At an innovation panel held on the first day of the Paris Air Show, FAA Acting Administrator Dan Elwell announced a Notice of Proposed Rulemaking that modifies and clarifies the existing regulatory procedures to obtain FAA approval to test supersonic aircraft. This NPRM is described by the FAA as "a first, necessary milestone toward the reintroducing civil supersonic flight."
The FAA's aim is to support the various supersonic aircraft (SST) currently under development in the U.S., all of which are coming up against overland noise rules that were instrumental in preventing overland flights of Concorde aircraft. While the new NPRM that Elwell announced on Monday suggests that those noise rules will stay on the books for regular commercial SST operations, it aims to make flight testing the aircraft easier and support rapid development.
“The U.S. Department of Transportation and the FAA are committed toward the safe and environmentally-sound research and development of supersonic aircraft,” Elwell told attendees at Le Bourget. “We are confident in the next generation of aviation pioneers who want to open new opportunities for business, economic, and aviation growth.”
But can a relaunch of commercial supersonic flight be "environmentally sound"? And should it be a priority even as subsonic flight comes under greater scrutiny for its environmental impact? The company responsible for developing the Concorde believes that aeronautical innovation is better invested in other areas.
During Airbus Innovation Days, held in May at the company's facilities in Toulouse, Grazia Vittadini, Chief Technology Officer at Airbus, addressed this question directly, saying:
"Who built the last business supersonic aircraft? You are on the site where this happened. We do have the history. We do have the heritage. We do have the skills and competency. Let’s not forget defense, space and military aircraft—the Tornados and the Eurofighters are part of Airbus. We have it, if we wanted to go there. The question we ask ourselves is how is this possibly compatible with the environmental sustainability targets which we are committed to? Not just because it is the flavor of the year, but because we deeply believe that is the direction we need to take. As of today, we cannot reconcile skills and competencies that we have in-house with products where market interest needs to be confirmed and with no reconciliation with the environmental sustainability targets which animate us in all we do, and in all the technologies that we develop."
Instead, Airbus is investing its innovative capabilities on addressing the environmental backlash against commercial aviation, including the exploration and development of hybrid electric propulsion systems that will support commercial flights and noise reduction in all aircraft operations.
Airbus is not alone in questioning the viability of supersonic transport on environmental grounds. The International Council On Clean Transportation, a think tank dedicated to studying the environmental impact of civil aviation, published a detailed report last year which warned that supersonic commercial flights were incompatible with environmental targets for civil aviation.
"The potential return of supersonic flights could have large environmental and noise pollution consequences. In 2015, aviation was responsible for about 800 million metric tons of CO2 emissions, or about as much as the German economy. New supersonic aircraft could lead to further emission increases if they are less fuel-efficient than new subsonic aircraft," the authors stated. "The previous generation of civil supersonic aircraft, the Aérospatiale/BAC Concorde and Tupolev Tu-144, took their first flights five decades ago. Currently, there are no environmental standards applicable to new supersonic designs."
In a post published last week, Nikita Pavlenko senior researcher at ICCT, said that supersonic transport would have a higher environmental impact than subsonic operations, even if the SST flights were operated using biofuels. Even a flight in a business class seat on a subsonic aircraft is more environmentally-friendly than a supersonic flight using hybrid biofuels might be. This is not only because the biofuel itself would be less efficient in supersonic operations, but also because the lower number of passengers who could fly on a supersonic aircraft increases the flight's environmental impact per seat.
"That SST flight to London, using the bare minimum CORSIA-eligible fuel barely makes a dent in the per-passenger emissions (5%), whereas even a blend of UCO-based HEFA would make a 40% cut. An SST powered by UCO-based HEFA at the maximum blend level will still generate twice the per-passenger emissions of an average, conventional flight," Pavlenko wrote.
Airlines are under pressure to lessen their environmental footprint, especially in Europe where Green party politicians are arguing in favor of substituting rail for short-haul journeys. While SST programs, like Boom, count on support from Japan Airlines and the Virgin Group, it's not clear that Europe would have the appetite for SST operations that it did during the less environmentally conscious hey-days of Concorde. If the FAA will still not allow supersonic operations over the continental U.S., then the routes on which SST aircraft might one-day fly are more limited.
As Vittadini suggested, market interest in these aircraft is dubious. What is clear is that environmentalists have already put SST aircraft on a no-fly list.
