Electric, vertical-lift air-taxis may someday criss-cross the skies, but the timelines their advocates are proposing are ambitious, to say the least. Uber, for example, predicted at its Elevate conference last month that it would begin deploying its system, UberAIR, in 2023. That’s going to be a stretch: the autonomous control systems that will make such flight practical and affordable are in utero, the air traffic control integration necessary to make it safe and efficient are barely a twinkle in the FAA’s eye, and the regulatory blessing necessary from federal and city governments—well, let’s just say there’s nothing to bless yet.
Then there’s the issue of the aircraft themselves. Uber, the dominant player trying to bring this industry to life, insists that an electric vertical takeoff and landing (e-VTOL) aircraft is the way to go, arguing that nothing else can match it for efficiency, speed, reliability, safety, and quietness. (Picture monster drones, or multiblade insectoid contraptions with passenger pods slung underneath, as shown in Uber’s videos.) Such a craft won’t simply evolve from existing hardware, either. The aviation industry will have to develop entirely new classes of aircraft that fly in new ways, using new means of propulsion, flight control, and situational awareness.
It’s actually an opportunity to rework an industry that’s starting to look a bit crusty. “It’s time to rethink a lot about aviation,” says René Landry, an aviation systems researcher at ETS, a technical university in Montreal. “The avionics we use now are based on a general architecture that was developed during World War II. The hardware, for instance, is duplicated for redundancy, using huge, low-efficiency cables. We could use some game changers in there.”
As an example of one of these game changers, he notes that the software used for flight planning didn’t join the 21st century until the iPad came out. “Ten years ago we would have said the iPad would never be certified for cockpit use,” he says. “But within six months it was certified and more than 400 businesses that made electronic flight bag systems closed their doors. They were no longer necessary—it could all go on the iPad.” But something like flight-planning software, of course, is only the first challenge facing a potential flying-car network.
Challenge #1: Hand off the flying to computers
Our air taxis of tomorrow will have to do most of the piloting work themselves, using autonomous or at least highly automated systems. Uber has stated that it expects its service will start with human pilots, but given the extreme shortage of pilots anticipated by the airline industry over the coming decades, that’s not sustainable. Self-flying systems are already in the works, but they are nowhere close to being ready for widespread adoption.
One interim step, then, would to simply take the edge off. “Work at NASA has demonstrated the viability of what’s called simplified vehicle operation,” says aerospace engineer Brian German, an associate professor at the Georgia Institute of Technology. In this scenario, most of the systems that either manage the act of flying or the processes of navigation and communication are controlled by the computer, with the pilot essentially telling it what to do and where to go. “A pilot can’t be in control of 8 or 10 different rotors and expect to maintain any degree of situational awareness,” he says. “So when you push on the stick in this system, everything that happens to point the aircraft in the desired direction is automated.”
That sort of flying is within reach right now, and is how most drone flying (and certain aspects of many particularly advanced military and commercial aircraft) works. But a safety-certified, passenger-carrying version operated by truly minimally trained pilots in commercial airspace—the system that Uber will need—is still a long way off. This is especially true because the systems will also have to function perfectly in urban canyons and in inclement weather.
Autopilot systems also lack the kind of judgement possessed by human pilots. “It’s really hard for autonomous systems to understand different scenarios,” German says. “Maybe, for instance, you’re flying an airplane and you see a forest fire out of the left window. A human pilot knows immediately that’s it’s probably not a good idea to fly right over it. But how will an autonomous system know that? We’re going to run into ‘failures of creativity’ on the part of the system.”
Challenge #2: Electrify the aircraft
Though plenty of small aircraft—from two-seat helicopters like the Robinson R-22 to any number of conventional airplanes—could theoretically form a fleet of air taxis today, Uber and its partners think electric is the way to go. This is primarily because electric propulsion is simpler, more reliable, and more precisely controllable than combustion engines. Though scientists think that we’re still decades away from the kind of jump in battery energy density required to allow, say, regional aircraft to fly several hundred miles at a time, German thinks that the kinds of short hops an air taxi might make can actually be sustained with today’s technology.
