As with any discipline, a field is best able to grow and evolve when new ideas and products are shared among the community. To support this, the FAA hosts an annual meeting for researchers and industry professionals to come together and discuss research, lessons learned, and active projects. This meeting, the S&T Electrical Systems and Wiring Inter-Agency Meeting, was held virtually in December 2021. The following sections briefly discuss some of the topics of interest at this year’s meeting.
eVTOL
The direction of innovation within the industry is presently led by electric aircraft with a particular interest in electric Vertical TakeOff and Landing (eVTOL) and Urban Air Mobility (UAM). A quick web search will verify that there are dozens of eVTOL vehicles in development or concept worldwide. A common goal is to provide an alternative to ground vehicle travel (cars, buses, etc.) for densely populated areas such as large cities. With fully electric aircraft, developers seek to create a cleaner, safer alternative for relatively short-range aircraft by reducing/eliminating fuel emissions and avoiding the dangers of dense traffic.
The challenges that the eVTOL community faces align with the challenges that small aircraft manufacturers often face (namely spacing), but also how to manage the requirements for the energy storage system (e.g. batteries) and mitigation of the risks of high-voltage. Lectromec has written several articles on the risks of high voltage and how to mitigate them as they relate to the EWIS [link], and we will have several more in the first half of 2022.
Certification
One of the common issues aircraft designers are actively experiencing is the lack of certification guidance for fully electric aircraft. Current aerospace standards are a good starting place for designers to look for guidance, but the industry needs to develop official certification standards to address the unique needs of electric aircraft. Electric aircraft performance requirements, safety concerns, and battery capacity are all examples of new topics to define that are not specified in existing standards, not to mention that high-voltage systems are not clearly defined or regulated in aerospace.
This effort will require input from both industry and standard committees to determine the scope of and acceptable limits for electric aircraft. Industry experts may be able to offer valuable perspectives regarding the new technologies being developed that may drive the development of certification criteria.
Industry guidance, such as can be found in ASTM F3230, leave much of the work of defining the certification path and assessing the risks on the designer. While the FAA does not dictate design, additional guidance to help OEMs bridge the gap from new vehicle design to certified vehicle would be advantageous to the industry.
Thermal Runaway
Thermal Runaway was a common topic of discussion at this year’s meeting. Thermal runaway is a phenomenon that occurs when a battery is unable to dissipate heat as rapidly as it produces heat. Such phenomena can quickly cause permanent damage which is of particular concern in fully electric aircraft where battery reliability is crucial for safety as well as long-term product viability.
Example photograph of thermal runaway testing on battery cells performed by NASA. Other trials tested different orientation(s) of cells.
The research shown at the meeting shows different paths and approaches that were taken to assess thermal runaway and means to mitigate the risk. To support this, Standards will need to be developed to govern the heat production and dissipation surrounding energy storage systems. Presenters addressed a need for a system-level thermal runaway test method for electric aircraft with considerations on determining worst-case scenarios. Thorough testing of design concepts will be crucial in the development of these standard criteria and test methods.
Developments in Industry
Lectromec was also fortunate to present to the S&T committee. Our presentation focused on the developments within the SAE community as it relates to the wiring systems committees (AE-8), the high-voltage committee (AE-10), and the high-voltage modeling committee (AE-11). Within each of these committees, there is a great deal of work involving the development of new standards, in particular how to address the needs of more electric vehicles and high-voltage systems. In the first quarter of 2022, Lectromec will post this presentation on our website; sign up for Lectromec’s newsletter to be notified when this is published.
Conclusion
Undoubtedly, the annual S&T meeting provides beneficial insight into the current needs and challenges facing the ever-advancing aerospace industry. The coming together of professionals throughout the industry is not only a valuable source of information but also promotes connection and communication among the community to further spread information and advancements. With so many exciting new challenges and developments on the horizon, we certainly hope to be back together at an in-person S&T meeting in 2022.
Laura Wishart
Engineer, Lectromec
laura.wishart@lectromec.comLaura has been with Lectromec since 2019 and has been a key contributor on projects involving testing of EWIS/fuel system failure modes, the impact of poor installation practices on EWIS longevity, and wire/cable certification testing. Recent projects include work toward the definition and certification of high-voltage aircraft wiring systems. Laura’s knowledge and attention to detail have ensured consistent delivery of accurate test results from Lectromec’s lab.