MIAMI – There are dozens of eVTOL and eSTOL aircraft currently under planning, development, or even practical experiments. The infrastructure required to support them is also undergoing extensive analysis.
Take Airflow’s proposed eSTOL hybrid-electric platform, for example. Airflow designed a concept for medium-range freight missions, allowing journeys of up to 482km (300mil), directly linking warehouses or manufacturing sites.
Building Roofs as Runways
Speaking at the Vertical Flight Society’s Electric VTOL Symposium, Marc Ausman outlined the runway needs of airflow’s concept. He described it as 46m (150ft) of runway roll with a total requirement of 91m (300ft) in length. This is nearly three times the distance of the officially restricted touchdown-and-liftoff (TLOF) field plus the safety zone.
Ausman argued that such a runway could effectively be built into metropolitan environments by installing it on the roofs of buildings. He cited a survey by the Massachusetts Institute of Technology (MIT), which looked at many large cities. The survey discovered that Los Angeles had 6,200 such possible locations. In other cities, New York had 5,700, Dallas and Chicago about 3,800, and Boston 2,500.
“So even if one percent of those were viable, you would still have dozens of rooftops plus other areas around the city and suburban areas where these aircraft can land,” said Ausman.
eSTOL vs. eVTOL
Ausman contrasted the FAA’s approach and departure pathways for helipads and vertiports. He also acknowledged comparisons between the capabilities of the helicopters and the eSTOLs. The latter is capable of an even steeper approach to the slope (10 degrees) than the helicopters and eVTOLs (7 degrees). This enables a shift to vertical flight at the last available opportunity.
“It’s a bit of a misconception to think that an eVTOL will come in at a 305m (1,000ft) or 710m (2,000ft) AGL [above ground level] and then descend vertically and land on the helipad and that therefore it can kind of sneak into this little helipad between buildings,” Ausmus explained. “There’s just too much energy used to do that and it eats into the range significantly to be able to do that.”
On that basis, Ausmus suggested that those considering potential vertical ports should explore enlarging or elongating them to handle more complex aircraft. “What this means is that these two approach/departure paths and the way these planes operate are not as different as you might think at first blush, he noted. ”Any of these approach corridors designed for helicopters and VTOLs will also support the approach and departure of eSTOL aircraft.”
Featured image: ElectricFlyer, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons