With scores of eVTOL and eSTOL aircraft currently under design, construction, or even actual testing, the infrastructure needed to support them is also undergoing intense study. Take Airflow's planned hybrid-electric eSTOL model, for instance. It is being developed for middle-mile cargo missions, making trips of up to around 300 miles, directly connecting warehouses or industrial sites.
Speaking at the Vertical Flight Society's Electric VTOL Symposium, Marc Ausman described the runway needs of his proposed blown wing aircraft as being 150 feet of ground roll with an overall requirement of 300 feet in length. That is roughly three times the length of the currently proscribed touchdown-and-liftoff (TLOF) area plus safety zone, for a helipad.
Ausman maintained that such a runway could easily be integrated into urban environments by placing it on the roofs of existing buildings. He cited a study by the Massachusetts Institute of Technology (MIT), which examined several major cities and found that Los Angeles had 6,200 such potential sites, while New York had 5,700, Dallas and Chicago around 3,800 each, and Boston 2,500. “So even if one percent of those were actually viable, you would still have dozens of rooftops plus other areas around the city and suburban areas where these aircraft can land,” said Ausman.
He also compared the approach and departure corridors specified by the FAA for helipads and vertiports, and noted similarities between the capabilities of helicopters and eSTOLs, with the latter capable of an even steeper approach slope (10 degrees) than the helicopters and eVTOLs (7 degrees) which transition to vertical flight at the last possible moment.
“It’s a bit of a misconception to think that an eVTOL will come in at a 1,000 or 2,000 foot 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,” Ausman explained. “There’s just too much energy used to do that and it eats into the range significantly to be able to do that.”
Based on that, Ausman proposed that those who are planning future vertiports should consider enlarging or elongating them to accommodate more varied types of 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.”