Column: Airspace
Design guidelines for safe urban air mobility
S
afety regulations covering passenger aircraſt are by necessity strict and all-encompassing. Flying poses risks not only to on-board passengers but also people, infrastructure and property on the ground. Terefore, existing aviation safety standards and regulations
would require that urban air mobility (UAM)-type vehicles undergo rigorous testing and evaluation to meet strict safety requirements before they are approved for commercial operation. However, both the US Federal Aviation Administration (FAA)
and the European Union Aviation Safety Agency (EASA) have indicated that electric vertical take-off and landing (eVTOL) aircraſt – which are expected to dominate passenger UAM services like air taxi operations – will be considered a special class. EASA has stated that existing regulations, such as current CS-27 rules for small rotorcraſt with up to nine passenger seats and 3,175kg maximum take-off weight, may not adequately cover some types of VTOL aircraſt. It may also unfairly penalise innovative concepts. To combat this, EASA is developing a special means of compliance that should help the market for UAM services flourish.
Guidelines for VTOL aircraft EASA claims to be the first with a set of technical specifications with the launch of its “Special Condition for VTOL Aircraſt” document in 2019. Te guidelines cover all aspects of VTOL, including performance, manoeuvrability, stall characteristics, vibration, structural design, flight loads, fire prevention and special provisions for passenger safety, including protective systems and egress.
14 February 2024
www.electronicsworld.com
By Mark Patrick, Director of Technical Content, Mouser Electronics Electrical and electronic systems such as avionics and
propulsion, as well as lighting, are also covered by these guidelines. One important aspect is the safety of lithium batteries,
which typically power eVTOL aircraſt. Recognising the lack of service experience for such battery-powered aircraſt, EASA documentation acknowledges that some risks of battery damage leading to thermal runaway can be mitigated through proper adoption of processes throughout design, manufacturing, installation, operation and maintenance. Other risks, such as internal cell short circuits due to latent manufacturing defects, can’t be completely avoided. Te document recommends that these be mitigated in-service. EASA claims another world-first when it published safety
specifications for eVTOL vertiports, to enable the safe design of UAM ground infrastructure, much of which will be located in heavily-populated areas.
Electronic hardware regulations Whilst requirements related to the structure and flying characteristics understandably differ for various types and sizes of aircraſt, those that apply to systems such as avionics can apply more generally. EUROCAE ED-80 in Europe and RTCA DO-254 in the US are
the industry standards covering Design Assurance Guidance for Airborne Electronic Hardware. While the two are very similar in scope and requirements, a further advisory circular, AC20- 152A, recognises both, describing acceptable ways of showing compliance with applicable airworthiness regulations. It also
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