UAM AIRWORTHINESS CERTIFICATION STANDARDS AND REGULATIONS
Wassaf Akhtar Mohammed | 24/09/2021
Airspace authorities use certification to manage the safety of aircraft, operators, and operations. All of these aspects of certification are important to UAM, and UAM will face challenges in each of these areas. This analysis focuses on airworthiness certification, which addresses safety risks by setting requirements for aircraft design, manufacturing, performance, failure response, and maintenance.
Aircraft certification can act as a barrier for promoting rapid integration of emerging technologies for UAM. UAM aircraft challenge the existing certification process due to novel features and combinations of features, such as distributed electric propulsion / tilt-wing propulsion, VTOL, autonomy software, optionally piloted, energy storage, and ratio of aircraft to pilots being below 1.
Certification can delay deployment of the technologies as they go through certification process that may take several years and can increase costs of deployments if the burden of compliance is high. Certification can also be an enabler as it provides passengers comfort that the standard for safety is sufficiently high. Therefore trust in the technology is a critical societal barrier.
Airworthiness Certification Approaches:
Certification is a risk-based process. There is no such thing as zero risk aircraft operation. The certification framework is driven by questions about how society views the operations, such as: “What is society’s risk tolerance for certain applications?”, and “How strong is the desire for a low-cost solution?”.
The aircraft and operation are deemed low risk, and there is a strong desire for low cost solutions. As the vehicle size increases, so does the risk and the need for more rigor. As the operation increases in risk, for example by carrying passengers that expect a certain level of safety, the level or rigor is further increased.
NATO’s risk calculation is based on a Military standard handbook for a casualty model based on current reliability data compared to the planned test flight route and population densities in areas along the planned flight route.
Additional requirements are imposed on operations where less risk is accepted. Higher certification rigor means more cost and more time. Certification for Light Sport Aircraft can be in the hundreds of thousands of dollars, where Part 23 commercial aircraft can be in the tens to hundreds of millions of dollars. This tradeoff between risk tolerance and cost will drive the UAM certification approaches.
International UAM Certification Landscape:
FAA certification is supported by activities and standards at NASA, SAE, and ASTM. ICAO is supported by bodies such as the Joint Authorities for Rulemaking on Unmanned Systems (JARUS), Joint Aviation Authorities (JAA), Single European Sky ATM Research (SESAR), as well as accepting guidance from other nations, including FAA and EASA.
This is a quickly evolving ecosystem, and some recent developments are not reflected in this figure. For example, ICAO has established the Remotely Piloted Aircraft Systems Panel, Unmanned Aircraft Systems Advisory Group (UAS-AG), and Unmanned Aircraft System Task Force/Working Group (UAS-TF/WG) in the Legal Committee.
In Germany, the Volocopter VC200 was granted provisional certification from German Ultralight Flight Association as an ultralight aircraft, which provided a basis for a public test in Dubai. Also of note, Dubai has mandated a remote identification and tracking technology, Skytrax.
Another consideration in the regulatory landscape is the level of independence of the regulatory frameworks within specific countries. In this instance, independence is described as the degree to which the individuals overseeing compliance are independent from the product development process.
FAA has more independent Product Certification. Airworthiness relates to multi dimensions of framework including Process, Product, and Behavior. The level of independence may influence decision of where to certify. For reference, the Independence Levels are defined as follows:
• “5 — An independent regulatory organisation or person with authority underpinned by Government legislation. Alternatively, the regulatory organisation or person is fully independent from the owner/operator with independent lines of command. They are an external regulator.
• 4 — A regulatory organisation or person who is as independent as possible from the owner/operator, but still within the owner/operator lines of command. They are an internal regulator.
• 3 — A management organisation or person removed from the task/attestation development.
• 2 — A supervisor, organisation or a person who is independent from the task/attestation development.
• 1 — A person charged with the responsibility for performing the task, the practitioner.”
Domestic UAM Certification Landscape
UAM aircraft may vary in weight, type of service, propulsion, number of passengers, and speed, which may change their path to certification. New aircraft designs for UAM may have multiple paths to certification with FAA.
How Consensus Standards Support Certification: Means of Compliance
A requirement set forth in regulation may be met through more than one means of compliance that may include regulation, advisory circulars, or consensus standards. Some Part regulations depend more on industry standards than others. It does not prescribe specific technical solutions nor does it have tiers or categories. Many in the aviation community see this as an opportunity to develop detailed design standards through consensus standards for flight characteristics, performance, operating limits, structures, design, powerplant, propulsion, and energy storage.
Consensus standards could accelerate UAM certification through the following activities:
• Making tiers where it makes sense
• Providing specific technical solutions
• Providing test specifications
• Providing specific compliance methods
Current Standards Provide Means of Compliance:
This section provides a sample of some RTCA, SAE, and ASTM standards that support means of compliance. These standards support aspects such as design, testing, testing tools, software considerations, and verification. We have included some standards non-specific to aircraft that may potentially inform UAM certification such as SAE work on testing automated driving systems, which includes work on validation and verification and test scenarios that address identified risks for autonomous systems.
On my next Blog: Potential Certification Approaches for Air Taxi and Air Ambulance.