some twists and turns before clear, harmonized rules are established for every aspect of what it will take to safely operate the new aircraft.
For now, prospective investors, partners, and stakeholders would be well advised to be skeptical about the more aggressive timelines given for getting new aircraft to market. The level of complexity for meeting new requirements could well have an impact on overall development costs, with some of the projected budgets being far below those that have been spent on new aircraft developed by far more established aviation companies