For instance, Uber’s recently announced partnership with electric-aircraft startup Karem, which is developing variable-RPM rotors that can more efficiently modulate the power usage from existing batteries, is just one possible solution. And many aerospace and technology experts argue that short-haul flights of just 10 or 20 miles are possible even with current battery technology. The trick, though, will be achieving the kind of high-speed charging capabilities needed for quick-turnaround flights and overcoming the broader power-supply shortcomings endemic to dense urban environments.
Challenge #3: Build them cheap
Battery technology may not prove to be a limiting factor, but manufacturing likely will—particularly because a sustainable air taxi system that’s dependent on economies of scale will need thousands of aircraft flying as soon as possible. Other industries have solved such manufacturing challenges, but generally over very long periods. The automotive business, for example, has demonstrated in the past 20 to 30 years that modern manufacturing techniques can significantly reduce the costs of making even the most complex modern cars. This includes the integration of new high-tech composites and alloys that each have unique requirements during the manufacturing process. Achieving comparable production numbers in e-VTOL aircraft—i.e., hundreds of thousands per year, which may ultimately prove to be what’s needed to truly flesh out Uber’s global plan anyway—may be unrealistic, but transferring some volume-manufacturing techniques from automotive to aviation would be a start.
On the other hand, these are aircraft, not cars. Manufacturing lightweight, strong, crash-tested, and quiet aircraft made entirely out of composites, as opposed to merely containing composite components, presents yet another challenge. Building aircraft out of composite materials like carbon fiber remains a largely hand-executed process, because manufacturers still need skilled workers to lay up the materials, join elements together, and then scan for and eliminate the structural voids, air bubbles, and other weaknesses that might be acceptable for a car that has all four feet on the ground, so to speak, but not for a flying pod full of people hovering 1,000 feet in the air. “I’ve talked to composite manufacturers, and they don’t see a path to get to the kind of rates we’re talking about,” German says. It’s challenging and costly, and the aviation industry hasn’t been able to do it in significant volumes yet because the demand just hasn’t been there. The demand for hundreds of thousands of eVTOL aircraft might arrive eventually, and manufacturing techniques could very well continue to advance, but it will happen over decades, not a few years.
Challenge #4: Make them quiet
Finally, there’s noise. Air taxis will be operating in urban environments that are already tightly regulated when it comes to helicopter noise and the roar of airplanes at airports on the edge of town. If the vertiports that Uber imagines see hundreds of takeoffs and landings every hour, the aircraft will have to be exceptionally quiet. “Aviation is regulated federally, but a lot of issues are in urban air mobility are local,” German says.
For small vertical-lift aircraft, the challenge will not only be in decibel reduction, but in the acoustic signature as well—that is, how the noise blends in (or doesn’t) against the background of the city. Uber has been researching this, and argues that a reduction of 15 decibels will bring aircraft clatter down to acceptable levels, both in terms of sheer volume as well as its general detectability in urban environments. (Of course, most of the noise in urban environments comes from vehicular traffic, which itself could very well transition to mostly electric propulsion in the coming decades. So the challenges eVTOL aircraft face “blending in” might only get worse as a result.)
Achieving ultra-quiet electric aircraft will require significant innovation, given that the machines will still have to move the same volumes of air through the rotors in order to lift off and touch down. One approach is to reduce the tip speed of the rotor blades, since they get louder as they approach supersonic speeds. To do that, German says, engineers could add blades to each rotor, which would bring down the RPM while still maintaining the same lifting power. So-called distributed-rotor systems—that is, six or eight small rotors instead of, say, just two—will also help. German says he’s optimistic here, too. Indeed, Uber has played recordings comparing the systems at its industry conferences. German does add a final warning about “psychoacoustics.” That’s the tendency for people to find a sound disagreeable, not because it’s actually all that bad, but because it represents something yucky—in this case, wealthy elites flying over regular folk.
Five years doesn’t seem like enough time to conquer these challenges—which don’t even touch upon the broader economic and regulatory issues the plan faces, along with whatever enhancements will be required to integrate air taxis into the notoriously old-school commercial airspace system—but both Landry and German note that all the technology levels are within reach, as long as someone is willing to pay for them. “There is a degree of inevitability to this whole thing,” German says. “All these technologies are continuing to converge and mature. Even things like public perception can be overcome once people become aware of what the tech can do in their lives. Eventually it becomes a cultural phenomenon, where people suddenly rewire their lives around it.”
Kind of like, well, Uber.