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As the potential of distributed electric propulsion technology piques the interest of companies, militaries and governments around the world, these organizations are embarking on exploratory missions to determine how eVTOL aircraft can serve their purposes.
Some studies are more realistic than others — at least, in the short term.
One attractive concept pursued primarily by city and federal governments is that of an air metro transportation vehicle. Providing a public transportation service via four- to five-seat vehicles — the configuration being pursued by many leading eVTOL developers, including Joby Aviation and Lilium — is challenging with regards to capacity and affordability. Stakeholders in Canada and the United Kingdom are studying these applications with great interest.
The UK’s Future Flight Challenge, a government grant program exploring applications of electric and autonomous aviation systems, awarded £4.5 million ($6.1 million) to a consortium led by UK-based Tier 1 aerospace supplier GKN Aerospace to explore a transportation network based on eVTOL aircraft capable of carrying 30 to 50 passengers each.
Dubbed “Skybus,” the mass-transit feasibility project promises “not only direct benefits in reduced travel time at affordable fares but also [to] reduce the congestion on current ground transportation vehicles.” GKN is joined on the project by design firm Pascall+Watson, Swanson Aviation Consultancy and UK innovation accelerator Connected Places Catapult.
There’s just one problem with the Skybus proposal: such a vehicle is nowhere close to the bounds of the possible and won’t be for decades to come.
“The current state of the art, operational in the next three to four years, shows that an all-electric eVTOL is maxed out around five passengers with some basic capabilities — with more performance with better designs,” Mike Hirschberg, executive director of the Vertical Flight Society, told eVTOL.com. “Delivering an operational capability with six to 10 passengers can probably be attainable in the next five to 10 years with hybrid fossil fuel/electric and/or [short takeoff and landing] designs. Above that will require a significant amount of additional specific energy from a fuel source like hydrogen.”
Determining the technology approach for the aircraft is one of the program objectives, a spokesperson for GKN Aerospace told eVTOL.com in an email, and multiple trade studies will be conducted to find the “optimum combination of technologies” — but the focus is on fully-electric propulsion for sustainability.
“The goal is to deliver a techno-economic analysis on the Skybus transport system concept,” the spokesperson said. “The focus is in four areas: concept of operations and use cases, the vehicle itself, infrastructure designs and placements as well as an economic analysis looking at multiple business models.”
The project will also study methods via aircraft and flight path design as well as vertiport technology to reduce perceived noise. With the entire concept of eVTOL transportation premised on improved access to takeoff and landing sites due to greater public acceptance of quiet, affordable and safe electric aircraft, some leading eVTOL designers have commented that acoustics present an even greater challenge to the feasibility of larger aircraft than energy density.